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Fact Sheet 2009–3041

National Water-Quality Assessment Program

Redox Conditions in Selected Principal Aquifers of the United States


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Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami­nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+), hydrogen sulfide (H2S), and methane (CH4). Determining the kinds of redox processes that occur in an aquifer system, documenting their spatial distribution, and understanding how they affect concentrations of natural or anthropogenic contaminants are central to assessing and predicting the chemical quality of groundwater.

This Fact Sheet extends the analysis of U.S. Geological Survey authors to additional principal aquifer systems by applying a framework developed by the USGS to a larger set of water-quality data from the USGS national water databases. For a detailed explanation, see the "Introduction" in the Fact Sheet.

First posted June 26, 2009

For additional information contact:

Director, Colorado Water Science Center
United States Geological Survey
Box 25046, Mail Stop 415
Denver, CO 80225

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

McMahon, P.B., Cowdery, T.K., Chapelle, F.H., and Jurgens, B.C., 2009, Redox conditions in selected principal aquifers of the United States: U.S. Geological Survey Fact Sheet 2009-3041, 6 p.



Framework for Assessing Redox Processes

Source of Redox Data

Redox Processes in Selected Principal Aquifers

Effect of Redox on Water Quality


References Cited

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