密云水库上游流域氮流失规律研究

以1212.69km^2的密云水库上游流域为研究对象，研究了氮素在大尺度范围内的流失规律。结果表明，雨季中、雨季后氮的流失量明显高于雨季前，分别为雨季前的2.9倍、2.36倍;位于下游的监测点氮的浓度偏高;随着雨季的到来旅游景点、果园径流中氮的浓度会明显增加;各项污染物的季节变异系数较大的点，位于农业活动比较剧烈和径流季节变异较大的区域，而在水库或塘坝污染物的季节变异较小。不同水文期，河流水体中氮素的主要形态不同，各监测点雨季前、雨季后以溶解态氮为主，雨季中溶解态氮所占比例有所下降，在部分河道以颗粒态为主。雨季前径流中氮的流失以NO3^--N为主，约占总氮的65%，随着雨季的来临所占比例有所下降。

Nitrogen Loss in the Watershed Upstream of Miyun Reservoir

As an important water source,Miyun reservoir plays a crucial role in Beijing.The water quality is at medium-eutrophication state that mainly resulted from the non-point source pollution(NPS) in the watershed.At present,more research work mainly focuses on the characteristic of runoff and erosion from plots or fields,and seldom involves the moving process of nutrients and their impacts on water quality.Combining the monitoring data of surface water,the loss of nitrogen in the watershed upstream of Miyun reservoir with an area of 1 212.69 km2 was studied in this paper.The results showed that the nitrogen loss in rainy season and after rainy season were higher than that before rainy season obviously,up to 2.9 and 2.36 times of the value before rainy season,respectively.The concentration of N was much higher in the downstream,and with the rain season coming,touring spot,village and orchard increased the concentration of nitrogen.The area with stronger farming activity had higher coefficient of variation,while it is lower in reservoir and impoundment areas.Before rainy season,N existed mainly as the form of NO-3-N which accounted for 65% of the total nitrogen and decreased with the rain season coming.The form of nitrogen loss varied with different hydrological stages.Dissolved nitrogen was the main form in streams before rainy season and after rainy season,which decreased in rainy season,while particle nitrogen was the main form in some river.