Soil Heavy Metals Contamination of a Typical Calcium Carbide Slag Dump Sites: Source Apportionment and Risk Assessment

Source identification and risk assessment of heavy metals were the necessary preliminary work for the contaminated sites remediation. In this report, the As, Cd, Cr, Cu, Hg, Ni, Pb and Zn concentration in a typical calcium carbide slag dump site of thirty-four soil samples were collected to test. The source of heavy metals was analyzed by PMF model, and the apportionment of ecological risk and health risk with different pollution sources were calculated. The results show that Hg was the main polluted heavy metal in the site, with a maximum concentration of 112.19 mg.kg-1, and the soil in the site was accompanied by As, Cu and Pb co-contamination. The average Hg concentration in farmland samples was 0.13 mg.kg-1, which also exceeded the local soil background values, indicating that soil Hg contamination in the site had spread outwards. The sources of eight heavy metals were divided into oil refinery waste water and parent material mixed source (As, Cr, Cu and Pb), vinyl chloride waste source (Hg) and parent material source (Cd, Ni and Zn), respectively. The average potential ecological risk of soil in the site was 22344.39 and vinyl chloride waste source contributed 99.85% to ecological risk. The average CR of oil refinery waste-water and parent material mixed source for children and adults were 9.06×10-6 and 6.36×10-6, accounting for 99.9% and 99.48% of the total average CR for children and adults, respectively. The average HI of vinyl chloride waste source to children and adults were 0.6 and 0.38, accounting for 64.13% and 52.34% of the average total HI of child and adult, respectively. This indicates that children were more vulnerable to heavy metals. Compared with adults, the major pollution sources were more harmful to children.