Speciation and behavior of arsenic in evaporation basins,California, USA |
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| Authors: | Ji-Hun Ryu Suduan Gao Kenneth K Tanji |
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| Institution: | (1) Radioactive Waste Technology Development Division, Korea Atomic Energy Research Institute, Daedeokdaero 1045, Yuseong-gu, Daejeon, Republic of Korea;(2) Water Management Research Unit, San Joaquin Valley Agricultural Sciences Center, USDA-ARS, 9611 S. Riverbend Ave, Parlier, CA 93648, USA;(3) Hydrology Program, Department of Land Air and Water Resources, University of California, Davis, CA 95616, USA |
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| Abstract: | Disposal of saline subsurface drainage waters from croplands into evaporation basins (or ponds) in the San Joaquin Valley
of California causes excessive accumulation of salts and elevated concentrations of arsenic (As), a potentially high risk
element with little information about its fate, in the agricultural evaporation ponds. We examined dissolved As concentration,
speciation, and distribution in waters as well as As fractionation in sediments in the 10-cell South Evaporation Basin for
better understanding of processes and conditions affecting As transformations and fate in a specific drainage disposal facility.
The increase of total dissolved As concentrations were observed with higher Cl− and electric conductivity along flow path indicating that evaporation was an important factor regulating total dissolved
As concentration. The increases of reduced As species such as arsenite As(III)] and organic As (monomethylarsonic acid and
dimethylarsinic acid) were found towards the terminal flow pathway. However, arsenate As(V)], the oxidized species remained
greater than 67% of total dissolved As in all cell waters. Sequential extractions of sediments indicated that reducing conditions
may influence As behavior in sediments to be more soluble and exchangeable. Arsenic association with oxides was appreciable
only under oxidizing condition. Carbonate minerals played an important role in immobilizing As into the sediments under alkaline
condition and a broad range of redox conditions. However, these sink mechanisms did not significantly reduce As concentrations
in the cell waters. The reducing condition facilitated by high concentration of organic matter might be a major factor for
the increase in As mobility. |
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