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Global Themes of Arsenic Release from Soils and SedimentsEPA Grant Number: FP916394
Title: Global Themes of Arsenic Release from Soils and Sediments
Investigators: Polizzotto, Matthew L.
Institution: Stanford University
EPA Project Officer: Zambrana, Jose
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Environmental Chemistry and Environmental Material Science
Arsenic is a contaminant in many groundwater systems throughout the world, and consequently, millions of people routinely drink water with arsenic levels exceeding the limits suggested by the World Health Organization. Although much arsenic contamination of drinking water is anthropogenic, the most significant fraction of global contamination is actually the result of native arsenic release from sediments. The chemical mechanisms, however, mediating arsenic release often are not well understood. Most of our understanding of these mechanisms has been gleaned from aqueous analyses, whereas little attention has been paid to the chemical controls governed by the solid phase. The objective of this research project is to better understand the most important mechanisms stimulating arsenic release from soils and sediments. In my research, I seek to identify the chemical states of arsenic in sediments from contaminated aquifers, determine the dominant factors controlling the partitioning of arsenic, and establish criteria for recognizing potential areas where arsenic may be released to groundwater in the future.
My research consists of four parts. Because the mobility of arsenic in the subsurface environment is heavily dependent on redox chemistry, the first three studies examine arsenic release from reducing, oxidizing, and alternating redox environments. Field sites in Bangladesh (reducing), Argentina (oxidizing), and Idaho (alternating) have been chosen because arsenic has a tremendous impact on human health in these areas. Sediments will be analyzed by a suite of techniques, including X-ray absorption spectroscopy, scanning electron microscopy, Raman spectroscopy, and optical microscopy. Column and batch experiments with sediment slurries will be conducted to test previously suggested hypotheses concerning the release of arsenic, and solution chemistry will be analyzed by inductively coupled plasma–optical emission spectroscopy and ion chromatography. In my fourth study, I will attempt to stimulate arsenic release from natural sediments associated with pristine groundwaters to identify the potential for future arsenic contamination. Sediments from 10 locations throughout the United States will be used in a set of parallel batch experiments that will determine the effects of biological reductive dissolution, ion displacement, oxidation, and pH changes on arsenic release.
I expect that the greatest potential for arsenic release will occur when oxidized arsenic-bearing sediments are reduced. This process will most likely be a result of microbial activity stimulated by an influx of organic carbon. Furthering our understanding of how arsenic can be mobilized in aquifers will aid in the development of arsenic remediation strategies as well as help prevent future arsenic problems that could be both economically costly and detrimental to public health.