Research On Spatiotemporal Variation Characteristics And Source Apportionment Of Nitrogen And Phosphorus In The Songhua River

The Songhua River Basin(SHR)is one of the seven major river basins in China.In recent years,the water quality of the SHR has been continuously improved,but ammonia nitrogen and total phosphorus are the main pollution factors in the basin.For example,some of the worse V sections mainly caused by excess ammonia nitrogen.In this research,42 monitoring sections in SHR were selected to collect the monitoring data from 2003 to 2019,and the data of sampling and monitoring were combined for research.The environmental quality and the main pollution factors of SHR were studied by multivariate statistical analysis.In addition,the seasonal kendall test method and distribution diagram of NH4+-N,TN and CODMn were used to analyze the spatial and temporal distribution characteristics of nitrogen and phosphorus of SHR.Finally,815N-NP3 and δ18O-NP3 isotope analysis,Iso-Source mass balance model and multivariate statistical analysis were used to analyze the main sources of nitrogen and phosphorus in SHR.The research results can provide technical support for the control of nitrogen and phosphorus pollution in SHR.The main results are as follows.(1)Since 2011,the water quality of SHR was improved year by year.In 2019,the SHR was slightly polluted with COD,CODMn and NH4+-N as the main pollution indicators.In terms of time dimension,The concentration of NH4+-N and TN were the largest in the low flow season,and the smallest in the high flow season.NH4+-N,TN,TP and NO3--N are the main water quality parameters in low flow season.The concentration of TP and CODMn were the largest in the high flow season,and the smallest in the low flow season.The water quality influencing factor in high flow season were the most complex,which included NH4+-N,BOD5 and COD.In terms of spatial dimension,The concentration of nitrogen and phosphorus in urban section and tributaries of the SHR was higher.The concentration of NH4+-N,TN and TP in the downstream sections of cities were obviously higher than the upstream sections,and the concentration of NH4+-N,TN and TP in tributaries such as Yitong River and Ashi river were much higher than the main streams.(2)The main sources of nitrogen included soil organic nitrogen,living and manure sewage and nitrogenous fertilizers.Among them,soil organic nitrogen(60%)was the main source of nitrogen pollution in flat flow season.Living and manure sewage(53%)was the main source of nitrogen pollution in low flow season.The contribution rates of various sources of nitrogen in high flow season were relatively average,and the attention should be paid to nitrogenous fertilizer(27%)and living and manure sewage(41%).In addition,the main sources of phosphorus include phosphorus of municipal wastewater,soil organic phosphorus and phosphorus fertilizer.It was shown that domestic pollution,such as living and manure sewage,was the main source of nitrogen and phosphorus pollution in the SHR,followed by chemical fertilizer.It was shown that NH4+-N,TN and TP are the main indexes of water pollution in SHR.Domestic pollution,such as living and manure sewage,was the main source of nitrogen and phosphorus pollution in the SHR,followed by chemical fertilizer.The nitrogen and phosphorus pollution in the Yitong River and Ashi river and other heavily polluted tributaries were in urgent need of further treatment and control.