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.