Heavy Metal Contamination and Bioavailability in Huayuan Manganese and Lead/Zinc Mineland, Xiangxi
湘西花垣矿区土壤重金属污染及其生物有效性

An extensive sampling was conducted from 4 Manganese mine sites and 5 Lead/Zinc mine sites in Huayuan,Xiangxi.The total and diethylenetriaminepentaacetic(DTPA)-extractable heavy metal(Mn,Pb,Zn,Cu and Cd) concentrations were determined and the heavy metal contamination of mine soils was assessed with pollution index.A principal component analysis(PCA) was performed to identify the key parameters and a simple linear regression was employed to evaluate the relationships between the total and DTPA-extractable heavy metals.The results showed the following: ① The mine soils were characterized by elevated levels of Mn,Pb and Cd in terms of Hunan soil background concentrations,being 8.7,21.5 and 2.9 times of their local soil background values,respectively.According to China Environmental Quality Standard for Soils(GB 15618-1995),most Pb and Cd exceeded the threshold values of Class Ⅲ.② Pollution index showed the mine soil was slightly polluted by Pb and moderately to severely polluted by Cd.Comprehensive pollution index indicated slight to moderate pollution for Manganese mine and moderate to severe pollution for Lead/Zinc mine,respectively.③ The DTPA-extractable Pb and Cd concentrations were relatively high in Manganese and Lead/zinc mine soils and their fractions in comparison to the total metal concentrations exceeded 10%.A significant positive correlation was observed between DTPA-extractable and total concentrations of soil Mn,Pb,Zn and Cd(P<0.01).The principal component analysis showed the total and DTPA-extractable Mn,Pb,Zn and Cd were the key factors resulting heavy metal contamination of mine soils.Therefore,various protective measures should be taken to avoid heavy metal contamination.