Distribution and Risk Assessment of Heavy Metals in the Xinzhuangzi Reclamation Soil from the Huainan Coal Mining Area, China

The contamination of coal-mine soil by heavy metals is a widespread problem. This study analyzes the heavy metals (Cu, Zn, Ni, Pb, Cr, Cd, and Hg) found in 33 surface soil samples from Xinzhuangzi, China restored coal-mining land used as cultivated land. The results show that the selected elements were cumulative, especially for Cd. An index of geo-accumulation indicates that the soil was practically uncontaminated by Cu, Zn, Ni, and Hg, uncontaminated to moderately contaminated by Pb and Cr, and moderately to heavily contaminated by Cd. Based on the U.S. Environmental Protection Agency's ecological soil screening levels (Eco-SSLs) for Cu, Zn, Ni, Pb, and Cd and the Dutch Target and Intervention Values for Cr and Hg, the plants and soil invertebrates were not likely greatly influenced by the selected metals. Although the Cd concentration was found to have no significant effect on plants and soil invertebrates, it is the only metal with a concentration significantly above that required by Chinese standards (HJ/T 332-2006) for edible agricultural products, indicating that Cd is the predominant factor that determines the use of the reclaimed coal-mining area for farmland. Thus, employing the reclaimed land as farmland may not be a good option.