Pollution characteristics and ecological risk assessment of heavy metals in typical non-ferrous metal smelting areas
To analyze the characteristics of heavy metal pollution in a typical non-ferrous metal smelting area in China and to comprehensively understand the potential ecological risk and sources of heavy metal pollution,a typical non-ferrous metal smelting area in Zhehai Town,Huize County,Yunnan Province,China,was used as an example of the single-factor pollution,nemero comprehensive pollution,potential ecological risk,and water quality indices evaluation methods.The contamination characteristics and potential ecological risks of eight heavy metals,Cd,Hg,As,Pb,Cr,Cu,Ni,and Zn,in soil,river sediment and river water quality were evaluated and their sources were analyzed.The results revealed that the average values of the Nemero comprehensive pollution index(PN)of the soil and sediment in the study area were 84.1 and 215.5,respectively,which were both within the heavy pollution level.The average values of the heavy metal combined potential ecological hazard risk index(RI)were 3562.3 and 8907.0,respectively,which were both at a very high risk level.The contents of all heavy metal elements in the soil and substrate of the study area exceeded the background value of soil in Yunnan Province and was significantly higher than the national screening value for soil pollution risk in agricultural land.Among them,Cd was the most pollution-causing element,and the content of Cd in the soil and substrate was 8.2 times and 15.8 times the national soil pollution risk control value for agricultural land,respectively.Further,the RI contribution of Cd to soil and substrate reached 94.34%and 96.78%,respectively,which should be an area of focus.The water quality level of rivers in the study area were in the good to very poor level,and 56.25%and 6.25%of the sampling points of Ni and Zn in the water bodies exceeded the limited value of Class Ⅲ water,respectively,whereas other heavy metal elements did not exceed the standard.Cd,Hg,As,Pb,Cu,and Zn in soils and substrates of the study area mainly originated from local mining pollution,whereas Cr and Ni mainly originated from fuel combustion.In general,Cd pollution in the study area is serious and there is an extremely high potential risk;therefore,measures,such as safe utilization and remediation,should be taken to reduce the risk level.
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