Heavy Metals Research in the Black Soil Region of Liaoning Province, China: Spatial Patterns, Risk Assessment, and Sources Apportionment

Heavy metals are enriched in black soil area and affect human safety through the food chain. In this research, 149 soil samples were collected from the black soil region in Liaoning Province; seven heavy metals (Cu, Zn, Cr, Ni, Pb, As, and Cd) were investigated to determine the status, ecological-health risks, and contamination risks and to identify sources. The method of potential ecological risk assessment, Nemerow index, and geo-accumulation index were used to appraise the heavy-metal contamination. Principal component analysis was combined with an absolute factor score/multiple linear regression model to identify the heavy metals' sources in the soil. The average concentrations of Cu, Zn, Cr, Ni, Pb, As, and Cd were 0.92, 0.87, 0.84, 0.95, 1.09, 0.97, and 1.86 times of the soil background value, respectively. In the research area, Ni and Cr were basically non-enriched; As, Cu, and Zn were mildly enriched; Pb was moderately enriched; and Cd was seriously enriched. The source analysis identified three primary sources of heavy metals: the first was natural sources, including Cr, Ni, and Cu. The second was industrial sources, including smelting, with a high contribution from Cd and Zn. The third was human activities, such as mining operations, which have a high contribution rate to Pb and As. The research area was not heavily contaminated with heavy metals. This work lays a foundation for the environmental restoration of heavy-metals-polluted black soil, which is vital to restoring the ecology of and fostering sustainable agriculture in Liaoning's black soil region.