| Chishui River is the only primary tributary of the main river dam in the Yangtze River without dam construction.It is an important spawning site for many endemic fish in the Yangtze River,and has important ecological significance.the better ecological environment and lower development intensity of the Chishui River basin make it maintain the natural river characteristics overall.And the Chongqing section of the Yangtze River flows through the whole territory of Chongqing,which is affected by the input of urban sewage and coastal industrial wastewater in Chongqing,and represents the river affected by large cities.In this study,the Chishui River Basin and the Chongqing section of the Yangtze River were used as the study areas to explore the distribution and source characteristics of trace elements in rivers under different degrees of human activities.The main findings are as follows:(1)And the median concentrations of trace elements in study area were match well with the background values of Yangtze River,without significant trace elements pollution in Chishui River.Compared with other trace elements,the relatively high concentrations could be observed on Sr with a median concentration of 540.2 ug/L.Spatial structure analysis showed the high content of trace elements were mainly in the upper and middle reaches of Chishui River basin.The concentration of trace elements in Chongqing section of the Yangtze River is larger than the background value of the Yangtze River.in spatial distribution,12 trace elements showed higher concentration values in the Jialing River section and lower concentration levels in the Yangtze River section.(2)The results of water quality assessment and health risk assessment of dissolved trace elements in Chishui River Basin and Chongqing section of Yangtze River Basin show that the water quality of Chishui River Basin and Chongqing section of Yangtze River Basin is better and the health risk caused by trace elements is small.notably,the risk of non-cancerous exposure of trace elements to children is significantly greater than that of adults.(3)The correlation and principal component analysis of dissolved trace elements in Chishui River basin and Chongqing section of Yangtze River were carried out.The main sources of trace elements were analyzed according to the distribution of pollution sources:Mn and Cd were attributed to the soil parent material,geochemistry effects,as well as cultivation.The source of Al,Cr,Sr and Fe were associated with the rock weathering and domestic sewage.Based on the clustering analysis,four spatial regions were identified: C1(lower reaches of Chishui River Basin),C2(middle and upper reaches of Chishui River Basin),C3(Chishui Heyuan River Basin and Weihe River Basin),C4(Yanjin River Basin),The trace element concentration of four regions followed by C4>C2>C3>C1,The highest concentrations of Sr,Fe,As and Li occurred in C4;while Mn and Cd in C3,Al and Cr in C2.The Chongqing section of the Yangtze River is obviously affected by urban wastewater,and the As?Sr?Mo?Co and Cr elements in the basin are greatly affected by urban industrial and domestic wastewater except by rock weathering.The high Zn and Cd elements of Jialing River may be affected by the development of upstream mineral resources.Al?Mn and Fe are mainly derived from natural sources such as soil erosion and rock weathering.Ni and Rb in the Chongqing section of the Yangtze River are mainly due to the impact of industrial waste discharge.(4)Through analyzing the change of trace elements in different types of rivers,it is found that As?Cr and Ni are generally higher in urban areas.As?Cr and Ni may be used as representative elements of urban wastewater impact in river trace element analysis. |
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