Bio

Bio


Gordon Brown specializes in environmental geochemistry and aqueous and surface geochemistry. He and his research group focus on chemical and microbiological interactions at environmental interfaces, which are defined as interfaces between solids and aqueous solutions, solids and gases, aqueous solutions and gases, solids and microbial organisms (including microbial biofilms), and solids and natural organic matter. They utilize molecular-scale methods, particularly those involving very intense x-rays from synchrotron radiation sources, to study the interactions of contaminants and pollutants, particularly heavy metals such as lead and mercury, metalloids such as arsenic and selenium, and actinides such as uranium, with mineral surfaces, with the aim of understanding reactions that can sequester or release these species or transform them into more or less toxic forms.

Academic Appointments


Administrative Appointments


  • Chair, Department of Geological & Environmental Sciences, Stanford University (2012 - Present)
  • Professor (by courtesy) of Chemical Engineering, Stanford University (2008 - Present)
  • Director, Stanford Environmental Molecular Science Institute, Stanford University (2004 - 2011)
  • Chair Stanford Synchrotron Radiation Laboratory Faculty (now Department of Photon Science), SLAC National Accelerator Laboratory (1998 - 2007)
  • Acting Chair, Stanford Synchrotron Radiation Laboratory Faculty (now SLAC) (1997 - 1998)
  • Professor of Photon Science, Photon Science Department, SLAC National Accelerator Laboratory (1992 - Present)
  • Co-Director Center for Materials Research, Stanford University (1987 - 1990)
  • Chairman Geology Department, Stanford University (1986 - 1992)
  • Professor of Mineralogy and Geochemistry, Stanford University (1986 - Present)
  • Visiting Professor, Universite Pierre et Marie Curie Paris VI, Laboratoire de Mineralogie-Cristallographie (1984 - 1984)
  • Visiting Faculty Fellow High Temperature Chemistry and Ceramics Division, Sandia National Laboratory, Albuquerque, New Mexico (1983 - 1983)
  • Associate Professor of Mineralogy and Crystallography, Stanford University (1977 - 1986)
  • Assistant Professor of Mineralogy and Crystallography, Stanford University (1973 - 1977)
  • Scientific Collaborator, Chemistry Department, Brookhaven National Laboratory (1972 - 1973)
  • Assistant Professor of Mineralogy and Crystallography, Princeton University (1971 - 1973)
  • Postdoctoral Research Associate, State University of New York, Stony Brook (1970 - 1971)

Honors & Awards


  • Ian Campbell Medal,, American Geosciences Institute (2012)
  • Outstanding Paper Award (shared w/ Hayes, Roe, Hodgson, Leckie, Parks), Association of Environmental Engineering and Science Professors (2007)
  • Roebling Medal,, Mineralogical Society of America (2007)
  • Patterson Medal, The Geochemical Society (2007)
  • Hawley Medal, Canadian Mineralogist (2006), shared: Farges, Siewert, Ponader, Pichavant, Behrens, Mineralogical Association of Canada (2007)
  • Distinguished Lecturer, Distinguished Lecturer Series on Frontier Applications of Synchrotron Radiation, Cornell University (2004)
  • Fellow, American Association for the Advancement of Science (2000)
  • Best Paper Award 1999 (shared with G. Morin, F. Juillot, J. D. Ostergren, P. Ildefonse, G. Calas), Mineralogical Society of America (2000)
  • Umbgrove Lecturer, Utrecht University, The Netherlands (2000)
  • Edison Lecturer, University of Notre Dame (1999)
  • Fellow, European Association of Geochemistry (1999)
  • Fellow, Geochemical Society (1999)
  • Fellow, Geological Society of America (1997)
  • Docteur Honoris Causa, Universite Paris VII (1997)
  • Elected Vice President and President, Mineralogical Society of America (1994 - 1996)
  • 24th Hallimond Lecturer, Mineralogical Society of Great Britain and Ireland (1992)
  • Dorrell William Kirby Professor of Earth Sciences, Stanford University (1991 – Present)
  • French Government Fellowship as Professor associe, Universit Paris VI-VII (1984)
  • Fellow, Mineralogical Society of America (1975)
  • Graduate Fellow, National Defense Education Act (1966 – 1969)
  • Graduate Traineeship, National Science Foundation (1965 – 1966)

Boards, Advisory Committees, Professional Organizations


  • Member, Executive Committee of the Center for Materials Research, Stanford University (1978 - 1999)
  • Curator, Stanford Research Mineral Collection and Display, Stanford Univesity (1978 - Present)
  • Chair, Research Advisory Committee, Gemological Institute of America (1984 - 2008)
  • Member (Chair, 1990-92, 1999-2002), External Review Committee, Chemical Science and Technology Division (now Chemistry Division), Los Alamos National Laboratory (1988 - 2003)
  • Member, Board of Governors, Gemological Institute of America (1988 - 2008)
  • Member, Steering Committee, GeoSoilEnviro CARS, Advanced Photon Source, Argonne National Laboratory (1990 - Present)
  • Head, Environmental Sciences Section, Stanford Synchrotron Radiation Laboratory Research Department (1992 - Present)
  • Member and Co-organizer, Interdisciplinary Research Group on the Structure and Reactivity of Oxide Surfaces, Stanford Center for Materials Research (1993 - 1999)
  • Member, Visiting Committee, Department of Geological & Geophysical Sciences, Princeton University (1993 - 2000)
  • Chair, Chemical Sciences Division, Initiative in Molecular Environmental Science, U.S. Department of Energy, (1994 - 1997)
  • Chair, Search Committee for Soil/Environmental Geochemist, Stanford University (1994 - 1998)
  • Co-Chair, Beam Line 11 Technical Planning Group, Stanford Synchrotron Radiation Laboratory (1994 - 1998)
  • Co-Editor, Journal of Synchrotron Radiation (1995 - 2003)
  • Co-Chair, DOE Council on Chemical Sciences Workshop on Chemical Interactions at Metal Oxide-Aqueous Solution Interfaces (1996 - 1999)
  • Member, Visiting Committee, Geophysical Laboratory, Carnegie Institution of Washington (1996 - 2000)
  • Member, U.S. Department of Energy, Council on Chemical Sciences (1996 - 2001)
  • Organizer, DOE-Chemical Sciences Workshop on Molecular Environmental Science and Synchrotron Radiation Facilities, Stanford Synchrotron Radiation Laboratory (1997 - 1997)
  • Member, International Organizing Committee, 10th International Conference on X-ray Absorption Fine Structure (1997 - 1997)
  • Co-Convener, Symposium on Applications of Synchrotron Radiation in the Earth and Environmental Sciences,, American Geophysical Union Meeting, San Francisco, CA (1997 - 1997)
  • Participant, DOE Earth Sciences Council Workshop on Scaling in Geological Processes (1997 - 1997)
  • Co-Convener, DOE Workshop on Chemical Interactions at Metal Oxide-Aqueous Solution Interfaces, Santa Fe, NM (1997 - 1997)
  • Member, Visiting Committee, Department of Geology, Arizona State University (1997 - 1997)
  • Chair, Search Committee, Director of the Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University (1997 - 1998)
  • Member, Basic Energy Sciences Advisory Committee Panel on Synchrotron Radiation Sources and Science (1997 - 1998)
  • Member, Users Advisory Committee, Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory (1997 - 2000)
  • Member, Science Advisory Committee, Advanced Light Source, Lawrence Berkeley National Laboratory (1997 - 2001)
  • Member, Environmental Research Division Review Committee, Argonne National Laboratory (1997 - 2002)
  • Invited Lecturer, Keynote Address: Canadian Synchrotron Institute Workshop on Opportunities for Synchrotron Light in Mining, Natural Resources, and the Environment, Vancouver, B.C., Canada; (1998 - 1998)
  • Invited Lecturer, Nanostructures, Energy, and Technology Seminar, U.C. Davis, Davis, CA; San Francisco Gem and Mineral Society; DOE-BES Workshop on Building a Scientific Case for the Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA; Environmental Science Colloquium, Dept. of Physics, U.C. Riverside, Riverside, CA; Interface Science Seminar, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Hanford, WA; (1998 - 1998)
  • Plenary Lecture, Environmental Management Science Program Review, Chicago, IL (1998 - 1998)
  • Invited Lecturer, Advanced Photon Source Users Meeting Workshop on Environmental and Geosciences, Argonne National Laboratory, Argonne, IL; National Academy of Sciences Colloquium on Geology, Mineralogy, and Human Welfare, Irvine, CA (1998 - 1998)
  • Co-Convener, Symposium on Applications of Synchrotron Radiation in Mineralogy, 17th International Mineralogical Association Meeting, Toronto, Ontario, Canada (1998 - 1998)
  • Chair, Environmental Science/Geosciences Working Group, DOE-BES Workshop on Building a Scientific Case for the Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA (1998 - 1998)
  • Participant and Invited Speaker, National Academy of Sciences Colloquium on Geology, Mineralogy, and Human Welfare, Irvine, CA (1998 - 1998)
  • Participant, Department of Energy, Nuclear Energy Research Initiative Workshop, Washington, DC (1998 - 1998)
  • Member, Search Committee, Director of SLAC, SLAC, Stanford University (1998 - 1998)
  • Visiting Professor, Universite Paris VII (1998 - 1999)
  • Member, AGU Mineral and Rock Physics National Committee (1998 - 2001)
  • Chair, Search Committee for Two Senior Faculty Members at SSRL, Stanford University (1998 - 2001)
  • Co-Chair, EnviroSync, A National Organization of Environmental Science Users of U.S. Synchrotron Radiation Sources (1998 - 2004)
  • Chair, Stanford Synchrotron Radiation Laboratory Faculty, SLAC, Stanford University (1998 - 2007)
  • Participant, NSF Earth Sciences Workshop on Mineral and Rock Physics and Earth Materials (1999 - 1999)
  • Participant, NSF/DOE Chemistry Workshop on Energy and Environmental Science (1999 - 1999)
  • Invited Lecturer, DOE-BES Geosciences Research Symposium VI: Interfacial Processes, Pacific Northwest National Laboratory, Richland, WA (1999 - 1999)
  • Plenary Lecturer, NRCan Light Source Synchrotron Workshop, Ottawa, Canada (1999 - 1999)
  • Keynote Speaker, ACS Symposium on Interfacial and Colloidal Phenomena in Aquatic Environments, Environmental Chemistry Division, 217th American Chemical Society National Meeting, Anaheim, CA (1999 - 1999)
  • Edison Lecturer, Department of Civil Engineering and Geological Sciences, University of Notre Dame, South Bend, IN (1999 - 1999)
  • Keynote Speaker, Synchrotron Environmental Science Conference, Argonne National Laboratory, Argonne, IL (1999 - 1999)
  • Invited Lecturer, Corning Science Fellows Conference, Corning, NY; Invited Lecture: Mineralogy at the Millenium Symposium, Carnegie Institution of Washington, Geophysical Laboratory; New Opportunities in Molecular Environmental Science, Science Policy Committee Meeting, Stanford Linear Accelerator Center (1999 - 1999)
  • Invited Speaker, NSF/DOE Chemistry Workshop, Molecular Energy & Env Science, Chicago, IL; (1999 - 1999)
  • Invited Lecturer, Invited Lecture: 6th International Conference on the Structure of Surfaces (ICSOS-6), Vancouver, B.C., Canada; (1999 - 1999)
  • Plenary Lecture, ACS Symposium on First Accomplishments of the Environmental Management Science Program, Nuclear Chemistry Division, 218th American Chemical Society National Meeting, New Orleans, LA (1999 - 1999)
  • Keynote Speaker, Chemistry on Oxides Session, 46th American Vacuum Society International Symposium, Seattle, WA (1999 - 1999)
  • Invited Speaker, Krauskopf Symposium, Stanford University, Stanford, CA; Invited Speaker: Gibbs Symposium, American Geophysical Union Fall Meeting, San Francisco, CA (1999 - 1999)
  • Member, Search Committee, Ion Microprobe Faculty Position, Stanford University (1999 - 1999)
  • Invited Speaker, NSF Earth Sciences Workshop on Mineral and Rock Physics and Earth Materials, Scottsdale, AZ (1999 - 1999)
  • Co-Chair, GES Research Infrastructure Committee, Stanford University (1999 - 2000)
  • Member: Facility Advisory Committee, Canadian Light Source (1999 - 2001)
  • Member (Chair, 2002), MSA Distinguished Public Serve Award Committee (1999 - 2002)
  • Participant, American Academy of Microbiology Workshop on Geobiology, Tuscon, AZ (2000 - 2000)
  • Member, Advisory Board, NSF EPSCoR Interface Science Center, University of Nevada, Las Vegas (2000 - 2000)
  • Plenary Lecture, 2nd Euroconference and NEA Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, Grenoble, France (2000 - 2000)
  • Umbgrove Lecturer, Utrecht University, The Netherlands; (2000 - 2000)
  • Invited Speaker, SLAC High Energy Physics Symposium, Stanford Linear Accelerator Center, Stanford, CA; Environmental Science, Engineering, and Policy in the 21st Century Distinguished Lecture Series, University of Michigan, Ann Arbor, MI (2000 - 2000)
  • Invited Speaker, Advanced Light Source Division Seminars, Lawrence Berkeley National Laboratory, Berkeley, CA; (2000 - 2000)
  • Plenary Lecturer, Users Meeting, Advanced Photon Source, Argonne National Laboratory, Argonne, IL; (2000 - 2000)
  • Invited Speaker, Univ of Saskatchewan & Can. Light Source; DOE Wkshop, Soft X-Ray Sci Next Millennium, Pikeville, TN (2000 - 2000)
  • Chair, GES Graduate Admissions Committee, Stanford University (2000 - 2001)
  • Member, University Committee on Land and Building Development, Stanford University (2000 - 2003)
  • Invited Lecturer, Berkeley-Stanford Summer School on Synchrotron Radiation and Its Applications, Berkeley, CA; Symposium on Establishing a National Synchrotron Light Research Facility in Israel, SLAC, Stanford University; Departmental Seminar Series, Dept. of Earth and Space Sciences, University of Washington, Seattle, WA. (2001 - 2001)
  • Invited Speaker, Second International Workshop on Oxide Surfaces, Taos, NM; Session on Advances in the Development and Application for In Situ Techniques for the Investigation of Geochemical Systems, Goldschmidt Conference, The Homestead, Hot Springs, VA; (2001 - 2001)
  • Keynote Speaker, Session on Environmental Mineralogy and Geochemistry The Molecular Environmental Science Perspective, European Union of Geosciences Meeting, Strasbourg, France; (2001 - 2001)
  • Plenary Lecture, UK Natural Environment Research Council Workshop on Unlocking the Potential of DIAMOND and SOLIEL for Environmental Sciences, Strasbourg, France; Workshop on Molecular Environmental Science and Soft X-ray Sources, Lawrence Berkeley National Laboratory, Berkeley, CA; (2001 - 2001)
  • Member, External Review Committee, Columbia University NSF-DOE-Environmental Molecular Sciences Institute (2001 - 2001)
  • Invited Participant, National Academy of Sciences-National Research Council Workshop on Environmental Chemistry, Irvine, CA (Nov. 2002) (2002 - 2002)
  • Member, NSF Advisory Committee on Government Performance and Assessment (GPRA) Performance Assessment (2002 - 2002)
  • Panel Member, Chemistry Division, National Science Foundation, Collaborative Research in Chemistry Panel (2002 - 2002)
  • Invited Speaker, American Geophysical Union Fall Meeting, Union Session on National Facilities in the Earth Sciences:Overview of Applications to Low Temperature Geochemistry and Environmental Science, San Francisco, CA, December 2002. (2002 - 2002)
  • Invited Lecturer, Mineralogical Society of America-Geochemical Society Short Course on Applications of Synchrotron Radiation to Low Temperature Geochemistry and Environmental Science: Overview of Applications to Low Temperature Geochemistry and Environmental Science, Monterey, CA, December 2002; (2002 - 2002)
  • Invited Lecturer, Berkeley-Stanford Summer School on Synchrotron Radiation and Its Applications: Applications of Synchrotron Radiation in Environmental Science, Stanford, CA, July 2002; (2002 - 2002)
  • Invited Speaker, Spectroscopic Characterization of Speciation and Chemistry on Mineral Surfaces, Symposium on Chemistry and the Environment in the 21st Century - Session on Environmental Chemistry at Interfaces, 223rd National Meeting of the American Chemical Society, Orlando, FL, April 2002; (2002 - 2002)
  • Chair, Search Committee for Geomicrobiology Faculty Position, Stanford University (2002 - 2003)
  • Member (and Chair of X-ray and Neutron Science Subcommittee), Committee of Visitors, Materials Science and Engineering Division, Basic Energy Sciences, Department of Energy (2003 - 2003)
  • Invited Speaker, Mesilla Chemistry Workshop on Environmental Chemistry at Interfaces: Advances through Molecular-Level Insight: Approaching the Complexity of Natural Environmental Interfaces: Spectroscopic Studies of Aqueous Metal and Metalloid Reactions with Biofilm-Coated Metal Oxides, Mesilla, NM, February 2003; (2003 - 2003)
  • Invited Speaker, DOE Geosciences Program Principal Investigator Symposium on Surficial Geochemical Processes: Sorption Reactions at Mineral-Water Interfaces: X-ray Spectroscopy/Scattering Studies of Sorption Complex Geometries, Surface Structure, and Reactivity, Effects of Organic and Inorganic Ligands, and Complex Natural Samples, Argonne National Laboratory, Argonne, IL, March 2003; (2003 - 2003)
  • Plenary Science Lecture, American Chemical Society 225th National Meeting, Symposium on Synchrotron-Based Analytical Techniques for Nuclear and Environmental Sciences: Overview of Applications of Synchrotron-Based Techniques in Environmental and Nuclear Science, New Orleans, LA, March 2003; (2003 - 2003)
  • Invited Speaker, Berkeley-Stanford Summer School on Synchrotron Radiation and Its Applications: Applications of Synchrotron Radiation in Environmental Science, Berkeley, CA, June 2003; (2003 - 2003)
  • Plenary Lecturer, XAFS12 12th International Conference on X-ray Absorption Spectroscopy: Environmental Interfaces, Heavy Metals, Microbes, and Plants: Applications of XAFS Spectroscopy and Related Synchrotron Radiation Methods to Environmental Science, Malm, Sweden, June 2003; (2003 - 2003)
  • Invited Speaker, University of Paris VI-VII: From Subduction to Mercury in Tuna: Hg Mining and Contamination in the California Coast Range, USA, Paris, France, June 2003; (2003 - 2003)
  • Invited Speaker, Department of Geology and Geophysics Seminar Series, Yale University, From Subduction to Mercury in Tuna: Hg Mining and Contamination in the California Coast Range, USAî, New Haven, CN, November 2003 (2003 - 2003)
  • Chair, Core Disciplines Subcommittee, School of Earth Sciences, Stanford University (2003 - 2004)
  • Member, Grants Committee, Stanford Institute for the Environment, Stanford University (2003 - 2004)
  • Member, Science Advisory Committee, Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory (2003 - Present)
  • Member, Visiting Committee, Carnegie Institution of Washington, Geophysical Laboratory (2004 - 2004)
  • Invited Speaker, Environmental Protection Agency STAR Mercury Program Final Review, Processes Controlling the Chemical/Isotopic speciation and Distribution of Mercury from Contaminated Mine Wastes, Washington, DC, November 2003; (2004 - 2004)
  • Invited Speaker, Symposium on Synchrotron Radiation as a Frontier Multidisciplinary Scientific Tool, American Association for the Advancement of Science Annual Meeting, Shedding New Light on Environmental Problems: Applications of Synchrotron Radiation to Environmental Science at the Molecular Level, Seattle, WA, February 2004; (2004 - 2004)
  • Keynote Speaker, 7th Annual Environmental Chemistry Symposium, Pennsylvania State University Center for Environmental Chemistry and Geochemistry, From Subduction to Mercury in Tuna: Hg Mining and Contamination in the California Coast Range, USA and Environmental Interfaces, Heavy Metals, Microbes, and Plants: Applications of Synchrotron Radiation Methods to Environmental Science at the Molecular Level, University Park, PA, March 2004; (2004 - 2004)
  • Chair, Committee of Visitors, Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, Department of Eneregy (2004 - 2005)
  • Member, Search Committee in Chemical Engineering for New Faculty Member in Heterogeneous Catalysis, Stanford University (2004 - 2005)
  • 2004 – 2006 | Member, Search Committee, Junior Faculty Position in X-ray Imaging and Ultra-Fast Scattering, SSRL Faculty, Stanford University (2004 - 2006)
  • Member, Science Advisory Committee, Center for Advanced Microstructures and Devices, Lousiana State University, Baton Rouge, LA (2004 - Present)
  • Chair, Stanford Synchrotron Radiation Laboratory Director Search Committee, SLAC, Stanford University (2005 - 2005)
  • Invited Speaker, Stanford-Berkeley Summer School in Applications of Synchrotron Radiation in the Physical Sciences, Interfaces, Heavy Metals, Microbes, and Plants: Shedding New Light on Environmental Science at the Molecular Level, SLAC, June 2005. (2005 - 2005)
  • Invited Speaker, Symposium on Research, Education, and Outreach in the NSF Environmental Molecular Science Institutes, 230th American Chemical Society Meeting, ìResearch Overview of the Stanford EMSIî, Washington, DC, August 2005. (2005 - 2005)
  • Plenary Speaker, Workshop on In-Situ Characterization of Surface and Interface Structures and Processes, Argonne National Laboratory, Synchrotron-Based Studies of Environmental Surfaces, Interfaces, and Reactionsî, Argonne, IL, September 2005. (2005 - 2005)
  • Plenary Speaker, Synchrotron Environmental Science III, Synchrotron Environmental Science: What Have We Accomplished and What Lies Ahead?, Brookhaven National Laboratory, Upton, NY, September, 2005. (2005 - 2005)
  • Invited Speaker, Environmental Mineralogy Seminar Studies at the Molecular Level, Molecular-Level Studies of Chemical and Biological Interactions at Iron and Aluminum Oxide Surfacesî, Universite de Grenoble, Grenoble, France, October 2005. (2005 - 2005)
  • Invited Speaker, DOE Review and Site Visit of SSRL, Molecular Environmental and Interface Science Research at SSRLî, SLAC, Menlo Park, CA, January 2005 (2005 - 2005)
  • Invited Speaker, Stanford-Berkeley Summer School in Applications of Synchrotron Radiation in the Physical Sciences, Interfaces, Heavy Metals, Microbes, and Plants: Shedding New Light on Environmental Science at the Molecular Levelî, SLAC, June 2005. (2005 - 2005)
  • Invited Speaker, Bancroft Symposium, 88th Canadian Chemistry Conference, Synchrotron Radiation Studies of Environmental Interfaces, Saskatoon, Saskatchewan, May 2005. (2005 - 2005)
  • Invited Speaker, Symposium on Environmental Interfaces, American Physical Society March Meeting, Chemical Reactivity at Metal Oxide-Aqueous Solution Interfaces, Los Angeles, CA, March 2005. (2005 - 2005)
  • Invited Speaker, Symposium on Applications of Physical Chemistry to Environmental and Biogeochemical Research, 229th American Chemical Society National Meeting, The Role of Organic Molecules and Microbial Organisms in Metal Ion Sorption Processes, San Diego, CA, March 2005. (2005 - 2005)
  • Invited Speaker, Robinson Environmental Theme Dormitory Seminar Series, Stanford University, Exploring Environmental Science Issues at the Molecular Level, Stanford, CA, March 2005. (2005 - 2005)
  • Invited Speaker, Los Alamos National Lab Workshop on Addressing National Security Needs at DOE User Laboratories - Determining Structure-Function Relationships in Security-Relevant Materials, (1) Molecular Environmental Science: An Example of Applied Science at the User Facilities; (2) Research Opportunities at SSRL Relevant to National Security, Los Alamos, NM, February 2005. (2005 - 2005)
  • Invited Speaker, Chemistry Department Seminar Series, U.C. Irvine, Chemical and Biological Processes at Environmental Interfaces - A Reductionist Approach Using Synchrotron Radiation Methods, Irvine, CA, February 2005. (2005 - 2005)
  • Member, Local Organizing Committee, XAFS 13 (2005 - 2006)
  • Member, International Program Committee, XAFS13, 13th International Meeting on X-ray Absorption Fine Structure Spectroscopy, Stanford, CA (2005 - 2006)
  • Member, Science Advisory Council, Sincrotrone Trieste, ELETTRA, Trieste, Italy (2005 - Present)
  • Member, Search Committee, Senior Faculty Position in Molecular Theory, Photon Science Department, SLAC, Stanford University (2006 - 2009)
  • Keynote Speaker, Annual Meeting of the Center for Environmental Molecular Science, Stony Brook University: Chemical and Microbial Processes at Environmental Interfaces - From Molecular to Field Scales, Stony Brook, NY, November 2006. 2005 Invited Speaker: Department of Materials Science and Engineering Seminar Series, Stanford University, X-ray Spectroscopy and Microscopy Studies of Chemical and Biological Processes at Environmental Interfaces, Stanford, CA, January 2005 (2006 - 2006)
  • Invited Speaker, 232nd American Chemical Society National Meeting, Division of Colloid and Surface Chemistry Symposium on Environmental Interfaces, Soft X-ray Spectroscopy Studies of Environmental Interfaces, San Francisco, CA, September 2006. (2006 - 2006)
  • Invited Speaker, NSF Workshop on Preparing for an Academic Career in the Geosciences, Stanford Environmental Molecular Science Institute Overview, Stanford University, July 2006. (2006 - 2006)
  • Invited Speaker, Stanford Vice Provost for Undergraduate Education Seminar Series in Earth Sciences: Mercury in the Environment, Stanford University, July 2006. (2006 - 2006)
  • Invited Speaker, Workshop on the Development of New User Research Capabilities in Environmental Molecular Science: Stanford EMSI - Current and Future Research Efforts, W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, August 2006. (2006 - 2006)
  • Invited Speaker, Energy Recovery Linac Workshop on Frontier Applications of X-ray Science in Biology, Applications of X-ray Absorption Spectroscopy in Microbial Biomineralization, Cornell University, Ithaca, NY, June 2006. (2006 - 2006)
  • Invited Speaker, Stanford-Berkeley Summer School in Applications of Synchrotron Radiation in the Physical Sciences, Interfaces, Heavy Metals, Microbes, and Plants: Shedding New Light on Environmental Science at the Molecular Level, U.C. Berkeley, June 2006 (2006 - 2006)
  • Member, DOE Chemical Sciences Division Program Review Committee, Chemistry Division, Argonne National Laboratory, March 2006 (2006 - 2006)
  • Invited Speaker, Department of Chemstry Seminar, Autonomous University of Barcelona, "Environmental Interfaces, Heavy Metals, Microbes, and Plants: Shedding New Light on Environmental Science at the Molecular Level", Barcelona, Spain, April 2006 (2006 - 2006)
  • Invited Lecturer and Participant, DOE Workshop on Molecular Dynamics and Structure of Geofluids, Claremont Resort, Berkeley, CA (2007 - 2007)
  • Third Roebling Medallist Lecturer, “Reminiscences of a Mineralogist Who Went Astray”, Geological Society of America Annual Meeting, Denver, CO, October 2007 (2007 - 2007)
  • Invited Speaker, The Future of X-ray Science – A symposium in honor or Prof. Joachim Stohr, Director of SSRL, on his 60th birthday, “Molecular Environmental and Interface Science - Applications of Synchrotron X-rays to Pollutants and Their Interactions at Environmental Interfaces”, SLAC, Stanford, CA, September 2007. (2007 - 2007)
  • Invited Speaker:, Hudnall Symposium in Memory of Prof. Joseph V. Smith, “Applications of Synchrotron Radiation to Earth Materials”, Department of the Geophysical Sciences, University of Chicago, Chicago, IL, October 2007. (2007 - 2007)
  • Member, External Review Committee, Chemistry and Forensics Review, Los Alamos National Laboratory, Los Alamos, NM (2007 - 2007)
  • Plenary Lecturer, Goldschmidt Conference, Patterson Medal Lecture, A Geochemists View of the Environment from the Molecular Perspective, Cologne, Germany, August 2007. (2007 - 2007)
  • Invited Speaker, Goldschmidt Conference, Symposium on Speciation and Reactivity of Trace Elements in Natural Environments, Mercury Speciation in Mining Environments, Cologne, Germany, August 2007. (2007 - 2007)
  • Plenary Lecturer, 12th International Symposium on Water-Rock Interaction: Recent Advances in Surface, Interface, and Environmental Geochemistry, Kunming, China, August 2007. (2007 - 2007)
  • Participant and Discussion Leader, 2007 EnviroSync DOE Workshop: Assessing Synchrotron Radiation Capabilities and Future Needs for Molecular Environmental Science and Low Temperature Geochemistry, Rockville, MD, July 2007. (2007 - 2007)
  • Co-Organizer, SSRL Workshop on STXM and X-ray Nanoprobe Capabilities and Needs for Geological, Environmental, and Biological Sciences, Stanford University, July 2007. (2007 - 2007)
  • Member, Committee on Committees, Mineralogical Society of America 2007 | Keynote Speaker: Frontiers in Mineral Sciences 2007 Conference: Interaction of Organic Molecules and Microorganisms with Mineral Surfaces and Their Impact on Metal Ion Sorption Processes, Cambridge, U.K., June 2007. (2007 - 2007)
  • Invited Speaker, The FYSICUM, Stockholm University: Molecular Environmental Science-Applications of Synchrotron Radiation to Environmental Problems at the Molecular Level, Stockholm, Sweden, March 2007. (2007 - 2007)
  • Invited Speaker, Department of Chemistry Seminar, University of Paris VI: Factors Controlling Chemical Reactivity at Metal Oxide-Aqueous Solution Interfaces, Paris, France, March 2007. (2007 - 2007)
  • Invited Speaker, 1st ERA-Chemistry Flash Conference: Factors Controlling Chemical Reactivity at Metal Oxide-Aqueous Solution Interfaces, Autrans, France, March 2007. (2007 - 2007)
  • Invited Speaker, Workshop on Colloidal Ceramic Processing - The Role of Interfaces, University of Melbourne: Reactivity of Hematite Nanoparticles in the Presence of Zn(II)aq and Shewanella oneidensis, Melbourne, Australia, February 2007. (2007 - 2007)
  • Keynote Speaker, Australian Colloid and Interface Symposium - Inorganic Oxide Surfaces, Factors Controlling the Reactivity of Metal Oxide Surfaces, Sydney, Australia, February 2007. (2007 - 2007)
  • Invited Speaker, Glen T. Seaborg Institute for Transactinium Science Seminar Series, Lawrence Berkeley National Laboratory: Uranium Speciation in Contaminated Sediments: XAFS Studies of Model and Natural Systems, Berkeley, CA, January 2007 (2007 - 2007)
  • Member, Junior Faculty Search Committee, Dept. of Chemical Engineering, Stanford University (2007 - 2008)
  • Co-Chair, Task Force Team on Materials, Energy, Environment, and Techology, SLAC, Stanford University (2007 - 2008)
  • Member, SLAC Strategic Planning Committee, DOE Contract Competition, SLAC, Stanford University (2007 - 2008)
  • Member, Science Advisory Board, Calera Corporation, Cupertino, CA (2007 - Present)
  • Member: GES Graduate Admissions Committee, Stanford University (2007 - Present)
  • Member: SLAC Faculty Task Force, Stanford University (2007 - Present)
  • Member, School of Earth Sciences Council, Stanford University (2007 - Present)
  • Co-Organizer, Session on Nanoparticles in the Environment, American Geophysical Union Fall Meeting, San Francisco, CA, December (2008 - 2008)
  • Invited Speaker, Department of Environmental Science Seminar: “Microbial and Chemical Interactions at Mineral Surfaces and Their Impact on Trace Element Cycling”, ETH-Zurich, Zurich, Switzerland, November (2008 - 2008)
  • Invited Speaker, Institute Seminar, EAWAG, Swiss Federal Institute of Aquatic Science & Technology: “Mercury Pollution in California – From Subduction to Mercury in Tuna”, Dübendorf, Switzerland, November (2008 - 2008)
  • Invited Participant, DOE-BES Workshop on Solving Science and Energy Grand Challenges with Next Generation Photon Sources, Rockville, MD, October (2008 - 2008)
  • Invited Speaker, Department of Civil & Environmental Engineering Seminar Series, U.C. Berkeley: “Shedding New Light on Environmental Chemistry and Environmental Microbiology: Synchrotron-Based Studies of Complex Environmental Processes”, Berkeley, CA, September (2008 - 2008)
  • Invited Speaker, Cross-Cutting Review of Environmental Science at the Advanced Light Source, Lawrence Berkeley National Laboratory: “STXM Studies of Nanoscale Environmental and Geological Materials and Processes”, Berkeley, CA, October (2008 - 2008)
  • Member, External Review Committee, Geosciences, Environmental Sciences, and Planetary Sciences Programs, Advanced Photon Source, Argonne National Laboratory (2008 - 2008)
  • Invited Speaker, Stanford-Berkeley Summer School in Applications of Synchrotron Radiation in the Physical Sciences: “Applications of Synchrotron Radiation in the Environmental Sciences”, Stanford Linear Accelerator Center and Stanford University, Stanford, CA, August (2008 - 2008)
  • Invited Speaker, Geochemistry Division Symposium on Advanced Approaches to Investigating Adsorption at the Solid-Water Interface: “Factors Controlling the Reactivity of Metal Oxide Surfaces”, American Chemical Society 235th National Meeting, New Orleans, LA, April (2008 - 2008)
  • Invited Speaker, U.C. Berkeley Workshop on Imaging Complex Pore Structure of Cement: “ Synchrotron X-ray Spectromicroscopy Studies of Minerals and Biominerals in Complex, Multi-phase Samples”, Berkeley, CA, April (2008 - 2008)
  • Invited Speaker, Louisiana State University Office of Research and Economic Development Workshop - Enabling Grand Challenge Science: The Light Source of the Future, “A Case for Environmental Science at the ‘Next Generation’ Light Source”, Baton Rouge, LA, January (2008 - 2008)
  • Member, Proposal Review Panel, Geobiology and Low Temperature Geochemistry Program, Earth Sciences Division, National Science Foundation 2008 Keynote Speaker: Beveridge Symposium on the Interaction of Metal Ions with Bacteria: “Synchrotron X-ray Studies of Bacteria-Mineral-Metal Ion Interactions”, Goldschmidt Conference, Vancouver, British Columbia, Canada, July (2008 - 2009)
  • Invited Speaker, San Jose State University Geology Club: “From Subduction to Mercury in Tuna: The Legacy of Mercury and Gold Mining in California”, San Jose, CA, November (2009 - 2009)
  • Invited Speaker, Center for Environmental Implications of Nanotechnology Annual Meeting: “Surface Science Studies of Iron Oxide and Silver Nanoparticles”, Washington, DC, September (2009 - 2009)
  • Co-Organizer (with Abby Kavner, UCLA; Nancy Ross, Virginia Tech; Glenn Waychunas, LBNL), Mineralogical Society of America Symposium on “Frontiers in Mineral Sciences: Mineral/Melt Energetics, Mineral Surface Chemistry, Mineral Nanoscience, and High Pressure Mineralogy,” Geological Society of America Annual Meeting, Portland, OR, October (2009 - 2009)
  • Co-Organizer and Invited Speaker (with Georges Calas, University of Paris 6), Symposium on Environmental Mineralogy, French Academy of Sciences, Institut de France: “Environmental Mineralogy – Molecular-level Perspectives”, Paris, France, September (2009 - 2009)
  • Invited Speaker, Department of Earth & Environmental Sciences, Ludwig-Maximilians-Universität: “Applications of Synchrotron Radiation in the Earth, Environmental, and Energy Sciences”, Munich, Germany, June (2009 - 2009)
  • Invited Speaker, Department of Earth and Planetary Sciences Seminar: “Mercury Pollution in California - From Subduction to Mercury in Tuna”, Washington University St. Louis, April (2009 - 2009)
  • Co-Organizer (with Janet Hering, ETH), Session on “Mineral/Water Interface Chemistry: The Legacy of Stumm and Schindler and What We Have Learned Since,” 2009 | Goldschmidt Conference, Davos, Switzerland, June (2009 - 2009)
  • Invited Speaker, Symposium on Metal and Metalloid Speciation and Adsorption: “Interaction of Zn(II) with Mineral Nano- and Microparticles, Bacterial Surfaces, and Biofilm-Coated Metal Oxides”, 237th American Chemical Society National Meeting, Salt Lake City, UT, March (2009 - 2009)
  • Discussion Leader, Gordon Research Conference on Chemical Reactions at Surfaces, Session on “Environmental Surface Chemistry”, Ventura, CA, February (2009 - 2009)
  • Member, Stanford Faculty Senate, Stanford University (2009 - 2009)
  • Co-Chair, Science Theme Advisory Panel on Geochemistry, Biogeochemistry, and Subsurface Science, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory (2009 - 2010)
  • Affiliated Faculty, Woods Institute for the Environment, Stanford University (2009 - Present)
  • Invited Speaker, Symposium on Environmental Implications of Nanotechnology, PacifiChem Meeting: “Structure and Reactivity of Silver and Iron Oxide Nanoparticles”, Honolulu, HI, December 2010. (2010 - 2010)
  • Invited Speaker, Symposium on Environmental Interfaces, 57th Annual American Vacuum Society Meeting: “Environmental Interfaces: Where the Vacuum, Cleanliness, and Size Gaps Must be Minimized”, Albuquerque, NM, October 2010. (2010 - 2010)
  • Invited Speaker, Session on Biotic and Abiotic Transformations and Effects of Manufactured Nanomaterials – Fundamental Environmental Aspects, Goldschmidt 2010 Conference: “Sulfidation of Silver Nanoparticles”, Knoxville, TN, June 2010. (2010 - 2010)
  • Invited Speaker, Symposium on Spectroscopic Investigations of Metal Interactions at Mineral/Water/Microbial Interfaces: “Spectroscopic Investigations of Metal Ion Interactions with Mineral Surfaces – What Have We Learned in the Last 30 Years?”, 239th American Chemical Society Meeting, San Francisco, CA, March (2010 - 2010)
  • Member, Provost's Committee on Postdoctoral Students, Stanford University (2010 - Present)
  • Invited Speaker, NSF Chemistry Workshop on Nanomaterials and the Environment: “Surface Adsorption and Reaction Processes Relevant to Environmental Science” and “Infrastructure and Human Resources Needs in Nano/Environmental Science: Computational Tools”, Arlington, VA, June (2011 - 2011)
  • Keynote Speaker, Session on Chemical and Microbial Electron Transfer Processes at Mineral Surfaces, Goldschmidt 2011 Conference: “Element Attachment and Electron Transfer Reactions at Mineral-Water and Mineral-Microbe Interfaces”, Prague, The Czech Republic, August (2011 - 2011)
  • Member, Organizing Committee, NSF Chemistry Workshop on "Nanomaterials and the Environment: The Role of Chemists", Arlington, VA, June 28-30 (2011 - 2011)
  • Co-Organizer (with Georges Calas, Univerisity of Paris 6), Session on Actinides in the Environment, AGU Fall National Meeting, San Francisco, CA, December (2011 - 2011)
  • Member, Basic Energy Sciences Advisory Committee, Department of Energy (2011 - Present)
  • Member, Basic Energy Sciences Advisory Committee Subcommittee on Mesoscale Science & Engineering, Department of Energy (2011 - Present)
  • Organizer, Session on “Surface Adsorption and Reaction Processes of Nanomaterials Relevant to Environmental Science.” Division of Colloid and Surface Science, 243rd American Chemical Society National Meeting, San Diego, CA, March (2012 - 2012)
  • Invited Talk, “Probing Environmental Nanoparticles and Chemical Reactions at Solid-Water-Microbial Biofilm Interfaces with Synchrotron Light.” Synchrotron Soleil – French National Synchrotron Facility Seminar, Gif-sur-Yvette, France, May (2012 - 2012)
  • Invited Talk, "Mesoscale Phenomena Associated with Mineral Surfaces and Pathway-Dependent Chemical Processes." Session on Earth Materials at the Mesoscale: Characterization and Applications. American Geoophysical Union Meeting, San Francisco, CA, December (2012 - 2012)
  • Invited Talk and Co-Organizer, “Molecular Characterization of Natural Organic Matter”, Workshop on Belowground Carbon Cycling Processes at the Molecular Scale, Environmental Molecular Science Laboratory, Pacific Northwest National Lab, Richland, WA, February (2013 - 2013)
  • Smith Lecturer, "Mineral-Aqueous Solution Interfacial Processes and Their Impact on the Environment". Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, March (2013 - 2013)
  • Invited Talk, “Mineral-aqueous solution interfacial processes and their impact on the environment". 2013 Gordon Research Conference on Chemical Reactions on Surfaces. Les Diablerets, Switzerland, April (2013 - 2013)
  • Invited Talk, “Mineral-aqueous solution interfacial processes and their impact on the environment.” U.S.G.S. Western Region Colloquium, Menlo Park, CA, May (2013 - 2013)
  • Invited Lecturer, ”Applications of XAFS Spectroscopy to Molecular Environmental Science”, SLAC National Accelerator Laboratory Summer School on Applications of Synchrotron X-ray Absorption Spectroscopy, SLAC National Accelerator Laboratory, June (2013 - 2013)
  • Invited Talk, “Environmental Geochemistry of the Light Actinides” Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), Universite Paris VI, Paris, France, June (2013 - 2013)
  • Invited Talk, “Mineral-Aqueous Solution Interface Reactions and Their Impact on the Environment”, Centre Européen de Recherche et d’Enseignement des Géosciences de l’Environnement (CEREGE), Universite Aix-Marseilles, Aix-in-Provence, France, June (2013 - 2013)
  • Member, Geological Society of America Geology and Public Policy Committee (2013 - 2013)
  • Member, DOE - Basic Energy Sciences Advisory Committee (BESAC) Sub-Committee on Major Facilities (2013 - 2013)
  • Member, DOE - BESAC Sub-Committee on Synchrotron Light Sources (2013 - 2013)
  • Invited Talk, “Mineral-Aqueous Solution Interface Reactions and Their Impact on the Environment”, Frontiers in Geosciences Seminar Series. Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, July (2013 - 2013)
  • Keynote Speaker, “Beneficial Uses of Engineered Nanoparticles and the Behavior of Natural and Engineered Nanoparticles in the Environment", Session on Environmental Application of Engineered Nanomaterials: Benefits and Risks. In Theme on Anthropogenic Impacts on Pollutant Dynamics, Goldschmidt 2013 Conference, Florence, Italy, August (2013 - 2013)
  • Lead, Task on Complex Environmental Interfaces under Realistic Conditions, SLAC Initiative on Controlling Chemical Reactivity for Energy and the Environment (2013 - 2013)
  • Invited Talk, “Factors Controlling Chemical Reactions at Environmental Interfaces”, Session on Behavior of Contaminants at Environmental Interfaces, Division of Colloid and Surface Chemistry, 246th American Chemical Society Meeting, Indianapolis, IN, September (2013 - 2013)
  • Member, Committee on Synchrotron Light Sources, National Science Foundation Mathematics and Physical Science Directorate (2013 - 2013)
  • Member, Science Advisory Board, Blue Planet Ltd. (2013 - 2013)
  • Invited Speaker, Institut de Mineralogie et de Physique des Milieux CondensÈs, University of Paris VI-VII: Uranium Speciation in Contaminated Sediments: XAFS Studies of Model and Natural Systems, Paris, France, March 2007. (2013 - Present)
  • Member, University Committee on Environmental Health & Safety, Stanford University (2013 - Present)

