Characteristics and sources analysis of heavy metal pollution in key monitoring units and surrounding soil in Weihai City

This study focuses 8 key soil pollution monitoring units and their surrounding areas in 5 industrial parks in Weihai City, systematically revealed the characteristics, spatial distribution patterns and potential ecological risks of heavy metal pollution in the soil of the monitoring unit and its surrounding areas. By setting up 33 surface soil sampling points, the mass fractions of Cr, Ni, Cu, As, Pb, Cd and Hg were measured. According to the different locations of the soil samples, they were divided into 1 to 5 zones. Multiple pollution indices are comprehensively used to evaluate the pollution level of different zones, and the sources of pollution are analyzed through correlation analysis, principal component analysis and cluster analysis. The results showed that the average mass fractions of Cr, Ni, Cu, As, Pb and Cd in the samples were 1.7, 2.1, 2.2, 1.2, 1.2 and 2.1 times higher than the background values, respectively. The coefficients of variation of Cd and Hg were as high as 184.2% and 152.4%, indicated significant human interference. The spatial distribution of heavy metals in soil showed regional differences. The concentrations of Cr, Ni and Cu were the highest in zone 5, As was enriched in Zone 2, the contents of Cd and Pb were prominent in zone 4, and Hg was only slightly higher than the background value in zone 1. The pollution assessment showed that Cu, Ni, and Cd in the soil are slightly polluted, Cr, Pb, and As in the soil are mildly polluted, and Hg in the soil is not polluted. The calculation results of the Nemero comprehensive pollution index indicated that 39.4% of the points were slightly polluted, 45.5% were moderately polluted, and the overall level belonged to mild pollution. The potential ecological risk index showed that Cd and Hg caused moderate and minor hazard risks respectively, and the comprehensive risk level was minor hazard. Source analysis indicated that Cr, Ni and Cu mainly originated from domestic sewage and the electronics and electroplating industries, while Cd, Hg and Pb were related to the printing, plastic, medical and auto repair industries, and As came from the process of kitchen waste treatment. The research results can provide a scientific data for the prevention and control of regional soil pollution in Weihai City. It is suggested to strengthen the supervision of key monitoring units of soil pollution and take targeted remediation measures.