基于改进SWAT模型的非点源磷污染特征研究OACHSSCD

Phosphorus non-point source pollution in river basins across China has become increasingly prominent,serving as a major contributor to ecological problems such as water quality deterioration and algal blooms.A systematic understanding of its driving factors and spatio-temporal distribution is of great scientific and practical significance for pollution control.Soil and Water Assessment Tool(SWAT)is one of the most widely used watershed-scale environmental models in analyzing phosphorus non-point source pollution.To address issues that hinder the application of SWAT model in China-such as high parameter uncertainty,complex model configuration,and difficulties in obtaining agricultural management input data-this study developed a localized version of SWAT named the SWAT-SPM model.By simplifying the process simulation of soil phosphorus cycle and incorporating measured and region-specific research data as core model parameters,the model's applicability and reliability in Chinese basins have been significantly improved.Application of the model in a typical agricultural watershed in southern China-the Jiulong River Basin in Fujian Province-demonstrated high accuracy in simulating monthly streamflow and total phosphorus load.Simulation results revealed significant interannual fluctuations in phosphorus export load from 2015 to 2022(ranging from 175 to 1848 t/a),showing a significant positive correlation with runoff(r=0.59,P＜0.01),but a weak correlation with newly added annual phosphorus inputs(r=0.23,P=0.13).Further analysis indicated that phosphorus export is primarily driven by the combined effects of historically accumulated soil phosphorus and hydrological conditions,while newly added phosphorus inputs play an insignificant role.Even under similar hydrological conditions,differences in soil phosphorus accumulation can lead to interannual variations in watershed phosphorus export of up to 78％.These findings suggest that in basins with a large legacy soil phosphorus pool,measures focusing solely on reducing external phosphorus inputs are unlikely to be effective in the short term.There is an urgent need to develop integrated mitigation strategies that account for various sources of phosphorus and shifting hydrological condition due to climate change.Additionally,the spatial heterogeneity of phosphorus pollution across all sub-basins in the target watershed was notable,with a small number of sub-basins contributing disproportionately to the total watershed pollution load relative to their area.This highlights the importance of precisely targeting these critical areas in future pollution control efforts,so that non-point source phosphorus pollution control could be achieved in a cost-effective way,especially in places where only limited resources are allocated for environmental protection.