西笤溪流域不同土地利用类型营养盐输出系数估算

各种土地利用类型营养盐输出系数是建立非点源污染模型的重要参数。以位于太湖地区的西苕溪流域为研究区,利用G IS技术进行子流域划分并选择了11个典型小流域,通过对2004年Spot遥感影像解译获得流域土地利用数据,于2004年分3次监测了各个小流域出口的TN、TP浓度。基于以上数据,定性分析了小流域土地利用结构与营养盐输出关系,表明随着耕地面积比例增大或林地面积比例减小,营养盐输出水平增大;在此分析基础上,建立了小流域不同土地利用类型（耕地、林地）面积比例与TN、TP浓度的定量关系,并进而计算获得西苕溪流域耕地的TN、TP输出系数分别为4.747 3 m g/L,0.089 6 m g/L,林地的TN、TP输出系数分别为0.271 3m g/L,0.007 5 m g/L,为流域尺度的营养盐输出负荷估算提供重要参数。

Estimation of Nutrient Export Coefficient from Different Land Use Types in Xitiaoxi Watershed

Nutrient export coefficient of land use is an important parameter for constructing model of non-point source pollution. Xitiaoxi watershed located in Taihu lake region, 11 representative sub-watersheds were delineated and selected by GIS. Land use data derived from Spot satellite images in 2004. TN/TP concentrations were measured by 3 times in Jul. , Sep. and Dec. of 2004 at outlets of these sub-watersheds. The relationship between land use composition and nutrient export was qualitatively analyzed, the result showed that nutrient export increase with a higher percentage of arable land area and a lower percentage of forest land area. Based on this result, the quantitative equation between percentage of land use area and TN/TP concentration was established. TN/TP export coefficient for arable land is 4. 747 3 mg/L and 0. 089 6 mg/L, and TN/TP export coefficient for forest land is 0. 271 3 mg/L and 0. 007 5 mg/L.