| Autor: |
Sprague LA; US Geological Survey, Denver Federal Center, Box 25046 MS 415, Denver, Colorado 80225, United States. lsprague@usgs.gov, Hirsch RM, Aulenbach BT |
| Jazyk: |
angličtina |
| Zdroj: |
Environmental science & technology [Environ Sci Technol] 2011 Sep 01; Vol. 45 (17), pp. 7209-16. Date of Electronic Publication: 2011 Aug 09. |
| DOI: |
10.1021/es201221s |
| Abstrakt: |
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. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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