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Wiley InterScience | ||||
  Ground WaterVolume 26 Issue 3, Pages 333 - 347 Published Online: 21 Mar 2006 Journal compilation © 2010 National Ground Water Association
Abstract | References | Full Text: PDF (Size: 1165K) | Related Articles | Citation Tracking  Arsenic in Ground Water of the Western United States Discussion open until November 1, 1988. Alan H. Welch has authored over 30 publications on the various aspects of aqueous geochemistry on geothermal and regional hydrologic systems and the geochemistry of arsenic. Welch is currently a Project Chief on a pilot NAWQA (National Water-Quality Assessment) project in the Carson Basin in northwestern Nevada. Welch holds B.A. and M.A. degrees in Geology from the University of California at Santa Barbara and a Ph.D. in Hydrology and Hydrogeology from the University of Nevada, Reno. Prior to joining the U.S. Geological Survey in 1978, he was associated with the Desert Research Institute and the Pennsylvania Department of Environmental Resources. Michael S. Lico is a Hydrologist with the Water Resources Division of the U.S. Geological Survey in Carson City, Nevada. He received a B.S. in Chemistry in 1976 and an M.S. in Geology in 1983 from San Jose State University. He has done extensive research on the geochemistry of geopressured geothermal systems in California and the Gulf Coast. His current research interests include defining the mobilization and reaction paths of oxyanions and other trace elements in ground-water systems. Jennifer L. Hughes received a B.S. in Geology from Colorado State University in 1983. Since 1984 she has been a Hydrologist with the Water Resources Division of the U.S. Geological Survey in Carson City, Nevada. Her principal interests include the geochemistry and water quality of regional ground-water systems. Copyright 1988 National Ground Water Association ABSTRACT
Natural occurrences of ground water with moderate (10 to 50 micrograms per liter) to high (greater than 50 micrograms per liter) concentrations of arsenic are common throughout much of the Western United States. High concentrations of arsenic are generally associated with one of four geochemical environments: (1) basin-fill deposits of alluvial-lacustrine origin, particularly in semiarid areas, (2) volcanic deposits, (3) geothermal systems, and (4) uranium and gold-mining areas. These findings are based on an extensive literature review, compilation of unpublished reports and data, and the review of data bases containing more than 7,000 analyses of ground-water samples for arsenic. In the first two environments, arsenic appears to be associated with sediments derived, in part, from volcanic rocks of intermediate to acidic composition. Dissolved arsenic concentrations in water from volcanic aquifers in the same regions, however, may be low (less than 10 micrograms per liter). Solid phases (minerals, amorphous solids, and sedimentary organic matter) that supply the dissolved arsenic have not been identified in most areas. Alluvial and lacustrine sedimentary deposits appear to be an important source of arsenic in volcanic areas (such as Lane County, Oregon) and in areas underlain by basin-fill deposits (such as Carson Desert in Nevada and the Tulare Lake basin in California). Mobilization of arsenic in sedimentary aquifers may be, in part, a result of changes in the geochemical environment due to agricultural irrigation. In the deeper subsurface, elevated arsenic concentrations are associated with compaction caused by groundwater withdrawals. Received July 1987, revised November 1987, accepted November 1987. |
