Nitrous oxide (N2O) emissions from the high dam reservoir in longitudinal range-gorge regions on the Lancang-Mekong River, southwest China

Nitrous oxide (N2O) is a greenhouse gas that should not be overlooked, and its emissions from plain reservoirs as well as small- and medium-sized reservoirs have been extensively studied; however, N2O emission patterns from high-dam reservoirs in longitudinal range-gorge regions remain unclear. In this study, the N2O concentration and emission flux from the high-dam Xiaowan Reservoir were investigated using static headspace gas chromatography and a boundary layer approach in the Lancang River. The factors influencing N2O production and emissions, especially the influence of damming, were explored. Our results demonstrated that the Xiaowan Reservoir, a source of N2O emissions, had an N2O emission flux of 15.48 +/- 2.87 mu mol m(2).d(-1) in 2019; the N2O concentration and emission flux exhibited an increasing trend along the flow direction within the Xiaowan Reservoir but decreased downstream of the dam. During the two water seasons, water temperature, the concentration of DO, NO3- and NH4+ are all influencing factors of the N2O concentration in the XWR. the N2O in the XWR during the wet season was produced by nitrification, during the dry season the production mechanism of N2O was relatively complicated, but mainly produced by nitrification. This study advances our knowledge of N2O emissions from high-dam reservoirs in longitudinal range-gorge regions.

Automated summary

This study investigated the N2O concentration and emission flux from the high-dam Xiaowan Reservoir in the Lancang River region, revealing that various factors such as water temperature, DO concentration, and nutrients influence N2O emissions. The study advances our understanding of N2O emissions from high-dam reservoirs in longitudinal range-gorge regions.