Nitrous oxide emissions from streams in agricultural and natural areas

Streams and rivers have been highlighted as significant but poorly constrained sources of nitrous oxide (N2O), a greenhouse gas ≈300 times more potent than carbon dioxide. A large share of stream N2O emissions arises from the use of nitrogen (N) fertilizers by agriculture and therefore most of the research on N2O emissions from streams has focused on agricultural areas, especially on fertile calcareous soils having near-neutral pH.However, recent research suggests that streams located in regions having low pH (<5.5) and high iron content in soils may promote disproportionally high N2O emissions. We tested this hypothesis by investigating the drivers of N2O emissions in agricultural and natural streams located in regions of Denmark where soils with low pH and high iron contents are prevalent.We measured N2O emissions monthly for a year in 10 streams located in agricultural and natural areas. Furthermore, we also measured N2O emissions four times a year in 80 streams covering a broad gradient of land-use and soil properties.The preliminary results indicate that, within agricultural and natural areas, streams with low pH have higher emissions of N2O than those with higher pH. We will compare our results with the estimates calculated using the IPCC methodology and discuss the implications of our findings for national greenhouse gas inventories.