Solid/solution partitioning and speciation of heavy metals in the contaminated agricultural soils around a copper mine in eastern Nanjing city, China

摘要

Solid/solution partition coefficient (K_d) and speciation of soil heavy metals can be used for predicting their environmental risks. The K_d values and solution speciation of soil Cu, Cd and Zn were analyzed in 40 samples of contaminated agricultural soils around Jiuhua copper mine in eastern Nanjing city, China. The K_d ranges (and mean values) for soil Cu, Cd and Zn are 703-7418 (3453), 37.3-3963 (940) and 319-17 965 (7244) L kg~(-1), respectively, showing a large variability both for metals and soils. The results of differential pulse anodic stripping voltammetry (DPASV) indicates that 95.6% solution Cu is bound to dissolved organic ligands. About half of the dissolved Zn is DPASV-labile at pH < 6, while 92.1% solution Zn is in the form of organic complexes at pH > 6. DPASV-labile Cd is ranged from 22.6 to 98.7% with the mean value of 56.3%. Multiple linear regressions indicate that K_d, the dissolved and DPASV-labile concentrations of Cd and Zn are mostly influenced by the soil solution pH with R~2 of 0.50, 0.59 and 0.63, respectively for Cd, and 0.58, 0.72 and 0.64, respectively for Zn. Considering the second parameter of corresponding soil metal, the linear relationships of K_d with pH were improved with R~2 of 0.70 and 0.73 for Cd and Zn, respectively. However, the solubility of soil Cu was insensitive to pH. Only SOC shows a weak relationship to the dissolved Cu with R~2 of 0.21. As for its K_d, total soil Cu is the most significant factor. But for DPASV-labile Cu, no soil parameters were found to be good predictors.