Regional‐scale controls on dissolved nitrous oxide in the Upper Mississippi River

The U.S. Corn Belt is one of the most intensive agricultural regions of the world and is drained by the Upper Mississippi River (UMR), which forms one of the largest drainage basins in the U.S. While the effects of agricultural nitrate (NO3−) on water quality in the UMR have been well documented, it...

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Published inGeophysical research letters Vol. 43; no. 9; pp. 4400 - 4407
Main Authors Turner, P. A., Griffis, T. J., Baker, J. M., Lee, X., Crawford, J. T., Loken, L. C., Venterea, R. T.
Format Journal Article
LanguageEnglish
Published Washington John Wiley & Sons, Inc 16.05.2016
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Summary:The U.S. Corn Belt is one of the most intensive agricultural regions of the world and is drained by the Upper Mississippi River (UMR), which forms one of the largest drainage basins in the U.S. While the effects of agricultural nitrate (NO3−) on water quality in the UMR have been well documented, its impact on the production of nitrous oxide (N2O) has not been reported. Using a novel equilibration technique, we present the largest data set of freshwater dissolved N2O concentrations (0.7 to 6 times saturation) and examine the controls on its variability over a 350 km reach of the UMR. Driven by a supersaturated water column, the UMR was an important atmospheric N2O source (+68 mg N2O N m−2 yr−1) that varies nonlinearly with the NO3− concentration. Our analyses indicated that a projected doubling of the NO3− concentration by 2050 would cause dissolved N2O concentrations and emissions to increase by about 40%. Key Points The Mississippi River is an important N2O source throughout the ice‐free period The N2O:NO3− mass ratio is nonlinear, implying an upper bound on N2O concentrations A doubling of riverine NO3− would increase N2O emissions by about 40%
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ISSN:0094-8276
1944-8007
DOI:10.1002/2016GL068710