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Open-File Report 2009–1004

National Water-Quality Assessment Program
Transport of Anthropogenic and Natural Contaminants (TANC) to Public-Supply Wells

An Excel® Workbook for Identifying Redox Processes in Ground Water

By Bryant C. Jurgens, Peter B. McMahon, Francis H. Chapelle, and Sandra M. Eberts


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The reduction/oxidation (redox) condition of ground water affects the concentration, transport, and fate of many anthropogenic and natural contaminants. The redox state of a ground-water sample is defined by the dominant type of reduction/oxidation reaction, or redox process, occurring in the sample, as inferred from water-quality data. However, because of the difficulty in defining and applying a systematic redox framework to samples from diverse hydrogeologic settings, many regional water-quality investigations do not attempt to determine the predominant redox process in ground water. Recently, McMahon and Chapelle (2008) devised a redox framework that was applied to a large number of samples from 15 principal aquifer systems in the United States to examine the effect of redox processes on water quality. This framework was expanded by Chapelle and others (in press) to use measured sulfide data to differentiate between iron(III)- and sulfate-reducing conditions. These investigations showed that a systematic approach to characterize redox conditions in ground water could be applied to datasets from diverse hydrogeologic settings using water-quality data routinely collected in regional water-quality investigations.

This report describes the Microsoft® Excel® workbook, RedoxAssignment_McMahon&Chapelle.xls, that assigns the predominant redox process to samples using the framework created by McMahon and Chapelle (2008) and expanded by Chapelle and others (in press). Assignment of redox conditions is based on concentrations of dissolved oxygen (O2), nitrate (NO3), manganese (Mn2+), iron (Fe2+), sulfate (SO42–), and sulfide (sum of dihydrogen sulfide [aqueous H2S], hydrogen sulfide [HS], and sulfide [S2–]). The logical arguments for assigning the predominant redox process to each sample are performed by a program written in Microsoft® Visual Basic® for Applications (VBA). The program is called from buttons on the main worksheet. The number of samples that can be analyzed is only limited by the number of rows in Excel® (65,536 for Excel® 2003 and XP®; and 1,048,576 for Excel® 2007), and is therefore appropriate for large datasets.

For additional information contact:
Director, California Water Science Center
U.S. Geological Survey
6000 J Street, Placer Hall
Sacramento, California 95619-6129

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:

Jurgens, B.C., McMahon, P.B., Chapelle, F.H., and Eberts, S.M., 2009, An Excel® workbook for identifying redox processes in ground water: U.S. Geological Survey Open-File Report 2009–1004 8 p.





Description of Spreadsheet Program

Example Dataset



References Cited

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