Research on soil cadmium and lead speciation and their transfers from soil to crop in southern Jiangsu

The southern Jiangsu is one of developed areas in China. Intensive anthropogenic activities conduce the toxic metal contamination of soils. Cadmium and Lead are common toxic metals in soils. They have significant impacts on corps. Analysis results of samples showed Pb was even distributed and Cd was variable distributed in the study area. Difference presented in the chemical forms of Pb and Cd in soils. Lead fractions followed the order Fe-Mn Oxide > residual > organic and sulfide > carbonate >exchangeable. Cadmium fractions revealed exchangeable > organic and sulfide > carbonate > residual > Fe-Mn Oxide. The transfer coefficients from soil to rice and wheat grain also exhibited a large dissimilarity for Pb and Cd. Rice and wheat grain only assimilated 0.18%–0.67% of soil Pb, but absorbed 1.1%–88.9% of soil Cd, which was remarkable high for Cd in the soil-crop system. Correlations between soil components and transfer coefficients showed those components made different effects on absorption of crops. The elevations of TOC, pH and Ca of soil can restrain crop absorption on Pb and Cd, and high Al and Fe can promote crop absorption on Pb and Cd in southern Jiangsu.