Professional Education


  • Ph.D., Virginia Polytechnic Institute and State University, Mineralogy and Crystallography (1970)
  • M.S., Virginia Polytechnic Institute and State University, Mineralogy and Crystallography (1968)
  • B.S., Millsaps College, Chemistry and Geology (1965)

Research & Scholarship

Current Research and Scholarly Interests


Research
My research interests involve five main areas: (1) geochemistry of mineral surfaces and their reactivity with aqueous metal complexes, organic matter, and microbial organisms; (2) structure and properties of natural and manufactured nanoparticles; (3) environmental chemistry/geochemistry of heavy metal and actinide contaminants; (4) experimental studies of carbon sequestration through mineral carbonation reactions; and (5) structure-property relationships of silicate liquids and glasses. The first four areas have bearing on the sequestration, transport, and transformations of environmental contaminants (e.g., mercury, lead, arsenic, uranium, and CO2) in aquatic systems, soils, and the atmosphere; the last focuses on the high-temperature geochemistry of silicate magmas and their trace elements. My students and I utilize various types of macroscopic and microscopic measurements, including the very intense x-rays from synchrotron radiation sources, as well as field investigations.

Teaching
I teach courses at both the undergraduate and graduate levels, including Earth Materials (GES 102), the basic sophomore-level course required of GES majors on minerals and rocks and the processes that form and modify them; Environmental Geochemistry (GES 170), a senior-, first-year graduate-level course on the chemistry of the environment; and Physics and Chemistry of Minerals and Mineral Surfaces (GES 261), a graduate-level course on my specialty. I also occasionally teach a sophomore seminar on environment and human health as well as graduate seminars on current topics in environmental geochemistry and mineral surface and aqueous geochemistry.

Professional Activities
Ian Campbell Medal, American Geosciences Institute (2012); Patterson Medal, Geochemical Society for Environmental Geochemistry Research (2007); Roebling Medal, Mineralogical Society of America (2007); director, Stanford-NSF Environmental Molecular Science Institute (2004-2011); member, Science Advisory Committees of the DOE Office of Basic Energy Sciences (2011-present); Environmental Molecular Science Laboratory-PNNL (2003-present); Sincrotrone Trieste-Italian National Synchrotron Laboratory (2005-2011); Center for Advanced Microdevices-LSU (2005-2010); Advanced Light Source-LBNL (1997-2000); Canadian Light Source (1999-2002); Chemistry Division-Los Alamos National Laboratory (1988-2003); fellow, American Association for the Advancement of Science (2000); fellow, Geochemical Society and European Association of Geochemistry (1999); fellow, Geological Society of America (1997); fellow, Mineralogical Society of America (1975); Docteur Honoris Causa degree, Universite Paris 7 (1997); president, Mineralogical Society of America (1996); professor (1988-present) and chair (1998-2007), Stanford Synchrotron Radiation Laboratory Faculty (now Department of Photon Science), SLAC; member, Board of Governors, Gemological Institute of America (1988-2008); chair, Department of Geology, Stanford (1986-1992); co-director, Stanford-NSF Center for Materials Research (1987-1989); chair, Department of Geological & Environmental Sciences (2012-present).

Teaching

2013-14 Courses


Postdoctoral Advisees


Publications

Journal Articles


  • Properties of impurity-bearing ferrihydrite II: Insights into the surface structure and composition of pure, Al- and Si-bearing ferrihydrite from Zn(II) sorption experiments and Zn K-edge X-ray absorption spectroscopy GEOCHIMICA ET COSMOCHIMICA ACTA Cismasu, A. C., Levard, C., Michel, F. M., Brown, G. E. 2013; 119: 46-60
  • Quantification of the ferric/ferrous iron ratio in silicates by scanning transmission X-ray microscopy at the Fe L-2,L-3 edges CONTRIBUTIONS TO MINERALOGY AND PETROLOGY Bourdelle, F., Benzerara, K., Beyssac, O., Cosmidis, J., Neuville, D. R., Brown, G. E., Paineau, E. 2013; 166 (2): 423-434
  • Mercury Isotope Signatures as Tracers for Hg Cycling at the New Idria Hg Mine ENVIRONMENTAL SCIENCE & TECHNOLOGY Wiederhold, J. G., Smith, R. S., Siebner, H., Jew, A. D., Brown, G. E., Bourdon, B., Kretzschmar, R. 2013; 47 (12): 6137-6145

    Abstract

    Mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes provides a new tool for tracing Hg in contaminated environments such as mining sites, which represent major point sources of Hg pollution into surrounding ecosystems. Here, we present Hg isotope ratios of unroasted ore waste, calcine (roasted ore), and poplar leaves collected at a closed Hg mine (New Idria, CA, U.S.A.). Unroasted ore waste was isotopically uniform with δ(202)Hg values from -0.09 to 0.16‰ (± 0.10‰, 2 SD), close to the estimated initial composition of the HgS ore (-0.26‰). In contrast, calcine samples exhibited variable δ(202)Hg values ranging from -1.91‰ to +2.10‰. Small MIF signatures in the calcine were consistent with nuclear volume fractionation of Hg isotopes during or after the roasting process. The poplar leaves exhibited negative MDF (-3.18 to -1.22‰) and small positive MIF values (Δ(199)Hg of 0.02 to 0.21‰). Sequential extractions combined with Hg isotope analysis revealed higher δ(202)Hg values for the more soluble Hg pools in calcines compared with residual HgS phases. Our data provide novel insights into possible in situ transformations of Hg phases and suggest that isotopically heavy secondary Hg phases were formed in the calcine, which will influence the isotope composition of Hg leached from the site.

    View details for DOI 10.1021/es305245z

    View details for Web of Science ID 000320749000010

    View details for PubMedID 23662941

  • Presentation of the Mineralogical Society of America Award for 2012 to Karim Benzerara AMERICAN MINERALOGIST Brown, G. E. 2013; 98 (5-6): 1088-1088
  • Environmental Speciation of Actinides INORGANIC CHEMISTRY Maher, K., Bargar, J. R., Brown, G. E. 2013; 52 (7): 3510-3532

    Abstract

    Although minor in abundance in Earth's crust (U, 2-4 ppm; Th, 10-15 ppm) and in seawater (U, 0.003 ppm; Th, 0.0007 ppm), light actinides (Th, Pa, U, Np, Pu, Am, and Cm) are important environmental contaminants associated with anthropogenic activities such as the mining and milling of uranium ores, generation of nuclear energy, and storage of legacy waste resulting from the manufacturing and testing of nuclear weapons. In this review, we discuss the abundance, production, and environmental sources of naturally occurring and some man-made light actinides. As is the case with other environmental contaminants, the solubility, transport properties, bioavailability, and toxicity of actinides are dependent on their speciation (composition, oxidation state, molecular-level structure, and nature of the phase in which the contaminant element or molecule occurs). We review the aqueous speciation of U, Np, and Pu as a function of pH and Eh, their interaction with common inorganic and organic ligands in natural waters, and some of the common U-containing minerals. We also discuss the interaction of U, Np, Pu, and Am solution complexes with common Earth materials, including minerals, colloids, gels, natural organic matter (NOM), and microbial organisms, based on simplified model system studies. These surface interactions can inhibit (e.g., sorption to mineral surfaces, formation of insoluble biominerals) or enhance (e.g., colloid-facilitated transport) the dispersal of light actinides in the biosphere and in some cases (e.g., interaction with dissimilatory metal-reducing bacteria, NOM, or Mn- and Fe-containing minerals) can modify the oxidation states and, consequently, the behavior of redox-sensitive light actinides (U, Np, and Pu). Finally, we review the speciation of U and Pu, their chemical transformations, and cleanup histories at several U.S. Department of Energy field sites that have been used to mill U ores, produce fissile materials for reactors and weapons, and store high-level nuclear waste from both civilian and defense operations, including Hanford, WA; Rifle, CO; Oak Ridge, TN; Fernald, OH; Fry Canyon, UT; and Rocky Flats, CO.

    View details for DOI 10.1021/ic301686d

    View details for Web of Science ID 000317094300009

    View details for PubMedID 23137032

  • Sulfidation Mechanism for Zinc Oxide Nanoparticles and the Effect of Sulfidation on Their Solubility ENVIRONMENTAL SCIENCE & TECHNOLOGY Ma, R., Levard, C., Michel, F. M., Brown, G. E., Lowry, G. V. 2013; 47 (6): 2527-2534

    Abstract

    Environmental transformations of nanoparticles (NPs) affect their properties and toxicity potential. Sulfidation is an important transformation process affecting the fate of NPs containing metal cations with an affinity for sulfide. Here, the extent and mechanism of sulfidation of ZnO NPs were investigated, and the properties of resulting products were carefully characterized. Synchrotron X-ray absorption spectroscopy and X-ray diffraction analysis reveal that transformation of ZnO to ZnS occurs readily at ambient temperature in the presence of inorganic sulfide. The extent of sulfidation depends on sulfide concentration, and close to 100% conversion can be obtained in 5 days given sufficient addition of sulfide. X-ray diffraction and transmission electron microscopy showed formation of primarily ZnS NPs smaller than 5 nm, indicating that sulfidation of ZnO NPs occurs by a dissolution and reprecipitation mechanism. The solubility of partially sulfidized ZnO NPs is controlled by the remaining ZnO core and not quenched by a ZnS shell formed as was observed for partially sulfidized Ag NPs. Sulfidation also led to NP aggregation and a decrease of surface charge. These changes suggest that sulfidation of ZnO NPs alters the behavior, fate, and toxicity of ZnO NPs in the environment. The reactivity and fate of the resulting <5 nm ZnS particles remains to be determined.

    View details for DOI 10.1021/es3035347

    View details for Web of Science ID 000316594000013

    View details for PubMedID 23425191

  • Highly Compressed Two-Dimensional Form of Water at Ambient Conditions SCIENTIFIC REPORTS Kaya, S., Schlesinger, D., Yamamoto, S., Newberg, J. T., Bluhm, H., Ogasawara, H., Kendelewicz, T., Brown, G. E., Pettersson, L. G., Nilsson, A. 2013; 3

    Abstract

    The structure of thin-film water on a BaF(2)(111) surface under ambient conditions was studied using x-ray absorption spectroscopy from ambient to supercooled temperatures at relative humidity up to 95%. No hexagonal ice-like structure was observed in spite of the expected templating effect of the lattice-matched (111) surface. The oxygen K-edge x-ray absorption spectrum of liquid thin-film water on BaF(2) exhibits, at all temperatures, a strong resemblance to that of high-density phases for which the observed spectroscopic features correlate linearly with the density. Surprisingly, the highly compressed, high-density thin-film liquid water is found to be stable from ambient (300 K) to supercooled (259 K) temperatures, although a lower-density liquid would be expected at supercooled conditions. Molecular dynamics simulations indicate that the first layer water on BaF(2)(111) is indeed in a unique local structure that resembles high-density water, with a strongly collapsed second coordination shell.

    View details for DOI 10.1038/srep01074

    View details for Web of Science ID 000313551300002

    View details for PubMedID 23323216

  • Photoemission and DFT study of the reaction of water vapor with the Fe3O4 (100) surface at near-ambient conditions Journal of Physical Chemistry C Kendelewicz, T., Kaya, S., Newberg, J. E., Bluhm, H., Mulakluri, N., Mortitz, W., Scheffler, M., Nilsson, A., Pentcheva, R., Brown, Jr., G. E. 2013; 117: 2719-2733
  • A sequential chemical extraction and spectroscopic assessment of the potential bioavailability of mercury released from the inoperative New Idria Mercury Mine, San Benito, Co., CA Geochimica et Cosmochimica Acta Jew, A. D., Luong, P. M., Rytuba, J. J., Brown, Jr., G. E. 2013
  • Structure and reactivity of As(III)- and As(V)-rich schwertmannites and ferric arsenate sulfate from the Carnoules acid mine drainage, France: Comparison with biotic and abiotic model compounds and implications for As remediation Geochimica et Cosmochimica Acta Maillot, F., Morin, G., Juillot, F., Buneel, O., Casiot, C., Ona-Nguema, G., Wang, Y., Lebrun, S., Aubrey, E., Vlaic, G., Brown, Jr., G. E. 2013; 104: 310-329
  • Opportunities with Synchrotron Radiation at the Mesoscale Synchrotron Radiation News Bargar, J. R., Brown, Jr., G. E., Crabtree, G. W. 2013; 26 (4)
  • Effect of chloride on the dissolution rate and toxicity of silver nanoparticles to E. coli Environmental Science & Technology Levard, C., Mitra, S., Yang, T., Jew, A. D., Badireddy, A. R., Lowry, G. V., Brown, Jr., G. E. 2013; 47 (1): 5738-5745

    View details for DOI 10.102/es400396f

  • Ni speciation in a New Caledonian lateritic regolith: A quantitative X-ray absorption spectroscopy investigation GEOCHIMICA ET COSMOCHIMICA ACTA Dublet, G., Juillot, F., Morin, G., Fritsch, E., Fandeur, D., Ona-Nguema, G., Brown, G. E. 2012; 95: 119-133
  • Properties of impurity-bearing ferrihydrite I. Effects of Al content and precipitation rate on the structure of 2-line ferrihydrite GEOCHIMICA ET COSMOCHIMICA ACTA Cismasu, A. C., Michel, F. M., Stebbins, J. F., Levard, C., Brown, G. E. 2012; 92: 275-291
  • Environmental Transformations of Silver Nanoparticles: Impact on Stability and Toxicity ENVIRONMENTAL SCIENCE & TECHNOLOGY Levard, C., Hotze, E. M., Lowry, G. V., Brown, G. E. 2012; 46 (13): 6900-6914

    Abstract

    Silver nanoparticles (Ag-NPs) readily transform in the environment, which modifies their properties and alters their transport, fate, and toxicity. It is essential to consider such transformations when assessing the potential environmental impact of Ag-NPs. This review discusses the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity. Thermodynamic arguments are used to predict what forms of oxidized silver will predominate in various environmental scenarios. Silver binds strongly to sulfur (both organic and inorganic) in natural systems (fresh and sea waters) as well as in wastewater treatment plants, where most Ag-NPs are expected to be concentrated and then released. Sulfidation of Ag-NPs results in a significant decrease in their toxicity due to the lower solubility of silver sulfide, potentially limiting their short-term environmental impact. This review also discusses some of the major unanswered questions about Ag-NPs, which, when answered, will improve predictions about their potential environmental impacts. Research needed to address these questions includes fundamental molecular-level studies of Ag-NPs and their transformation products, particularly Ag(2)S-NPs, in simplified model systems containing common (in)organic ligands, as well as under more realistic environmental conditions using microcosm/mesocosm-type experiments. Toxicology studies of Ag-NP transformation products, including different states of aggregation and sulfidation, are also required. In addition, there is the need to characterize the surface structures, compositions, and morphologies of Ag-NPs and Ag(2)S-NPs to the extent possible because they control properties such as solubility and reactivity.

    View details for DOI 10.1021/es2037405

    View details for Web of Science ID 000305876500003

    View details for PubMedID 22339502

  • An Early-Branching Microbialite Cyanobacterium Forms Intracellular Carbonates SCIENCE Couradeau, E., Benzerara, K., Gerard, E., Moreira, D., Bernard, S., Brown, G. E., Lopez-Garcia, P. 2012; 336 (6080): 459-462

    Abstract

    Cyanobacteria have affected major geochemical cycles (carbon, nitrogen, and oxygen) on Earth for billions of years. In particular, they have played a major role in the formation of calcium carbonates (i.e., calcification), which has been considered to be an extracellular process. We identified a cyanobacterium in modern microbialites in Lake Alchichica (Mexico) that forms intracellular amorphous calcium-magnesium-strontium-barium carbonate inclusions about 270 nanometers in average diameter, revealing an unexplored pathway for calcification. Phylogenetic analyses place this cyanobacterium within the deeply divergent order Gloeobacterales. The chemical composition and structure of the intracellular precipitates suggest some level of cellular control on the biomineralization process. This discovery expands the diversity of organisms capable of forming amorphous calcium carbonates.

    View details for DOI 10.1126/science.1216171

    View details for Web of Science ID 000303233400043

    View details for PubMedID 22539718

  • Morphological preservation of carbonaceous plant fossils in blueschist metamorphic rocks from New Zealand GEOBIOLOGY Galvez, M. E., Beyssac, O., Benzerara, K., Bernard, S., Menguy, N., Cox, S. C., Martinez, I., Johnston, M. R., Brown, G. E. 2012; 10 (2): 118-129

    Abstract

    Morphological and chemical evidence of ancient life is widespread in sedimentary rocks retrieved from shallow depths in the Earth's crust. Metamorphism is highly detrimental to the preservation of biological information in rocks, thus limiting the geological record in which traces of life might be found. Deformation and increasing pressure/temperature during deep burial may alter the morphology as well as the composition and structure of both the organic and mineral constituents of fossils. However, microspore fossils have been previously observed in intensely metamorphosed rocks. It has been suggested that their small size, and/or the nature of the polymer composing their wall, and/or the mineralogy of their surrounding matrix were key parameters explaining their exceptional preservation. Here, we describe the remarkable morphological preservation of plant macrofossils in blueschist metamorphic rocks from New Zealand containing lawsonite. Leaves and stems can be easily identified at the macroscale. At the microscale, polygonal structures with walls mineralized by micas within the leaf midribs and blades may derive from the original cellular ultrastructure or, alternatively, from the shrinkage during burial of the gelified remnants of the leaves in an abiotic process. Processes and important parameters involved in the remarkable preservation of these fossils during metamorphism are discussed. Despite the excellent morphological preservation, the initial biological polymers have been completely transformed to graphitic carbonaceous matter down to the nanometer scale. This occurrence demonstrates that plant macrofossils may experience major geodynamic processes such as metamorphism and exhumation involving deep changes and homogenization of their carbon chemistry and structure but still retain their morphology with remarkable integrity even if they are not shielded by any hard-mineralized concretion.

    View details for DOI 10.1111/j.1472-4669.2011.00316.x

    View details for Web of Science ID 000299941800002

    View details for PubMedID 22299653

  • Size-Controlled Dissolution of Organic-Coated Silver Nanoparticles ENVIRONMENTAL SCIENCE & TECHNOLOGY Ma, R., Levard, C., Marinakos, S. M., Cheng, Y., Liu, J., Michel, F. M., Brown, G. E., Lowry, G. V. 2012; 46 (2): 752-759

    Abstract

    The solubility of Ag NPs can affect their toxicity and persistence in the environment. We measured the solubility of organic-coated silver nanoparticles (Ag NPs) having particle diameters ranging from 5 to 80 nm that were synthesized using various methods, and with different organic polymer coatings including poly(vinylpyrrolidone) and gum arabic. The size and morphology of Ag NPs were characterized by transmission electron microscopy (TEM). X-ray absorption fine structure (XAFS) spectroscopy and synchrotron-based total X-ray scattering and pair distribution function (PDF) analysis were used to determine the local structure around Ag and evaluate changes in crystal lattice parameters and structure as a function of NP size. Ag NP solubility dispersed in 1 mM NaHCO(3) at pH 8 was found to be well correlated with particle size based on the distribution of measured TEM sizes as predicted by the modified Kelvin equation. Solubility of Ag NPs was not affected by the synthesis method and coating as much as by their size. Based on the modified Kelvin equation, the surface tension of Ag NPs was found to be ∼1 J/m(2), which is expected for bulk fcc (face centered cubic) silver. Analysis of XAFS, X-ray scattering, and PDFs confirm that the lattice parameter, a, of the fcc crystal structure of Ag NPs did not change with particle size for Ag NPs as small as 6 nm, indicating the absence of lattice strain. These results are consistent with the finding that Ag NP solubility can be estimated based on TEM-derived particle size using the modified Kelvin equation for particles in the size range of 5-40 nm in diameter.

