重金属污染的长春水田黑土对菲的吸附作用

以菲为多环芳烃(PAHs)代表物,研究了Pb、Zn、Cu污染后黑土对PAHs的吸附作用.结果表明,分配作用是黑土吸附菲的主要机制,无论重金属污染与否,黑土对菲的等温吸附曲线均呈线性.实验条件下,重金属污染后黑土对菲的吸附作用明显增强,且随重金属含量提高,黑土对菲的吸附系数(Kd)和有机碳标化的吸附系数(Koc)增大.由于重金属的“键桥”作用,黑土吸附菲的平衡溶液中水溶性有机质(DOM)浓度降低,土壤固相有机质含量略有增加(不超过原有有机质含量的0.53%).计算了这部分增加的固相有机质对菲的吸附系数K_Ph/soc,并分析了溶液中DOM对土壤吸附菲的影响.结果显示,溶液中DOM浓度变化及其与菲的结合作用对重金属影响土壤吸附菲的贡献甚微;而K_Ph/soc值则比土壤原有有机质对菲的吸附系数K_d值大2～3个数量级,这是重金属污染导致土壤吸附作用增强的根本原因.

The sorption of phenathrene by heavy metal-contaminated Changchun water field black soils

Phenanthrene sorption by black soils that have been contaminated by Pb, Zn and Cu was investigated using a batch experimental method. Phenanthrene sorption isotherms by the soil samples with or without the contamination of heavy metals were well described by a linear sorption model with the R2 values greater than 0.92. The distribution coefficients (Kd) and the soil organic carbon-normalized distribution coefficients (Koc) by heavy metal-contaminated soils were significantly higher than those by the control soil. The soil samples contaminated with higher contents of heavy metals manifested the larger sorption coefficients (Kd and Koc). The concentrations of dissolved organic matter (DOM) in equilibrium solution for phenanthrene sorption were observed lower than those by control soil. The less competition for phenanthrene sorption from the decreased DOM contributed little to the enhanced phenanthrene sorption by heavy metal-contaminated soils. But the calculated sorption coefficients of phenanthrene by the DOM sorbed on soil surfaces (KPh/soc) were about 2~3 orders of magnitude larger than the sorption coefficient by the inherent soil organic matters, which we attribute to be the predominant mechanism responsible for the enhanced sorption by the soil samples contaminated with heavy metals.