用物理与化学相结合的方法研究了2个污染土壤剖面中有机质结合重金属(Cd、Cu、Pb和Zn)的分布,把有机质相结合态重金属分为颗粒状有机质(POM)结合的重金属和与细土腐殖质结合的重金属.结果表明,土壤POM对重金属有明显的富集作用,其中>2 mm POM重金属Cd、Cu、Pb和Zn的富集系数分别在1.4～3.2、2.5～2.6、2.8～3.9和3.0～3.9之间;而0.05～2 mm POM重金属Cd、Cu、Pb和Zn的富集系数分别在2.7～7.8、3.2～6.4、3.2～9.3和3.2～5.6之间,0.05～2 mm POM组分中重金属的平均富集高于>2 mm POM组分.POM中重金属的富集程度与土壤重金属的积累呈正相关.有机质结合态重金属占土壤重金属总量的比例随土壤有机质积累而增高,表土层约40%以上的重金属以有机质结合态存在.
Soils can often be contaminated simultaneously by more than one heavy metal. The sorption-desorption behavior of a metal in a soil will be affected by the presence of other metals. Therefore, selective retention and competitive adsorption of the soils to heavy metals can affect their availability and movement through the soils. In this study, the simultaneous competitive adsorption of four heavy metals (Cd, Cu, Hg, and Pb) on ten agricultural soils collected from the Changjiang and Zhujiang deltas, China was assessed. The results showed that the competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Cd and Hg, and more Pb and Cu with increasing total metal concentrations, regardless of the molar concen- tration applied. As the applied concentrations increased, Pb and Cu adsorption increased, while Cd and Hg adsorption decreased. The adsorption sequence most found was Pb>Cu>Hg>Cd. The maximum adsorption capacity for the heavy metal cations was calculated, and affected markedly by soil properties. The results suggest that Hg and Cd have higher mobility associated to the lower adsorption and that Pb and Cu present the opposite behavior. Significant correlations were found between the maximum adsorption capacity of the metals and pH value and exchangeable acid, suggesting that soil pH and exchangeable acid were key factors controlling the solubility and mobility of the metals in the agricultural soils.
Heavy metals can be introduced into urban soils at the same time. Therefore, their selective retention and competitive adsorption by the soils become of major importance in determining their availability and movement throughout the soil. In this study, the availability and mobility of six heavy metals in eight urban soils collected from different cities of Zhejiang Province, southeastern China were assessed using distribution coefficients（Kd） and retardation factor（Rf）. The results showed that there were great differences in the Kd and Rfamong the tested soils. The adsorption sequences were Cr〉Pb〉Cu〉Cd〉Zn〉Ni, and the Kd decreased with increasing levels of metal addition. Ni generally has the lowest Rf values followed closely by Cd, and Zn whereas Cr and Pb reached the highest values. The results suggest that Ni and Zn have the highest mobility associated to the lowest adsorption, Cr and Pb present the opposite behavior. Correlation analysis indicates that soil pH, CaCO3 content, and cation exchange capacity （CEC） are key factors controlling the solubility and mobility of the metals in the urban soils.
