Evaluation of Heavy Metal Content, Sources, and Potential Ecological Risks in Soils of Southern Hilly Areas

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In order to explore the characteristics of soil heavy metal pollution and ecological risk status in southern hilly areas, a hilly area of a southern province was selected as the research area, using soil samples collected at 60 points in 2017. The single factor pollution index (Pi), Nemero comprehensive pollution index, and potential ecological risk index (RI) were used to evaluate the content characteristics and potential ecological risks of eight heavy metal elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn), and positive definite matrix factor analysis models (PMF) were used to analyze their sources of pollution. The results were as follows:① the content of eight heavy metal elements in the study area exceeded the standard, and the Nemeiro comprehensive pollution index showed that the proportions of light, moderate, and heavy pollution in the study area were 63%, 8%, and 2%, respectively. Unpolluted and lightly polluted samples accounted for 27% and were thus basically lightly polluted. ②The comprehensive potential ecological risk index showed that the RI of soil heavy metals was 39.58-224.15, the proportions of samples with low and medium ecological risks were 73.33% and 25%, respectively, and the proportion of sites with severe ecological risks was 1.67%. Although this site had the highest ecological risk, the content of heavy metals was lower than the background value of soil elements in the province. ③Six pollution sources were obtained through the PMF model:natural sources, agricultural activity sources, mixed sources composed of copper mining and transportation, industrial activity sources, transportation sources, and domestic waste emission sources. The contribution rates of each source were 24.8%, 17.7%, 17.7%, 17.6%, 12.0%, and 10.2%, respectively.