白洋淀府河下游汛期与非汛期水质变化特征及源解析OACHSSCD

Against the background that point source pollution has been basically effectively controlled,non-point source pollution driven by rainfall during the flood season has become a key bottleneck restricting the improvement of watershed water environment quality.To reveal the spatiotemporal variation patterns,rainfall response characteristics,and pollutant sources of water quality in the lower reaches of the Fuhe River in Baiyangdian Lake,this study conducted an 8-month hydrological and water quality monitoring campaign with high-density site distribution in the basin from February to September 2025.High-frequency,hourly-scale sampling during rainfall events was carried out in the flood season(June—August),with a total of 8 rainfall events monitored.The spatiotemporal variation characteristics of water quality in the lower reaches of the Fuhe River were systematically analyzed,focusing on water quality changes across different rainfall events and during individual rainfall processes.The Positive Matrix Factorization(PMF)model was applied for pollutant source apportionment.The results showed that nitrogen pollution dominated the lower reaches of the Fuhe River,with nitrate accounting for the highest proportion of total nitrogen(81.07%in the non-flood season and 47.29%in the flood season).Agricultural fertilization in April had a significant ＂ fertilizer effect pulse＂ on river water quality,with phosphorus showing a particularly prominent response.Driven by rainfall,the concentrations of ammonia nitrogen and phosphate in the flood season were significantly higher than those in the non-flood season.Water quality changes during individual rainfall events exhibited a typical pattern of ＂ fast phosphorus response and slow nitrogen response ＂.Different types of rainfall had significant impacts on water quality:short-duration,high-intensity rainfall dominated ammonia nitrogen and nitrate pollution,while long-duration,low-intensity rainfall led to increased concentrations of total phosphorus and phosphate.Exposed soil areas,farmland,and villages had significant impacts on the water quality of the lower Fuhe River.The contribution ratios of pollutant sources were in the order of industrial point sources(32%),agricultural and urban non-point sources(29%),domestic sewage sources(26%),and livestock and poultry breeding sources(13%).This study reveals the complete picture of water quality variations in the lower Fuhe River under the influence of multiple factors during both flood and non-flood seasons,clarifies the water quality driving effects of different rainfall characteristics and land use types as well as the mechanisms of pollutant migration and transformation,and provides a scientific basis for the precise management of non-point source pollution and emergency control of flood season pollution in the Baiyangdian Lake basin.