    View details for DOI 10.1021/es201686j

    View details for Web of Science ID 000299136200026

    View details for PubMedID 22142034

  • Sulfidation decreases silver nanoparticle growth inhibition effect for Escherichia coli Environmental Science & Technology Reinsch, B. C., Levard, C. M., Li, Z., Ma, R., Wise, A., Gregory, K. B., Brown, Jr., G. E., Lowry, G. V. 2012; 46 (3): 6992-7000
  • Mineral-aqueous solution interfaces and their impact on the environment Geochemical Perspectives Brown, Jr., G. E., Calas, G. 2012; 1: 483-742
  • EXAFS and SEM evidence for zinc sulfide solid phases in riverine suspended matter from the Seine River, France Environmental Science & Technology Priadi, C., Morin, G., Ayrault, S., Maillot, F., Juillot, F., Alliot, I., Testemale, D., Proux, O., Bonté, P., Brown, Jr., G. E. 2012; 46: 3712-3720
  • Neutron Pair Distribution Function Study of Two-Line Ferrihydrite ENVIRONMENTAL SCIENCE & TECHNOLOGY Harrington, R., Hausner, D. B., Xu, W., Bhandari, N., Michel, F. M., Brown, G. E., Strongin, D. R., Parise, J. B. 2011; 45 (23): 9883-9890

    Abstract

    Pair distribution function (PDF) analysis of neutron total scattering data from deuterated two-line ferrihydrite is consistent with the Keggin-related structural model for ferrihydrite published by Michel et al. (2007). Other models proposed in the literature, such as that of Drits et al. (1993), lead to inferior fits. Bond valence sums indicate that O(1) is bonded to a hydrogen atom, but the quality of the data is such that the exact position of the hydrogen could not be elucidated with confidence.

    View details for DOI 10.1021/es2020633

    View details for Web of Science ID 000297382700012

    View details for PubMedID 21955257

  • Probing Ag nanoparticle surface oxidation in contact with (in)organics: an X-ray scattering and fluorescence yield approach JOURNAL OF SYNCHROTRON RADIATION Levard, C., Michel, F. M., Wang, Y., Choi, Y., Eng, P., Brown, G. E. 2011; 18: 871-878

    Abstract

    Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag-Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag-Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag(+) from oxidation/dissolution of Ag-Nps may strongly impact ecosystems. In this context, Ag-Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) and Cl(-) in solution] has been investigated. A combination of synchrotron-based X-ray standing-wave fluorescence yield- and X-ray diffraction-based experiments on a sample consisting of an approximately single-particle layer of Ag-Nps deposited on a silicon substrate and coated by a thin film of PAA containing Cl revealed the formation of a stable AgCl corrosion product despite the presence of potential surface stabilizers (PVP and PAA). Diffusion and precipitation processes at the Ag-Nps-PAA interface were characterized with a high spatial resolution using this new approach.

    View details for DOI 10.1107/S090904951103843X

    View details for Web of Science ID 000296736400006

    View details for PubMedID 21997911

  • Molecular-level modes of As binding to Fe(III) (oxyhydr)oxides precipitated by the anaerobic nitrate-reducing Fe(II)-oxidizing Acidovorax sp strain BoFeN1 GEOCHIMICA ET COSMOCHIMICA ACTA Hohmann, C., Morin, G., Ona-Nguema, G., Guigner, J., Brown, G. E., Kappler, A. 2011; 75 (17): 4699-4712
  • Distinctive Arsenic(V) Trapping Modes by Magnetite Nanoparticles Induced by Different Sorption Processes ENVIRONMENTAL SCIENCE & TECHNOLOGY Wang, Y., Morin, G., Ona-Nguema, G., Juillot, F., Calas, G., Brown, G. E. 2011; 45 (17): 7258-7266

    Abstract

    Arsenic sorption onto iron oxide spinels such as magnetite may contribute to arsenic immobilization at redox fronts in soils, sediments, and aquifers, as well as in putative remediation and water treatment technologies. We have investigated As(V) speciation resulting from different sorption processes on magnetite nanoparticles, including both adsorption and precipitation, using X-ray absorption fine structure (XAFS) spectroscopy and transmission electron microscopy (TEM). XAFS results suggest that AsO(4) tetrahedra form predominantly inner-sphere bidentate corner-sharing ((2)C) complexes and outer-sphere complexes on magnetite in the adsorption experiments. In the precipitation experiments, an increasing fraction of AsO(4) tetrahedra appears to be incorporated in clusters having a magnetite-like local structure with increasing As loading, the remaining fraction of As being adsorbed at the surface of magnetite particles. In the sample with the highest As loading (15.7 μmol/m(2)) XAFS data indicate that As(V) is fully incorporated in such clusters. Such processes help to explain the significantly higher arsenic uptake in precipitation samples compared to those generated in adsorption experiments. In addition, for the precipitation samples, TEM observations indicate the formation of amorphous coatings and small (~3 nm) nanoparticles associated with larger (~20-40 nm) magnetite nanoparticles, which are absent in the adsorption samples. These results suggest that As(V) could form complexes at the surfaces of the small nanoparticles and could be progressively incorporated in their structure with increasing As loading. These results provide some of the fundamental knowledge about As(V)-magnetite interactions that is essential for developing effective water treatment technologies for arsenic.

    View details for DOI 10.1021/es200299f

    View details for Web of Science ID 000294373400025

    View details for PubMedID 21809819

  • Study of the crystallographic architecture of corals at the nanoscale by scanning transmission X-ray microscopy and transmission electron microscopy ULTRAMICROSCOPY Benzerara, K., Menguy, N., Obst, M., Stolarski, J., Mazur, M., Tylisczak, T., Brown, G. E., Meibom, A. 2011; 111 (8): 1268-1275

    Abstract

    We have investigated the nanotexture and crystallographic orientation of aragonite in a coral skeleton using synchrotron-based scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM). Polarization-dependent STXM imaging at 40-nm spatial resolution was used to obtain an orientation map of the c-axis of aragonite on a focused ion beam milled ultrathin section of a Porites coral. This imaging showed that one of the basic units of coral skeletons, referred to as the center of calcification (COC), consists of a cluster of 100-nm aragonite globules crystallographically aligned over several micrometers with a fan-like distribution and with the properties of single crystals at the mesoscale. The remainder of the skeleton consists of aragonite single-crystal fibers in crystallographic continuity with the nanoglobules comprising the COC. Our observation provides information on the nm-scale processes that led to biomineral formation in this sample. Importantly, the present study illustrates how the methodology described here, which combines HRTEM and polarization-dependent synchrotron-based STXM imaging, offers an interesting new approach for investigating biomineralizing systems at the nm-scale.

    View details for DOI 10.1016/j.ultramic.2011.03.023

    View details for Web of Science ID 000300461100040

    View details for PubMedID 21864767

  • Sulfidation Processes of PVP-Coated Silver Nanoparticles in Aqueous Solution: Impact on Dissolution Rate ENVIRONMENTAL SCIENCE & TECHNOLOGY Levard, C., Reinsch, B. C., Michel, F. M., Oumahi, C., Lowry, G. V., Brown, G. E. 2011; 45 (12): 5260-5266

    Abstract

    Despite the increasing use of silver nanoparticles (Ag-NPs) in nanotechnology and their toxicity to invertebrates, the transformations and fate of Ag-NPs in the environment are poorly understood. This work focuses on the sulfidation processes of PVP-coated Ag-NPs, one of the most likely corrosion phenomena that may happen in the environment. The sulfur to Ag-NPs ratio was varied in order to control the extent of Ag-NPs transformation to silver sulfide (Ag?S). A combination of synchrotron-based X-ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure spectroscopy shows the increasing formation of Ag?S with an increasing sulfur to Ag-NPs ratio. TEM observations show that Ag?S forms nanobridges between the Ag-NPs leading to chain-like structures. In addition, sulfidation strongly affects surface properties of the Ag-NPs in terms of surface charge and dissolution rate. Both may affect the reactivity, transport, and toxicity of Ag-NPs in soils. In particular, the decrease of dissolution rate as a function of sulfide exposure may strongly limit Ag-NPs toxicity since released Ag? ions are known to be a major factor in the toxicity of Ag-NPs.

    View details for DOI 10.1021/es2007758

    View details for Web of Science ID 000291422200030

    View details for PubMedID 21598969

  • Density functional theory investigation of the interaction of water with alpha-Al2O3 and alpha-Fe2O3 (1(1)over-bar02) surfaces: Implications for surface reactivity PHYSICAL REVIEW B Aboud, S., Wilcox, J., Brown, G. E. 2011; 83 (12)
  • Environmental mineralogy - Understanding element behavior in ecosystems COMPTES RENDUS GEOSCIENCE Brown, G. E., Calas, G. 2011; 343 (2-3): 90-112
  • Environmental mineralogy COMPTES RENDUS GEOSCIENCE Calas, G., Brown, G. E. 2011; 343 (2-3): 83-89
  • Composition and structural aspects of naturally occurring ferrihydrite COMPTES RENDUS GEOSCIENCE Cismasu, A. C., Michel, F. M., Tcaciuc, A. P., Tyliszczak, T., Brown, G. E. 2011; 343 (2-3): 210-218
  • New Technique for Quantification of Elemental Hg in Mine Wastes and Its Implications for Mercury Evasion Into the Atmosphere ENVIRONMENTAL SCIENCE & TECHNOLOGY Jew, A. D., Kim, C. S., Rytuba, J. J., Gustin, M. S., Brown, G. E. 2011; 45 (2): 412-417

    Abstract

    Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended X-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234 K) results in its transformation to crystalline ?-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77 K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs % Hg(0), corresponding to silica-carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica-carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range.

    View details for DOI 10.1021/es1023527

    View details for Web of Science ID 000286090500014

    View details for PubMedID 21121657

  • Water reaction with MgO(100) probed by ambient pressure XPS Journal of Physical Chemistry C Newberg, J. T., Starr, D. E., Posgaard, S., Yamamoto, S., Kaya, S., Kendelewicz, T., Mysak, E., Salmeron, M. B., Nilsson, A., Brown, Jr., G. E., Bluhm, H. 2011; 115: 12864-12872
  • Evidence for contrasted isotopic signatures between anthropogenic and natural Zn in smelter-impacted soils from Northern France Geochimica et Cosmochimica Acta Juillot, F., Maréchal, C., Morin, G., Jouvin, D., Cacaly, S., Telouk, P., Benedetti, M. F., Ildefonse, P., Sutton, S., Guyot, F., Brown, Jr., G. E. 2011; 75: 2295-2308
  • Formation of hydroxyl and water layers on MgO films studied with ambient pressure XPS SURFACE SCIENCE Newberg, J. T., Starr, D. E., Yamamoto, S., Kaya, S., Kendelewicz, T., Mysak, E. R., Porsgaard, S., Salmeron, M. B., Brown, G. E., Nilsson, A., Bluhm, H. 2011; 605 (1-2): 89-94
  • Multiscale characterization of pyritized plant tissues in blueschist facies metamorphic rocks GEOCHIMICA ET COSMOCHIMICA ACTA Bernard, S., Benzerara, K., Beyssac, O., Brown, G. E. 2010; 74 (17): 5054-5068
  • XANES, Raman and XRD study of anthracene-based cokes and saccharose-based chars submitted to high-temperature pyrolysis CARBON Bernard, S., Beyssac, O., Benzerara, K., Findling, N., Tzvetkov, G., Brown, G. E. 2010; 48 (9): 2506-2516
  • XANES Evidence for Rapid Arsenic(III) Oxidation at Magnetite and Ferrihydrite Surfaces by Dissolved O-2 via Fe2+-Mediated Reactions ENVIRONMENTAL SCIENCE & TECHNOLOGY Ona-Nguema, G., Morin, G., Wang, Y., Foster, A. L., Juillot, F., Calas, G., Brown, G. E. 2010; 44 (14): 5416-5422

    Abstract

    To reduce the adverse effects of arsenic on humans, various technologies are used to remove arsenic from groundwater, most relying on As adsorption on Fe-(oxyhydr)oxides and concomitant oxidation of As(III) by dissolved O(2). This reaction can be catalyzed by microbial activity or by strongly oxidizing radical species known to form upon oxidation of Fe(II) by dissolved O(2). Such catalyzed oxidation reactions have been invoked to explain the enhanced kinetics of As(III) oxidation in aerated water, in the presence of zerovalent iron or dissolved Fe(II). In the present study, we used arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy to investigate the role of Fe(II) in the oxidation of As(III) at the surface of magnetite and ferrihydrite under oxygenated conditions. Our results show rapid oxidation of As(III) to As(V) upon sorption onto magnetite under oxic conditions at neutral pH. Moreover, under similar oxic conditions, As(III) oxidized upon sorption onto ferrihydrite only after addition of Fe(II)(aq) within the investigated time frame of 24 h. These results confirm that Fe(II) is able to catalyze As(III) oxidation in the presence of dissolved O(2) and suggest that oxidation of As(III) upon sorption on magnetite under oxic conditions can be explained by an Fe(2+)-mediated Fenton-like reactions. Thus, the present study shows that magnetite might be an efficient alternative to the current use of oxidants and Fe(II) to remove As from aerated water. In addition, this study emphasizes that special care is needed to preserve arsenic oxidation state during laboratory sorption experiments as well as in collecting As-bearing samples from natural environments.

    View details for DOI 10.1021/es1000616

    View details for Web of Science ID 000279747100020

    View details for PubMedID 20666402

  • Presentation of the Mineralogical Society of America Award for 2009 Thomas Patrick Trainor AMERICAN MINERALOGIST Brown, G. E. 2010; 95 (4): 662-663
  • Ordered ferrimagnetic form of ferrihydrite reveals links among structure, composition, and magnetism PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Michel, F. M., Barron, V., Torrent, J., Morales, M. P., Serna, C. J., Boily, J., Liu, Q., Ambrosini, A., Cismasu, A. C., Brown, G. E. 2010; 107 (7): 2787-2792

    Abstract

    The natural nanomineral ferrihydrite is an important component of many environmental and soil systems and has been implicated as the inorganic core of ferritin in biological systems. Knowledge of its basic structure, composition, and extent of structural disorder is essential for understanding its reactivity, stability, and magnetic behavior, as well as changes in these properties during aging. Here we investigate compositional, structural, and magnetic changes that occur upon aging of "2-line" ferrihydrite in the presence of adsorbed citrate at elevated temperature. Whereas aging under these conditions ultimately results in the formation of hematite, analysis of the atomic pair distribution function and complementary physicochemical and magnetic data indicate formation of an intermediate ferrihydrite phase of larger particle size with few defects, more structural relaxation and electron spin ordering, and pronounced ferrimagnetism relative to its disordered ferrihydrite precursor. Our results represent an important conceptual advance in understanding the nature of structural disorder in ferrihydrite and its relation to the magnetic structure and also serve to validate a controversial, recently proposed structural model for this phase. In addition, the pathway we identify for forming ferrimagnetic ferrihydrite potentially explains the magnetic enhancement that typically precedes formation of hematite in aerobic soil and weathering environments. Such magnetic enhancement has been attributed to the formation of poorly understood, nano-sized ferrimagnets from a ferrihydrite precursor. Whereas elevated temperatures drive the transformation on timescales feasible for laboratory studies, our results also suggest that ferrimagnetic ferrihydrite could form naturally at ambient temperature given sufficient time.

    View details for DOI 10.1073/pnas.0910170107

    View details for Web of Science ID 000274599500017

    View details for PubMedID 20133643

  • Water Adsorption on alpha-Fe2O3(0001) at near Ambient Conditions JOURNAL OF PHYSICAL CHEMISTRY C Yamamoto, S., Kendelewicz, T., Newberg, J. T., Ketteler, G., Starr, D. E., Mysak, E. R., Andersson, K. J., Ogasawara, H., Bluhm, H., Salmeron, M., Brown, G. E., Nilsson, A. 2010; 114 (5): 2256-2266

    View details for DOI 10.1021/jp909876t

    View details for Web of Science ID 000274269700040

  • Extended x-ray absorption fine structure analysis of arsenite and arsenate adsorption on green rust Environmental Science & Technology Wang, Y., Morin, G., Ona-Nguema, G., Juillot, F., Guyot, F., Calas, G., Brown, Jr., G. E. 2010; 44: 109-115
  • Evidence for Different Surface Speciation of Arsenite and Arsenate on Green Rust: An EXAFS and XANES Study ENVIRONMENTAL SCIENCE & TECHNOLOGY Wang, Y., Morin, G., Ona-Nguema, G., Juillot, F., Guyot, F., Calas, G., Brown, G. E. 2010; 44 (1): 109-115

    Abstract

    The knowledge of arsenic speciation at the surface of green rusts (GRs), [Fe(II)((1-x))Fe(III)(x) (OH)(2)](x+) (CO(3), Cl, SO(4))(x-), is environmentally relevant because arsenic sorption onto GRs could contribute to arsenic retention in anoxic environments (hydromorphic soils, marine sediments, etc.). The nature of arsenic adsorption complexes on hydroxychloride green rust 1 (GR1Cl) at near-neutral pH under anoxic conditions was investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy at the As K-edge. Sorption data indicate that As(V) sorbs more efficiently than As(III) at the studied As loadings (0.27 micromol m(-2) and 2.7 micromol m(-2)). EXAFS results indicate that arsenite [As(III)] and arsenate [As(V)] form inner-sphere complexes on the surface of GR1Cl at arsenic surface coverages of 0.27 and 2.70 micromol m(-2), with distinct types of As(III) and As(V) sorption complexes, which change in relative concentration as a function of arsenic loading. For As(V), the EXAFS-derived As-Fe distances (3.34 +/- 0.02 and 3.49 +/- 0.02 A) suggest the presence of binuclear bidentate double-corner complexes ((2)C) and monodentate mononuclear corner-sharing complexes ((1)V). For As(III), EXAFS-derived As-As distance (3.32 +/- 0.02 A) and As-Fe distances (3.49 +/- 0.02 and 4.72 +/- 0.02 A) are consistent with the presence of dimers of As(III) pyramids binding to the edges of the GR1Cl layers by corner sharing with FeO(6) octahedra. However, (2)C and (1)V As(III) complexes cannot be excluded. These results improve our knowledge of the mode of As(V) and As(III) inner-sphere adsorption on green rusts, which will help to constrain sorption modeling of arsenic in soils, sediments, and aquifers.

    View details for DOI 10.1021/es901627e

    View details for Web of Science ID 000273267000022

    View details for PubMedID 20039740

  • Role of extracellular polymeric substances in metal ion complexation on Shewanella oneidensis: Batch uptake, thermodynamic modeling, ATR-FTIR, and EXAFS study GEOCHIMICA ET COSMOCHIMICA ACTA Ha, J., Gelabert, A., Spormann, A. M., Brown, G. E. 2010; 74 (1): 1-15
  • Organic matter heterogeneities in 2.72 Ga stromatolites: Alteration versus preservation by sulfur incorporation GEOCHIMICA ET COSMOCHIMICA ACTA Lepot, K., Benzerara, K., Rividi, N., Cotte, M., Brown, G. E., Philippot, P. 2009; 73 (21): 6579-6599
  • Uranyl-chlorite sorption/desorption: Evaluation of different U(VI) sequestration processes GEOCHIMICA ET COSMOCHIMICA ACTA Singer, D. M., Maher, K., Brown, G. E. 2009; 73 (20): 5989-6007
  • XANES Evidence for Oxidation of Cr(III)) to Cr(VI) by Mn-Oxides in a Lateritic Regolith Developed on Serpentinized Ultramafic Rocks of New Caledonia ENVIRONMENTAL SCIENCE & TECHNOLOGY Fandeur, D., Juillot, F., Morin, G., Olivi, L., Cognigni, A., Webb, S. M., Ambrosi, J., Fritsch, E., Guyot, F., Brown, G. E. 2009; 43 (19): 7384-7390

    Abstract

    Although several laboratory studies showed that Mn-oxides are capable of oxidizing Cr(II) to Cr(VI), very few have reported evidence for such a reaction in natural systems. This study presents new evidence for this redox reaction between Cr(III) and Mn-oxides in a lateritic regolith developed on ultramafic rocks in New Caledonia. The studied lateritic regolith presents several units with contrasting amounts of major (Fe, Al, Si, and Mg) and trace (Mn, Cr, Ni, Co) elements, which are related to varying mineralogical compositions. Bulk XANES analyses show the occurrence of Cr(VI) (up to 20 wt % of total chromium) in the unit of the regolith which is also enriched in Mn (up to 21.7 wt % MnO), whereas almost no Cr(VI) is detected elsewhere. X-ray powder diffraction indicates that the large amounts of Mn in this unit of the regolith are due to the occurrence of Mn-oxides (identified as a mixture of asbolane, lithiophorite and birnessite) and Mn K-edge XANES data indicate that Mn occurs mainly as Mn(IV) in this unit, although small amounts of Mn(III) could also be detected. These results strongly suggest a direct role of the Mn-oxides on the occurrence of Cr(VI) through a redox reaction between Cr(III) and Mn(IV) and/or Mn(III). Owing to the much larger toxicity and solubility of Cr(VI), such a co-occurrence of Cr and Mn-oxides in these soils could then represent an important risk for the environment. However, the significant amounts of Cr(VI) released after reacting the samples from the studied sequence with a 0.1 M (NH)4H2PO4 solution, designed to remove tightly sorbed chromate species, suggest that Cr(VI) mainly occurs as sorption complexes. This hypothesis is reinforced by spatially resolved XANES analyses, which show that Cr(VI) is associated with both Mn- and Fe-oxides, and especially at the boundary between these two mineral species. Such a distribution of Cr(VI) suggests a possible readsorption of Cr(VI) onto surrounding Fe-oxyhydroxides (mainly goethite) after oxidation by the Mn(IV)-oxides. These results, added to leaching tests with a 0.01 M CaCl2 solution indicative of low exchangeability of Cr in the investigated samples, suggest that secondary sorption reactions onto Fe-oxides might significantly decrease the environmental impact of the oxidation of Cr(III) to Cr(VI) by Mn-oxides.

    View details for DOI 10.1021/es900498r

    View details for Web of Science ID 000270136500038

    View details for PubMedID 19848150

  • Cation field strength effects on high pressure aluminosilicate glass structure: Multinuclear NMR and La XAFS results GEOCHIMICA ET COSMOCHIMICA ACTA Kelsey, K. E., Stebbins, J. F., Singer, D. M., Brown, G. E., Mosenfelder, J. L., Asimow, P. D. 2009; 73 (13): 3914-3933
  • Ultrastructural and chemical study of modern and fossil sporoderms by Scanning Transmission X-ray Microscopy (STXM) REVIEW OF PALAEOBOTANY AND PALYNOLOGY Bernard, S., Benzerara, K., Beyssac, O., Brown, G. E., Stamm, L. G., Duringer, P. 2009; 156 (1-2): 248-261
  • Biogenic nanoparticulate UO2: Synthesis, characterization, and factors affecting surface reactivity GEOCHIMICA ET COSMOCHIMICA ACTA Singer, D. M., Farges, F., Brown, G. E. 2009; 73 (12): 3593-3611
  • Iron biomineralization by neutrophilic nitrate-reducing iron-oxidizing bacteria GEOCHIMICA ET COSMOCHIMICA ACTA Miot, J., Benzerara, K., Morin, G., Kappler, A., Obst, M., Brown, G. E., Guyot, F. 2009; 73 (13): A884-A884
  • Interaction of Zn(II) with Hematite Nanoparticles and Microparticles: Part 2. ATR-FTIR and EXAFS Study of the Aqueous Zn(II)/Oxalate/Hematite Ternary System LANGMUIR Ha, J., Trainor, T. P., Farges, F., Brown, G. E. 2009; 25 (10): 5586-5593

    Abstract

    Sorption of Zn(II) to hematite nanoparticles (HN) (av diam=10.5 nm) and microparticles (HM) (av diam=550 nm) was studied in the presence of oxalate anions (Ox2-(aq)) in aqueous solutions as a function of total Zn(II)(aq) to total Ox2-(aq) concentration ratio (R=[Zn(II)(aq)]tot/[Ox2-(aq)]tot) at pH 5.5. Zn(II) uptake is similar in extent for both the Zn(II)/Ox/HN and Zn(II)/Ox/HM ternary systems and the Zn(II)/HN binary system at [Zn(II)(aq)](tot)<4 mM, whereas it is 50-100% higher for the Zn(II)/Ox/HN system than for the Zn(II)/Ox/HM ternary and the Zn(II)/HN and Zn(II)/HM binary systems at [Zn(II)(aq)]tot>4 mM. In contrast, Zn(II) uptake for the Zn(II)/HM binary system is a factor of 2 greater than that for the Zn(II)/Ox/HM and Zn(II)/Ox/HN ternary systems and the Zn(II)/HN binary system at [Zn(II)(aq)]tot<4 mM. In the Zn(II)/Ox/HM ternary system at both R values examined (0.16 and 0.68), attenuated total reflectance Fourier transform infrared (ATR-FTIR) results are consistent with the presence of inner-sphere oxalate complexes and outer-sphere ZnOx(aq) complexes, and/or type A ternary complexes. In addition, extended X-ray absorption fine structure (EXAFS) spectroscopic results suggest that type A ternary surface complexes (i.e., >O2-Zn-Ox) are present. In the Zn(II)/Ox/HN ternary system at R=0.15, ATR-FTIR results indicate the presence of inner-sphere oxalate and outer-sphere ZnOx(aq) complexes; the EXAFS results provide no evidence for inner-sphere Zn(II) complexes or type A ternary complexes. In contrast, ATR-FTIR results for the Zn/Ox/HN sample with R = 0.68 are consistent with a ZnOx(s)-like surface precipitate and possibly type B ternary surface complexes (i.e., >O2-Ox-Zn). EXAFS results are also consistent with the presence of ZnOx(s)-like precipitates. We ascribe the observed increase of Zn(II)(aq) uptake in the Zn(II)/Ox/HN ternary system at [Zn(II)(aq)]tot>or=4 mM relative to the Zn(II)/Ox/HM ternary system to formation of a ZnOx(s)-like precipitate at the hematite nanoparticle/water interface.

    View details for DOI 10.1021/la802895a

    View details for Web of Science ID 000266081000026

    View details for PubMedID 19326938

  • Interaction of Aqueous Zn(II) with Hematite Nanoparticles and Microparticles. Part 1. EXAFS Study of Zn(II) Adsorption and Precipitation LANGMUIR Ha, J., Trainor, T. P., Farges, F., Brown, G. E. 2009; 25 (10): 5574-5585

    Abstract

    Sorption of Zn(II)(aq) on hematite (alpha-Fe2O3) nanoparticles (average diameter 10.5 nm) and microparticles (average diameter 550 nm) has been examined over a range of total Zn(II)(aq) concentrations (0.4-7.6 mM) using Zn K-edge EXAFS spectroscopy and selective chemical extractions. When ZnCl2 aqueous solutions were reacted with hematite nanoparticles (HN) at pH 5.5, Zn(II) formed a mixture of four- and six-coordinated surface complexes [Zn(O,OH)4 and Zn(O,OH)6] with an average Zn-O distance of 2.04+/-0.02 A at low sorption densities (Gammaor=3.38 micromol/m2), we observed the formation of Zn(O,OH)6 surface complexes, with an average Zn-O distance of 2.09+/-0.02 A, a Zn-Zn distance of 3.16+/-0.02 A, and a linear multiple-scattering feature at 6.12+/-0.06 A. Formation of a Zn(OH)2(am) precipitate for the higher sorption density samples (Gamma>or=3.38 micromol/m2) is suggested on the basis of comparison of the EXAFS spectra of the sorption samples with that of synthetic Zn(OH)2am. In contrast, EXAFS spectra of Zn(II) sorbed on hematite microparticles (HM) under similar experimental conditions showed no evidence of surface precipitates even at the same total [Zn(II)(aq)] that resulted in precipitate formation in the nanoparticle system. Instead, Zn(O,OH)6 octahedra (d(Zn-O)=2.10+/-0.02 A) were found to sorb dominantly in an inner-sphere, bidentate, edge-sharing fashion on Fe3+(O,OH)6 octahedra at hematite microparticle surfaces, based on an EXAFS-derived Zn-Fe3+ distance of 3.44+/-0.02 A. CaCl2 selective extraction experiments showed that 10-15% of the sorbed Zn(II) was released from Zn/HN sorption samples, and about 40% was released from a Zn/HM sorption sample. These fractions of Zn(II) are interpreted as weakly bound, outer-sphere adsorption complexes. The combined EXAFS and selective chemical extraction results indicate that (1) both Zn(O,OH)4 and Zn(O,OH)6 adsorption complexes are present in the Zn/HN system, whereas dominantly Zn(O,OH)6 adsorption complexes are present in the Zn/HM system; (2) a higher proportion of outer-sphere Zn(II) surface complexes is present in the Zn/HM system; and (3) Zn-containing precipitates similar to Zn(OH)2(am) form in the nanoparticle system but not in the microparticle system, suggesting a difference in reactivity of the hematite nanoparticles vs microparticles with respect to Zn(II)(aq).

    View details for DOI 10.1021/la8028947

    View details for Web of Science ID 000266081000025

    View details for PubMedID 19371051

  • Speciation of Arsenic in Euglena gracilis Cells Exposed to As(V) ENVIRONMENTAL SCIENCE & TECHNOLOGY Miot, J., Morin, G., Skouri-Panet, F., Ferard, C., Poitevin, A., Aubry, E., Ona-Nguema, G., Juillot, F., Guyot, F., Brown, G. E. 2009; 43 (9): 3315-3321

    Abstract

    Euglena gracilis is a photosynthetic eukaryote ubiquitous in arsenic-polluted acid mine drainages and is locally exposed to As(III) and As(V) concentrations up to 250 and 100 mg L(-1), respectively. Here, arsenic speciation in E. graciliswas determined by X-ray absorption spectroscopy and selected (bio)chemical methods on cells grown at nonlimiting phosphate concentrations. Our results suggest the following detoxification scheme: (1) uptake of As(V) from solution in competition with phosphate, (2) intracellular reduction to As(III), (3) complexation by cytoplasmic proteic thiol ligands of low molecular weight, and (4) As(III) export from the cell. However, at As(V) concentrations >100 mg L(-1), growth rate is markedly lowered and As(V) remains mostly unreduced during the extended lag period. Intracellular As(V) is found to be exclusively concentrated in the membrane + nucleus fraction, suggesting that arsenate could substitute for phosphate groups in membranes or in phosphate-containing macromolecules. Thus, arsenic species are partitioned, with As(III)-thiol compounds concentrated in the cytoplasmic proteic pool and As(V)-compounds associated with the membrane + nucleus fraction. The increasing growth delay observed with increasing initial As(V) concentration in the culture medium is proposed to result from the combination of a higher As(V) uptake and limiting intracellular As(V) reduction rate and As(III) export rate. Under high As(V) exposure conditions (200 mg L(-1)) the reduction step is found to be the most limiting step for detoxification.

