2023-2025年北运河水体质量时空演变特征评价OA

To reveal the evolution pattern of water quality in the North Canal,this study collected monthly monitoring data from 9 monitoring sites from January 2023 to August 2025,and selected 6 key indicators including chlorophyll-a,total nitrogen,and total phosphorus,etc.The Water Quality Index(WQI),time series analysis and spatial interpolation method were adopted to analyze the spatio-temporal variation characteristics of water quality and its key limiting factors.The results showed that the median WQI of the main stream was 70,indicating the overall water quality was moderately good.Moreover,this stream presented a typical seasonal characteristic of"deterioration in the flood season and optimization in the non-flood season",which marked the flood season as the critical period for water quality prevention and control.Spatially,the water quality showed a gradient of"poor in the upstream and excellent in the downstream".For example,the water quality at Caonian Rubber Dam was the worst,while that at Niumutun was the best,and the water quality at Gantang Sluice declined significantly during the flood season.The Xiaozhong River,a major tributary,suffered from serious pollution with total nitrogen and total phosphorus exceeding standards.Total nitrogen was the key regional limiting factor except for the wetland outlet.TN concentration ranged from 3.36 to 12.69 mg/L,far exceeding the Class Ⅴ standard limit,and the localized sluice and dam sections faced eutrophication risks.Accordingly,this study recommended focusing on flood season prevention and control,prioritizing total nitrogen reduction,and implementing differentiated water quality management through tributary source emission reduction,hydrodynamic regulation of sluices and dams,and wetland purification.