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|Transformation, fixation, and mobilization of arsenic and antimony in contaminated sediments
|Brannon, James M.
Dredging Operations Technical Support Program (U.S.)
|U.S. Army Engineer Waterways Experiment Station
|Technical Report (Dredging Operations Technical Support Program (U.S.)) ; no.Technical Report D-84-1
|The potential environmental impacts of arsenic (As) and antimony (Sb) contaminated sediments were studied with emphasis placed on short- and long-term leaching and sediment conditions that affect mobilization. Under anaerobic conditions, arsenate [As(V)] was reduced to arsenite [As(III)] in a wide range of sediments. In anaerobic Texas City sediment slurries, 70% of added As(V) was recovered as water soluble As(III) following three weeks of incubation. Formation of organic As following addition of AS(V) to anaerobic sediments was also demonstrated. Short-term leaching was conducted with anaerobically incubated unamended and As amended sediments using either distilled or saline water. In both amended and unamended sediment, As(III) was the predominant species released. Releases of As(III) were greatest when sediments were low in iron and high in interstital water and exchangeable phase As(III). Releases of As(V), As(III), and organic As from sediments were found to be relatively insensitive to the salinity of the mixing water. Aerobic leaching experiments of six months duration were conducted to determine what As species would be released, the duration of the releases, and the sediment factors affecting releases. Arsenic releases usually persisted throughout the leaching period; releases were higher from amended compared with unamended sediments. Generally, As(III) release predominated initially, followed by As(V) and organic As releases in the first three months. The final three months of leaching were characterized by predomiant release of As(V). Conversely, leaching of Black Rock sediments under anaerobic conditions for three months resulted in almost exclusive release of As(III). These results indicate that soluble As releases from sediments are undesirable during the first months of aerobic leaching or at any time during anaerobic conditions because of the high toxicity of As(III). Arsenic releases following six months of leaching were related to sediment iron content and to sediment calcium carbonate (CaCO3) equivalent concentration. Short-term releases of Sb from freshwater sediments were enhanced by leaching with saline water. Many sediments amended with Sb also released volatile Sb compounds. In many other ways, Sb behavior in amended and unamended sediment paralleled As behavior, especially short- and long-term releases and sediment properties affecting releases.
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|Technical Report D-84-1
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|Technical Report D-84-1