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PH16 Metals in the Environment: Chemistry and Fate Issues
(PH147) Do Arsenic-Containing Products Influence Arsenic Concentrations in Subsurface Drinking Water Supplies?
Saxe, J1, Saba, T1, Wannamaker, E1, 1 Gradient Corporation, Cambridge, MA
ABSTRACT- The recent decrease in the arsenic drinking water maximum contaminant level (MCL) has heightened scrutiny of natural and anthropogenic arsenic contributions to subsurface drinking water supplies. Naturally-occurring arsenic originating from environmental conditions (e.g., geology, evaporative concentration) results in groundwater that exceeds the new MCL in regions of New England, the upper Midwest, and Western states. In contrast, Florida groundwater, used as a drinking water source for more than 90% of the state's population, contains low natural arsenic concentrations. A large extent of Florida contains a shallow water table and sandy soil, which poorly retains arsenic. These conditions increase the possibility for anthropogenic arsenic additions to soil to result in MCL exceedances in subsurface drinking water. Research and environmental monitoring efforts in Florida have focused on arsenic-containing products as potential arsenic sources to groundwater. Wood preserved with chromated copper arsenate (CCA) is widely used in Florida and commonly disposed of in unlined landfills. The herbicide monosodium methanearsenate (MSMA) is used for weed control on most of Florida's 1,400 golf courses. An analysis of groundwater data obtained by Florida environmental agencies near unlined landfills and golf courses did not indicate that these products have resulted in exceedances of the arsenic MCL in groundwater used as drinking water. The data showed that some highly localized areas at the water table, and some areas where chemical spills occurred, contain arsenic concentrations that exceed the MCL. However, the arsenic assimilatory capacity of soil and subsurface aquifer solids is large compared to the arsenic mass potentially introduced to soil through disposal of CCA-treated wood or application of MSMA, and the majority of groundwater samples, including all those analyzed from nearby potable wells, were not elevated above background concentrations.
Key words: CCA-treated wood, arsenic, MSMA, Florida
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