根际效应下镉在土壤中的吸附与解吸

根际微区是联系植物与土壤之间的纽带,控制着重金属等污染物从土壤向植物的迁移.以黑土为研究对象,采用根际箱装置培养根际土壤,研究了不同强度玉米根际效应下,土壤对Cd的吸附与解吸.结果表明,相比于非根际土壤,根际土壤中的可溶性有机碳（DOC）含量显著增加,不同处理下根际土壤DOC含量与根系的干物质重量二者呈显著正相关（P＜0.001）;根际土壤pH显著提高.根际土壤对Cd的吸附量显著高于非根际土壤,且在较高的Cd浓度下这种差异表现的更明显,不同pH下土壤吸附试验表明,根际pH的升高是造成这种现象的主要原因.可以用Freundrich方程来描述Cd离子在根际效应下黑土中的吸附特征.根际土壤的解吸量显著低于非根际土壤,相关分析表明,平均的解吸百分数与根际土壤DOC含量呈显著负相关（P=0.011）,说明根系分泌的可溶性有机物质与Cd离子的络和作用,是导致根际土壤中Cd较难解吸的重要原因.

Adsorption and Desorption of Cadmium in Soil with Rhizosphere Effects

Rhizosphere is an important environmental micro-zone, controlling the transfer of pollutants from soil to plant. Rhizospheric soil incubated by a modified rhizospheric box was used to investigate the adsorption and desorption of Cd by soil under different rhizosphere effects. Compared with non-rhizosperic soil, the concentration of dissolved organic carbon (DOC) in rhizospheric soil increased significantly, and positively correlated to dry biomass of roots (P<0.001). Rhizospheric effect resulted in significant increase of soil pH. Isothermal experiment showed that the Cd adsorption in rhizospheric soil was markedly higher than that in non-rhizospheric soil and the difference was more significant at higher concentration of Cd, which may contribute to the increase of pH in rhizosphere. Freundrich equation could be used to describe the characteristics of Cd adsorption in soil with rhizospheric effect. Desorption amount in rhizospheric soil was significantly lower than that in non-rhizospheric soil. The average desorped percentage negatively correlated to the soil DOC concentration ((P=0.011), indicating that the DOC excreted by root was a key factor that resulted in the difficulty of Cd desorption in rhizospheric soil.