    View details for DOI 10.1021/es802833s

    View details for Web of Science ID 000265781100056

    View details for PubMedID 19534152

  • Arsenite sequestration at the surface of nano-Fe(OH)(2), ferrous-carbonate hydroxide, and green-rust after bioreduction of arsenic-sorbed lepidocrocite by Shewanella putrefaciens GEOCHIMICA ET COSMOCHIMICA ACTA Ona-Nguema, G., Morin, G., Wang, Y., Menguy, N., Juillot, F., Olivi, L., Aquilanti, G., Abdelmoula, M., Ruby, C., Bargar, J. R., Guyot, F., Calas, G., Brown, G. E. 2009; 73 (5): 1359-1381
  • Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria GEOCHIMICA ET COSMOCHIMICA ACTA Miot, J., Benzerara, K., Morin, G., Kappler, A., Bernard, S., Obst, M., Ferard, C., Skouri-Panet, F., Guigner, J., Posth, N., Galvez, M., Brown, G. E., Guyot, F. 2009; 73 (3): 696-711
  • Uranium Speciation As a Function of Depth in Contaminated Hanford Sediments - A Micro-XRF, Micro-XRD, and Micro- And Bulk-XAFS Study ENVIRONMENTAL SCIENCE & TECHNOLOGY Singer, D. M., Zachara, J. M., Brown, G. E. 2009; 43 (3): 630-636

    Abstract

    The distribution and speciation of U and Cu in contaminated vadose zone and aquifer sediments from the U.S. DOE Hanford site (300 Area) were determined using a combination of synchrotron-based micro-X-ray fluorescence (microXRF) imaging, micro-X-ray absorption near edge structure (microXANES) spectroscopy, and micro-X-ray diffraction (microXRD) techniques combined with bulk U LIII-edge X-ray absorption fine structure (XAFS) spectroscopy. Samples were collected from within the inactive North Process Pond (NPP2) at 8 ft (2.4 m, NPP2-8) depth and 12 ft (3.7 m, NPP2-12) depth in the vadose zone, and fines were isolated from turbid groundwater just below the water Table (12-14 ft, approximately 4 m, NPP2-GW). microXRF imaging, microXRD, and microXANES spectroscopy revealed two major U occurrences within the vadose and groundwater zones: (1) low to moderate concentrations of U(VI) associated with fine-textured grain coatings that were consistently found to contain clinochlore (referred to here as chlorite) observed in all three samples, and (2) U(VI)-Cu(II) hotspots consisting of micrometer-sized particles associated with surface coatings on grains of muscovite and chlorite observed in samples NPP2-8' and NPP2-GW. In the aquifer fines (NPP2-GW), these particles were identified as cuprosklodowskite (cps: Cu[(UO2)(SiO2OH)]2 x 6H2O) and metatorbernite (mtb: Cu(UO2)2(PO4)2 x 8H2O). In contrast, the U-Cu-containing particles in the vadose zone were X-ray amorphous. Analyses of U LIII-edge XAFS spectra by linear-combination fitting indicated that U speciation consisted of (1) approximately 75% uranyl sorbed to chlorite and approximately 25% mtb-like X-ray amorphous U-Cu-phosphates (8 ft depth), (2) nearly 100% sorbed uranyl (12 ft depth), and (3) approximately 70% uranyl sorbed to chlorite and approximately 30% cps/mtb (groundwater zone). These findings suggest that dissolution of U(VI)-Cu(II)-bearing solids as well as desorption of U(VI), mainly from phyllosilicates, are important persistent sources of U(VI) to the associated uranium groundwater plume in Hanford Area 300.

    View details for DOI 10.1021/es8021045

    View details for Web of Science ID 000262926400020

    View details for PubMedID 19244994

  • EXAFS and HRTEM evidence for surface precipitation of arsenic(III) on nanocrystalline magnetite: Implications for As sequestration Langmuir Morin, G., Wang, Y., Ona-Nguema, G., Juillot, F., Calas, G., Menguy, N., Aubry, E., Bargar, J. R., Brown, Jr., G. E. 2009; 25: 9119-9128
  • A pre-edge analysis of Mn K-edge XANES spectra to help determine the speciation of manganese in minerals and glasses CONTRIBUTIONS TO MINERALOGY AND PETROLOGY Chalmin, E., Farges, F., Brown, G. E. 2009; 157 (1): 111-126
  • Study of iodide adsorption on organobentonite using x-ray absorption spectroscopy Journal of the Mineral Society of Korea Yoon, J., Ha, J., Hwang, J., Hwang, B-H., Brown, Jr., G. E. 2009; 22: 23-34
  • Sequestration of Sr(II) by calcium oxalate - A batch uptake study and EXAFS analysis of model compounds and reaction products GEOCHIMICA ET COSMOCHIMICA ACTA Singer, D. M., Johnson, S. B., Catalano, J. G., Farges, F., Brown, G. E. 2008; 72 (20): 5055-5069
  • XAS study of arsenic coordination in Euglena gracilis exposed to arsenite ENVIRONMENTAL SCIENCE & TECHNOLOGY Miot, J., Morin, G., Skouri-Panet, F., Ferard, C., Aubry, E., Briand, J., Wang, Y., Ona-Nguema, G., Guyot, F., Brown, G. E. 2008; 42 (14): 5342-5347

    Abstract

    Among the few eukaryotes adapted to the extreme conditions prevailing in acid mine drainage, Euglenae are ubiquitous in these metal(loid)-impacted environments, where they can be exposed to As(III) concentrations up to a few hundreds of mg x L(-1). In order to evaluate their resistance to this toxic metalloid and to identify associated detoxification mechanisms, we investigated arsenic coordination in the model photosynthetic protozoan, Euglena gracilis, cultured at pH 3.2 and exposed to As(III) at concentrations ranging from 10 to 500 mg x L(-1). E. gracilis is shown to tolerate As(III) concentrations up to 200 mg * L(-1), without accumulating this metalloid. X-ray absorption spectroscopy at the As K-edge shows that, in the cells, arsenic mainly binds to sulfur ligands, likely in the form of arsenic-trisglutathione (As-(GS)3) or arsenic-phytochelatin (As-PC) complexes, and to a much lesser extent to carbon ligands, presumably in the form of methylated As(III)-compounds. The key role of the glutathione pathway in As(III) detoxification is confirmed by the lower growth rate of E. gracilis cultures exposed to arsenic, in the presence of buthionine sulfoximine, an inhibitor of glutathione synthesis. This study provides the first investigation at the molecular scale of intracellular arsenic speciation in E. gracilis and thus contributes to the understanding of arsenic detoxification mechanisms in a eukaryotic microorganism under extreme acid mine drainage conditions.

    View details for DOI 10.1021/es703072d

    View details for Web of Science ID 000257620000053

    View details for PubMedID 18754391

  • Acceptance of the 2007 Clair C. Patterson Award GEOCHIMICA ET COSMOCHIMICA ACTA Brown, G. E. 2008; 72 (12): S10-S11
  • Adsorption of organic matter at mineral/water interfaces: 7. ATR-FTIR and quantum chemical study of lactate interactions with hematite nanoparticles LANGMUIR Ha, J., Yoon, T. H., Wang, Y., Musgrave, C. B., Brown, G. E. 2008; 24 (13): 6683-6692

    Abstract

    The interaction of the l-lactate ion ( l-CH3CH(OH)COO(-), lact(-1)) with hematite (alpha-Fe2O3) nanoparticles (average diameter 11 nm) in the presence of bulk water at pH 5 and 25 degrees C was examined using a combination of (1) macroscopic uptake measurements, (2) in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and (3) density functional theory modeling at the B3LYP/6-31+G* level. Uptake measurements indicate that increasing [ lact(-1)]aq results in an increase in lact(-1) uptake and a concomitant increase in Fe(III) release as a result of the dissolution of the hematite nanoparticles. The ATR-FTIR spectra of aqueous lact(-1) and lact(-1) adsorbed onto hematite nanoparticles at coverages ranging from 0.52 to 5.21 micromol/m2 showed significant differences in peak positions and shapes of carboxyl group stretches. On the basis of Gaussian fits of the spectra, we conclude that lact(-1) is present as both outer-sphere and inner-sphere complexes on the hematite nanoparticles. No significant dependence of the extent of lact(-1) adsorption on background electrolyte concentration was found, suggesting that the dominant adsorption mode for lact(-1) is inner sphere under these conditions. On the basis of quantum chemical modeling, we suggest that inner-sphere complexes of lact(-1) adsorbed on hematite nanoparticles occur dominantly as monodentate, mononuclear complexes with the hydroxyl functional group pointing away from the Fe(III) center.

    View details for DOI 10.1021/la800122v

    View details for Web of Science ID 000257101100042

    View details for PubMedID 18522441

  • Acceptance of the Mineralogical Society of America Roebling Medal for 2007 AMERICAN MINERALOGIST Brown, G. E. 2008; 93 (5-6): 956-957
  • Microbially influenced formation of 2,724-million-year-old stromatolites NATURE GEOSCIENCE Lepot, K., Benzerara, K., Brown, G. E., Philippot, P. 2008; 1 (2): 118-121

    View details for DOI 10.1038/ngeo107

    View details for Web of Science ID 000256433300016

  • EXAFS analysis of arsenite and arsenate adsorption on maghemite Environmental Science & Technology Morin, G., Ona-Nguema, G., Wang, Y., Menguy, N., Juillot, F., Proux, O., Guyot, F., Calas, G., Brown, Jr., G. E. 2008; 42: 2361-2366
  • Arsenite adsorption at the magnetite-water interface during aqueous precipitation of magnetite: EXAFS evidence for a new arsenite surface compolex Geochimica et Cosmochimica Acta Wang, Y., Morin, G., Ona-Nguema, G., Menguy, N., Juillot, F., Aubry, E., Guyot, F., Calas, G., Brown, Jr., G. E. 2008; 72: 2573-2586
  • SSRL Workshop on STXM and X-ray Nanoprobe Capabilities and Needs in the Environmental, Geological, and Biomedical Sciences Synchrotron Radiation News Bargar, J. R., Brown, Jr., G. E., DeBeer-George, S., Ohldag, H. 2008; 21: 22-24
  • Nanoscale study of As transformations by bacteria in an acid mine drainage system Geochimica et Cosmochimica Acta Benzerara, K., Morin, G., TYoon, T. H., Miot, J., Tyliszczak, T., Casiot, C., Farges, F., Brown, Jr., G. E. 2008; 72: 3949-3963
  • Change in arsenic speciation through a contaminated soil profile: an XAS based study Science of the Total Environment Cancès, B., Juillot, F., Morin, G., Laperche, V., Polya, D., Vaughan, D. J., Hazemann, J-L., Proux, O., Brown, Jr., G.E., Calas, G. 2008; 397: 178-189
  • Speciation and colloid transport of arsenic from mine tailings APPLIED GEOCHEMISTRY Slowey, A. J., Johnson, S. B., Newville, M., Brown, G. E. 2007; 22 (9): 1884-1898
  • Alteration of submarine basaltic glass from the Ontong Java Plateau: A STXM and TEM study EARTH AND PLANETARY SCIENCE LETTERS Benzerara, K., Menguy, N., Banerjee, N. R., Tyliszczak, T., Brown, G. E., Guyot, F. 2007; 260 (1-2): 187-200
  • Citation for presentation of the 2006 F. W. Clarke Award to Alexis S. Templeton GEOCHIMICA ET COSMOCHIMICA ACTA Brown, G. E. 2007; 71 (15): S22-S23
  • Transformations of mercury, iron, and sulfur during the reductive dissolution of iron oxyhydroxide by sulfide GEOCHIMICA ET COSMOCHIMICA ACTA Slowey, A. J., Brown, G. E. 2007; 71 (4): 877-894
  • Surface diffraction study of the hydrated hematite (1(1)over-bar-02) surface SURFACE SCIENCE Tanwar, K. S., Lo, C. S., Eng, P. J., Catalano, J. G., Walko, D. A., Brown, G. E., Waychunas, G. A., Chaka, A. M., Trainor, T. P. 2007; 601 (2): 460-474
  • Recent advances in surface, interface, and environmental geochemistry WATER-ROCK INTERACTION, VOLS 1 AND 2, PROCEEDINGS Brown, G. E., Kendelewicz, T., Trainor, T. P., Tanwar, K. S., Chaka, A. M., Eng, P. J., Yamamoto, S., Nilsson, A., Bluhm, H., Starr, D. E., Salmeron, M., Catalano, J. G., Yoon, T. H., Benzerara, K., Morin, G., Ona-Nguema, G., Juillot, F., Cances, B., Farges, F., CALAS, G. 2007: 3-11
  • EXAFS signatures of structural Zn at trace levels in layered minerals X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Juillot, F., Morin, G., Hazemann, J., Proux, O., Belin, S., Briois, V., Brown, G. E., Calas, G. 2007; 882: 247-249
  • Durability of silicate glasses: An historical approach X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Farges, F., Etcheverry, M., Haddi, A., Trocellie, P., Curti, E., Brown, G. E. 2007; 882: 44-50
  • On the coordination of actinides and fission products in silicate glasses X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Haddi, A., Farges, F., Trocellier, P., Curti, E., Harfouche, M., Brown, G. E. 2007; 882: 256-258
  • Adsorption mechanisms of trivalent gold onto iron Oxy-Hydroxides: From the molecular scale to the model X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Cances, B., Benedetti, M., Farges, F., Brown, G. E. 2007; 882: 217-219
  • Discovery of unusual minerals in paleolithic black pigments from lascaux (France) and Ekain (Spain) X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Chalmin, E., Farges, F., Vignaud, C., Susini, J., Menu, M., Brown, G. E. 2007; 882: 220-222
  • Selenium speciation in biofilms from granular sludge bed reactors used for wastewater treatment X-RAY ABSORPTION FINE STRUCTURE-XAFS13 van Hullenbusch, E., Farges, F., Lenz, M., Lens, P., Brown, G. E. 2007; 882: 229-231
  • Chrysocolla redefined as spertiniite X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Farges, F., Benzerara, K., Brown, G. E. 2007; 882: 223-225
  • Study of interactions between microbes and minerals by scanning transmission X-ray microscopy (STXM) X-RAY ABSORPTION FINE STRUCTURE-XAFS13 Benzerara, K., Tyliszczak, T., Brown, G. E. 2007; 882: 726-730
  • Biogenic UO2 characterization and surface reactivity Am. Inst. Phys. Conf. Proc., 13th Int. XAFS Conf. 882 Singer, D. M., Farges, F., Brown, Jr., G. E. 2007: 277-279
  • Exceptional preservation of fossil plants spores in high-pressure metamorphic rocks Earth and Planetary Science Letters Bernard, S., Benzerara, K., Beyssac, O., Menguy, N., Guyot, F., Brown, Jr., G. E., Goffe, B. 2007; 262: 257-272
  • Coordination environments of higly charged cations (Ti, Cr, and Light REEís) in borosilicate glass/melts to 1120°C Am. Inst. Phys. Conf. Proc., 13th Int. XAFS Conf. 882 Farges, F., Brown, Jr., G. E. 2007: 208-210
  • Search for microbial signatures within human and microbial calcifications using soft X-ray spectromicroscopy JOURNAL OF INVESTIGATIVE MEDICINE Benzerara, K., Miller, V. M., Barell, G., Kumar, V., Miot, J., Brown, G. E., Lieske, J. C. 2006; 54 (7): 367-379

    Abstract

    The origin of advanced arterial and renal calcification remains poorly understood. Self-replicating, calcifying entities have been detected and isolated from calcified human tissues, including blood vessels and kidney stones, and are referred to as nanobacteria. However, the microbiologic nature of putative nanobacteria continues to be debated, in part because of the difficulty in discriminating biomineralized microbes from minerals nucleated on anything else (eg, macromolecules, cell membranes). To address this controversy, the use of techniques capable of characterizing the organic and mineral content of these self-replicated structures at the submicrometer scale would be beneficial.Calcifying gram-negative bacteria (Caulobacter crescentus, Ramlibacter tataouinensis) used as references and self-replicating calcified nanoparticles cultured from human samples of calcified aneurysms were examined using a scanning transmission x-ray microscope (STXM) at the Advanced Light Source at Lawrence Berkeley National Laboratory. This microscope uses a monochromated and focused synchrotron x-ray beam (80-2,200 eV) to yield microscopic and spectroscopic information on both organic compounds and minerals at the 25 nm scale.High-spatial and energy resolution near-edge x-ray absorption fine structure (NEXAFS) spectra indicative of elemental speciation acquired at the C K-edge, N K-edge, and Ca L(2,3)-edge on a single-cell scale from calcified C. crescentus and R. tataouinensis displayed unique spectral signatures different from that of nonbiologic hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2)). Further, preliminary NEXAFS measurements of calcium, carbon, and nitrogen functional groups of cultured calcified nanoparticles from humans revealed evidence of organics, likely peptides or proteins, specifically associated with hydroxyapatite minerals.Using NEXAFS at the 25 nm spatial scale, it is possible to define a biochemical signature for cultured calcified bacteria, including proteins, polysaccharides, nucleic acids, and hydroxyapatite. These preliminary studies suggest that nanoparticles isolated from human samples share spectroscopic characteristics with calcified proteins.

    View details for DOI 10.2310/6650.2006.06016

    View details for Web of Science ID 000243556000015

    View details for PubMedID 17169258

  • Nanometer-scale chemical heterogeneities of black carbon materials and their impacts on PCB sorption properties: Soft X-ray spectromicroscopy study ENVIRONMENTAL SCIENCE & TECHNOLOGY Yoon, T. H., Benzerara, K., Ahn, S., Luthy, R. G., Tyliszczak, T., Brown, G. E. 2006; 40 (19): 5923-5929

    Abstract

    Synchrotron-based soft X-ray spectromicroscopy was used to probe nanometer-scale chemical heterogeneities of black carbon (BC) materials, including anthracite coal, coke, and activated carbon (AC), and to study their impact on the partitioning of one type of polychlorinated biphenyls (PCB-166: 2,3,4,4',5,6 hexachloro biphenyl) onto AC particles. Various carbon species (e.g., aromatic, ketonic/ phenolic, and carboxylic functional groups) were found in all of the BC materials examined, and impurities (e.g., carbonate and potassium ions in anthracite coal) were identified in nanometer-scale regions of these samples. We show that these chemical heterogeneities in AC particles influence their sorption of hydrophobic organic compounds (HOCs). PCB-166 was found to accumulate preferentially on AC particles with the highest content of aromatic functionalities. These new findings from X-ray spectromicroscopy have the following implications for the role of BC materials in the environment: (1) the functional groups of BC materials vary on a 25-nanometer scale, and so does the abundance of the HOCs; (2) molecular-level characterization of HOC sorption preferences on AC will lead to an improved understanding of AC sorption properties for the remediation of HOCs in soils and sediments.

    View details for DOI 10.1021/es060173+

    View details for Web of Science ID 000240826000022

    View details for PubMedID 17051780

  • EXAFS signature of structural Zn at trace levels in natural and synthetic trioctahedral 2 : 1 phyllosilicates AMERICAN MINERALOGIST Juillot, F., Morin, G., Ildefonse, P., Calas, G., Brown, G. E. 2006; 91 (8-9): 1432-1441
  • Nanoscale detection of organic signatures in carbonate microbialites PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Benzerara, K., Menguy, N., Lopez-Garcia, P., Yoon, T., Kazmierczak, J., Tyliszczak, T., Guyot, F., Brown, G. E. 2006; 103 (25): 9440-9445

    Abstract

    Microbialites are sedimentary deposits associated with microbial mat communities and are thought to be evidence of some of the oldest life on Earth. Despite extensive studies of such deposits, little is known about the role of microorganisms in their formation. In addition, unambiguous criteria proving their biogenicity have yet to be established. In this study, we characterize modern calcareous microbialites from the alkaline Lake Van, Turkey, at the nanometer scale by combining x-ray and electron microscopies. We describe a simple way to locate microorganisms entombed in calcium carbonate precipitates by probing aromatic carbon functional groups and peptide bonds. Near-edge x-ray absorption fine structure spectra at the C and N K-edges provide unique signatures for microbes. Aragonite crystals, which range in size from 30 to 100 nm, comprise the largest part of the microbialites. These crystals are surrounded by a 10-nm-thick amorphous calcium carbonate layer containing organic molecules and are embedded in an organic matrix, likely consisting of polysaccharides, which helps explain the unusual sizes and shapes of these crystals. These results provide biosignatures for these deposits and suggest that microbial organisms significantly impacted the mineralogy of Lake Van carbonates.

    View details for Web of Science ID 000238660400013

    View details for PubMedID 16772379

  • Redox and speciation of tin in hydrous silicate glasses: A comparison with Nb, Ta, Mo and W CANADIAN MINERALOGIST Farges, F., Linnen, R. L., Brown, G. E. 2006; 44: 795-810
  • Structural environments around molybdenum in silicate glasses and melts. I. Influence of composition and oxygen fugacity on the local structure of molybdenum CANADIAN MINERALOGIST Farges, F., Siewert, R., Brown, G. E., Guesdon, A., Morin, G. 2006; 44: 731-753
  • Changes in uranium speciation through a depth sequence of contaminated Hanford sediments ENVIRONMENTAL SCIENCE & TECHNOLOGY Catalano, J. G., McKinley, J. P., Zachara, J. M., Heald, S. M., Smith, S. C., Brown, G. E. 2006; 40 (8): 2517-2524

    Abstract

    The disposal of basic sodium aluminate and acidic U(VI)-Cu(ll) wastes in the now-dry North and South 300 A Process Ponds atthe Hanford site resulted in a groundwater plume of U(VI). To gain insight into the geochemical processes that occurred during waste disposal and those affecting the current and future fate and transport of this uranium plume, the solid-phase speciation of uranium in a depth sequence of sediments from the base of the North Process Pond through the vadose zone to groundwater was investigated using standard chemical and mineralogical analyses, electron and X-ray microprobe measurements, and X-ray absorption fine structure spectroscopy. Near-surface sediments contained uranium coprecipitated with calcite, which formed due to overneutralization of the waste ponds with base (NaOH). At intermediate depths in the vadose zone, metatorbernite [Cu(UO2PO4)2 x 8H2O] precipitated, likely during pond operations. Uranium occurred predominantly sorbed onto phyllosilicates in the deeper vadose zone and groundwater; sorbed uranium was also an important component at intermediate depths. Since the calcite-bearing pond sediments have been removed in remediation efforts, uranium fate and transport will be controlled primarily by desorption of the sorbed uranium and dissolution of metatorbernite.

    View details for Web of Science ID 000236992700009

    View details for PubMedID 16683586

  • Scientific advances made possible by user facilities ELEMENTS Brown, G. E., Calas, G., Hemley, R. J. 2006; 2 (1): 23-30
  • New opportunities at emerging facilities ELEMENTS Parise, J. B., Brown, G. E. 2006; 2 (1): 37-42
  • User facilities around the world ELEMENTS Brown, G. E., Sutton, S. R., Calas, G. 2006; 2 (1): 9-14
  • Soft X-ray microscopy and spectroscopy at the molecular environmental science beamline at the Advanced Light Source JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Bluhm, H., Andersson, K., Araki, T., Benzerara, K., Brown, G. E., Dynes, J. J., Ghosal, S., Gilles, M. K., Hansen, H. C., Hemminger, J. C., Hitchcock, A. P., Ketteler, G., Kilcoyne, A. L., Kneedler, E., Lawrence, J. R., Leppard, G. G., Majzlan, J., Mun, B. S., Myneni, S. C., Nilsson, A., Ogasawara, H., Ogletree, D. F., Pecher, K., Salmeron, M., Shuh, D. K., Tonner, B., Tyliszczak, T., Warwick, T., Yoon, T. H. 2006; 150 (2-3): 86-104
  • The Stanford Environmental Molecular Science Institute: A Focus on Chemical and Microbial Processes at Environmental Interfaces The Geochemical News Brown, Jr., G. E., Nilsson, A., Spormann, A. M., Addiego, W. P., Benzerara, K., Bergmann, U., Bluhm, H., Brown, B. A., Calas, G., Chaka, A. M., Constantz, B. R., Farges, F., Fendorf, S. E., Foster, A. L., Juillot, F., Morin, G., Myneni, S. C. B., Pettersson, L. G. M., Rosso, K. M., Rytuba, J. J., Salmeron, M., Saltzman, J., Toney, M., Trainor, T. P., Yoon, T-H. 2006; 128: 7-30
  • XAS evidence of As(V) association with iron oxyhydroxides in a contaminated soil at a former arsenical pesticide processing plant ENVIRONMENTAL SCIENCE & TECHNOLOGY Cances, B., Juillot, F., Morin, G., Laperche, V., ALVAREZ, L., Proux, O., Hazemann, J. L., Brown, G. E., CALAS, G. 2005; 39 (24): 9398-9405

    Abstract

    The molecular-level speciation of arsenic has been determined in a soil profile in the Massif Central near Auzon, France that was impacted by As-based pesticides by combining conventional techniques (XRD, selective chemical extractions) with X-ray absorption spectroscopy (XAS). The arsenic concentration is very high at the top (>7000 mg kg(-1)) and decreases rapidly downward to a few hundreds of milligrams per kilogram. A thin layer of schultenite (PbHAsO4), a lead arsenate commonly used as an insecticide until the middle of the 20th century, was found at 10 cm depth. Despite the occurrence of this As-bearing mineral, oxalate extraction indicated that more than 65% of the arsenic was released upon dissolution of amorphous iron oxides, suggesting a major association of arsenic with these phases within the soil profile. Since oxalate extraction cannot unambiguously distinguish among the various chemical forms of arsenic, these results were confirmed by a direct in situ determination of arsenic speciation using XAS analysis. XANES data indicate that arsenic occurs mainly as As(V) along the soil profile except for the topsoil sample where a minor amount (7%) of As(III) was detected. EXAFS spectra of soil samples were fit by linear combinations of model compounds spectra and by a shell-by-shell method. These procedures clearly confirmed that As(V) is mainly (at least 80 wt %) associated with amorphous Fe(III) oxides as coprecipitates within the soil profile. If any, the proportion of schultenite, which was evidenced by XRD in a separate thin white layer, does not account for more than 10 wt % of arsenic in soil samples. This study emphasizes the importance of iron oxides in restricting arsenic dispersal within soils following dissolution of primary As-bearing solids manufactured for use as pesticides and released into the soils.

    View details for DOI 10.1021/es050920n

    View details for Web of Science ID 000234133300007

    View details for PubMedID 16475314

  • EXAFS analysis of arsenite adsorption onto two-line ferrihydrite, hematite, goethite, and lepidocrocite ENVIRONMENTAL SCIENCE & TECHNOLOGY Ona-Nguema, G., Morin, G., Juillot, F., CALAS, G., Brown, G. E. 2005; 39 (23): 9147-9155

    Abstract

    The modes of As(III) sorption onto two-line ferrihydrite (Fh), hematite (Hm), goethite (Gt), and lepidocrocite (Lp) have been investigated under anoxic condition using X-ray absorption spectroscopy (XAS). X-ray absorption near-edge structure spectroscopy (XANES) indicates that the absence of oxygen minimized As(III) oxidation due to Fenton reactions. Extended X-ray absorption fine structure spectroscopy (EXAFS) indicates thatAs(III)forms similar inner-sphere surface complexes on two-line ferrihydrite and hematite that differ from those formed on goethite and lepidocrocite. At high surface coverage, the dominant complex types on Fh and Hm are bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C), with As-Fe distances of 2.90 +/- 0.05 and 3.35 +/- 0.05 A, respectively. The same surface complexes are observed for ferrihydrite at low surface coverage. In contrast, As(III) forms dominantly bidentate binuclear corner-sharing (2C) sorption complexes on Gt and Lp [d(As-Fe) = 3.3-3.4 A], with a minor amount of monodentate mononuclear corner-sharing (1V) complexes [d(As-Fe) = 3.5-3.6 A]. Bidentate mononuclear edge-sharing (2E) complexes are virtually absent in Gt and Lp at the high surface coverages that were investigated in the present study. These results are compared with available literature data and discussed in terms of the reactivity of iron(III) (oxyhydr)oxide surface sites.

    View details for DOI 10.1021/es050889p

    View details for Web of Science ID 000233712700027

    View details for PubMedID 16382936

  • Role of organic acids in promoting colloidal transport of mercury from mine tailings ENVIRONMENTAL SCIENCE & TECHNOLOGY Slowey, A. J., Johnson, S. B., Rytuba, J. J., Brown, G. E. 2005; 39 (20): 7869-7874

    Abstract

    A number of factors affect the transport of dissolved and particulate mercury (Hg) from inoperative Hg mines, including the presence of organic acids in the rooting zone of vegetated mine waste. We examined the role of the two most common organic acids in soils (oxalic and citric acid) on Hg transport from such waste by pumping a mixed organic acid solution (pH 5.7) at 1 mL/min through Hg mine tailings columns. For the two total organic acid concentrations investigated (20 microM and 1 mM), particle-associated Hg was mobilized, with the onset of particulate Hg transport occurring later for the lower organic acid concentration. Chemical analyses of column effluent indicate that 98 wt % of Hg mobilized from the column was particulate. Hg speciation was determined using extended X-ray absorption fine structure spectroscopy and transmission electron microscopy, showing that HgS minerals are dominant in the mobilized particles. Hg adsorbed to colloids is another likely mode of transport due to the abundance of Fe-(oxyhydr)oxides, Fe-sulfides, alunite, and jarosite in the tailings to which Hg(II) adsorbs. Organic acids produced by plants are likely to enhance the transport of colloid-associated Hg from vegetated Hg mine tailings by dissolving cements to enable colloid release.

    View details for DOI 10.1021/es0504643

    View details for Web of Science ID 000232758400020

    View details for PubMedID 16295849

  • Multi-spectroscopic study of Fe(II) in silicate glasses: Implications for the coordination environment of Fe(II) in silicate melts GEOCHIMICA ET COSMOCHIMICA ACTA Jackson, W. E., Farges, F., Yeager, M., Mabrouk, P. A., Rossano, S., WAYCHUNAS, G. A., SOLOMON, E. I., Brown, G. E. 2005; 69 (17): 4315-4332
  • Water in silicate glasses and melts of environmental interest: from volcanoes to cathedrals PHYSICS AND CHEMISTRY OF GLASSES Farges, F., Djanarthany, S., De Wispelaere, S., Munoz, M., Magassouba, B., Haddi, A., Wilke, M., Schmidt, C., Borchert, M., Trocellier, P., Crichton, W., Simionovici, A., Petit, P. E., Mezouar, M., Etcheverry, M. P., Pallot-Frossard, I., Bargar, J. R., Brown, G. E., Grolimund, D., Scheidegger, A. 2005; 46 (4): 350-353
  • Adsorption of organic matter at mineral/water interfaces. 6. Effect of inner-sphere versus outer-sphere adsorption on colloidal stability LANGMUIR Johnson, S. B., Brown, G. E., HEALY, T. W., Scales, P. J. 2005; 21 (14): 6356-6365

    Abstract

    The effects of the adsorption modes of several low molecular weight (LMW) organic anions (maleate, oxalate, and citrate) on the colloidal stability of corundum-water suspensions have been examined using electrokinetic and shear yield stress (tau(y)) measurements over a broad range of pH conditions and LMW organic anion concentrations. Consistent with previous studies, increasing concentrations of maleate, oxalate, and citrate progressively shift the electrokinetic isoelectric point and pH of the maximum shear yield stress (tau(y,max)) to more acidic conditions. Due to its predominant electrostatic driving force for adsorption, outer-spherically adsorbed maleate possesses a very limited ability to charge reverse the corundum-water interface or bind to the negatively charged corundum surface. By contrast, inner-spherically adsorbed oxalate and citrate can significantly charge reverse the corundum-water interface, with the extent of charge reversal being related to the relative binding strengths of the oxalate and citrate anions. Adsorbed maleate, oxalate, and citrate generate steric barriers to interparticle approach, leading to substantial reductions in the magnitude of tau(y,max) at low to intermediate concentrations of those LMW anions. At the highest anion concentrations investigated, however, increases in tau(y,max) are observed, and can be attributed to the formation of bridging Al(III)-organic surface precipitates, as suggested by in situ attenuated total reflectance Fourier transform infrared spectroscopic measurements of corundum-oxalate suspensions at high oxalate concentrations. The extent of precipitate formation is greatest for the corundum-oxalate system due to the strong dissolution-enhancing properties of the inner-spherically adsorbed oxalate anion (i.e., its ability to generate enhanced concentrations of dissolved Al(III) which can then participate in precipitate formation). The effects of the LMW organic anion adsorption modes on both the forms of the measured tau(y) versus pH data, and the ability to quantitatively compare tau(y) and zeta potential data measured at different corundum concentrations, are also discussed.

