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Publication Date

January 2007

Publication Title

Illinois Department of Natural Resources

Issue Number



About half the residents living in the area of southwestern Illinois known as the sinkhole plain obtain their potable water from the region's shallow karst aquifer. Previous work has shown that the groundwater from approximately 18% of the wells in the sinkhole plain has nitrate concentrations in excess of the U.S. Environmental Protection Agency's drinking water standard of 10 mg of N/L of water. The nitrate concentrations in water samples collected from approximately 50% of the wells and from all of the springs in the sinkhole plain area are greater than background concentrations, suggesting that sources other than naturally occuring organic matter in soil have contributed additional nitrate to groundwater in the shallow karst aquifer. This investigation characterized the geochemistry of the groundwater to determine which sources of nitrogen in the sinkhole plain is the major contributor to the anomalous concentration of nitrate observed in the shallow karst aquifer.

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