密云水库小流域土地利用方式与氮磷流失规律

在密云水库石匣小流域对农田、林果地、荒草坡、村庄等4种不同类型的非点源污染发生区，进行降雨、径流量、径流水质同步监测，分析不同土地利用类型小区地表径流和泥沙中氮磷污染物的流失情况。结果表明，径流中总磷的浓度以村庄最高，其次为坡耕地、林果地和荒草坡。村庄径流的溶解态磷浓度为荒草坡径流的10倍。不同地表径流中的溶解态氮浓度的差别较大，村庄最高，其次是耕地、荒草坡、林果地。在降雨初期，随着径流量的增大，径流中总氮的浓度迅速降低，呈线性递减，此后随着径流的减少，总氮的浓度下降速度极其缓慢。不同土地利用类型中吸附态磷占总磷的比重都在90％以上，与泥沙结合的吸附态磷的浓度远大于溶解态磷的浓度，吸附态磷是磷流失的主要形态。

The Character of Nutrient Loss and Land Use in A Small Watershed of Miyun Reservoir

Synchronous monitoring of rainfall,runoff and water quality was performed and loss of N and P pollutants in the runoffs and sediments analyzed in four types of non-point pollution generating areas,i.e.farmland,forestland and orchard,barren grassland and village,in Shixia small watershed of Miyun Reservoir.The results show that TP concentration in village runoff is highest,and then is in runoff from sloping cultivated land,orchard and forestland.Soluble phosphorus concentration in village runoff is 10 times of that in barren grassland runoff.Soluble nitrogen concentration in surface runoff from cultivated land is highest,and then is in runoff from village,barren grassland and orchard.At the initial stage of rainfall,the TN concentration in runoff decreased rapidly and linearly with the increase of runoff;and then with the decrease of runoff,the TN concentration decreased very slowly.Sediment content in runoff of village is low and adsorbent nitrogen is lower than other land use types.Adsorbent phosphorus is 90% of TP in various land use types,and the adsorbent phosphorus bonded with sediments is much higher than soluble phosphorus and is the main form of phosphorus loss.