分布式水土流失型面源污染模型初探

为研究丘陵山区水土流失与面源污染协同过程机理对丘陵山区环境改善的作用，本研究研发出一种分布式水土流失型面源污染模型，该模型通过耦合多个水土流失型面源污染关键过程模块，从源、流、汇等角度精准刻画水土流失型面源污染过程机理；进而开发了基于优化算法的汇流模块，解决了分布式模型运算效率低等技术问题。本研究利用新模型评价了三峡库区菁林溪流域水土流失型面源污染时空演变规律，并模拟了退耕还林、化肥减量、坡改梯和滨岸缓冲带对水土流失型面源污染的防治效果。结果表明：菁林溪流域年均泥沙、吸附态磷、溶解态磷的负荷量分别为17.23 t·hm^-2、1.22 kg·hm^-2和0.56 kg·hm^-2，入河量分别为9 032.2 t·a^-1、601.3 kg·a^-1和541.7 kg·a^-1，分别占负荷量的54.32%、50.87%和72.99%。不同土地利用类型的吸附态磷负荷强度为坡耕地>林地>水田，溶解态磷负荷强度为坡耕地>水田>林地，表明水土流失型面源污染优先控制区与传统农业面源有所差异。同时，滨岸缓冲带的防控效果最好，可减少25.01%的泥沙量和26.22%的吸附态磷。本模型较好地模拟了水土流失型面源污染及防控措施效果，可为水土流失型面源污染过程机理精准解析和优化防控提供依据。

Preliminary study on distributed erosion-type non-point source pollution model

Soil erosion and non-point source pollution are serious issues in hilly and mountainous areas. Studying the synergistic process mechanism is important to enable environmental improvements in hilly and mountainous areas. There is limited knowledge of erosion-type non-point source pollution in hilly and mountainous areas. In particular, refined evaluations need to be further improved. In this study, a distributed erosion-type non-point source pollution model was developed. By coupling multiple key process of erosion-type non-point source pollution, the mechanism of this pollution process was accurately described from the perspective of source, flow, and sink. A confluence module based on an optimization algorithm was developed to solve technical problems, such as low execution efficiency, of the distributed model. The new model was used to evaluate the temporal and spatial evolution of erosion-type non-point source pollution in the Jinglinxi watershed of the Three Gorges Reservoir region, and to evaluate the effects of returning farmland to forest, fertilizer reduction, slope modification, and coastal buffer zone on erosion-type non-point source pollution. The results indicated that the average load of introduced sediment, adsorbed phosphorus, and dissolved phosphorus in Jinglinxi watershed was 17.23 t·hm^-2, 1.22 kg·hm^-2 and 0.56 kg·hm^-2, and the annual average amount of introduced sediment, adsorbed phosphorus, and dissolved phosphorus was 9 032.2 t·a^-1, 601.3 kg·a^-1 and 541.7 kg·a^-1, which accounted for 54.32%, 50.87%, and 72.99% of the total load respectively. The load of adsorbed phosphorus for different land uses was ranked as sloping farmland > forest land > paddy field. The load of dissolved phosphorus was ranked as sloping farmland > paddy field > forest land. These findings indicated that the priority control area of erosion-type non-point source pollution differed from that of traditional agricultural non-point sources. The coastal buffer zone was best in reducing erosion-type non-point source pollution, with reductions of 25.01% and 26.22% in the amount of sediment and adsorbed phosphorus entering the watershed, respectively. The new model better simulates the erosion-type non-point source pollution and the reducing effect of prevention measures, and provides a basis for accurate analysis of the process mechanism of erosion-type non-point source pollution and optimized prevention measures.