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Arsenic Speciation in Groundwater: Role of Thioanions
WILKIN, R. T., R. G. FORD, AND D. G. Beak. Arsenic Speciation in Groundwater: Role of Thioanions. In Proceedings, The American Geophysical Union Fall Meeting 2008, San Francisco, CA, December 15 - 19, 2008. American Geophysical Union, Washington, DC, , (2008).
The objective is to better understand the behavior of arsenic in groundwater environments.
The behavior of arsenic in groundwater environments is fundamentally linked to its speciation. Understanding arsenic speciation is important because chemical speciation impacts reactivity, bioavailability, toxicity, and transport and fate processes. In aerobic environments arsenic is mainly present as arsenate. In the subsurface, reducing conditions frequently prevail and arsenite species dominate. At sites where groundwater remediation is necessary, understanding arsenic speciation is critical, especially when technologies that strategically manipulate redox conditions are used. In sulfate-reducing environments and where free sulfide is available thioarsenic species are known to exist, yet compared to the oxyanion species of arsenic little is know about the formation, structure, chemistry, and stability of arsenic thioanions in the environment. In particular, data are lacking that pertain to the redox behavior of arsenate and arsenite in the presence of aqueous sulfide and at variable pH. In this presentation, results are discussed of recent speciation studies using extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge spectroscopy (XANES), and chromatographic analysis. Data from both experimental and field systems will be presented. Results indicate that both thioarsenite and thioarsenate species exist and both forms of thioarsenic species need to be considered in sulfidic environments.
URLs/Downloads:ARSENIC SPECIATION IN GROUNDWATER: ROLE OF THIOANIONS (ABSTRACT) (PDF,NA pp, 7 KB, about PDF)
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Record Details:Record Type: DOCUMENT (PAPER IN NON-EPA PROCEEDINGS)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
GROUND WATER AND ECOSYSTEMS RESTORATION DIVISION