[Quantifying the Contribution of Soil Heavy Metals to Ecological and Health Risk Sources]

Quantifying the risk of soil heavy metal sources can identify the main pollution sources. It can provide a scientific basis for reducing the ecological and human health risks of soil heavy metals. Taking the shallow soil in a Pb-Zn mine watershed in northern Guangxi as a research object， ecological and human health risk assessments were conducted using potential ecological risk assessment （RI） and human health risk assessment （HRA）， and the source apportionment of soil heavy metals was completed using the absolute principal component-multiple linear regression receptor （APCS-MLR） model and random forest （RF） model. Then， a combined risk assessment model， consisting of RI， HRA， and APCS-MLR， was used to quantify the risk of soil heavy metal sources. The results showed that the contents of Pb， Zn， Cu， and Cd exceeded the environmental screening values for agricultural land with mean values of 342.77， 693.34， 61.27， and 3.08 mg·kg^-1， respectively， and there was a certain degree of contamination. Pb， Cr， and As were the main health risk impact factors， with higher health risks for children than for adults. Three sources were identified： mining activities （Source Ⅰ）， soil parent material sources and original formation （Source Ⅱ）， and unknown sources. Pb， Zn， Cu， and Cd were mainly derived from Source Ⅰ， and Cr and As were controlled by unknown sources and Source Ⅱ. The source risk assessment results of soil heavy metals indicated that the potential ecological risk and non-carcinogenic risk were mainly from Source Ⅰ and Source Ⅱ， and carcinogenic risk was mainly from unknown sources. The unknown sources had a high proportion in source apportionment and risk assessment， and should be further researched to provide scientific basis for soil heavy metal control. The combined risk assessment model based on source analysis， focusing on the risk characteristics of different sources， can accurately identify high-risk pollution sources. It is a more reasonable and reliable risk assessment method.