Origin and spatial distribution of heavy metals and carcinogenic risk assessment in mining areas at You'xi County southeast China

An extensive study on the spatial distribution and source apportionment of heavy metals in soils and so by risk assessment at Youki County, a major Pb Zn mining area southeast China, was conducted in this contribution. A total of 93 soil samples were examined with the concentration of heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn), pH, and soil organic matter (SOM) contents by using geostatistical approaches combined with geographic information system (GIS) analysis. The mean values of heavy metals were determined to be 7.9 +/- 5.8, 12.8 +/- 14.1, 80.4 +/- 42.0, 34.4 +/- 45.0, 0.12 +/- 0.13 +/- 368.5 +/- 873.6, and 369.6 +/- 505.5 mg kg(-1) (mean +/- SD) for As, Cd, Cr, Cu, Hg, Pb, and Zn, respectively. Contents of all heavy metals present in the study area were considerably higher than their background values of provincial and national standards except for As. A principle component analysis revealed the main origin of heavy metals: soil parent materials for Cu, Pb, and Zn; atmospheric deposition during mining processes for Cr, and Hg; and human farming activities for Cd. Carcinogenic risk was assessed with an average value of 69.3 x 10(-6) mg kg(-1), suggesting an average of 69 individuals per million people being predisposed to cancer. Meanwhile, the identification of heavy metal sources in agricultural soils might be beneficial to local soil protection and soil quality improvement.