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Arsenic and Geochemical Characteristics of Groundwater from Domestic Wells in Greater Augusta, Maine, USA
Presentation (pdf document)
Yan Zheng, Queens College and Graduate School and University Center, City University of New York, Flushing, NY; Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY
Naturally occurring arsenic in groundwater affects the health of tens of millions of people around the world, including Maine , United States . To investigate the geological, mineralogical and hydrological processes related to arsenic mobilization, water samples from about 800 private wells were collected between June and August, 2006 in 12 communities encompassing ~ 1000 km2 around the Greater Augusta area of Maine. The area was chosen because detailed bedrock maps are available, and some wells were known to have high arsenic concentrations. Samples were analyzed for a wide range of parameters, including dissolved oxygen, pH, major cations and anions, and trace elements (As, Fe, Mn and U, etc.)
Arsenic concentrations ranged from <0.01 ug/L to 325 ug/L, with 31% > 10 ug/L, the current EPA Maximum Contaminant Level (MCL). and 5% > 50 ug/L. Manganese concentrations ranged from 0.62 ug/L to 7190 ug/L, with 22.5% > 50 ug/L, EPA secondary MCL. Uranium concentrations ranged from < 0.01 ug/L to 484 ug/L, with 4% > 30 ug/L,EPA MCL, consistent with high concentrations of Rn (>10,000 pCi/L) from the same set of samples. The spatial patterns of the geochemical parameters and their relationship to the bedrock geology and hydrology will be further investigated to elucidate mechanisms of As release.
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