Nitrous oxide emission from denitrification in stream and river networks

Nitrous oxide (N(2)O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N(2)O via microbial denitrification that converts N to N(2)O and dinitrogen (N(2)). The fraction of denitrified N that escapes as N(2)O rather than N(2) (i.e., the N(2)O yield) is an important determinant of how much N(2)O is produced by river networks, but little is known about the N(2)O yield in flowing waters. Here, we present the results of whole-stream (15)N-tracer additions conducted in 72 headwater streams draining multiple land-use types across the United States. We found that stream…