Study on The N2O Flux Across the Sediment-Water Interface in the Lancang River Reservoir
Abstract: As a sort of environment boundary between water and sediment, sediment-water interface is the main channel for nitrogen and phosphorus circulation in lakes and reservoirs, and plays the role of “source” and “sink” of N2O. With the increasing proportion of N2O emissions in greenhouse gases, its related research has become one of the hot spots in the field of environmental science. Based on the environment in the region,the flux of N2O between bottom sediment and water layer at 3 reservoirs ( DCS : the Dachaoshan Reservoir, NZD : the Nuozhadu Reservoir, JH : the Jinghong Reservoir ) in the Lancang River of Southwest China is studied in this paper from August in 2018, and the lab incubation method is adopted to simulate and measure the N2O exchange flux under sediment-water interface in order to study the effect of related factors. It is found that there is a very significant positive relationship between the N2O fluxes across the sediment-water interface and the concentration of NO3- in overlying water(P﹤0.01). There is also a very significant negative relationship between the N2O fluxes across the sediment-water interface and the concentration of NH4+ in overlying water(P﹤ 0.05). The nitrite in overlying water can promote the production of N2O in sediment. The ammonia nitrogen in overlying water can repress the production of N2O in sediment. Results showed that the sediment-water interface N2O flux from the reservoirs of DCS, NZD, JH were 1.3±0.67μmol/(m2·d), -0.42±1.26μmol /(m2·d), -0.43±1.13μmol /(m2·d),respectively, the N2O is diffused from the overlying water into sediment in the reservoirs of DCS（F > 0）, reflecting that sediment was the source of N2O, and the N2O is diffused from the sediment into overlying water in the reservoirs of NZD and JH（F < 0）, reflecting that sediment was the sink of N2O. From the above results, it can be seen that the Lancang River was the “source” and “sink” of atmospheric N2O.
Key words: The Lancang River, The sediment-water interface, N2O
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