Abstract: Most of rivers over the world are impounded. The effects of the impoundment on greenhouse gas emission have attracted much attention in recent years. Studies on production and emission of nitrous oxide (N₂O) are important for better understanding of nitrogen biogeochemicalcycling in reservoirs and impounded rivers and important for assessing the emission fluxes of N₂O from reservoirs. However, the knowledge on N₂O emissions and related mechanisms is still limited, especially on key processes, emission fluxes, and driving factors. Here, we reviewed theresearches on nitrogen biogeochemical cycling and N₂O emissions worldwide and proposed future research trends for further research and the unresolved key questions, aiming to accurately evaluate the emission fluxes of N₂O in river reservoir systems under impoundment.

Key words: ecological barrier, non-point source pollution, location design, river-type reservoir, flux analysis