猫跳河流域梯级水库夏季N2O的产生与释放机理

为了研究河流筑坝对河流氮生物地球化学循环的影响，在夏季水体分层期间对猫跳河梯级水库坝前分层采集水样进行了相关地球化学分析。结果显示，在上游的两座水库存在2个明显的温度分层现象，并影响到了水体N2O的产生和分布。红枫水库整个剖面的氮分布主要受硝化作用控制，而百花湖、修文及红岩水库则表现为上层水体为硝化作用，中层为硝化反硝化共同作用。所有水库表层水和下泄水高饱和度的N2O含量表明这些水体为大气N2O的源。百花湖底层反硝化作用强烈，中间产物N2O大量消耗。底层泄水的方式对于温室气体释放影响重大，因此不同水库下泄水的N2O含量在时间和空间上的变化与水库运行和调蓄模式有关。研究结果表明，梯级水库过程对N2O的排放影响很大，在水电开发的环境保护中应当引起重视。

PRODUCING AND RELEASING MECHANISM OF N2O IN CASCADE RESERVOIRS OF MAOTIAO RIVER IN SUMMER

In order to make clear that what kind of impacts the cascade reservoirs play on the nitrogen biogeochemistry circle in the river, we sampled water by different layers in front of the each dam and outflow water in the cascade reservoirs of Maotiao River, Guizhou Province, Southwest China. The water chemistry of the cascade reservoirs is discussed in terms of the physical and chemical parameters, together with N2O distribution in summer. The results indicate that discontinuity layers of temperature plays an important role in production and distribution of N2O in reservoirs of Maotiao River. The N2O distribution in the layer above the SDL (secondary discontinuity layer) in the four cascade reservoirs is dominated by nitrification, while between the SDL and PDL (primary discontinuity layer) is controlled by both of nitrification and denitrification. As two main processes that affect the production of the N2O, nitrification and denitrification change the distribution of N2O in cascade reservoirs. The contents of N2O in reservoirs are higher than that in the atmospheres. This suggests that high contents of the N2O in the reservoir are the N2O source of the atmosphere. However, N2O contents decrease at depth below 15 m with low contents of DO indicates that denitrification produced N2 by consuming a large part of N2O. The water discharge from bottom of cascade reservoirs along Maotiao River released large amount of N2O into atmosphere, which should be taken into account for improving environmental protection of waters in cascade reservoirs when hydroelectric power will be developed.