    View details for DOI 10.1021/la047030q

    View details for Web of Science ID 000230248500036

    View details for PubMedID 15982042

  • Uranyl adsorption onto montmorillonite: Evaluation of binding sites and carbonate complexation GEOCHIMICA ET COSMOCHIMICA ACTA Catalano, J. G., Brown, G. E. 2005; 69 (12): 2995-3005
  • Adsorption of organic matter at mineral/water interfaces. IV. Adsorption of humic substances at boehmite/water interfaces and impact on boehmite dissolution LANGMUIR Yoon, T. H., Johnson, S. B., Brown, G. E. 2005; 21 (11): 5002-5012

    Abstract

    The adsorption of Suwannee River fulvic acid (SRFA) and Pahokee peat humic acid (PPHA) at the boehmite (gamma-AlOOH)/water interface and the impact of SRFA on boehmite dissolution have been examined over a wide range of solution pH conditions (pH 2-12), SRFA surface coverages (Gamma(SRFA), total SRFA binding site concentration normalized by the boehmite surface area) of 0.0-5.33 micromol m(-2), and PPHA surface coverages (Gamma(PPHA), PPHA binding site concentration normalized by boehmite surface area) of 0.0-4.0 micromol m(-2), using macroscopic adsorption and in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. At relatively high SRFA surface coverages (Gamma(SRFA) = 5.33 micromol m(-2)), in situ ATR-FTIR spectral features of adsorbed SRFA are very similar to those measured for SRFA in solution at approximately 1-3 pH units higher. At sub-monolayer surface coverages (Gamma(SRFA) = 1.20 and 2.20 micromol m(-2)), several new peaks and enhancements of the intensities of a number of existing peaks are observed. The latter spectral changes arise from several nonorganic extrinsic species (i.e., adsorbed carbonate and water, for alkaline solution conditions), partially protonated SRFA carboxyl functional groups (near-neutral pH conditions), and small quantities of inner-spherically adsorbed SRFA carboxyl groups and/or Al(III)-SRFA complexes (for acidic conditions). The spectra of PPHA adsorbed at boehmite/water interfaces also showed changes generally consistent with our observations for SRFA sorbed on boehmite. These observations confirm that SRFA and PPHA are predominantly adsorbed at the boehmite/water interface in an outer-sphere fashion, with minor inner-sphere adsorption complexes being formed only under quite acidic conditions. They also suggest that the positively charged boehmite/water interface stabilizes SRFA and PPHA carboxyl functional groups against protonation at lower pH. Measurements of the concentration of dissolved Al(III) ions in the absence and presence of SRFA showed that the boehmite dissolution process is clearly inhibited by the adsorption of SRFA, which is consistent with previous observations that outer-spherically adsorbed organic anions inhibit Al-(oxyhydr)oxide dissolution.

    View details for DOI 10.1021/la0476276

    View details for Web of Science ID 000229243800038

    View details for PubMedID 15896043

  • Trace metal ion partitioning at polymer film-metal oxide interfaces: Long-period X-ray standing wave study LANGMUIR Yoon, T. H., Trainor, T. P., Eng, P. J., Bargar, J. R., Brown, G. E. 2005; 21 (10): 4503-4511

    Abstract

    The distributions of Pb(II) and As(V)O4(3-) ions in the interfacial region between thin poly(acrylic acid) (PAA) coatings and aalpha-A12O3(0001), alpha-Al2O3(1-102), and alpha-Fe2O3(0001) single-crystal substrates were studied using long-period X-ray standing wave fluorescent yield (XSW-FY) and X-ray reflectivity techniques. The PAA film serves as a simplified analogue of natural organic matter (NOM) coatings on mineral surfaces. Such coatings are often assumed to play an important role in the partitioning and speciation of trace heavy metals in soils and aquatic systems. On the alpha-Al2O3(1-102) surface, Pb(II) ions were found to preferentially bind to the PAA coating, even at sub-micromolar Pb(II) concentrations, and to partition increasingly onto the metal oxide surface as the Pb(II) concentration was increased ([Pb(II)] = 5 x 10(-8) to 2 x 10(-5) M, pH = 4.5; 0.01 M NaCl background electrolyte). This observation suggests that the binding sites in the PAA coating outcompete those on the alpha-Al2O3(1-102) surface for Pb(II) under these conditions. The As(V)O4(3-) oxoanion partitions preferentially to the L-Al2O3(1-102) surface for the As(V)O4(3-) concentrations examined (1 x 10(-7) to 5 x 10(-7) M, pH = 4.5; 0.01 M NaCl background electrolyte). Partitioning of Pb(II) (at 1 x 10(-7) M and pH 4.5) was also examined at PAA/alpha-Al2O3(0001), and PAA/alpha-Fe2O3(0001) interfaces using XSW-FY measurements. Our results show that the PAA coating was the dominant sink for Pb(II) in all three samples; however, the relative order of reactivity of these metal oxide surfaces with respect to Pb(II) sorption is alpha-Fe2O3(0001) > alpha-Al2O3(1-102) > alpha-Al2O3(0001). This order is consistent with that found in previous studies of the PAA-free surfaces. These XSW results strongly suggest that the characteristics of the organic film (i.e., binding affinity, type, and density of binding sites) as well as metal oxide substrate reactivity are key factors determining the distribution and speciation of Pb(II) and As(V)O4(3-) at organic film/metal oxide interfaces.

    View details for DOI 10.1021/la047271y

    View details for Web of Science ID 000228983700039

    View details for PubMedID 16032866

  • Adsorption of organic matter at mineral/water interfaces: 5. Effects of adsorbed natural organic matter analogues on mineral dissolution LANGMUIR Johnson, S. B., Yoon, T. H., Brown, G. E. 2005; 21 (7): 2811-2821

    Abstract

    The effects of the adsorption of pyromellitate, an analogue for natural organic matter, on the dissolution behavior of corundum (alpha-Al2O3) have been examined over a wide range of pyromellitate concentrations (0-2.5 mM) and pH conditions (2-10). The adsorption modes of pyromellitate on corundum have first been examined using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and are shown to be dominated by a fully deprotonated, outer-sphere pyromellitate species ([triple bond]AlOH2+. . .Pyr4-) at pH >/= 5.0. At lower pH conditions, however, an additional protonated outer-sphere species ([triple bond]AlOH2+. . .H2Pyr2-) and an inner-sphere species are also evident. In accordance with the ATR-FTIR findings, modeling of macroscopic pyromellitate adsorption data using an extended constant capacitance treatment was possible using two outer-sphere ([triple bond]AlOH2+. . .Pyr4- and [triple bond]AlOH2+. . .H2Pyr2-) and one inner-sphere ([triple bond]AlPyr3-) adsorbed pyromellitate species. The presence of adsorbed pyromellitate strongly inhibited the dissolution of corundum under acidic (pH < 5) conditions, consistent with a mechanism previously proposed by Johnson et al. whereby outer-spherically adsorbed Pyr4- species sterically protect dissolution-active surface sites from attack by dissolution-promoting species such as protons. A reduction in the protolytic dissolution rate of corundum results. A reference Suwannee River fulvic acid, which also adsorbs to aluminum (oxyhydr)oxide surfaces in a predominantly outer-sphere manner, was similarly shown to strongly inhibit the dissolution of corundum at pH = 3.

    View details for DOI 10.1021/la0481041

    View details for Web of Science ID 000228042400031

    View details for PubMedID 15779953

  • Speciation of mercury and mode of transport from placer gold mine tailings ENVIRONMENTAL SCIENCE & TECHNOLOGY Slowey, A. J., Rytuba, J. J., Brown, G. E. 2005; 39 (6): 1547-1554

    Abstract

    Historic placer gold mining in the Clear Creek tributary to the Sacramento River (Redding, CA) has highly impacted the hydrology and ecology of an important salmonid spawning stream. Restoration of the watershed utilized dredge tailings contaminated with mercury (Hg) introduced during gold mining, posing the possibility of persistent Hg release to the surrounding environment, including the San Francisco Bay Delta. Column experiments have been performed to evaluate the extent of Hg transport under chemical conditions potentially similar to those in river restoration projects utilizing dredge tailings such as at Clear Creek. Physicochemical perturbations, in the form of shifts in column influent ionic strength and the presence of a low molecular weight organic acid, were applied to coarse and fine sand placer tailings containing 109-194 and 69-90 ng of Hg/g, respectively. Significant concentrations of mercury, up to 16 microg/L, leach from these sediments in dissolved and particle-associated forms. Sequential chemical extractions (SCE) of these tailings indicate that elemental Hg initially introduced during gold mining has been transformed to readily soluble species, such as mercury oxides and chlorides (3-4%), intermediately extractable phases that likely include (in)organic sorption complexes and amalgams (75-87%), and fractions of highly insoluble forms such as mercury sulfides (6-20%; e.g., cinnabar and metacinnabar). Extended X-ray absorption fine structure (EXAFS) spectroscopic analysis of colloids obtained from column effluent identified cinnabar particles as the dominant mobile mercury-bearing phase. The fraction of intermediately extractable Hg phases also likely includes mobile colloids to which Hg is adsorbed.

    View details for DOI 10.1021/es049113z

    View details for Web of Science ID 000227636300028

    View details for PubMedID 15819208

  • Nanoscale environments associated with bioweathering of a Mg-Fe-pyroxene PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Benzerara, K., Yoon, T. H., Menguy, N., Tyliszczak, T., Brown, G. E. 2005; 102 (4): 979-982

    Abstract

    Microorganisms are believed to create microenvironments leading to reaction products not predictable from equilibrium thermodynamics and to unique biomineral morphologies. Unambiguous evidence for such environments is, however, rare in natural samples. We have used scanning transmission x-ray microscopy and spectromicroscopy at the sub-40-nm scale, coupled with transmission electron microscopy, to examine bioweathering products on a meteoritic Fe-Mg-orthopyroxene colonized by a filamentous microorganism. Our measurements reveal an amorphous Al-rich layer beneath the microorganism, calcium carbonates of unique morphology intimately associated with polysaccharides adjacent to the microorganism, and regions surrounding the microorganism with different iron oxidation states. Our results confirm the presence of different microenvironments at this microorganism-mineral interface and provide unique nanometer-scale views of microbially controlled pyroxene weathering products.

    View details for DOI 10.1073/pnas.0409029102

    View details for Web of Science ID 000226617900006

    View details for PubMedID 15647362

  • Sorption and precipitation of Co(II) in alkali aluminate solutions and Hanford sediments Applied Geochemistry Catalano, J. G., Warner, J. A., Brown, Jr., G. E. 2005; 20: 193-205
  • Environmental interfaces, heavy metals, microbes, and plants: Applications of XAFS spectroscopy and related synchrotron radiation methods to environmental science PHYSICA SCRIPTA Brown, G. E., Catalano, J. G., Templeton, A. S., Trainor, T. P., Farges, F., Bostick, B. C., Kendelewicz, T., Doyle, C. S., Spormann, A. M., Revill, K., Morin, G., Juillot, F., Calas, G. 2005; T115: 80-87
  • Tin and niobium in dry and fluid-rich (H2O, F) silicate glasses PHYSICA SCRIPTA Piilonen, P. C., Farges, F., Linnen, R. L., Brown, G. E. 2005; T115: 405-407
  • Archeological applications of XAFS: Prehistorical paintings and medieval glasses PHYSICA SCRIPTA Farges, F., Chalmin, E., Vignaud, C., Pallot-Frossard, I., Susini, J., Bargar, J., Brown, G. E., Menu, M. 2005; T115: 885-887
  • Iron in silicate glasses: a systematic analysis of pre-edge, XANES and EXAFS features PHYSICA SCRIPTA Farges, F., Rossano, S., Lefrere, Y., Wilke, M., Brown, G. E. 2005; T115: 957-959
  • Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: arsenate on hematite (0001) and (1-102) Analytical and Bioanalytical Chemistry Waychunas, G. A., Trainor, T. P., Eng, P., Catalano, J. G., Brown, Jr., G. E., Davis, J. A., Rogers, J., Bargar, J. R. 2005; 383: 12-27
  • CTR diffraction and grazing incidence XAFS study of U(VI) adsorption to α-Al2O3 and α-Fe2O3 (1-102) surfaces Geochimica et Cosmochimica Acta Catalano, J. G., Trainor, T. P., Eng, P. J., Waychunas, G. A., Brown, Jr., G. E. 2005; 69: 3555-3572
  • Adsorption of organic matter at mineral/water interfaces: 3. Implications of surface dissolution for adsorption of oxalate LANGMUIR Johnson, S. B., Yoon, T. H., Slowey, A. J., Brown, G. E. 2004; 20 (26): 11480-11492

    Abstract

    The adsorption of oxalate on a model aluminum oxide, corundum (alpha-Al2O3), has been examined over a broad range of oxalate concentrations (0.125-25.0 mM) and pH conditions (2-10). In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) measurements indicate that at low to intermediate concentrations ([oxalate] < or = 2.50 mM), oxalate adsorbs to corundum predominantly as a bidentate, mononuclear, inner-sphere complex involving both carboxyl groups. Significant contributions from outer-spherically bound oxalate and aqueous Ox(2-) are additionally observed at higher oxalate concentrations. Consistent with the ATR-FTIR findings, macroscopic adsorption data measured for oxalate concentrations of 0.125-2.50 mM can be generally well modeled with a single bidentate, inner-sphere oxalate complex using the charge distribution multisite complexation (CD-MUSIC) model. However, at intermediate oxalate concentrations (0.50 and 1.25 mM) and pH <5, the extent of oxalate adsorption measured experimentally is found to fall significantly below that predicted by CD-MUSIC simulations. The latter finding is interpreted in terms of competition for oxalate from dissolved Al(III), the formation of which is promoted by the dissolution-enhancing properties of the adsorbed oxalate anion. In accordance with this expectation, increasing concentrations of dissolved Al(III) in solution are found to significantly decrease the extent of oxalate adsorption on corundum under acidic pH conditions, presumably through promoting the formation of Al(III)-oxalate complexes with reduced affinities for the corundum surface compared with the uncomplexed oxalate anion.

    View details for DOI 10.1021/la048559q

    View details for Web of Science ID 000225816800030

    View details for PubMedID 15595773

  • Structure and reactivity of the hydrated hematite (0001) surface SURFACE SCIENCE Trainor, T. P., Chaka, A. M., Eng, P. J., Newville, M., WAYCHUNAS, G. A., Catalano, J. G., Brown, G. E. 2004; 573 (2): 204-224
  • In situ characterization of aluminum-containing mineral-microorganism aqueous suspensions using scanning transmission X-ray microscopy LANGMUIR Yoon, T. H., Johnson, S. B., Benzerara, K., Doyle, C. S., Tyliszczak, T., Shuh, D. K., Brown, G. E. 2004; 20 (24): 10361-10366

    Abstract

    In situ characterization of colloidal particles under hydrous conditions is one of the key requirements for understanding their state of aggregation and impact on the transport of pollutants in aqueous environments. Scanning transmission X-ray microscopy (STXM) is one of the few techniques that can satisfy this need by providing element- and chemical-state-specific 2-D maps at a spatial resolution better than 50 nm using soft X-rays from synchrotron radiation wiggler or undulator sources tuned to the absorption edges of different elements. X-ray absorption near-edge structure (XANES) spectra can also be collected simultaneously at a similar spatial resolution and can provide phase identification in many cases. In this study, we report STXM images and XANES spectroscopy measurements at or above the Al K-edge (E = 1559.6 eV) of various Al-containing minerals and synthetic oxides [alpha-Al2O3 (corundum), gamma-Al2O3, gamma-AlOOH (boehmite), alpha-Al(OH)3 (bayerite), KAl2(AlSi3O10)(OH)2 (muscovite), (Al,Mg)8(Si4O10)4(OH)8.nH2O (montmorillonite), and Mg6Al2(OH)16CO3.4H2O (hydrotalcite)] and demonstrate the capability of this spectromicroscopic tool to identify different Al-containing mineral colloids in multiphase mixtures in aqueous solution. We also demonstrate that STXM imaging at or above the C K-edge (E = 284.2 eV) and Al K-edge can provide unique information on the interactions between bacteria and Al-containing nanoparticles in aqueous suspensions. STXM images of a mixture of Caulobacter crescentus and montmorillonite and corundum particles just above the C and Al K-edges show that the mineral particles and bacteria are closely associated in aggregates, which is likely due to the binding of bacteria to clay and corundum particles by extracellular polysaccharides.

    View details for DOI 10.1021/la048558y

    View details for Web of Science ID 000225207400001

    View details for PubMedID 15544358

  • Adsorption of organic matter at mineral/water interfaces: I. ATR-FTIR spectroscopic and quantum chemical study of oxalate adsorbed at boehmite/water and corundum/water interfaces GEOCHIMICA ET COSMOCHIMICA ACTA Yoon, T. H., Johnson, S. B., Musgrave, C. B., Brown, G. E. 2004; 68 (22): 4505-4518
  • Experimental and theoretical characterization of the structure of defects at the pyrite FeS2(100) surface PHYSICAL REVIEW B Andersson, K., Nyberg, M., Ogasawara, H., Nordlund, D., Kendelewicz, T., Doyle, C. S., Brown, G. E., Pettersson, L. G., Nilsson, A. 2004; 70 (19)
  • Soft X-ray spectroscopic studies of the reaction of fractured pyrite surfaces with Cr(Vl)-containing aqueous solutions GEOCHIMICA ET COSMOCHIMICA ACTA Doyle, C. S., Kendelewicz, T., Bostick, B. C., Brown, G. E. 2004; 68 (21): 4287-4299
  • Scanning transmission X-ray microscopy study of microbial calcification GEOBIOLOGY Benzerara, K., Yoon, T. H., Tyliszczak, T., Constantz, B., Spormann, A. M., Brown, G. E. 2004; 2 (4): 249-259
  • Macroscopic and microscopic observations of particle-facilitated mercury transport from new idria and sulphur bank mercury mine tailings ENVIRONMENTAL SCIENCE & TECHNOLOGY Lowry, G. V., Shaw, S., Kim, C. S., Rytuba, J. J., Brown, G. E. 2004; 38 (19): 5101-5111

    Abstract

    Mercury (Hg) release from inoperative Hg mines in the California Coast Range has been documented, but little is known about the release and transport mechanisms. In this study, tailings from Hg mines located in different geologic settings--New Idria (NI), a Si-carbonate Hg deposit, and Sulphur Bank (SB), a hot-spring Hg deposit--were characterized, and particle release from these wastes was studied in column experiments to (1) investigate the mechanisms of Hg release from NI and SB mine wastes, (2) determine the speciation of particle-bound Hg released from the mine wastes, and (3) determine the effect of calcinations on Hg release processes. The physical and chemical properties of tailings and the colloids released from them were determined using chemical analyses, selective chemical extractions, XRD, SEM, TEM, and X-ray absorption spectroscopy techniques. The total Hg concentration in tailings increased with decreasing particle size in NI and SB calcines (roasted ore), but reached a maximum at an intermediate particle size in the SB waste rock (unroasted ore). Hg in the tailings exists predominantly as low-solubility HgS (cinnabar and metacinnabar), with NI calcines having >50% HgS, SB calcines having >89% HgS, and SB waste rock having approximately 100% HgS. Leaching experiments with a high-ionic-strength solution (0.1 M NaCl) resulted in a rapid but brief release of soluble and particulate Hg. Lowering the ionic strength of the leach solution (0.005 M NaCI) resulted in the release of colloidal Hg from two of the three mine wastes studied (NI calcines and SB waste rock). Colloid-associated Hg accounts for as much as 95% of the Hg released during episodic particle release. Colloids generated from the NI calcines are produced by a breakup and release mechanism and consist of hematite, jarosite/alunite, and Al-Si gel with particle sizes of 10-200 nm. ATEM and XAFS analyses indicate that the majority (approximately 78%) of the mercury is present in the form of HgS. SB calcines also produced HgS colloids. The colloids generated from the SB waste rockwere heterogeneous and varied in composition according to the column influent composition. ATEM and XAFS results indicate that Hg is entirely in the HgS form. Data from this study identify colloidal HgS as the dominant transported form of Hg from these mine waste materials.

    View details for DOI 10.1021/es034636c

    View details for Web of Science ID 000224234100035

    View details for PubMedID 15506205

  • The effect of redox state on the local structural environment of iron in silicate glasses: a molecular dynamics, combined XAFS spectroscopy, and bond valence study JOURNAL OF NON-CRYSTALLINE SOLIDS Farges, F., Lefrere, Y., Rossano, S., Berthereau, A., CALAS, G., Brown, G. E. 2004; 344 (3): 176-188
  • Adsorption of Suwannee River fulvic acid on aluminum oxyhydroxide surfaces: An in situ ATR-FTIR study LANGMUIR Yoon, T. H., Johnson, S. B., Brown, G. E. 2004; 20 (14): 5655-5658

    Abstract

    The adsorption of Suwannee River fulvic acid (SRFA) on boehmite, gamma-AlO(OH), has been examined by both macroscopic adsorption and in situ ATR-FTIR spectroscopic techniques. At a SRFA concentration approaching surface saturation (F = 5.3 micromol m(-2)), adsorption is at a maximum at low pH and decreases as pH is increased. The ATR-FTIR spectral features of adsorbed SRFA are very similar to those measured approximately 1-2 pH units higher in solution, indicating that (i) the SRFA appears to be predominantly adsorbed at the boehmite/water interface in an outer-sphere complexation mode and (ii) the positively charged boehmite/water interface stabilizes SRFA molecules against protonation at low pH.

    View details for DOI 10.1021/la0499214

    View details for Web of Science ID 000222429200004

    View details for PubMedID 16459573

  • Adsorption mechanisms of trivalent gold on iron- and aluminum-(oxy)hydroxides. Part 1: X-ray absorption and Raman scattering spectroscopic studies of Au(III) adsorbed on ferrihydrite, goethite, and boehmite GEOCHIMICA ET COSMOCHIMICA ACTA Berrodier, I., Farges, F., Benedetti, M., Winterer, M., Brown, G. E., Deveughele, M. 2004; 68 (14): 3019-3042
  • Analysis of uranyl-bearing phases by EXAFS spectroscopy: Interferences, multiple scattering, accuracy of structural parameters, and spectral differences AMERICAN MINERALOGIST Catalano, J. G., Brown, G. E. 2004; 89 (7): 1004-1021
  • Adsorption of organic matter at mineral/water interfaces. 2. Outer-sphere adsorption of maleate and implications for dissolution processes LANGMUIR Johnson, S. B., Yoon, T. H., Kocar, B. D., Brown, G. E. 2004; 20 (12): 4996-5006

    Abstract

    The effects of the adsorption of a simple dicarboxylate low molecular weight organic anion, maleate, on the dissolution of a model aluminum oxide, corundum (alpha-Al2O3), have been examined over a range of different maleate concentrations (0.125-5.0 mM) and pH conditions (2-10). In situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic measurements indicate that maleate binds predominantly as an outer-sphere, fully deprotonated complex ([triple bond]AlOH2+ -Mal2-) at the corundum surface over the entire range of maleate concentrations and pH conditions investigated. In accordance with the ATR-FTIR findings, macroscopic adsorption data can be modeled as a function of maleate concentration and pH using an extended constant capacitance approach and a single [triple bond]AlOH2+ -Mal2- species. Outer-sphere adsorption of maleate is found to significantly reduce the protolytic dissolution rate of corundum under acidic conditions (pH < 5). A likely mechanism involves steric protection of dissolution-active surface sites, whereby strong outer-sphere interactions with maleate hinder attack on those surface sites by dissolution-promoting species.

    View details for DOI 10.1021/la036288y

    View details for Web of Science ID 000221846000032

    View details for PubMedID 15984260

  • Initial oxidation of fractured surfaces of FeS2(100) by molecular oxygen, water vapor, and air SURFACE SCIENCE Kendelewicz, T., Doyle, C. S., Bostick, B. C., Brown, G. E. 2004; 558 (1-3): 80-88
  • Inhibition of the reduction of Cr(VI) at the magnetite-water interface by calcium carbonate coatings APPLIED SURFACE SCIENCE Doyle, C. S., Kendelewicz, T., Brown, G. E. 2004; 230 (1-4): 260-271
  • Spectroscopic and diffraction study of uranium speciation in contaminated vadose zone sediments from the Hanford site, Washington state ENVIRONMENTAL SCIENCE & TECHNOLOGY Catalano, J. G., Heald, S. M., Zachara, J. M., Brown, G. E. 2004; 38 (10): 2822-2828

    Abstract

    Contamination of vadose zone sediments under tank BX-102 at the Hanford site, Washington, resulted from the accidental release of 7-8 metric tons of uranium dissolved in caustic aqueous sludge in 1951. We have applied synchrotron-based X-ray spectroscopic and diffraction techniques to characterize the speciation of uranium in samples of these contaminated sediments. UIII-edge X-ray absorption fine structure (XAFS) spectroscopic studies demonstrate that uranium occurs predominantly as a uranium(VI) silicate from the uranophane group of minerals. XAFS cannot distinguish between the members of this mineral group due to the near identical local coordination environments of uranium in these phases. However, these phases differ crystallographically, and can be distinguished using X-ray diffraction (XRD) methods. As the concentration of uranium was too low for conventional XRD to detect these phases, X-ray microdiffraction (microXRD) was used to collect diffraction patterns on approximately 20 microm diameter areas of localized high uranium concentration found using microscanning X-ray fluorescence (microSXRF). Only sodium boltwoodite, Na(UO2)(SiO3OH) x 1.5H20, was observed; no other uranophane group minerals were present. Sodium boltwoodite formation has effectively sequestered uranium in these sediments under the current geochemical and hydrologic conditions. Attempts to remediate the uranium contamination will likely face significant difficulties because of the speciation and distribution of uranium in the sediments.

    View details for DOI 10.1021/es049963e

    View details for Web of Science ID 000221502800019

    View details for PubMedID 15212255

  • Geological and anthropogenic factors influencing mercury speciation in mine wastes: an EXAFS spectroscopy study APPLIED GEOCHEMISTRY Kim, C. S., Rytuba, J. J., Brown, G. E. 2004; 19 (3): 379-393
  • EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides I. Effects of pH JOURNAL OF COLLOID AND INTERFACE SCIENCE Kim, C. S., Rytuba, J. J., Brown, G. E. 2004; 271 (1): 1-15

    Abstract

    The study of mercury sorption products in model systems using appropriate in situ molecular-scale probes can provide detailed information on the modes of sorption at mineral/water interfaces. Such studies are essential for assessing the influence of sorption processes on the transport of Hg in contaminated natural systems. Macroscopic uptake of Hg(II) on goethite (alpha-FeOOH), gamma-alumina (gamma-Al(2)O(3)), and bayerite (beta-Al(OH)(3)) as a function of pH has been combined with Hg L(III)-edge EXAFS spectroscopy, FTIR spectroscopy, and bond valence analysis of possible sorption products to provide this type of information. Macroscopic uptake measurements show that Hg(II) sorbs strongly to fine-grained powders of synthetic goethite (Hg sorption density Gamma=0.39-0.42 micromol/m(2)) and bayerite (Gamma=0.39-0.44 micromol/m(2)), while sorbing more weakly to gamma-alumina (Gamma=0.04-0.13 micromol/m(2)). EXAFS spectroscopy on the sorption samples shows that the dominant mode of Hg sorption on these phases is as monodentate and bidentate inner-sphere complexes. The mode of Hg(II) sorption to goethite was similar over the pH range 4.3-7.4, as were those of Hg(II) sorption to bayerite over the pH range 5.1-7.9. Conversion of the gamma-Al(2)O(3) sorbent to a bayerite-like phase in addition to the apparent reduction of Hg(II) to Hg(I), possibly by photoreduction during EXAFS data collection, resulted in enhanced Hg uptake from pH 5.2-7.8 and changes in the modes of sorption that correlate with the formation of the bayerite-like phase. Bond valence calculations are consistent with the sorption modes proposed from EXAFS analysis. EXAFS analysis of Hg(II) sorption products on a natural Fe oxyhydroxide precipitate and Al/Si-bearing flocculent material showed sorption products and modes of surface attachment similar to those for the model substrates, indicating that the model substrates are useful surrogates for the natural sediments.

    View details for DOI 10.1016/S0021-9797(03)00330-8

    View details for Web of Science ID 000188778600001

    View details for PubMedID 14757070

  • EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides - II. Effects of chloride and sulfate JOURNAL OF COLLOID AND INTERFACE SCIENCE Kim, C. S., Rytuba, J., Brown, G. E. 2004; 270 (1): 9-20

    Abstract

    Common complexing ligands such as chloride and sulfate can significantly impact the sorption of Hg(II) to particle surfaces in aqueous environmental systems. To examine the effects of these ligands on Hg(II) sorption to mineral sorbents, macroscopic Hg(II) uptake measurements were conducted at pH 6 and [Hg](i)=0.5 mM on goethite (alpha-FeOOH), gamma-alumina (gamma-Al(2)O(3)), and bayerite (beta-Al(OH)(3)) in the presence of chloride or sulfate, and the sorption products were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of chloride resulted in reduced uptake of Hg(II) on all three substrates over the Cl(-) concentration ([Cl(-)]) range 10(-5) to 10(-2) M, lowering Hg surface coverages on goethite, gamma-alumina, and bayerite from 0.42 to 0.07 micromol/m(2), 0.06 to 0.006 micromol/m(2), and 0.55 to 0.39 micromol/m(2) ([Cl(-)]=10(-5) to 10(-3) M only), respectively. This reduction in Hg(II) uptake is primarily a result of the formation of stable, nonsorbing aqueous HgCl(2) complexes in solution, limiting the amount of free Hg(II) available to sorb. At higher [Cl(-)] beam reduction of Hg(II) to Hg(I) was observed, resulting in the possible formation of aqueous Hg(2)Cl(2) species and the precipitation of calomel, Hg(2)Cl(2(s)). The presence of sulfate caused enhanced Hg(II) uptake over the sulfate concentration ([SO(4)(2-)]) range 10(-5) to 0.9 M, increasing Hg surface coverages on goethite, gamma-alumina, and bayerite from 0.39 to 0.45 micromol/m(2), 0.11 to 0.38 micromol/m(2), and 0.36 to 3.33 micromol/m(2), respectively. This effect is likely due to the direct sorption or accumulation of sulfate ions at the substrate interface, effectively reducing the positive surface charge that electrostatically inhibits Hg(II) sorption. Spectroscopic evidence for ternary surface complexation was observed in isolated cases, specifically in the Hg-goethite-sulfate system at high [SO(4)(2-)] and in the Hg-goethite-chloride system.

