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National Analysis of Trace Elements - Publications

Figure 3
from Fact Sheet 063-00, Arsenic in Ground-Water Resources of the United States

This map has been superseded. A new county map was published in the November 2001 issue of Geotimes. The original county map, below, was based on 18,850 ground-water samples and showed arsenic concentrations found in at least 10% of samples per county. The new county map is based on 31,350 samples and shows arsenic concentrations found in at least 25% of samples per county. In addition, a new equal-area map shows arsenic concentrations found in at least 25% of samples within a moving 100km radius.

Map-- U.S. counties colored by arsenic in ground water

Figure 3. Counties with arsenic concentrations exceeding possible new MCLs in 10 percent or more of ground-water samples.

[dark] Counties with arsenic concentrations exceeding 10 µg/L in 10 percent or more of samples.
[ ] Counties with arsenic concentrations exceeding 5 µg/L in 10 percent or more of samples.
[ ] Counties with arsenic concentrations exceeding 3 µg/L in 10 percent or more of samples.
[ ] Counties with fewer than 10 percent of samples exceeding 3 µg/L, representing areas of lowest concentration.
[light] Counties with insufficient data in the USGS data base to make estimates.

Citation:
Welch, A.H., Watkins, S.A., Helsel, D.R., and Focazio, M.F., 2000, Arsenic in ground-water resources of the United States: U.S. Geological Survey Fact Sheet 063-00, 4p.

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National Analysis of Trace Elements - Publications
National Water-Quality Assessment

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Last Modified: 8May2000

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