20年来密云水库主要入库河流总氮变化趋势和影响因素

Trends in the total nitrogen concentration and the major influencing factors in the main rivers flowing into the Miyun Reservoir in recent 20 years

密云水库是北京市最主要的饮用水源地,但近年来,密云水库遭遇了氮类污染物浓度逐渐增加的问题.因此,本文分析了密云水库主要入库河流潮河和白河在1990—2010年的总氮变化趋势和影响因素.结果表明,1990—2010年期间,潮河、白河的总氮浓度呈明显增加的趋势,且TN浓度随流量的增加呈减小趋势,经流量校正后,潮河在非汛期和白河的TN浓度显著增加,2000年后汛期潮河的TN浓度减小;总氮主要以硝态氮存在,与总硬度的相关系数最大;20年来,区域人类活动逐渐增强,水利水保措施并未改变总氮浓度增加的趋势.农业非点源污染物和畜禽养殖污染物的增加是入库河流总氮增加的主要原因,径流量减少又放大了这一效应,污染物主要通过淋溶作用补给到地下水,再补给到河流水体中.研究表明,要有效控制河流的总氮浓度,应把重点放在减小地下水的过度利用和控制区域内的非点源污染上.

Miyun Reservoir is the main source of drinking water in Beijing, while it has been suffering from increasing nitrogen concentration in recent years. This manuscript analyzes the total nitrogen （TN） trends and influencing factors of Chaohe River and Baihe River flowing into the Miyun Reservoir from 1990 to 2010. The results show that trends in the TN concentration increased significantly, the TN concentration decreased first and then increased as the flow increased;after being adjusted by the flow, the trend still increased significantly in the two rivers;nitrate was the major present state of nitrogen, and had a good correlation with the total hardness. Human activities in the region gradually increased in the 20 years, while water conservation measures since 2000 did not change the increasing trend of TN concentrations. The increase of agricultural nonpoint source pollution and livestock pollution was the main reason for the increased trend of TN in rivers. Our findings indicate that in order to control the increasing trend of TN concentration effectively, the government should focus on the protection of the groundwater and reduce the nonpoint source pollution in the basin.