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United States Department of Agriculture

Agricultural Research Service

Title: Transformation Of Arsenic In Agricultural Drainage Water Disposed Into An Evaporation Basin In California, USA.

Authors
item GAO, SUDUAN
item Ryu, J. - UC DAVIS
item Tanji, K. - UC DAVIS

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 18, 2006
Publication Date: N/A

Technical Abstract: Evaporation basins have been widely used for the disposal of agricultural drainage in areas requiring subsurface drainage in the San Joaquin Valley of California, a high agricultural production area in USA. The irrigation drainage water contains elevated concentrations of trace elements, including Se, As, B, V, and Mo. Little information is available on As (an environmental risk element) in drainage disposal systems. The objective of this study was to investigate As transformation and accumulation in an agricultural drainage disposal facility for better understanding of As behavior and its environmental fate. The study site was a 726 ha evaporation basin facility (containing 10 cells with water flowing in series) in the hydrologically closed Tulare Basin. Water chemistry, As concentration and speciation in water following the flow path as well as within the cells were examined. Total As [mainly arsenate, As(V)] concentrations in the water increased linearly with increases in Cl-, a conservative ion, from evapoconcentration. The reduced As species arsenite [As(III)] and organic arsenic (org-As) also increased with increases in Cl- and salinity. Water samples with high EC also had high dissolved organic matter (DOC), low dissolved oxygen, and elevated sulfide concentrations, indicating the development of reducing conditions. Elevated As in sediment profiles indicated a solid-phase sink mechanism, but not significant enough to remove and reduce As concentrations in water. These findings may apply to environments with similar climatic and hydrogeochemical conditions.

Last Modified: 7/25/2014
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