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Lower Mississippi-Gulf Water Science Center - Mississippi
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Denitrification Processes in Surface Water
Large inputs of nitrogen from agriculture, atmospheric deposition, and point sources occur annually in the Big Sunflower River Basin. A substantial portion of these nitrogen inputs eventually discharge to streams, the Mississippi River, and ultimately the Gulf of Mexico where they are believed to contribute to increases in eutrophication and an expanding hypoxic zone (Goolsby and Battaglin, 2001; Rabalais et al., 1996; Rabalais and Turner, 2001).In recent publications, the Yazoo River Basin, which contains the Big Sunflower River Basin, has been identified as having a high proportion of nitrogen delivered to the Gulf of Mexico (Alexander and others, 2008). The two major variables that affect denitrification rates are temperature and stream velocity, both of which are different in the Big Sunflower River Basin as compared to basins of the upper Midwest. The differences, slower stream velocities and higher temperatures, would be expected to increase the denitrification rate in the Big Sunflower River Basin compared to basins in the upper Midwest. A 3-year study of denitrification in the Big Sunflower River and its major tributaries will be conducted. The objective of this study will be to determine if there is significant denitrification occurring in the streams of the Big Sunflower River Basin and to determine a denitrification rate and the total mass of nitrogen lost from the rivers due to denitrification. The primary method used would be based on a mass balance for nitrate determined using samples collected using a Lagrangian sampling approach; that is following a mass of water from the headwaters until it passes the downstream gage on the Yazoo River and measuring the change in nitrogen mass.
Sampling from the side of a bridge.
USGS employee sampling from the side of a bridge.
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