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Nitrate in the Mississippi River and its tributaries, 1980 to 2008: Are we making progress?

December 18, 2011

Changes in nitrate concentration and flux between 1980 and 2008 at eight sites in the Mississippi River basin were determined using a new statistical method that accommodates evolving nitrate behavior over time and produces flow-normalized estimates of nitrate concentration and flux that are independent of random variations in streamflow. The results show that little consistent progress has been made in reducing riverine nitrate since 1980, and that flow-normalized concentration and flux are increasing in some areas. Flow-normalized nitrate concentration and flux increased between 9 and 76% at four sites on the Mississippi River and a tributary site on the Missouri River, but changed very little at tributary sites on the Ohio, Iowa, and Illinois Rivers. Increases in flow-normalized concentration and flux at the Mississippi River at Clinton and Missouri River at Hermann were more than three times larger than at any other site. The increases at these two sites contributed much of the 9% increase in flow-normalized nitrate flux leaving the Mississippi River basin. At most sites, concentrations increased more at low and moderate streamflows than at high streamflows, suggesting that increasing groundwater concentrations are having an effect on river concentrations.

Publication Year 2011
Title Nitrate in the Mississippi River and its tributaries, 1980 to 2008: Are we making progress?
DOI 10.1021/es201221s
Authors Lori A. Sprague, Robert M. Hirsch, Brent T. Aulenbach
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70006337
Record Source USGS Publications Warehouse
USGS Organization Colorado Water Science Center