| The Beiyun River,originating in the mountainous area of western Beijing,is a vital ecological corridor connecting Beijing,Tianjin and Hebei,whinch take on the tasks of water supply,flood control and landscape.With the development of the city,various environmental risks such as water environment,water ecology,and water resources in the Beiyun River Basin are prominent.The quantitative analysis of the above eco-environmental problems and the establishment of pollution source inventory are the important premise and basis for watershed comprehensive management.This study takes ArcGis as the main research technology,takes the control unit of the BeiYun River divided by the Ministry of Ecology and Environment as the datum,the industrial source and the urban living sources are obtained by using the direct and indirect calculation,the method system of pollution source assessment model for the Beiyun River Basin was established to carry out quantitative analysis of pollution load in the Beiyun River Basin in ten years(2009-2018).A dynamic discharge inventory of river basin water pollutants with spatiotemporal distribution characteristics is formed since we have mastered the time and space distribution characteristics of pollution in the Beiyun River Basin and have explored the source of pollution.This study provides valid uphold for management sections to control pollution source pollution in the basin and ameliorate.valley water environment.The study indicates:(1)The emission of pollutants from industrial sources and urban household sources in each control unit of Beiyun River Basin showed a decreasing trend year by year,indicating that the emission of pollutants from point sources of Beiyun River Basin control unit showed a decreasing trend year by year.The point source is no longer the main source of pollution in the Beiyun River Basin.(2)The discharge load of nitrogen(TN and NH4+-N)non-point source pollution is more prominent in the middle area of the Beiyun River Basin.The average discharge load of TN and NH4+-N from non-point sources in the Beiyun River Basin was 0.31 t/km2 and 0.23 t/km2,the average discharge was 1858 t and 1370 t,and the average discharge into the river was 228 t and 166.4 t,respectively from 2009 to 2018.The discharge load of nitrogen non-point source pollution in Beiyun River Basin was relatively high in 2015,2016 and 2017,and the discharge load was the most prominent in 2016 from the perspective of time sequence.The reason was that the nitrogen surplus was relatively high,and the rainfall was also higher than the multi-year average,leading to the most prominent nitrogen nonpoint source pollution in the basin in 2016.The crop production has always been the ultimate source of nitrogen non-point source pollution with the perspective of pollution kinds in the Beiyun River Basin,and the average proportion of TN and NH4+-N emissions from farmland runoff was 65.7%during the study period.(3)The discharge load of phosphorus(TP)non-point source pollution is more prominent in the middle and south area of the Beiyun River Basin.The average discharge load of TP from non-point sources in the Beiyun River Basin was 0.02 t/km2,the average discharge was 147 t and the average discharge into the river was 16 t,respectively from 2009 to 2018.The TP non-point source pollution discharge load was comparatively high in 2015,2016 and 2017,and was also relatively prominent in 2009 and 2012 becase of the synthetical influence of precipitation,mass balance of nitrogen and phosphorus in farmland and other factors in Beiyun River Basin with the perspective of time sequence.The primary sources of phosphorus non-point source pollution in Beiyun River Basin are crop production and poultry farming with the perspective of pollution types.The average proportion of runoff TP emissions in farmland was 42.6%during the study period.In recent years,with the gradual increase of livestock and poultry manure treatment rate,the total phosphorus pollution caused by livestock and poultry breeding generally showed a downward trend.(4)The discharge load of CODcr non-point source pollution is more prominent in the middle and south of Beiyun River Basin,which is characterized by the prominent distribution in the central urban areas of Beijing,Tianjin and Hebei Province,and scattered distribution in other areas.The average discharge load of CODCr from non-point sources in Beiyun River Basin was 2.72 t/km2,and the average discharge and river inflow were 16,070 t and 1,718 t,respectively from 2009 to 2018.The emission load of CODcr non-point source pollution was generally high during the study period in Beiyun River with the perspective of time sequence.The primary sources of CODcr non-point source pollution was poultry farming and city runoff in the Beiyun River Basin.The average proportion of CODCr emissions is 51.0%in city runoff during the study period,and is 41.6%in poultry farming with the perspective of pollution types. |
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