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Scientific Investigations Report 2012–5220

National Water-Quality Assessment Program

Use of Classes Based on Redox and Groundwater Age to Characterize the Susceptibility of Principal Aquifers to Changes in Nitrate Concentrations, 1991 to 2010

By P.B. McMahon

Thumbnail of and link to report PDF (5.19 MB)Abstract

The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey is using multiple approaches to measure and explain trends in concentrations of nitrate in principal aquifers of the United States. Near decadal sampling of selected well networks is providing information on where long-term changes in nitrate concentrations have occurred. Because those studies do not include all the NAWQA well networks, a determination has yet to be made as to what might be expected in networks from which timeseries data have not been collected. Characterizing aquifer susceptibility to changes in nitrate concentrations on the basis of data collected from all the NAWQA well networks would be a step toward extrapolating findings from those studies to broader regions.

First posted December 20, 2012

For additional information contact:
Director, Colorado Water Science Center
U.S. Geological Survey
Box 25046, Mail Stop 415
Denver, CO 80225
http://co.water.usgs.gov

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Suggested citation:

McMahon, P.B., 2012, Use of classes based on redox and groundwater age to characterize the susceptibility of principal aquifers to changes in nitrate concentrations, 1991 to 2010: U.S. Geological Survey Scientific Investigations Report 2012–5220, 41 p.



Contents

Foreword

Abstract

Introduction

Methods

Evaluation of Redox-Age Classes

Relation Between Redox-Age Classes and Changes in Nitrate Concentrations in Trend-Well Networks.

Redox-Age Classes in Principal Aquifers

Summary and Conclusions

Acknowledgments

References Cited

Appendix 1


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