The influence of climate on in-stream removal of nitrogen

Abstract

Nitrogen (N) removal via benthic denitrification in large river systems can be a significant sink of terrestrial N and a source of nitrous oxide (N2O) to the atmosphere. Recent studies have demonstrated the fraction of in-stream N removed from a river reach is related to the water residence time. We used the HYDRA aquatic transport model to examine the sensitivity of in-stream N removal and the associated N 2O emissions in the Mississippi River system to the interannual variability in climate. The results suggested an almost two-fold range in the percent of N removed in the Mississippi River system and a three-fold range in the associated N2O emissions, with the lowest percent removed (10-33%) and the highest N 2O emissions (15.5-26.0 106 kg N) occurring in the wettest years. The results demonstrate the importance of considering climate variability and change in the management of nutrient export by large rivers. Copyright 2004 by the American Geophysical Union.