Lead arsenate pesticides were widely used in apple orchards from 1925 to 1955. Soils from historic orchards in four counties in Virginia and West Virginia contained elevated concentrations of As and Pb, consistent with an arsenical pesticide source. Arsenic concentrations in approximately 50% of the orchard site soils and approximately 1% of reference site soils exceed the USEPA Preliminary Remediation Goal (PRG) screening guideline of 22 mg kg(-1) for As in residential soil, defined on the basis of combined chronic exposure risk. Approximately 5% of orchard site soils exceed the USEPA PRG for Pb of 400 mg kg(-1) in residential soil; no reference site soils sampled exceed this value. A variety of statistical methods were used to characterize the occurrence, distribution, and dispersion of arsenical pesticide residues in soils, stream sediments, and ground waters relative to landscape features and likely background conditions. Concentrations of Zn, Pb, and Cu were most strongly associated with high developed land density and population density, whereas elevated concentrations of As were weakly correlated with high orchard density, consistent with a pesticide residue source. Arsenic concentrations in ground water wells in the region are generally <0.005 mg L(-1). There was no spatial association between As concentrations in ground water and proximity to orchards. Arsenic had limited mobility into ground water from surface soils contaminated with arsenical pesticide residues at concentrations typically found in orchards.

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Private and public wells throughout Morgan County, W. Va., were tested to determine aquifer hydraulic, geochemical, and water-quality characteristics. The entire study area is located in the Valley and Ridge Physiographic Province, a region of complex geologic structure and lithology. Aquifers in the study area are characterized by thin to thick bedded formations with interbedding among the various limestones, shales, sandstones, and siltstones that are folded into a series of steeply dipping north-south trending anticlines and synclines. Zones of groundwater production typically consist of one to two fracture sets, with little to no production from unfractured bedrock matrix. Measurements of transmissivity range from 2 to 1,490 feet squared per day, with the larger transmissivities occurring near bedding contacts and in zones with cross-faulting or jointing. Ground water flows from recharge areas in the uplands to local drainages and to deeper flow systems that appear to be controlled by regional geologic structure. The overall flow direction is from south to north within the study area. Ground water within the study area is predominantly a calcium-bicarbonate type water reflecting contact with carbonate rocks. Sodium-bicarbonate and calcium-magnesium-sulfate end-members also exist, with many samples exhibiting mixing, which may be the result of flow between the differing rock types or within units containing both carbonate rocks and shales. Values of water-quality characteristics that were greater than U.S. Environmental Protection Agency drinking-water standards included radon-222, pH, turbidity, iron, manganese, aluminum, and total-and fecal-coliform and Escherichia coli (E. coli) bacteria. Concentrations of radon-222 were detected in all samples from all units, with the largest concentrations (1,330 and 2,170 picocuries per liter) from the Clinton Formation.

Lake Tahoe has long been admired for its alpine setting and the clarity of its water. During the last half-century, however, human activity in the lake basin has increased while the lake has been losing water clarity at a rate of about 1 foot (ft) per year. The Tahoe Regional Planning Agency (TRPA), the U.S. Geological Survey (USGS), and the Tahoe Research Group of the University of California, Davis (TRG) are monitoring loads of sediment and important nutrients flowing into the lake from the streams and groundwater aquifers in the basin. This fact sheet provides an overview of that monitoring program and summarizes some of the results regarding loads of sediment and nutrients to the lake.

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