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ResearchI am interested in the chemical and biological processes that govern the fate and transport (and thus cycling) of contaminants (such as arsenic) and nutrients (such as phosphate) within soils, sediments, and surface waters. My research group examines the chemical environments that develop as a result of both biotic and abiotic processes, and we strive to account for the physical complexity, inclusive of solute transport, within natural settings. Our particular emphasis is on reactions that change the oxidation state (redox reactions) and associated speciation of contaminants and nutrients, or solids that control their partitioning, within soils and sediments.TeachingI teach a range of courses on soils and soil processes that encompass their rates of development, unique features for plant growth, ability to filter contaminants, management for sustained agricultural productivity, and their sensitivity to human disturbance. I am also a co-instructor for a course on field research in Earth Systems.Professional ActivitiesFaculty Director for Environmental Measurements Facility (2006-present); Terman Fellow, Stanford University (1999-2002); Stanford University Fellow (2004-06); National Research Council Committee for Defining Contaminant Bioavailability in Soils and Sediments (2000-02); Advisory Council and Faculty Representative for Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory (2007-present); Chemical Geology Editor for the special issue "Controls on Arsenic Transport in Near-Surface Aquatic Systems" (2006); NAS panel for Frontiers in Soil Science Research (2005); Panel organizer for DOE Environmental Remediation Science Program's "Influence of Coupled Biological, Chemical, and Physical Processes on Contaminant Fate and Transport" (2006)