    View details for DOI 10.1016/j.jcis.2003.07.029

    View details for Web of Science ID 000187883900002

    View details for PubMedID 14693130

  • In-situ grazing incidence EXAFS study of Pb(II) chemisorption on hematite (0001) and (1-102) Langmuir Bargar, J. R., Trainor, T. P., Fitts, J. P., Chambers, S. A., Brown, Jr., G. E. 2004; 20: 1667-1673
  • Chromium speciation and mobility in a high level nuclear waste vadose zone plume GEOCHIMICA ET COSMOCHIMICA ACTA Zachara, J. M., Ainsworth, C. C., Brown, G. E., Catalano, J. G., McKinley, J. P., Qafoku, O., Smith, S. C., Szecsody, J. E., Traina, S. J., Warner, J. A. 2004; 68 (1): 13-30
  • A novel spectrometer system for hard x-ray interfacial environmental chemistry SYNCHROTRON RADIATION INSTRUMENTATION Rogers, J. H., Bargar, J. R., WAYCHUNAS, G. A., Yoon, T. H., Brown, G. E. 2004; 705: 981-984
  • Soft X-ray scanning transmission microscope working in an extended energy range at the advanced light source SYNCHROTRON RADIATION INSTRUMENTATION Tyliszczak, T., Warwick, T., Kilcoyne, A. L., Fakra, S., Shuh, D. K., Yoon, T. H., Brown, G. E., Andrews, S., Chernbrolu, V., Strachan, J., Acremann, Y. 2004; 705: 1356-1359
  • Mercury speciation by X-ray absorption fine structure spectroscopy and sequential chemical extractions: A comparison of speciation methods ENVIRONMENTAL SCIENCE & TECHNOLOGY Kim, C. S., Bloom, N. S., Rytuba, J. J., Brown, G. E. 2003; 37 (22): 5102-5108

    Abstract

    Determining the chemical speciation of mercury in contaminated mining and industrial environments is essential for predicting its solubility, transport behavior, and potential bioavailability as well as for designing effective remediation strategies. In this study, two techniques for determining Hg speciation--X-ray absorption fine structure (XAFS) spectroscopy and sequential chemical extractions (SCE)--are independently applied to a set of samples with Hg concentrations ranging from 132 to 7539 mg/kg to determine if the two techniques provide comparable Hg speciation results. Generally, the proportions of insoluble HgS (cinnabar, metacinnabar) and HgSe identified by XAFS correlate well with the proportion of Hg removed in the aqua regia extraction demonstrated to remove HgS and HgSe. Statistically significant (>10%) differences are observed however in samples containing more soluble Hg-containing phases (HgCl2, HgO, Hg3S2O4). Such differences may be related to matrix, particle size, or crystallinity effects, which could affect the apparent solubility of Hg phases present. In more highly concentrated samples, microscopy techniques can help characterize the Hg-bearing species in complex multiphase natural samples.

    View details for DOI 10.1021/es0341485

    View details for Web of Science ID 000186601300004

    View details for PubMedID 14655695

  • Selenium speciation and partitioning within Burkholderia cepacia biofilms formed on alpha-Al2O3 surfaces GEOCHIMICA ET COSMOCHIMICA ACTA Templeton, A. S., Trainor, T. P., Spormann, A. M., Brown, G. E. 2003; 67 (19): 3547-3557
  • Speciation of Pb(II) sorbed by Burkholderia cepacia/goethite composites ENVIRONMENTAL SCIENCE & TECHNOLOGY Templeton, A. S., Spormann, A. M., Brown, G. E. 2003; 37 (10): 2166-2172

    Abstract

    Bacterial-mineral composites are important in the retention of heavy metals such as Pb due to their large sorption capacity under a wide range of environmental conditions. However, the partitioning of heavy metals between components in such composites is not probed directly. Using Burkholderia cepacia biofilms coated with goethite (alpha-FeOOH) particles, the partitioning of Pb(II) between the biological and iron-(oxyhydr)oxide surfaces has been measured using an X-ray spectroscopic approach. EXAFS spectra were fit to quantitatively determine the fraction of Pb(II) associated with each component as a function of pH and [Pb]. At pH < 5.5, at least 50% of the total sorbed Pb(II) is associated with the biofilm component, whereas the total uptake within the composite is dominated by goethite (> 70% Pb/goethite) above pH 6. Direct comparison can be made between the amount of Pb(II) bound to each component in the composite vs separate binary systems (i.e., Pb/biofilm or Pb/goethite). At high pH, Pb(II) uptake on the biofilm is dramatically decreased due to competition with the goethite surface. In contrast, Pb uptake on goethite is significantly enhanced at low pH (2-fold increase at pH 5) compared to systems with no complexing ligands. The mode of Pb(II)-binding to the goethite component changes from low to high [Pb]. Structural fitting of the EXAFS spectra collected from 10(-5.6) to 10(-3.6) M [Pb]eq at pH 6 shows that the Pb-goethite surface complexes at low [Pb] are dominated by inner-sphere bidentate, binuclear complexes bridging two adjacent singly coordinated surface oxygens, giving rise to Pb-Fe distances of approximately 3.9 A. At high [Pb], the dominant Pb(II) inner-sphere complexes on the goethite surface shift to bidentate edge-sharing complexes with Pb-Fe distances of approximately 3.3 A.

    View details for DOI 10.1021/es026081b

    View details for Web of Science ID 000182866000020

    View details for PubMedID 12785522

  • Occurrence of Zn/Al hydrotalcite in smelter-impacted soils from northern France: Evidence from EXAFS spectroscopy and chemical extractions AMERICAN MINERALOGIST Juillot, F., Morin, G., Ildefonse, P., Trainor, T. P., Benedetti, M., Galoisy, L., CALAS, G., Brown, G. E. 2003; 88 (4): 509-526
  • Sorption versus biomineralization of Pb(II) within Burkholderia cepacia biofilms ENVIRONMENTAL SCIENCE & TECHNOLOGY Templeton, A. S., Trainor, T. P., Spormann, A. M., Newville, M., Sutton, S. R., Dohnalkova, A., Gorby, Y., Brown, G. E. 2003; 37 (2): 300-307

    Abstract

    X-ray spectroscopy measurements have been combined with macroscopic uptake data and transmission electron microscopy (TEM) results to show that Pb(II) uptake by Burkholderia cepacia is due to simultaneous sorption and biomineralization processes. X-ray microprobe mapping of B. cepacia biofilms formed on alpha-Al2O3 surfaces shows that Pb(II) is distributed heterogeneously throughout the biofilms because of the formation of Pb "hot spots". EXAFS data and TEM observations show that the enhanced Pb accumulation is due to the formation of nanoscale crystals of pyromorphite (Pb5(PO4)3(OH)) adjacent to the outer-membrane of a fraction of the total population of B. cepacia cells. In contrast, B. cepacia cell suspensions or biofilms that were heat-killed or pretreated with X-rays do not form pyromorphite, which suggests that metabolic activity is required. Precipitation of pyromorphite occurs over several orders of magnitude in [H-] and [Pb] and accounts for approximately 90% of the total Pb uptake below pH 4.5 but only 45-60% at near-neutral pH because of the formation of additional Pb(II) adsorption complexes. Structural fits of Pb L(III) EXAFS data collected for heat-treated cells at near-neutral pH suggest that Pb(II) forms inner-sphere adsorption complexes with carboxyl functional groups in the biofilms.

    View details for DOI 10.1021/es025972g

    View details for Web of Science ID 000180501500014

    View details for PubMedID 12564901

  • XAFS study of As(V) and Se(IV) sorption complexes on hydrous Mn oxides Geochimica et Cosmochimica Acta Foster, A. L., Brown, Jr., G. E., Parks, G. A. 2003; 67: 1937-1953
  • Application of the long-period X-ray standing wave technique to the analysis of surface reactivity: Pb(II) sorption at alpha-Al2O3/aqueous solution interfaces in the presence and absence of Se(VI) LANGMUIR Trainor, T. P., Templeton, A. S., Brown, G. E., Parks, G. A. 2002; 18 (15): 5782-5791

    View details for DOI 10.1021/la015740f

    View details for Web of Science ID 000176903500024

  • Bond valence in silicate glasses JOURNAL OF NON-CRYSTALLINE SOLIDS Rossano, R., Farges, F., Ramos, A., Delaye, J. M., Brown, G. E. 2002; 304 (1-3): 167-173
  • Molecular beam epitaxial growth and properties of CoFe2O4 on MgO(001) JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Chambers, S. A., Farrow, R. F., Maat, S., Toney, M. F., Folks, L., Catalano, J. G., Trainor, T. P., Brown, G. E. 2002; 246 (1-2): 124-139
  • An overview of synchrotron radiation applications to low temperature geochemistry and environmental science APPLICATIONS OF SYNCHROTRON RADIATION IN LOW-TEMPERATURE GEOCHEMISTRY AND ENVIRONMENTAL SCIENCES Brown, G. E., Sturchio, N. C. 2002; 49: 1-115
  • Crystal truncation rod diffraction study of the clean and hydrated α-Al2O3 (1-102) surface Surface Science Trainor, T. P., Eng, P., Brown, Jr., G. E., Robinson, I. K., De Santis, M. 2002; 496: 238-250
  • Grazing-incidence XAFS study of aqueous Zn(II) sorption on alpha-Al2O3 single crystals Journal of Colloid and Interface Science Trainor, T. P., Fitts, J. P., Templeton, A. S., Grolimund, D., Brown, Jr., G. E. 2002; 244: 239-244
  • Pb(II) distributions at biofilm-metal oxide interfaces PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Templeton, A. S., Trainor, T. P., Traina, S. J., Spormann, A. M., Brown, G. E. 2001; 98 (21): 11897-11902

    Abstract

    The distribution of aqueous Pb(II) sorbed at the interface between Burkholderia cepacia biofilms and hematite (alpha-Fe(2)O(3)) or corundum (alpha-Al(2)O(3)) surfaces has been probed by using an application of the long-period x-ray standing wave technique. Attached bacteria and adsorbed organic matter may interfere with sorption processes on metal oxide surfaces by changing the characteristics of the electrical double layer at the solid-solution interface, blocking surface sites, or providing a variety of new sites for metal binding. In this work, Pb L(alpha) fluorescence yield profiles for samples equilibrated with 10(-7) to 10(-3.8) M Pb(II) were measured and modeled to determine quantitatively the partitioning of Pb(II) at the biofilm-metal oxide interface. Our data show that the reactive sites on the metal oxide surfaces were not passivated by the formation of a monolayer biofilm. Instead, high-energy surface sites on the metal oxides form the dominant sink for Pb(II) at submicromolar concentrations, following the trend alpha-Fe(2)O(3) (0001) > alpha-Al(2)O(3) (1102) > alpha-Al(2)O(3) (0001), despite the greater site density within the overlying biofilms. At [Pb] > 10(-6) M, significant Pb uptake by the biofilms was observed.

    View details for Web of Science ID 000171558900016

    View details for PubMedID 11572932

  • Surface science - How minerals react with water SCIENCE Brown, G. E. 2001; 294 (5540): 67-?

    View details for Web of Science ID 000171448800029

    View details for PubMedID 11588241

  • Sorption of trace elements from aqueous media: Modern perspectives from spectroscopic studies and comments on adsorption in the marine environment International Geology Review Brown, Jr., G. E., Parks, G. A. 2001; 43: 867-976
  • Mineralogy of lead in a soil developed on a Pb-mineralized sandstone (Largentiere, France) AMERICAN MINERALOGIST Morin, G., Juillot, F., Ildefonse, P., CALAS, G., Samama, J. C., Chevallier, P., Brown, G. E. 2001; 86 (1-2): 92-104
  • Transition elements in water-bearing silicate glasses/melts. Part I. A high resolution and anharmonic EXAFS analysis of Ni coordination environments in crystals, glasses, and melts Geochimica et Cosmochimica Acta Farges, F., Brown, Jr., G. E., Petit, P.-E., Munoz, M. 2001; 65: 1665-1678
  • Oxidation state and coordination of Fe in minerals: an Fe K-XANES study American Mineralogist Wilke, M., Farges, F., Petit, P-E., Brown, Jr., G. E., Martin, F. 2001; 86: 714-730
  • Inside rocks Geotimes, American Geological Institute Astheimer, R., Kristin, B., Brown, Jr., G. E., Hoy, J., Jones, K. W., Sturchio, N. C., Sutton, S. R., Waychunas, G. A., Woodward, N. B. 2001: 20-23
  • Transition elements in water-bearing silicate glasses/melts. Part II. Ni in water-bearing glasses Geochimica et Cosmochimica Acta Farges, F., Munoz, M., Siewert, R., Malavergne, V., Brown, Jr., G. E., Behrens, H., Nowak, M., Petit, P.-E. 2001; 65: 1679-1693
  • Structural evolution of Cr(III) polymeric species at the gamma-Al2O3/water interface ENVIRONMENTAL SCIENCE & TECHNOLOGY Fitts, J. P., Brown, G. E., Parks, G. A. 2000; 34 (24): 5122-5128

    View details for DOI 10.1021/es9914285

    View details for Web of Science ID 000165887800009

  • Structure of the hydrated alpha-Al2O3 (0001) surface SCIENCE Eng, P. J., Trainor, T. P., Brown, G. E., WAYCHUNAS, G. A., Newville, M., Sutton, S. R., Rivers, M. L. 2000; 288 (5468): 1029-1033
  • Reaction of water with the (100) and (111) surfaces of Fe3O4 SURFACE SCIENCE Kendelewicz, T., Liu, P., Doyle, C. S., Brown, G. E., Nelson, E. J., Chambers, S. A. 2000; 453 (1-3): 32-46
  • Growth and electronic structure of vanadium on alpha-Al2O3(0001) SURFACE SCIENCE Biener, J., Baumer, M., Madix, R. J., Liu, P., Nelson, E., Kendelewisz, T., Brown, G. 2000; 449 (1-3): 50-60
  • Adsorption and Precipitation of Aqueous Zn(II) on Alumina Powders. Journal of colloid and interface science Trainor, T. P., Brown, G. E., Parks, G. A. 2000; 231 (2): 359-372

    Abstract

    The products of aqueous Zn(II) sorption on high-surface-area alumina powders (Linde-A) have been studied using XAFS spectroscopy as a function of Zn(II) sorption density (Gamma=0.2 to 3.3 µmol/m(2)) at pH values of 7.0 to 8.2. Over equilibration times of 15-111 h, we find that at low sorption densities (Gamma=0.2-1.1 µmol/m(2)) Zn(II) forms predominantly inner-sphere bidentate surface complexes with AlO(6) polyhedra, whereas at higher sorption densities (Gamma=1.5 to 3.5 µmol/m(2)), we find evidence for the formation of a mixed-metal Zn(II)-Al(III) hydroxide coprecipitate with a hydrotalcite-type local structure. These conclusions are based on an analysis of first- and second-neighbor interatomic distances derived from EXAFS spectra collected under ambient conditions on wet samples. At low sorption densities the sorption mechanism involves a transformation from six-coordinated Zn-hexaaquo solution complexes (with an average Zn-O distance of 2.07 Å) to four-coordinated surface complexes (with an average Zn-O distance of 1.97 Å) as described by the reaction identical withAl(OH(a))(OH(b))+Zn (H(2)O)(6)(2+)--> identical withAl(OH(a)') (OH(b)')Zn(OH(c)')(OH(d)'+4H(2)O+zH(+), where identical withAl(OH(a))(OH(b)) represents edge-sharing sites of Al(O,OH,OH(2))(6) octahedra to which Zn(O,OH,OH(2))(4) bonds in a bidentate fashion. The proton release consistent with this reaction (z=a-a'+b-b'+4-c'-d'), and with bond valence analysis falls in the range of 0 to 2 H(+)/Zn(II) when hydrolysis of the adsorbed Zn(II) complex is neglected. This interpretation suggests that proton release is likely a strong function of the coordination chemistry of the surface hydroxyl groups. At higher sorption densities (1.5 to 3.5 µmol/m(2)), a high-amplitude, second-shell feature in the Fourier transform of the EXAFS spectra indicates the formation of a three-dimensional mixed-metal coprecipitate, with a hydrotalcite-like local structure. Nitrate anions presumably satisfy the positive layer charge of the Al(III)-Zn(II) hydroxide layers in which the Zn/Al ratio falls in the range of 1 : 1 to 2 : 1. Our results for the higher Gamma-value sorption samples suggest that Zn-hydrotalcite-like phases may be a significant sink for Zn(II) in natural or catalytic systems containing soluble alumina compounds. Copyright 2000 Academic Press.

    View details for PubMedID 11049686

  • Inorganic Ligand Effects on Pb(II) Sorption to Goethite (alpha-FeOOH). Journal of colloid and interface science Ostergren, J. D., Brown, G. E., Parks, G. A., Persson, P. 2000; 225 (2): 483-493

    Abstract

    The effects of sulfate anions on the uptake of Pb(II) onto goethite were investigated at the molecular level using in situ Pb L(III)-EXAFS and ATR-FTIR spectroscopies. Macroscopic uptake data show that Pb uptake can be enhanced by at least 30% at pH 5 in the presence of 3.16 mM sulfate and that sulfate uptake at pH 7 can be enhanced by more than a factor of 3 in the presence of 1.0 mM Pb. Consistent with behavior in sulfate-free systems, Pb(II) forms inner-sphere complexes sharing either corners or edges with Fe(O,OH)(6) octahedra under all conditions studied. The relative fraction of corner-sharing complexes is, however, significantly enhanced in the presence of sulfate at pH 5, 6, and 7 (all conditions studied) and additional sulfate species with C(3v) or lower point symmetry were noted in the presence of Pb by ATR-FTIR. Drawing on bond valence and structural constraints developed in J. D. Ostergren et al. (2000, J. Colloid Interface Science 224, 000-000), these results indicate formation of Type A ternary complexes bonded to the surface through Pb that is bound as a bridging bidenate complex to two adjacent A-type (singly coordinated) surface oxygens (( identical withFe-O)(2)-Pb-OSO(3)). Copyright 2000 Academic Press.

    View details for PubMedID 11254288

  • Formation and Release of Cobalt(II) Sorption and Precipitation Products in Aging Kaolinite-Water Slurries. Journal of colloid and interface science Thompson, H. A., Parks, G. A., Brown, G. E. 2000; 222 (2): 241-253

    Abstract

    The uptake and release behavior of cobalt(II) was studied over thousands of hours in CO(2)-free aqueous suspensions of kaolinite under three pairs of total cobalt concentration (Co(T)) and near-neutral pH (7.5-7.8) conditions. Dissolved cobalt, aluminum, and silicon concentrations were monitored by ICPMS, and cobalt-containing products were identified by EXAFS spectroscopy. In each uptake experiment, cobalt sorbed to kaolinite as a mixture of surface-adsorbed monomers or polymers and hydrotalcite-like precipitates of the approximate composition Co(x)Al(OH)(2x+2)(A(n-))(1/n), where 2

    View details for PubMedID 10662519

  • Structure of the hydrated alpha-Al(2)O(3) (0001) surface Science (New York, N.Y.) Eng, P. J., Trainor, T. P., Brown, G. E., Waychunas, G. A., Newville, M., Sutton, S. R., Rivers, M. L. 2000; 288 (5468): 1029-33

    Abstract

    The physical and chemical properties of the hydrated alpha-Al(2)O(3) (0001) surface are important for understanding the reactivity of natural and synthetic aluminum-containing oxides. The structure of this surface was determined in the presence of water vapor at 300 kelvin by crystal truncation rod diffraction at a third-generation synchrotron x-ray source. The fully hydrated surface is oxygen terminated, with a 53% contracted double Al layer directly below. The structure is an intermediate between alpha-Al(2)O(3) and gamma-Al(OH)(3), a fully hydroxylated form of alumina. A semiordered oxygen layer about 2.3 angstroms above the terminal oxygen layer is interpreted as adsorbed water. The clean alpha-Al(2)O(3) (0001) surface, in contrast, is Al terminated and significantly relaxed relative to the bulk structure. These differences explain the different reactivities of the clean and hydroxylated surfaces.

    View details for PubMedID 10807569

  • Inorganic Ligand Effects on Pb(II) Sorption to Goethite (alpha-FeOOH). Journal of colloid and interface science Ostergren, J. D., Trainor, T. P., Bargar, J. R., Brown, G. E., Parks, G. A. 2000; 225 (2): 466-482

    Abstract

    Macroscopic measurements show that Pb(II) uptake on iron-(hydr)oxides can be altered significantly by dissolved carbonate (enhanced up to 18% at pH 5 and decreased above pH approximately 6.5 in analyses at 1 atm CO(2)). This study elucidates the molecular-scale processes giving rise to these macroscopic effects by characterizing the structures of Pb(II) sorption complexes formed on goethite (alpha-FeOOH) in the presence of carbonate using in situ Pb L(III)-EXAFS and ATR-FTIR spectroscopies. Bond valence and structural constraints are applied to develop mineral surface site-specific models for Pb sorption. Under all conditions studied (pH 5-7, Gamma(Pb)=0.4-4µmol/m(2), and P(CO(2))=0-1 atm), Pb(II) forms predominantly inner-sphere edge-sharing (bidentate and/or tridentate) complexes with Fe(O,OH)(6) octahedra (R(Pb-Fe) approximately 3.3 Å). Corner-sharing complexes (R(Pb-Fe) approximately 3.9 Å) are observed only in low pH (5) samples (P(CO(2)) 0-1 atm). Consistent with this pH sensitivity, site-specific analyses suggest that the relative abundance of corner-sharing sites reflects changes in the proton affinity of triply coordinated sites on the goethite (110) surface as suggested previously. FTIR results suggest the existence of ternary surface complexes in which carbonate groups bond to Pb as monodentate ligands. EXAFS data indicate that these ternary complexes are bound to the surface through Pb, forming metal-bridged (Type A) complexes. Findings are summarized as structural models and corresponding mineral surface site-specific chemical reactions. Copyright 2000 Academic Press.

    View details for PubMedID 11254287

  • XAFS study of copper model compounds and copper(II) sorption on amorphous SiO2, α-Al2O3, and anatase American Mineralogist Cheah, S.-F., Brown, Jr., G. E., Parks, G. A. 2000; 85: 118-132
  • Spectroscopic study of the reaction of Cr(VI)aqueous with Fe3O4 (111) surfaces Surface Science Kendelewicz, T., Liu, P., Doyle, C. S., Brown, Jr., G. E. 2000; 469: 144-163
  • Reaction of CO2 with MgO(100) surfaces SURFACE REVIEW AND LETTERS Carrier, X., Doyle, C. S., Kendelewicz, T., Brown, G. E. 1999; 6 (6): 1237-1245
  • Reaction of water with clean surfaces of MnO(100) SURFACE REVIEW AND LETTERS Kendelewicz, T., Doyle, C. S., Carrier, X., Brown, G. E. 1999; 6 (6): 1255-1263
  • A synchrotron study of the growth of vanadium oxide on Al2O3(0001) SURFACE SCIENCE Biener, J., Baumer, M., Madix, R. J., Liu, P., Nelson, E. J., Kendelewicz, T., Brown, G. E. 1999; 441 (1): 1-9
  • Outer-sphere adsorption of Pb(II)EDTA on goethite GEOCHIMICA ET COSMOCHIMICA ACTA Bargar, J. R., Persson, P., Brown, G. E. 1999; 63 (19-20): 2957-2969
  • Structural investigation of platinum solubility in silicate glasses AMERICAN MINERALOGIST Farges, F., Neuville, D. R., Brown, G. E. 1999; 84 (10): 1562-1568
  • Structure and composition of copper(II)-2,2 '-bipyridine sorption complexes on amorphous SiO2 GEOCHIMICA ET COSMOCHIMICA ACTA Cheah, S. F., Brown, G. E., Parks, G. A. 1999; 63 (19-20): 3229-3246
  • Ambient-temperature synthesis, evolution, and characterization of cobalt-aluminum hydrotalcite-like solids CLAYS AND CLAY MINERALS Thompson, H. A., Parks, G. A., Brown, G. E. 1999; 47 (4): 425-438
  • Dynamic interactions of dissolution, surface adsorption, and precipitation in an aging cobalt(II)-clay-water system GEOCHIMICA ET COSMOCHIMICA ACTA Thompson, H. A., Parks, G. A., Brown, G. E. 1999; 63 (11-12): 1767-1779
  • Grazing-incidence XAFS studies of aqueous Zn(II) on sapphire single crystals JOURNAL OF SYNCHROTRON RADIATION Trainor, T. P., Fitts, J. P., Grolimund, D., Bargar, J. R., Brown, G. E. 1999; 6: 618-620

    View details for Web of Science ID 000081221700178

    View details for PubMedID 15263400

  • Utility of EXAFS in characterization and speciation of mercury-bearing mine wastes JOURNAL OF SYNCHROTRON RADIATION Kim, C. S., Rytuba, J. J., Brown, G. E. 1999; 6: 648-650

    View details for Web of Science ID 000081221700188

    View details for PubMedID 15263410

  • Combined EXAFS and FTIR investigation of sulfate and carbonate effects on Pb(II) sorption to goethite (alpha-FeOOH) JOURNAL OF SYNCHROTRON RADIATION Ostergren, J. D., Bargar, J. R., Brown, G. E., Parks, G. A. 1999; 6: 645-647

    View details for Web of Science ID 000081221700187

    View details for PubMedID 15263409

  • Surface structure of MBE-grown alpha-Fe2O3(0001) by intermediate-energy X-ray photoelectron diffraction SURFACE SCIENCE Thevuthasan, S., Kim, Y. J., Yi, S. I., Chambers, S. A., Morais, J., Denecke, R., Fadley, C. S., Liu, P., Kendelewicz, T., Brown, G. E. 1999; 425 (2-3): 276-286
  • X-ray absorption and photoemission study of the adsorption of aqueous Cr(VI) on single crystal hematite and magnetite surfaces SURFACE SCIENCE Kendelewicz, T., Liu, P., Doyle, C. S., Brown, G. E., Nelson, E. J., Chambers, S. A. 1999; 424 (2-3): 219-231
  • XAFS determination of the chemical form of lead in smelter-contaminated soils and mine tailings: Importance of adsorption processes AMERICAN MINERALOGIST Morin, G., Ostergren, J. D., Juillot, F., Ildefonse, P., CALAS, G., Brown, G. E. 1999; 84 (3): 420-434
  • Sorption of Co(II) on Metal Oxide Surfaces. Journal of colloid and interface science Towle, S. N., Bargar, J. R., Brown, G. E., Parks, G. A. 1999; 217 (2): 312-321

    Abstract

    We have characterized the adsorption of Co(II) on the (0001) and (1102) surfaces of alpha-Al(2)O(3) single crystals under ambient conditions using polarization-dependent grazing-incidence X-ray absorption fine structure spectroscopy, in combination with bond valence modeling. Co(II) ions were found to be adsorbed on both surfaces in an inner-sphere fashion. Adions were found to adsorb dominantly in a tridentate fashion (i.e., bonded to three surface oxygens) on the (0001) surface and dominantly in a tetradentate fashion on the (1102) surface. Based on EXAFS results and bond valence analysis, plausible surface complexation reactions for Co(II) sorption on these two surfaces can be written as represent surface water molecules, hydroxyl groups, and oxygens bonded to one, two, and three Al cations, respectively. Copyright 1999 Academic Press.

    View details for PubMedID 10469539

  • Sorption of Co(II) on Metal Oxide Surfaces. Journal of colloid and interface science Towle, S. N., Brown, G. E., Parks, G. A. 1999; 217 (2): 299-311

    Abstract

    We have examined the molecular-scale details of aqueous Co(II) surface complexes and the types of surface sites to which these complexes bind on the (110) and (001) surfaces of single-crystal TiO(2) (rutile) using polarization-dependent grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy under ambient conditions in a humid atmosphere. On both surfaces, Co(II) adsorbs at sites corresponding to Ti-equivalent positions in an extension of the rutile structure. This result suggests that even if different crystallographic surfaces of metal oxides have strongly differing adsorption properties for gaseous species in ultra-high vacuum, they can have similar properties for adsorption of metal ions in aqueous solution, probably due to the tendency of liquid water to heal defects and satisfy the bonding requirements of coordinatively unsaturated surface atoms. Using a bond valence approach in combination with the XAFS results, we have proposed specific surface reactions for sorption of Co(II) on the (110) and (001) rutile surfaces as a function of pH and Co surface concentration. No evidence was found for well-ordered Co(II)-hydroxide-like precipitates that would show Co-Co pair correlations, or for Co-Ti pair correlations similar to those in anatase, as have been observed in other studies. These results demonstrate the utility of GI-XAFS spectroscopy on adsorbed metal ions at submonolayer surface coverages for determining the types of reactive sorption sites on metal oxide surfaces. Copyright 1999 Academic Press.

    View details for PubMedID 10469538

  • Structure and Bonding of Cu(II)-Glutamate Complexes at the gamma-Al(2)O(3)-Water Interface. Journal of colloid and interface science Fitts, J. P., Persson, P., Brown, G. E., Parks, G. A. 1999; 220 (1): 133-147

    Abstract

    Thecomposition and mode of attachment of Cu(II) complexes at the gamma-Al(2)O(3)-water interface in suspensions containing a simple amino acid (glutamate) were characterized with EXAFS and FTIR spectroscopies. The spectroscopic results indicate that two types of Cu(II)-glutamate-alumina interactions are primarily responsible for Cu(II) and glutamate uptake between pH 4 and 9. In acidic suspensions of alumina, glutamate forms a bridge between Cu(II) ions and the (hydr)oxide surface (Type B complex). In this Type B surface complex, Cu(II) is bonded to amino acid headgroups (i.e., (+)H(3)NCHRCOO(-)) of two glutamate molecules. Spectroscopic and ionic strength dependent uptake results are combined to propose that the nonbonded side chain carboxylate groups of this complex are attracted to the oxide surface through long-range forces, leading to enhanced Cu(II) uptake relative to the glutamate-free system. In alkaline suspensions the relative amount of surface-bound Cu(II) complexed by glutamate decreases, and a direct Cu(II)-surface bond becomes the dominant mode of attachment (Type A complex). These surface complexes differ markedly from the species found in the alumina-free Cu(II)-glutamate aqueous system under similar solution conditions, where Cu(H(2)O)(2+)(6) and Cu(glutamate)(2-)(2) are the dominant species in acidic and alkaline solutions, respectively. Based on these spectroscopic results, surface complexation reactions are proposed for the Cu(II) and glutamate ternary interactions with the alumina surface in this system. Similarities between the results of this study and Cu(II) uptake behavior and complexation in the presence of natural organic material (NOM) indicate that Cu(II)-glutamate interactions mimic those in more complex Cu(II)-NOM-mineral-water systems. Copyright 1999 Academic Press.

