SPARROW模型的传输过程研究——以新安江流域总氮为例

建立新安江流域总氮的SPARROW模型,以土-水传输因子(LDF)表示降雨、坡度、气温3个土-水传输变量的影响,结合农业源、林草地源、生活源3个污染源排放系数,分析总氮经过土-水传输之后到达河道的比例(LDR),由此揭示总氮的非点源污染特征。结果显示坡度的影响在整个流域范围内差异相对较大,LDF为0.86~1.06,因而对3类污染源进入河道的传输比差异亦较大。综合考虑3个土-水传输变量作用下,子流域60土-水传输因子最大,而子流域225最小,因此若制定减排措施要求入河减少量相同,管理上会优先考虑子流域60所在的地区。研究采用改进的河流衰减方程同时描述水文和非水文因素的影响,代替河流分级衰减系数,引进传质系数作为模型模拟参数,削减速率与流量呈负相关关系,且大部分河段削减速率均在以往文献研究范围之内,表明改进的传质速率用于新安江流域总氮模型具有可行性。

Research on the transport processes of SPARROW model:A case study for total nitrogen in Xin'anjiang River Basin

A SPARROW (Spatially Referenced Regression on Watershed attributes) model was established to estimate total nitrogen (TN) in Xin''anjiang River Basin. The land-to-water delivery factor (LDF) denoted the influences of three land-water variables of rainfall, slope and air temperature, combined with discharge coefficients of three pollutant sources, i.e., agricultural source, forestland-grassland source and life source, the delivery ratio (LDR) of total nitrogen after transported by land-water and reached river channel was analyzed, thus to reveal the nonpoint source pollution of the total nitrogen. The results showed that, the influences of slope differed greatly in the whole basin, LDF value ranged between 0.86 and 1.06, therefore, the transport ratios of three pollution sources into the stream channels had large differences. Considering the overall effects of three land-to-water delivery variables, the maximum and minimum LDF occurred in the 60th and 225th subbasins, respectively. Thus the areas where the 60th subbasin located was considered prior to the other subbasins in the management if the emission reduction measures required the same reductions into the river. The influences of hydrological and non-hydrological factors were described by using a improved stream attenuation equation. Instead of the first-order reaction coefficient, the mass transfer coefficient was taken as the model simulation parameter. The reduction rate was negatively correlated with the flow rate, and most of reach reduction rates were within the value scopes of the previous literatures. It showed that the improved mass transfer rate was feasible for the TN model of Xin''anjiang River Basin.