    View details for PubMedID 10550251

  • Metal oxide surfaces and their interactions with aqueous solutions and microbial organisms CHEMICAL REVIEWS Brown, G. E., Henrich, V. E., Casey, W. H., Clark, D. L., Eggleston, C., Felmy, A., Goodman, D. W., Gratzel, M., Maciel, G., McCarthy, M. I., Nealson, K. H., Sverjensky, D. A., Toney, M. F., Zachara, J. M. 1999; 99 (1): 77-174
  • XAFS and XSW studies of the distribution and chemical speciation of Pb sorbed to biofilms on α-Al2O3 and α-FeOOH surfaces Journal of Synchrotron Radiation Templeton, A. S., Ostergren, J. D., Trainor, T. P., Foster, A. L., Traina, S. J., Spormann, A., Brown, Jr., G. E. 1999; 6: 642-644
  • Adsorption of Au on iron oxy-hydroxides using Au L3-edge XAFS spectroscopy Journal of Synchrotron Radiation Berrodier, I., Farges, F., Benedetti, M., Brown, Jr., G. E. 1999; 6: 651-652
  • Quantitative lead speciation in selected mine tailings from Leadville, CO Environmental Science & Technology Ostergren, J. D., Brown, Jr., G. E., Parks, G. A., Tingle, T. N. 1999; 33: 1627-1636
  • Al-XANES studies of aluminum-rich surface phases in the soil environment Journal of Synchrotron Radiation Doyle, C. S., Traina, S. J., Ruppert, H., Kendelewicz, T., Rehr, J. J., Brown, Jr., G. E. 1999; 6: 621-623
  • Grazing-incidence XAFS investigations of Cu(II) sorption products at the oxide-water interface Journal of Synchrotron Radiation Fitts, J. P., Trainor, T. P., Grolimund, D., Bargar, J. R., Parks, G. A., Brown, Jr., G. E. 1999; 6: 627-629
  • Identification of Cr species at the solution-hematite interface after Cr(VI)-Cr(III) reduction using GI-XAFS and Cr L-edge NEXAFS Journal of Synchrotron Radiation Grolimund, D., Kendelewicz, T., Trainor, T. P., Liu, P., Fitts, J. P., Chambers, S. A., Brown, Jr., G. E. 1999; 6: 612-614
  • XAFS spectroscopy study of Cu(II) sorption on amorphous SiO2 and gamma-Al2O3: Effect of substrate and time on sorption complexes JOURNAL OF COLLOID AND INTERFACE SCIENCE Cheah, S. F., Brown, G. E., Parks, G. A. 1998; 208 (1): 110-128
  • Reaction of water vapor with alpha-Al2O3(0001) and alpha-Fe2O3(0001) surfaces: synchrotron X-ray photoemission studies and thermodynamic calculations SURFACE SCIENCE Liu, P., Kendelewicz, T., Brown, G. E., Nelson, E. J., Chambers, S. A. 1998; 417 (1): 53-65
  • Reaction of water with vacuum-cleaved CaO(100) surfaces: an X-ray photoemission spectroscopy study SURFACE SCIENCE Liu, P., Kendelewicz, T., Brown, G. E., Parks, G. A., Pianetta, P. 1998; 416 (1-2): 326-340
  • Reaction of water with MgO(100) surfaces: Part III. X-ray standing wave studies SURFACE SCIENCE Liu, P., Kendelewicz, T., Nelson, E. J., Brown, G. E. 1998; 415 (1-2): 156-169
  • Reaction of water with MgO(100) surfaces. Part I: Synchrotron X-ray photoemission studies of low-defect surfaces SURFACE SCIENCE Liu, P., Kendelewicz, T., Gordon, G. E., Parks, G. A. 1998; 412-13: 287-314
  • Reaction of water with MgO(100) surfaces. Part II: Synchrotron photoemission studies of defective surfaces SURFACE SCIENCE Liu, P., Kendelewicz, T., Brown, G. E. 1998; 412-13: 315-332
  • Interaction of sodium overlayers with the PbS(100) (galena) surface: evidence for a Na <-> Pb exchange reaction SURFACE SCIENCE Kendelewicz, T., Liu, P., Brown, G. E., Nelson, E. J. 1998; 411 (1-2): 10-22
  • X-ray absorption fine-structure spectroscopy study of photocatalyzed, heterogeneous As(III) oxidation on kaolin and anatase ENVIRONMENTAL SCIENCE & TECHNOLOGY Foster, A. L., Brown, G. E., Parks, G. A. 1998; 32 (10): 1444-1452
  • Quantitative arsenic speciation in mine tailings using X-ray absorption spectroscopy AMERICAN MINERALOGIST Foster, A. L., Brown, G. E., Tingle, T. N., Parks, G. A. 1998; 83 (5-6): 553-568
  • Atomic geometry of the PbS(100) surface SURFACE SCIENCE Kendelewicz, T., Liu, P., Brown, G. E., Nelson, E. J. 1998; 395 (2-3): 229-238
  • XAFS Spectroscopy Study of Cu(II) Sorption on Amorphous SiO2 and gamma-Al2O3: Effect of Substrate and Time on Sorption Complexes. Journal of colloid and interface science Cheah, S. F., Brown, G. E., Parks, G. A. 1998; 208 (1): 110-128

    Abstract

    We have used X-ray absorption fine structure (XAFS) spectroscopy to investigate Cu(II) sorption complexes on high surface area amorphous silica (am-SiO2) and gamma-Al2O3. For Cu(II) on gamma-Al2O3, analysis of XAFS data collected after a solution-solid total contact time of 80-170 h showed that monomeric Cu(II) species predominate at surface coverages of 0.007 and 0.05 µmol m-2. Cu(II) on the gamma-Al2O3 surface has aluminum second neighbors at about 2.8 Å. Geometrical considerations indicate that this distance is consistent with models of Cu(II) binding to the gamma-Al2O3 surface in inner-sphere bidentate or monodentate modes on Al(O,OH)6 octahedra. For Cu(II) sorbed on am-SiO2, analysis of XAFS data collected after a solution-solid total contact time of 80-110 h showed that a dimeric Cu(II)-surface complex predominates, along with a minority monomeric Cu(II) surface species, at 0.03 and 0.05 µmol m-2. The XAFS-derived Cu-Si distance is in the range of 2.98 to 3.05 Å, suggesting that Cu(II) binds to am-SiO2 in an inner-sphere, monodentate fashion. XAFS spectra of Cu(II) sorbed on am-SiO2 collected after 20-30 h total contact time are quantitatively different from those collected after 80-90 h contact time. Analyses of these spectra indicate that the ratio of dimeric to monomeric Cu(II) surface complexes has increased with contact time. A discussion of the processes responsible for the different Cu(II) complexes on am-SiO2 and gamma-Al2O3 is presented. Copyright 1998 Academic Press.

    View details for PubMedID 9820755

  • Surface complexation of Pb(II) at oxide-water interfaces: III. XAFS determination of Pb(II) and Pb(II)-chloro adsorption complexes on goethite and alumina GEOCHIMICA ET COSMOCHIMICA ACTA Bargar, J. R., Brown, G. E., Parks, G. A. 1998; 62 (2): 193-207
  • Abiotic selenium redox transformations in the presence of Fe(II,III) oxides SCIENCE Myneni, S. C., TOKUNAGA, T. K., Brown, G. E. 1997; 278 (5340): 1106-1109
  • Prediction of extended x-ray-absorption fine-structure spectra from molecular interaction models: Na+(H2O)(n)-MgO (100) interface PHYSICAL REVIEW B McCarthy, M. I., Schenter, G. K., CHACONTAYLOR, M. R., Rehr, J. J., Brown, G. E. 1997; 56 (15): 9925-9936
  • Differential redox and sorption of Cr(III/VI) on natural silicate and oxide minerals: EXAFS and XANES results GEOCHIMICA ET COSMOCHIMICA ACTA Peterson, M. L., Brown, G. E., Parks, G. A., Stein, C. L. 1997; 61 (16): 3399-3412
  • Ti K-edge XANES studies of Ti coordination and disorder in oxide compounds: Comparison between theory and experiment PHYSICAL REVIEW B Farges, F., Brown, G. E., Rehr, J. J. 1997; 56 (4): 1809-1819
  • Surface complexation of Pb(II) at oxide-water interfaces .1. XAFS and bond-valence determination of mononuclear and polynuclear Pb(II) sorption products on aluminum oxides GEOCHIMICA ET COSMOCHIMICA ACTA Bargar, J. R., Brown, G. E., Parks, G. A. 1997; 61 (13): 2617-2637
  • Surface complexation of Pb(II) at oxide-water interfaces .2. XAFS and bond-valence determination of mononuclear Pb(II) sorption products and surface functional groups on iron oxides GEOCHIMICA ET COSMOCHIMICA ACTA Bargar, J. R., Brown, G. E., Parks, G. A. 1997; 61 (13): 2639-2652
  • XAFS spectroscopic study of uranyl coordination in solids and aqueous solution AMERICAN MINERALOGIST Thompson, H. A., Brown, G. E., Parks, G. A. 1997; 82 (5-6): 483-496
  • Surface passivation of magnetite by reaction with aqueous Cr(VI): XAFS and TEM results ENVIRONMENTAL SCIENCE & TECHNOLOGY Peterson, M. L., White, A. F., Brown, G. E., Parks, G. A. 1997; 31 (5): 1573-1576
  • Coordination chemistry of titanium(IV) in silicate glasses and melts .4. XANES studies of synthetic and natural volcanic glasses and tektites at ambient temperature and pressure GEOCHIMICA ET COSMOCHIMICA ACTA Farges, F., Brown, G. E. 1997; 61 (9): 1863-1870
  • Ti K-edge XANES studies of oxides: Theory vs. experiment JOURNAL DE PHYSIQUE IV Farges, F., Brown, G. E., Rehr, J. J. 1997; 7 (C2): 191-193
  • Oxidation state, local structure, and ab-initio XAFS modeling of chromium in contaminated soils and model compounds JOURNAL DE PHYSIQUE IV Peterson, M. L., Brown, G. E., Parks, G. A. 1997; 7 (C2): 781-783
  • Coordination of actinides in silicate melts JOURNAL DE PHYSIQUE IV Farges, F., Brown, G. E., Wu, Z. 1997; 7 (C2): 1009-1010
  • Selenium transport between ponded waters and sediments Environmental Science & Technology Tokunaga, T. K., Brown, Jr., G. E., Pickering, I. J., Sutton, S. R., Bajt, S. 1997; 31: 1419-1425
  • XAFS and Bond-Valence Determination of the Structures and Compositions of Surface Functional Groups and Pb(II) and Co(II) Sorption Products on Single-Crystal alpha-Al2O3 Journal of colloid and interface science Bargar, J. R., Towle, S. N., Brown, G. E., Parks, G. A. 1997; 185 (2): 473-92

    Abstract

    The structures and compositions of Pb(II) adsorption complexes and surface binding sites on alpha-Al2O3 (0001) and (1&1macr;02) surfaces were investigated in the presence of water using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy. Pb(II) ions were found to adsorb in an inner-sphere mode on alpha-Al2O3 (1&1macr;02) but as outer-sphere complexes on alpha-Al2O3 (0001). The distance between the outer-sphere complexes and the surface places useful constraints on double-layer properties of water. A bond-valence model is described that relates the reactivities of surface functional groups and adsorption complexes to their molecular structures and compositions, and places constraints on the stoichiometries of adsorption reactions, including proton release. The EXAFS and modeling results suggest that Pb(II) and Co(II) ions bond to [AlAlAl-->O-1/2--> and [Al-OH+1/22] surface functional groups. In contrast, [AlAl > OH] groups complex Co(II) but not Pb(II). The results indicate the importance of using structurally defined surface sites to describe reactions at oxide-water interfaces.

    View details for PubMedID 9028903

  • Surface Precipitation of Co(II)(aq) on Al2O3 Journal of colloid and interface science Towle, S. N., Bargar, J. R., Brown, G. E., Parks, G. A. 1997; 187 (1): 62-82

    Abstract

    Surface precipitation is an important process in many areas of science and technology, including modeling contaminant segregation from groundwater to solid phases and dispersion of active phases on catalyst supports. XAFS, TEM, and XPS measurements of Co(II) sorbed on Al2O3 demonstrate that surface precipitates have formed from solutions that are undersaturated with respect to any known bulk solid phase. The precipitates have a structure similar to that of Co(OH)2(s), but are disordered and have a high concentration of Co vacancies. The data plus thermodynamic reasoning have been used to analyze the plausibility of various models for surface precipitation and to show that for Co(II)/Al2O3 it occurs by forming a double-hydroxide phase containing substrate-derived Al(III) ions. This idea was corroborated by mixing aqueous solutions of Al(III) and Co(II) at the pH and concentration of the sorption samples, forming a stable colloidal precipitate that is less soluble than either Al(OH)3 or Co(OH)2. The Co XAFS of this material was similar to that of the sorption samples. Successful quantitative models of metal ion transport in groundwater need to include the possibility of forming ternary and higher order precipitates that include ions derived from sparingly soluble solids. For catalyst impregnation, surface coprecipitation can prevent production of a well-dispersed precursor material.

    View details for PubMedID 9245316

  • Ca X-ray absorption spectroscopy of C-S-H and some model compounds ADVANCES IN CEMENT RESEARCH Kirkpatrick, R. J., Brown, G. E., Xu, N., Cong, X. D. 1997; 9 (33): 31-36
  • Quantitative determination of chromium valence in environmental samples using XAFS spectroscopy AQUEOUS CHEMISTRY AND GEOCHEMISTRY OF OXIDES, OXYHYDROXIDES, AND RELATED MATERIALS Peterson, M. L., Brown, G. E., Parks, G. A. 1997; 432: 75-80
  • The effect of substrate type and 2,2'-bipyridine on the sorption of copper(II) on silica and alumina AQUEOUS CHEMISTRY AND GEOCHEMISTRY OF OXIDES, OXYHYDROXIDES, AND RELATED MATERIALS Cheah, S. F., Brown, G. E., Parks, G. A. 1997; 432: 231-236
  • XAFS study of Pb(II)-chloro- and Hg(II)-chloro- ternary complexes on goethite Journal de Physique IV, Colloque C Bargar, J. R., Persson, P., Brown, Jr., G. E. 1997; 2: 825-826
  • Structure, composition, and reactivity of Pb(II) and Co(II) sorption products and surface functional groups on single-crystal α-Al2O3 Journal of Colloid and Interface Science Bargar, J. R., Towle, S. N., Brown, Jr., G. E., Parks, G. A. 1997; 185: 473-493
  • Co(II) sorption at the calcite-water interface .1. X-ray photoelectron spectroscopic study GEOCHIMICA ET COSMOCHIMICA ACTA Xu, N., Hochella, M. F., Brown, G. E., Parks, G. A. 1996; 60 (15): 2801-2815
  • X-ray absorption spectroscopy of Co(II) sorption complexes on quartz (alpha-SiO2) and rutile (TiO2) GEOCHIMICA ET COSMOCHIMICA ACTA ODAY, P. A., CHISHOLMBRAUSE, C. J., Towle, S. N., Parks, G. A., Brown, G. E. 1996; 60 (14): 2515-2532
  • An empirical model for the anharmonic analysis of high-temperature XAFS spectra of oxide compounds with applications to the coordination environment of Ni in NiO, gamma-Ni2SiO4 and Ni-bearing Na-disilicate glass and melt CHEMICAL GEOLOGY Farges, F., Brown, G. E. 1996; 128 (1-4): 93-106
  • Direct XAFS evidence for heterogeneous redox reaction at the aqueous chromium/magnetite interface COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS Peterson, M. L., Brown, G. E., Parks, G. A. 1996; 107: 77-88
  • Outer-sphere lead(II) adsorbed at specific surface sites on single crystal α-alumina Geochimica et Cosmochimica Acta Bargar, J. R., Towle, S. N., Brown, Jr., G. E., Parks, G. A. 1996; 60: 3541-3547
  • Coordination chemistry of titanium(IV) in silicate glasses and melts. I. XAFS study of Ti coordination in oxide model compounds Geochimica et Cosmochimica Acta Farges, F., Brown, Jr., G. E., Rehr, J. J. 1996; 60: 3023-3038
  • Coordination chemistry of titanium(IV) in silicate glasses and melts. Part III. Glasses and melts from ambient to high temperatures Geochimica et Cosmochimica Acta Farges, F., Brown, Jr., G. E., Navrotsky, A., Gan, H., Rehr, J.J. 1996; 60: 3055-3065
  • X-ray absorption spectroscopy studies of selenium transformations in ponded sediments Soil Science Society of America Journal Tokunaga, T. K., Pickering, I. J., Brown, Jr., G. E. 1996; 60: 781-790
  • Coordination chemistry of titanium(IV) in silicate glasses and melts. Part II. Glasses at ambient temperature and pressure Geochimica et Cosmochimica Acta Farges, F., Brown, Jr., G. E., Navrotsky, A., Gan, H., Rehr, J.J. 1996; 60: 3039-3053
  • X-RAY-ABSORPTION SPECTROSCOPIC STUDIES OF CADMIUM AND SELENITE ADSORPTION ON ALUMINUM-OXIDES LANGMUIR Papelis, C., Brown, G. E., Parks, G. A., Leckie, J. O. 1995; 11 (6): 2041-2048
  • CATIONS IN GLASSES UNDER AMBIENT AND NON-AMBIENT CONDITIONS NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS CALAS, G., Brown, G. E., Farges, F., Galoisy, L., Itie, J. P., Polian, A. 1995; 97 (1-4): 155-161
  • XAFS STUDY OF CO(II) SORPTION AT THE ALPHA-AL2O3-WATER INTERFACE PHYSICA B-CONDENSED MATTER Towle, S. N., BARGAR, J. A., Persson, P., Brown, G. E., Parks, G. A. 1995; 208 (1-4): 439-440
  • XAFS STUDY OF CO(II) AT THE ZNO-AQUEOUS AND ZNS-AQUEOUS INTERFACES PHYSICA B-CONDENSED MATTER Persson, P., Parks, G. A., Brown, G. E. 1995; 208 (1-4): 453-454
  • XAFS STUDY OF PB(II) SORPTION AT THE ALPHA-AL2O3-WATER INTERFACE PHYSICA B-CONDENSED MATTER Bargar, J. R., Brown, G. E., Parks, G. A. 1995; 208 (1-4): 455-456
  • AL AND SI K-ABSORPTION EDGES OF AL2SIO5 POLYMORPHS USING THE NEW YB66 SOFT-X-RAY MONOCHROMATOR PHYSICA B-CONDENSED MATTER Froba, M., Wong, J., Rowen, M., Brown, G. E., Tanaka, T., Rek, Z. 1995; 208 (1-4): 555-556
  • LOW AND AMBIENT-TEMPERATURE XAFS STUDY OF U(VI) IN SOLIDS AND AQUEOUS-SOLUTION PHYSICA B-CONDENSED MATTER Thompson, H. A., Brown, G. E., Parks, G. A. 1995; 208 (1-4): 167-168
  • NEW OPPORTUNITIES IN 1-2-KEV SPECTROSCOPY PHYSICA B-CONDENSED MATTER Wong, J., Rek, Z. U., Rowen, M., Tanaka, T., Schafers, F., Muller, B., George, G. N., Pickering, I. J., Via, G., DeVries, B., Brown, G. E., Froba, M. 1995; 208 (1-4): 220-222
  • SURFACE EXAFS AND X-RAY STANDING-WAVE STUDY OF THE CLEAVED CAO(100) SURFACE PHYSICA B-CONDENSED MATTER Kendelewicz, T., Liu, P., LABIOSA, W. B., Brown, G. E. 1995; 208 (1-4): 441-442
  • Intracrystalline distribution of nickel in San Carlos olivine: An EXAFS study American Mineralogist Galoisy, L., Calas, G., Brown, Jr., G. E. 1995; 80: 1089-1092
  • X-ray scattering and x-ray spectroscopy studies of silicate melts STRUCTURE, DYNAMICS AND PROPERTIES OF SILICATE MELTS Brown, G. E., Farges, F., CALAS, G. 1995; 32: 317-410
  • SORPTION AT MINERAL WATER INTERFACES - MACROSCOPIC AND MICROSCOPIC PERSPECTIVES MINERAL SURFACES Brown, G. E., Parks, G. A., ODAY, P. A. 1995; 5: 129-183
  • Coordination change around 2 wt% Ni in Na2Si2O5 glass/melt systems Physica B Farges, F., Brown, Jr., G. E., Calas, G., Galoisy, L., Waychunas, G. A. 1995; 208/209: 381-382
  • Adsorption and local environment of Co(II) at the zinc oxide- and zinc sulfide-aqueous interfaces Langmuir Persson, P., Parks, G. A., Brown, Jr., G. E. 1995; 11: 3782-3794
  • X-ray absorption spectroscopy of selenium transformations in Kesterson Reservoir soils Environmental Science & Technology Pickering, I.J., Brown, Jr., G. E., Tokunaga, T.K. 1995; 29: 2456-2459
  • Effect of surface structure on the adsorption of Co(II) on alpha-Al2O3: A glancing angle XAFS study STRUCTURE AND PROPERTIES OF INTERFACES IN CERAMICS Towle, S. N., Bargar, J. R., Brown, G. E., Parks, G. A., Barbee, T. W. 1995; 357: 23-28
  • X-RAY-ABSORPTION SPECTROSCOPY OF COBALT(II) MULTINUCLEAR SURFACE COMPLEXES AND SURFACE PRECIPITATES ON KAOLINITE JOURNAL OF COLLOID AND INTERFACE SCIENCE ODAY, P. A., Brown, G. E., Parks, G. A. 1994; 165 (2): 269-289
  • MOLECULAR-STRUCTURE AND BINDING-SITES OF COBALT(II) SURFACE COMPLEXES ON KAOLINITE FROM X-RAY-ABSORPTION SPECTROSCOPY CLAYS AND CLAY MINERALS ODAY, P. A., Parks, G. A., Brown, G. E. 1994; 42 (3): 337-355
  • EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE (EXAFS) ANALYSIS OF DISORDER AND MULTIPLE-SCATTERING IN COMPLEX CRYSTALLINE SOLIDS JOURNAL OF THE AMERICAN CHEMICAL SOCIETY ODAY, P. A., Rehr, J. J., Zabinsky, S. I., Brown, G. E. 1994; 116 (7): 2938-2949
  • Structural transformations in Ni-bearing Na2Si2O5 glass and melt Geophysical Research Letters Farges, F., Brown, Jr., G. E., Calas, G., Galoisy, L., Waychunas, G. A. 1994; 21: 1931-1934
  • FLUORESCENCE YIELD XANES AND EXAFS EXPERIMENTS - APPLICATION TO HIGHLY DILUTE AND SURFACE SAMPLES ADVANCES IN X-RAY ANALYSIS, VOL 37 WAYCHUNAS, G. A., Brown, G. E. 1994; 37: 607-617
  • New XAFS spectroscopic investigations in the 1-2 keV region Solid State Communications Wong, J., George, G. N., Pickering, I. J., Rek, Z. U., Rowen, M., Tanaka, T., Via, G. H., DeVries, B., Vaughan, D. E. W., Brown, Jr., G. E. 1994; 92: 559-562
  • X-ray spectroscopic study of the structural environment of Zr in two inosilicates from Cameroon: implications for substitution mechanisms and Zr-partitioning American Mineralogist Farges, F., Brown, Jr., G. E., Velde, D. 1994; 79: 838-847
  • HIGH-TEMPERATURE XAS STUDY OF FE2SIO4 LIQUID - REDUCED COORDINATION OF FERROUS IRON SCIENCE Jackson, W. E., DeLeon, J. M., Brown, G. E., WAYCHUNAS, G. A., Conradson, S. D., Combes, J. M. 1993; 262 (5131): 229-233

    Abstract

    X-ray absorption spectroscopy (XAS) of Fe(2+) in Fe(2)SiO(4) liquid at 1575 kelvin and 10(-4) gigapascal (1 bar) shows that the Fe(2+) -O bond length is 1.98 +/- 0.02 angstroms compared with approximately 2.22 angstroms in crystalline Fe(2)SiO(4) (fayalite) at the melting point (1478 kelvin), which indicates a decrease in average Fe(2+) coordination number from six in fayalite to four in the liquid. Anharmonicity in the liquid was accounted for using a data analysis procedure. This reduction in coordination number is similar to that observed on the melting of certain ionic salts. These results are used to develop a model of the medium-range structural environment of Fe(2+) in olivine-composition melts, which helps explain some of the properties of Fe(2)SiO(4) liquid, including density, viscosity, and the partitioning of iron and nickel between silicate melts and crystalline olivines. Some of the implications of this model for silicate melts in the Earth's crust and mantle are discussed.

    View details for Web of Science ID A1993MA66500031

    View details for PubMedID 17841870

  • LOCAL ENVIRONMENT AROUND GOLD(III) IN AQUEOUS CHLORIDE SOLUTIONS - AN EXAFS SPECTROSCOPY STUDY GEOCHIMICA ET COSMOCHIMICA ACTA Farges, F., SHARPS, J. A., Brown, G. E. 1993; 57 (6): 1243-1252
  • KINETICS AND MECHANISM OF LIGAND-EXCHANGE OF AU(III), ZN(II), AND CD(II) CHLORIDES IN AQUEOUS-SOLUTION - AN NMR-STUDY FROM 28-98-DEGREES-C GEOCHIMICA ET COSMOCHIMICA ACTA SHARPS, J. A., Brown, G. E., Stebbins, J. F. 1993; 57 (4): 721-731
  • The structure of aperiodic, metamict, (Ca,Th)2Zr2Ti4O14: an EXAFS study of the Zr, Th, and U sites Journal of Materials Research Farges, F., Ewing, R. C., Brown, Jr., G. E. 1993; 8: 1983-1995
  • First XAFS spectra with a YB66 monochromator Synchrotron Radiation News Rowen, M., Rek, Z. U., Wong, J., Tanaka, T., George, G. N., Pickering, I. J., Via, G.H., Brown, Jr., G.E. 1993; 6: 25-27
  • STRUCTURAL ENVIRONMENTS OF INCOMPATIBLE ELEMENTS IN SILICATE GLASS MELT SYSTEMS .2. UIV, UV, AND UVI GEOCHIMICA ET COSMOCHIMICA ACTA Farges, F., Ponader, C. W., CALAS, G., Brown, G. E. 1992; 56 (12): 4205-4220
  • EXAFS SPECTROSCOPIC STUDY OF NEPTUNIUM(V) SORPTION AT THE ALPHA-FEOOH WATER INTERFACE ENVIRONMENTAL SCIENCE & TECHNOLOGY Combes, J. M., CHISHOLMBRAUSE, C. J., Brown, G. E., Parks, G. A., Conradson, S. D., Eller, P. G., Triay, I. R., Hobart, D. E., Meijer, A. 1992; 26 (2): 376-382
  • STRUCTURAL ENVIRONMENTS OF INCOMPATIBLE ELEMENTS IN SILICATE GLASS MELT SYSTEMS .1. ZIRCONIUM AT TRACE LEVELS GEOCHIMICA ET COSMOCHIMICA ACTA Farges, F., Ponader, C. W., Brown, G. E. 1991; 55 (6): 1563-1574
  • SPECIATION OF AQUEOUS GOLD(III) CHLORIDES FROM ULTRAVIOLET VISIBLE ABSORPTION AND RAMAN RESONANCE RAMAN SPECTROSCOPIES GEOCHIMICA ET COSMOCHIMICA ACTA Peck, J. A., Tait, C. D., Swanson, B. I., Brown, G. E. 1991; 55 (3): 671-676
  • X-ray absorption study of lead complexes at α-FeOOH/water interfaces Langmuir Roe, A. L., Hayes, K. F., Chisholm-Brause, C. J., Brown, Jr., G. E., Hodgson, K. O., Parks, G. A., O., Leckie J. 1991; 7: 367-373
  • X-RAY ABSORPTION FINE-STRUCTURE OF SYSTEMS IN THE ANHARMONIC LIMIT X RAYS IN MATERIALS ANALYSIS II : NOVEL APPLICATIONS AND RECENT DEVELOPMENTS DeLeon, J. M., Conradson, S. D., Batistic, I., Bishop, A. R., Raistrick, I., Jackson, W. E., Brown, G. 1991; 1550: 85-96
  • EVIDENCE FOR MULTINUCLEAR METAL-ION COMPLEXES AT SOLID WATER INTERFACES FROM X-RAY ABSORPTION-SPECTROSCOPY NATURE CHISHOLMBRAUSE, C. J., ODAY, P. A., Brown, G. E., Parks, G. A. 1990; 348 (6301): 528-531

    Abstract

    Metals dissolved in natural waters often become sorbed onto oxide or clay minerals, so that prediction of their chemical behaviour and transport properties requires knowledge of the structure and bonding of metal species at the solid/water interface. For many sorption systems, X-ray absorption spectroscopy (XAS) can be used to determine the identity and number of nearest-neighbour atoms and interatomic distances in aqueous complexes on solid surfaces, and thus to identify the dominant type of surface complex and the partitioning mechanism. Here we describe an XAS study of divalent cobalt (Co(II)) complexes sorbed on three different solids, gamma-Al2O3, rutile (TiO2) and kaolinite (Al2Si2O5(OH)4). We find direct evidence for the presence of multinuclear sorption complexes at surface coverages below one monolayer of Co(II) atoms. Our spectroscopic data reveal distinct differences in the number of coordinating atoms and interatomic distances in the surface complexes formed on each of the solids at the same sorption density. These results suggest that different oxide and clay surfaces influence the structure and properties of aqueous surface complexes, and therefore must be accounted for in models of metal-ion sorption.

    View details for Web of Science ID A1990EL76000058

    View details for PubMedID 2247162

  • SPECTROSCOPIC INVESTIGATION OF PB(II) COMPLEXES AT THE GAMMA-AL2O3 WATER INTERFACE GEOCHIMICA ET COSMOCHIMICA ACTA CHISHOLMBRAUSE, C. J., Hayes, K. F., Roe, A. L., Brown, G. E., Parks, G. A., Leckie, J. O. 1990; 54 (7): 1897-1909
  • SYNCHROTRON RADIATION - APPLICATIONS IN THE EARTH SCIENCES ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES Bassett, W. A., Brown, G. E. 1990; 18: 387-447
  • POLARIZED X-RAY ABSORPTION-SPECTROSCOPY OF METAL-IONS IN MINERALS - APPLICATIONS TO SITE GEOMETRY AND ELECTRONIC-STRUCTURE DETERMINATION PHYSICS AND CHEMISTRY OF MINERALS WAYCHUNAS, G. A., Brown, G. E. 1990; 17 (5): 420-430
  • SPECTROSCOPIC STUDIES OF CHEMISORPTION REACTION-MECHANISMS AT OXIDE-WATER INTERFACES MINERAL-WATER INTERFACE GEOCHEMISTRY Brown, G. E. 1990; 23: 309-363
  • RARE-EARTH ELEMENTS IN SILICATE GLASS MELT SYSTEMS .2. INTERACTIONS OF LA, GD, AND YB WITH HALOGENS GEOCHIMICA ET COSMOCHIMICA ACTA Ponader, C. W., Brown, G. E. 1989; 53 (11): 2905-2914
  • SYNCHROTRON-BASED X-RAY ABSORPTION STUDIES OF CATION ENVIRONMENTS IN EARTH MATERIALS REVIEWS OF GEOPHYSICS Brown, G. E., Parks, G. A. 1989; 27 (4): 519-533
  • RARE-EARTH ELEMENTS IN SILICATE GLASS MELT SYSTEMS .1. EFFECTS OF COMPOSITION ON THE COORDINATION ENVIRONMENTS OF LA, GD, AND YB GEOCHIMICA ET COSMOCHIMICA ACTA Ponader, C. W., Brown, G. E. 1989; 53 (11): 2893-2903
  • INSITU X-RAY ABSORPTION SPECTROSCOPIC STUDIES OF IONS AT OXIDE-WATER INTERFACES CHIMIA Brown, G. E., Parks, G. A., CHISHOLMBRAUSE, C. J. 1989; 43 (9): 248-256
  • INSITU HIGH-TEMPERATURE X-RAY ABSORPTION STUDY OF IRON IN ALKALI SILICATE MELTS AND GLASSES PHYSICA B-CONDENSED MATTER WAYCHUNAS, G. A., Brown, G. E., Jackson, W. E., Ponader, C. W. 1989; 158 (1-3): 67-68
  • XANES AND EXAFS STUDY OF AQUEOUS PB(II) ADSORBED ON OXIDE SURFACES PHYSICA B-CONDENSED MATTER CHISHOLMBRAUSE, C. J., Roe, A. L., Hayes, K. F., Brown, G. E., Parks, G. A., Leckie, J. O. 1989; 158 (1-3): 674-675
  • EXAFS INVESTIGATION OF AQUEOUS CO(II) ADSORBED ON OXIDE SURFACES INSITU PHYSICA B-CONDENSED MATTER CHISHOLMBRAUSE, C. J., Brown, G. E., Parks, G. A. 1989; 158 (1-3): 646-648
  • Mineralogy in two dimensions: Scanning tunneling microscopy of semiconducting minerals with implications for geochemical reactivity American Mineralogist M. F. Hochella, Jr., Eggleston, C. M., Elings, V. B., Parks, G. A., Brown, Jr., G. E., Wu, C. M., Kjoller, K. 1989; 74: 1235-1248
  • Synchrotron radiation: applications in the earth sciences Report of the Mineral Physics Committee, American Geophysical Union Bassett, W. A., Brown, Jr., G. E. 1989: 1-28
  • ASPECTS OF SILICATE SURFACE AND BULK STRUCTURE-ANALYSIS USING X-RAY PHOTOELECTRON-SPECTROSCOPY (XPS) GEOCHIMICA ET COSMOCHIMICA ACTA Hochella, M. F., Brown, G. E. 1988; 52 (6): 1641-1648
  • EVIDENCE FROM X-RAY ABSORPTION FOR NETWORK-FORMING FE-2+ IN MOLTEN ALKALI SILICATES NATURE WAYCHUNAS, G. A., Brown, G. E., Ponader, C. W., Jackson, W. E. 1988; 332 (6161): 251-253
  • ELECTRONIC ABSORPTIONS IN THE HIGH-TC SUPERCONDUCTOR YBA2CU3OX JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Little, W. A., Collman, J. P., Yee, G. T., Holcomb, M. J., McDevitt, J. T., Brown, G. E. 1988; 110 (4): 1301-1302
  • Synchrotron x-ray sources in the earth sciences EOS, Transactions American Geophysical Union Sutton, S. R., Rivers, M. L., Smith, J. V., Brown, Jr., G. E., Jones, K. W. 1988; 69: 1666-1675

    View details for DOI 10.1029/88EO01258

  • INSITU X-RAY ABSORPTION STUDY OF SURFACE COMPLEXES - SELENIUM OXYANIONS ON ALPHA-FEOOH SCIENCE Hayes, K. F., Roe, A. L., Brown, G. E., Hodgson, K. O., Leckie, J. O., Parks, G. A. 1987; 238 (4828): 783-786

    Abstract

    A novel application of x-ray absorption spectroscopy has provided structural information for ions sorbed at oxide-water interfaces. As an example, in situ extended x-ray absorption fine structure (EXAFS) measurements of adsorbed selenate and selenite ions at ah alpha-FeOOH(goethite)-water interface have been performed; these measurements show that selenate forms a weakly bonded, outer-sphere complex and that selenite forms a strongly bonded, inner-sphere complex. The selenite ion is bonded directly to the goethite surface in a bidentate fashion with two iron atoms 3.38 angstroms from the selenium atom. Adsorbed selenate has no iron atom in the second coordination shell of selenium, which indicates retention of its hydration sphere upon sorption. This method provides direct structural information for adsorbed species at solid-liquid interfaces.

    View details for Web of Science ID A1987K681000027

    View details for PubMedID 17814706

  • X-RAY ABSORPTION STUDY OF THE POTASSIUM COORDINATION ENVIRONMENT IN GLASSES FROM THE NAALSI3O8-KALSI3O8 BINARY - STRUCTURAL IMPLICATIONS FOR THE MIXED-ALKALI EFFECT JOURNAL OF NON-CRYSTALLINE SOLIDS Jackson, W. E., Brown, G. E., Ponader, C. W. 1987; 93 (2-3): 311-322
  • PARTITIONING OF FE WITHIN HIGH-PRESSURE SILICATE PEROVSKITE - EVIDENCE FOR UNUSUAL GEOCHEMISTRY IN THE LOWER MANTLE GEOPHYSICAL RESEARCH LETTERS Jackson, W. E., Knittle, E., Brown, G. E., Jeanloz, R. 1987; 14 (3): 224-226
  • X-RAY ABSORPTION SPECTROSCOPIC STUDIES OF SILICATE-GLASSES AND MINERALS PHYSICS AND CHEMISTRY OF MINERALS CALAS, G., Brown, G. E., WAYCHUNAS, G. A., PETIAU, J. 1987; 15 (1): 19-29
  • NEAR-EDGE STRUCTURE OF OXYGEN IN INORGANIC OXIDES: EFFECT OF LOCAL GEOMETRY AND CATION TYPE JOURNAL DE PHYSIQUE Brown, G. E., WAYCHUNAS, G. A., Stohr, J., Sette, F. 1986; 47 (C-8): 163-167
  • ELECTRONIC-STRUCTURE FROM X-RAY K-EDGES IN ZNS-FE AND CUFES2 JOURNAL DE PHYSIQUE Sainctavit, P., CALAS, G., PETIAU, J., KARNATAK, R., Esteva, J. M., Brown, G. E. 1986; 47 (C-8): 411-414
  • EXAFS AND NEXAFS STUDIES OF CATION ENVIRONMENTS IN OXIDE GLASSES JOURNAL DE PHYSIQUE Brown, G. E., WAYCHUNAS, G. A., Ponader, C. W., Jackson, W. E., McKeown, D. A. 1986; 47 (C-8): 140-147
  • LITHIOPHILITE FORMATION IN GRANITIC PEGMATITES - A RECONNAISSANCE EXPERIMENTAL-STUDY OF PHOSPHATE CRYSTALLIZATION FROM HYDROUS ALUMINOSILICATE MELTS AMERICAN MINERALOGIST Shigley, J. E., Brown, G. E. 1986; 71 (3-4): 356-366
  • JAHNS,R.H. MEMORIAL ISSUE - THE MINERALOGY, PETROLOGY, AND GEOCHEMISTRY OF GRANITIC PEGMATITES AND RELATED GRANITIC-ROCKS - INTRODUCTION AMERICAN MINERALOGIST Brown, G. E., Ewing, R. C. 1986; 71 (3-4): 233-238
  • HIGH-TEMPERATURE STRUCTURE AND CRYSTAL-CHEMISTRY OF HYDROUS ALKALI-RICH BERYL FROM THE HARDING PEGMATITE, TAOS COUNTY, NEW-MEXICO AMERICAN MINERALOGIST Brown, G. E., MILLS, B. A. 1986; 71 (3-4): 547-556
  • MINERALOGY AND GEOCHEMICAL EVOLUTION OF THE LITTLE 3 PEGMATITE-APLITE LAYERED INTRUSIVE, RAMONA, CALIFORNIA AMERICAN MINERALOGIST Stern, L. A., Brown, G. E., Bird, D. K., JAHNS, R. H., Foord, E. E., Shigley, J. E., SPAULDING, L. B. 1986; 71 (3-4): 406-427
  • STRUCTURAL MECHANISMS OF ANOMALOUS THERMAL-EXPANSION OF CORDIERITE-BERYL AND OTHER FRAMEWORK SILICATES JOURNAL OF THE AMERICAN CERAMIC SOCIETY Hochella, M. F., Brown, G. E. 1986; 69 (1): 13-18
  • X-RAY K-EDGE ABSORPTION-SPECTRA OF FE MINERALS AND MODEL COMPOUNDS .2. EXAFS PHYSICS AND CHEMISTRY OF MINERALS WAYCHUNAS, G. A., Brown, G. E., Apted, M. J. 1986; 13 (1): 31-47
  • OCCURRENCE AND ALTERATION OF PHOSPHATE MINERALS AT THE STEWART PEGMATITE, PALA DISTRICT, SAN-DIEGO COUNTY, CALIFORNIA AMERICAN MINERALOGIST Shigley, J. E., Brown, G. E. 1985; 70 (3-4): 395-408
  • THE STRUCTURES OF ALBITE AND JADEITE COMPOSITION GLASSES QUENCHED FROM HIGH-PRESSURE GEOCHIMICA ET COSMOCHIMICA ACTA Hochella, M. F., Brown, G. E. 1985; 49 (5): 1137-1142
  • EXAFS AND XANES STUDY OF THE LOCAL COORDINATION ENVIRONMENT OF SODIUM IN A SERIES OF SILICA-RICH GLASSES AND SELECTED MINERALS WITHIN THE NA2O-AL2O3-SIO2 SYSTEM JOURNAL OF NON-CRYSTALLINE SOLIDS McKeown, D. A., WAYCHUNAS, G. A., Brown, G. E. 1985; 74 (2-3): 325-348
  • STRUCTURE AND SPECIFICATION OF IRON COMPLEXES IN AQUEOUS-SOLUTIONS DETERMINED BY X-RAY ABSORPTION-SPECTROSCOPY GEOCHIMICA ET COSMOCHIMICA ACTA Apted, M. J., WAYCHUNAS, G. A., Brown, G. E. 1985; 49 (10): 2081-2089
  • EXAFS STUDY OF THE COORDINATION ENVIRONMENT OF ALUMINUM IN A SERIES OF SILICA-RICH GLASSES AND SELECTED MINERALS WITHIN THE NA2O-AL2O3-SIO2 SYSTEM JOURNAL OF NON-CRYSTALLINE SOLIDS McKeown, D. A., WAYCHUNAS, G. A., Brown, G. E. 1985; 74 (2-3): 349-371
  • STRUCTURE AND VISCOSITY OF RHYOLITIC COMPOSITION MELTS GEOCHIMICA ET COSMOCHIMICA ACTA Hochella, M. F., Brown, G. E. 1984; 48 (12): 2631-2640
  • RAMAN STUDIES OF AL COORDINATION IN SILICA-RICH SODIUM ALUMINOSILICATE GLASSES AND SOME RELATED MINERALS JOURNAL OF NON-CRYSTALLINE SOLIDS McKeown, D. A., GALEENER, F. L., Brown, G. E. 1984; 68 (2-3): 361-378
  • Total electron yield K-XANES and EXAFS investigation of aluminum in amorphous and crystalline aluminosilicates Stanford Synchrotron Radiation Laboratory Report 83/01 Brown, Jr., G. E., Dikmen, F. D., Waychunas, G. A. 1983: 148-149
  • X-RAY K-EDGE ABSORPTION-SPECTRA OF FE MINERALS AND MODEL COMPOUNDS - NEAR-EDGE STRUCTURE PHYSICS AND CHEMISTRY OF MINERALS WAYCHUNAS, G. A., Apted, M. J., Brown, G. E. 1983; 10 (1): 1-9
  • POLYMERIZATION OF SILICATE AND ALUMINATE TETRAHEDRA IN GLASSES, MELTS, AND AQUEOUS-SOLUTIONS .3. LOCAL SILICON ENVIRONMENTS AND INTERNAL NUCLEATION IN SILICATE-GLASSES GEOCHIMICA ET COSMOCHIMICA ACTA DEJONG, B. H., Keefer, K. D., Brown, G. E., Taylor, C. M. 1981; 45 (8): 1291-1308
  • A neutron and x-ray diffraction study of Amelia low albite American Mineralogist Harlow, G. E., Brown, Jr., G. E. 1980; 65: 986-995
  • CRYSTAL-STRUCTURE OF RASVUMITE, KFE2S3 AMERICAN MINERALOGIST Clark, J. R., Brown, G. E. 1980; 65 (5-6): 477-482
  • STRUCTURE OF MINERAL GLASSES .3. NAALSI3O8 SUPERCOOLED LIQUID AT 805-DEGREES-C AND THE EFFECTS OF THERMAL HISTORY GEOCHIMICA ET COSMOCHIMICA ACTA Taylor, M., Brown, G. E., FENN, P. M. 1980; 44 (1): 109-117
  • POLYMERIZATION OF SILICATE AND ALUMINATE TETRAHEDRA IN GLASSES, MELTS, AND AQUEOUS-SOLUTIONS .1. ELECTRONIC-STRUCTURE OF H6SI2O7, H6ALSIO-1-(7), AND H6AL2O-2-(7) GEOCHIMICA ET COSMOCHIMICA ACTA DEJONG, B. H., Brown, G. E. 1980; 44 (3): 491-511
  • POLYMERIZATION OF SILICATE AND ALUMINATE TETRAHEDRA IN GLASSES, MELTS AND AQUEOUS-SOLUTIONS .2. THE NETWORK MODIFYING EFFECTS OF MG2+, K+, NA+, LI+, H+, OH-, F-, CL-, H2O, CO2 AND H3O+ ON SILICATE POLYMERS GEOCHIMICA ET COSMOCHIMICA ACTA DEJONG, B. H., Brown, G. E. 1980; 44 (11): 1627-1642
  • STRUCTURE OF MINERAL GLASSES .1. FELDSPAR GLASSES NAALSI3O8, KALSI3O8, CAAL2SI2O8 GEOCHIMICA ET COSMOCHIMICA ACTA Taylor, M., Brown, G. E. 1979; 43 (1): 61-75
  • HIGH-TEMPERATURE CRYSTAL-CHEMISTRY OF HYDROUS MG-CORDIERITES AND FE-CORDIERITES AMERICAN MINERALOGIST Hochella, M. F., Brown, G. E., Ross, F. K., Gibbs, G. V. 1979; 64 (3-4): 337-351
  • STRUCTURE OF MINERAL GLASSES .2. SIO2-NAALSIO4 JOIN GEOCHIMICA ET COSMOCHIMICA ACTA Taylor, M., Brown, G. E. 1979; 43 (9): 1467-1473
  • STRUCTURE ENERGIES OF THE ALKALI FELDSPARS PHYSICS AND CHEMISTRY OF MINERALS Brown, G. E., FENN, P. M. 1979; 4 (1): 83-100
  • CRYSTAL-STRUCTURE OF HYDROCHLORBORITE, CA2[B3O3(OH)4.OB(OH)3]CL.7H2O, A SEASONAL EVAPORITE MINERAL AMERICAN MINERALOGIST Brown, G. E., Clark, J. R. 1978; 63 (9-10): 814-823
  • CRYSTAL-STRUCTURES AND COMPOSITIONS OF SANIDINE AND HIGH ALBITE IN CRYPTOPERTHITIC INTERGROWTH AMERICAN MINERALOGIST Keefer, K. D., Brown, G. E. 1978; 63 (11-1): 1264-1273
  • CRYSTAL-STRUCTURE OF A SYNTHETIC, COMPOSITIONALLY INTERMEDIATE, HYPERSOLVUS ALKALI FELDSPAR - EVIDENCE FOR NA,K SITE ORDERING ZEITSCHRIFT FUR KRISTALLOGRAPHIE FENN, P. M., Brown, G. E. 1977; 145 (1-2): 124-145
  • HIGH-TEMPERATURE STRUCTURAL STUDY OF P21-AREVERSIBLEA2-A PHASE-TRANSITION IN SYNTHETIC TITANITE, CATISIO5 AMERICAN MINERALOGIST Taylor, M., Brown, G. E. 1976; 61 (5-6): 435-447
  • CATION ORDERING IN NI-MG OLIVINE AMERICAN MINERALOGIST Rajamani, V., Brown, G. E., Prewitt, C. T. 1975; 60 (3-4): 292-299
  • PYROXENES IN SHAW (L-7) CHONDRITE GEOCHIMICA ET COSMOCHIMICA ACTA DODD, R. T., Grover, J. E., Brown, G. E. 1975; 39 (12): 1585-?
  • FRANKDICKSONITE, BAF2, A NEW MINERAL FROM NEVADA AMERICAN MINERALOGIST Radtke, A. S., Brown, G. E. 1974; 59 (9-10): 885-888
  • Crystallography of pigeonites from basaltic vitrophyre 15597 Geochimica et Cosmochimica Acta Brown, Jr., G. E., Wechsler, B. A. 1973: 887-900
  • HIGH-TEMPERATURE CRYSTAL-CHEMISTRY OF HORTONOLITE AMERICAN MINERALOGIST Brown, G. E., Prewitt, C. T. 1973; 58 (7-8): 577-587
  • NEW SINGLE-CRYSTAL HEATER FOR PRECESSION CAMERA AND 4-CIRCLE DIFFRACTOMETER AMERICAN MINERALOGIST Brown, G. E., Sueno, S., Prewitt, C. T. 1973; 58 (7-8): 698-704
  • Apollo 12 clinopyroxenes: high temperature x-ray diffraction studies Proceedings of the 2nd Lunar Science Conference Prewitt, C. T., Brown, Jr., G. E., Papike, J. J. 1972; 1: 59-68
  • COMPARISON OF STRUCTURES OF LOW AND HIGH PIGEONITE JOURNAL OF GEOPHYSICAL RESEARCH Brown, G. E., Papike, J. J., Prewitt, C. T., Sueno, S. 1972; 77 (29): 5778-?
  • CRYSTAL-STRUCTURE OF HIGH CUMMINGTONITE JOURNAL OF GEOPHYSICAL RESEARCH Sueno, S., Brown, G. E., Prewitt, C. T., Papike, J. J. 1972; 77 (29): 5767-?
  • APOLLO-12 CLINOPYROXENES - EXSOLUTION AND EPITAXY EARTH AND PLANETARY SCIENCE LETTERS Papike, J. J., Bence, A. E., Brown, G. E., Prewitt, C. T., Wu, C. H. 1971; 10 (3): 307-?
  • STEREOCHEMISTRY AND ORDERING IN TETRAHEDRAL PORTION OF SILICATES AMERICAN MINERALOGIST Brown, G. E., Gibbs, G. V. 1970; 55 (9-10): 1587-?
  • REFINEMENT OF CRYSTAL STRUCTURE OF OSUMILITE AMERICAN MINERALOGIST Brown, G. E., Gibbs, G. V. 1969; 54 (1-2): 101-?
  • NATURE AND VARIATION IN LENGTH OF SI-O AND AL-O BONDS IN FRAMEWORK SILICATES TRANSACTIONS-AMERICAN GEOPHYSICAL UNION Brown, G. E., Gibbs, G. V., Ribbe, P. H. 1969; 50 (4): 358-?
  • NATURE AND VARIATION IN LENGTH OF SI-O AND AL-O BONDS IN FRAMEWORK SILICATES AMERICAN MINERALOGIST Brown, G. E., Gibbs, G. V., Ribbe, P. H. 1969; 54 (7-8): 1044-?
  • OXYGEN COORDINATION AND SI-O BOND AMERICAN MINERALOGIST Brown, G. E., Gibbs, G. V. 1969; 54 (11-1): 1528-?

Books and Book Chapters


  • From Quanta to the Continuum: Opportunities for Mesoscale Science A Report for the Basic Energy Sciences Advisory Committee, Mesoscale Science Subcommittee Crabtree, G. W., Sarrao, J., Alivisatos, P., Barletta, W., Bates, F., Brown, Jr., G. E., French, R., Green, L., Hemminger, J., Kastner, M., Kay, B., Lewis, J., Ratner, M., Rollett, A., Rubloff, G., Spence, J., Tobias, D., Tranquada, J. U.S. Department of Energy. 2012
  • Nanotextures of aragonite in stromatolites from the quasi-marine Satonda crater lake, Indonesia Tufas and Speleothems: Unraveling the Microbial and Physical Controls Benzerara, K., Meibom, A., Gautier, Q., Kazmierczak, J., Stolarski, J., Lopez-Garcia, P., Menguy, N., Brown, Jr., G. E. edited by Pedley, H. M., Rogerson, M. Geological Society of London. 2010: 211-224
  • Geochemistry of mineral surfaces and factors affecting their chemical reactivity Chemical Bonding at Surfaces and Interfaces Brown, Jr., G. E., Trainor, T. P., Chaka, A. M., Nilsson (ed.), A., Pettersson (ed.), L. M., Norskov (ed.), J. Elsevier, New York. 2007: 457-509
  • Molecular Environmental Science: An Assessment of Research Accomplishments, Available Synchrotron Radiation Facilities, and Needs A Report Prepared on Behalf of EnviroSync - A National Organization Representing Molecular Environmental Science Users of Synchrotron Radiation Sources Brown, Jr., G. E., Sutton, S. R., Bargar, J. R., Shuh, D. K., Bassett, W. A., Bertsch, P. M., Bisognano, J., Bleam, W. F., Clark, D. L., De Stasio, P., Fendorf , S. E., Fenter, P. A., Fontes, E., Hormes, J., Kemner, K. M., Myneni, S. B., O'Day, P. A., Pecher, K. H., Reeder, R. J., Roy, A., Traina, S. J., Willson, C., Zachara, J. M. SLAC. 2004: 60p.
  • Interaction of water and aqueous chromium ions with iron oxide surfaces Nuclear Site Remediation - First Accomplishments of the Environmental Management Science Program Brown, Jr. , G. E., Chambers, S. A., Amonette, J. E., Rustad, J. R., Kendelewicz, T., Liu, P., Doyle, C. S., Grolimund, D., Foster-Mills, N. S., Joyce, S.A., S. A., Thevuthasan, S. edited by Eller, P. G., Heineman, W. R. Am. Chem. Soc., Columbus, OH. 2001: 212-246
  • Use of x-ray absorption spectroscopy to study reaction mechanisms at metal oxide-water interfaces Am. Chem. Soc. Symposium Series 715, Kinetics and Mechanisms of Reactions at the Mineral/Water Interface Brown, Jr., G. E., Parks, G. A., Bargar, J. R., Towle, S. N. edited by Sparks, D. L., Grundl, T. 1998: 14-37
  • Structure and composition of uranium(VI) sorption complexes at the kaolinite-water interface Adsorption of Metals by Geomedia, Variables, Mechanisms, and Model Applications Thompson, H. A., Parks, G. A., Brown, Jr., G. E., Jenne (ed.), E. A. Academic Press. 1998: 349-370
  • Molecular Environmental Science: Speciation, Reactivity, and Mobility of Environmental Contaminants Report of the DOE Molecular Environmental Science Workshop, July 5-8, 1995, Airlie Center, VA edited by Brown, Jr., G. E., Chiamelli, R., Stock, L., Stults, R., Sutton, S. R., Traina, S. J. SLAC, Menlo Park, CA. 1995
  • Synchrotron radiation in the earth sciences Encyclopedia of Earth Systems Science (Vol 4) Bassett, W. A., Brown, Jr., G. E. Academic Press. 1992: 339-350
  • EXAFS study of aqueous Co(II) sorption complexes on kaolinite and quartz surfaces XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure O'Day, P. A., Brown, Jr., G. E., Parks, G. A., Hasnain, , S. S. Ellis Horwood Ltd. 1991: 260-262
  • In-situ EXAFS study of changes in Co(II) sorption complexes on gamma-Al2O3 with increasing sorption densities XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure Chisholm-Brause, C. J., Brown, Jr., G. E., Parks, G. A., Hasnain, S. S. Ellis Horwood Ltd. 1991: 263-265
  • X-ray absorption and Raman-UV/visible spectroscopic study of Au(III) complexes in chloride solutions: direct evidence for chlorine and oxychlorine complexes XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure Farges, F., Peck, J. A., Brown, Jr., G. E., Hasnain (ed.), S. S. Ellis Horwood Ltd. 1991: 478-480
  • EXAFS study of the structural environments of trace levels of Zr4+, Mo6+, and U6+/U5+/U4+ in silicate glass/melt systems XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure Farges, F., Brown, Jr., G. E., Ponader, C. W., Hasnain (ed.), S. S. Ellis Horwood Ltd. 1991: 309-311
  • XAFS analysis in the anharmonic limit: Applications to Hi-Tc superconductors and ferrosilicates XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure Mustre de Leon, J., Conradson, S. D., Batistic, I., Bishop, A. R., Raistrick, I., Jackson, W. E., Brown, Jr., G. E., Waychunas, G. A., Hasnain, S. S. Ellis Horwood Ltd. 1991: 54-57
  • In-situ high temperature x-ray absorption study of ferrous iron in orthosilicates crystals and liquids XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure Jackson, W. W., Brown, Jr., G. E., Waychunas, G. A., Mustre de Leon, J., Conradson, S. D., Combes, J., Hasnain (ed.), S. S. Ellis Horwood Ltd. 1991: 298-301
  • X-ray absorption study of the local Ca environment in silicate glasses XAFS VI, Sixth Internat. Conf. on X-ray Absorption Fine Structure Combes, J. M., Brown, Jr., G. E., Waychunas, G. A. edited by Hasnain, S. S. Ellis Horwood, Ltd. 1991: 312-314
  • Synchrotron radiation facilities: opportunities in the earth sciences Frontiers in Mineral Physics Brown, Jr., G. E., Bassett, W. A., Manghnani, M. H., Mao, H., Shankland, T. J. edited by Mackwell, S. J., Bassett, W. A., McMillan, P. F. American Geophysical Union. 1989: 87-96
  • X-ray absorption spectroscopy and its applications in mineralogy and geochemistry Spectroscopic Methods in Mineralogy and Geology Brown, Jr., G. E., Calas, G., Waychunas, G. A., Petiau, J. F. edited by Hawthorne, F. Mineralogical Society of America, Washington, DC. 1988: 431-512
  • Local coordination environment of Na in a series of silica-rich glasses and selected minerals within the Na2O-Al2O3-SiO2 system EXAFS and Near Edge Structure III McKeown, D. A., Brown, Jr., G. E., Waychunas, G. A. edited by Hodgson, K. O., Hedman, B., Penner-Hahn, J. E. Springer-Verlag. 1984: 308-310
  • Applications of EXAFS and XANES spectroscopy to problems in mineralogy and geochemistry EXAFS and Near Edge Structure III Waychunas, G. A., Brown, Jr., G. E. edited by Hodgson, K. O., Hedman, B., Penner-Hahn, J. E. Springer-Verlag. 1984: 336-342
  • Crystal chemistry of the olivines and silicate spinels Mineralogy (2nd edition, 1982) Brown, Jr. , G. E., Ribbe (ed.), P. H. Mineralogical Society of America. 1980: 275-381
  • The Feldspars, NATO Advanced Studies Institute on Feldspars Brown, Jr., G. E., Hamilton, W. C., Prewitt, C. T., Sueno, S. Manchester University Press. 1974: 68-80
  • Earth Materials Geology Today Brown, Jr., G. E., Ernst, W. G. Del Mar Books, Del Mar, California. 1974: 91-113

Conference Proceedings


  • Nanomaterials and the Environment: The Chemistry and Materials Perspective NSF-Chemistry Workshop on Nanomaterials and the Environment: The Chemistry and Materials Perspective Grassian, V., Hamers, R., Brown, Jr., G. E., Fairbrother, H., Johnston, M., Penn, R. L. 2011
  • Arsenic(III) polymerization upon sorption on iron(II,III)-(hydr)oxides surfaces: Implications for arsenic mobility under reducing conditions Morin, G., Ona-Nguema, G., Wang, Y., Juillot, F., Menguy, N., CALAS, G., Brown, G. E. PERGAMON-ELSEVIER SCIENCE LTD. 2009: A906-A906
  • Uranyl-chlorite sorption/desorption: Evaluation of different U(VI) sequestration processes Singer, D. M., Maher, K., Brown, G. E. AMER CHEMICAL SOC. 2009
  • Adsorption and precipitation of aqueous Zn(II) on hematite nano- and microparticles Ha, J., Farges, F., Brown, G. E. AMER INST PHYSICS. 2007: 238-240
  • Structural environment of Nb5+ in dry and fluid-rich (H2O, F) silicate glasses: A combined XANES and EXAFS study Piilonen, P. C., Farges, F., Linnen, R. L., Brown, G. E., Pawlak, M., Pratt, A. MINERALOGICAL ASSOC CANADA. 2006: 775-794
  • Structural environments around molybdenum in silicate glasses and melts. II. Effect of temperature, pressure, H2O, halogens and sulfur Farges, F., Siewert, R., Ponader, C. W., Brown, G. E., Pichavant, M., Behrens, H. MINERALOGICAL ASSOC CANADA. 2006: 755-773
  • In situ analysis of thioarsenite complexes in neutral to alkaline arsenic sulphide solutions Bostick, B. C., Fendorf, S., Brown, G. E. MINERALOGICAL SOC. 2005: 781-795
  • EXAFS study of uranyl adsorption on Wyoming montmorillonite 11th Internat. Symp. on Water-Rock Interaction Catalano, J. G., Brown, Jr., G. E., Wanty (ed.), R. B., Seal, II (ed.), R. R. 2004: 665-669
  • Synchrotron-based studies of microbe-metal ion-mineral interactions. 11th Internat. Symp. on Water-Rock Interaction Brown, Jr., , G. E., Templeton, A. S., Trainor, T. P., Spormann, A. M., Yoon, T. H., Benzerara, K. edited by Wanty, R. B., Seal II, R. R. 2004: 1069-1077
  • Actinides in silicate glasses and melts and on mineral surfaces: Information on local coordination environments from XAFS spectroscopy and bond valence theory Brown, Jr., G. E., Farges, F., Bargar, J. R., Berbeco, H. T., 2002 Nuclear Energy Agency/Organization for Economic Co-operation and Development, AEN/NEA 2002. 2002: 10-12
  • A new hard x-ray XAFS spectroscopy facility for environmental samples, including actinides, at the Stanford Synchrotron Radiation Laboratory Bargar, J. R., Brown, Jr., G. E., Evans, I., Rabedeau, T., Rowen, M., Rogers, J. Nuclear Energy Agency/Organization for Economic Co-operation and Development, AEN/NEA 2002. 2002: 10-12
  • Actinides in earth materials: The importance of natural analogues Farges, F., Harfouche, M., Petit, P-E., Brown, Jr., G. E. Nuclear Energy Agency/Organization for Economic Co-operation and Development, AEN/NEA 2002. 2002: 10-12
  • Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy Kim, C. S., Brown, G. E., Rytuba, J. J. ELSEVIER SCIENCE BV. 2000: 157-168

    Abstract

    Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg(-1) (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of +/-25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites.

    View details for Web of Science ID 000089587200016

    View details for PubMedID 11036987

  • Mineral surfaces and bioavailability of heavy metals: A molecular-scale perspective Brown, G. E., Foster, A. L., Ostergren, J. D. NATL ACAD SCIENCES. 1999: 3388-3395

    Abstract

    There is a continual influx of heavy metal contaminants and pollutants into the biosphere from both natural and anthropogenic sources. A complex variety of abiotic and biotic processes affects their speciation and distribution, including adsorption onto and desorption from mineral surfaces, incorporation in precipitates or coprecipitates, release through the dissolution of minerals, and interactions with plants and microbes. Some of these processes can effectively isolate heavy metals from the biosphere, whereas others cause their release or transformation to different species that may be more (or less) bioavailable and/or toxic to organisms. Here we focus on abiotic adsorption and precipitation or coprecipitation processes involving the common heavy metal contaminant lead and the metalloids arsenic and selenium in mine tailings and contaminated soils. We have used extremely intense x-rays from synchrotron sources and a structure-sensitive method known as x-ray absorption fine structure (XAFS) spectroscopy to determine the molecular-level speciation of these elements at concentrations of 50 to several thousand ppm in the contaminated environmental samples as well as in synthetic sorption samples. Our XAFS studies of As and Pb in the mine tailings show that up to 50% of these contaminants in the samples studied may be present as adsorbed species on mineral surfaces, which makes them potentially more bioavailable than when present in sparingly soluble solid phases. Our XAFS studies of Se(VI) sorption on Fe2+-containing sulfates show that this element undergoes redox reactions that transform it into less bioavailable and less toxic species. This type of information on molecular-level speciation of heavy metal and metalloid contaminants in various environmental settings is needed to prioritize remediation efforts and to assess their potential hazard to humans and other organisms.

    View details for Web of Science ID 000079507900013

    View details for PubMedID 10097048

  • XAFS study of Cu(II) at the water-goethite (alpha-FeOOH) interface Bochatay, L., Persson, P., Lovgren, L., Brown, G. E. EDP SCIENCES S A. 1997: 819-820
  • XAFS determination of As(V) associated with Fe(III) oxyhydroxides in weathered mine tailings and contaminated soil from California, USA Foster, A. L., Brown, G. E., Parks, G. A., Tingle, T. N., Voigt, D. E., Brantley, S. L. EDP SCIENCES S A. 1997: 815-816
  • Surface precipitation in the Co(II)/Al2O3 sorption system Towle, S. N., Bargar, J. R., Persson, P., Brown, G. E., Parks, G. A. MATERIALS RESEARCH SOCIETY. 1997: 237-242
  • Photoemission study of Na and Cs adsorption on MgO(100)1 x 1 Kendelewicz, T., Liu, P., Brown, G. E., Nelson, E. J., Pianetta, P. ELSEVIER SCIENCE BV. 1996: 451-456
  • X-RAY ABSORPTION-SPECTROSCOPY OF IONS AT SOLID WATER INTERFACES Brown, G. E., Chisholm, C. J., Parks, G. A., Hayes, K. F., Leckie, J. O., Roe, A. L. AMER CHEMICAL SOC. 1988: 66-GEOC

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