铅、镉在典型植烟土壤中的吸附-解吸特性及环境风险评估

Adsorption-Desorption Behaviors and Environmental Risk Assessment of Lead,Cadmium in Typical Tobacco Growing Soils

以我国主要产烟区4种典型植烟土壤(红壤、水稻土、黄壤、褐土)为试材,采用一次平衡法研究了外加铅、镉在植烟土壤中的吸附-解吸行为,并利用保留因子对铅、镉在4种土壤中的环境风险进行了评估。结果显示:4种植烟土壤对铅、镉的吸附存在很大差异,褐土对铅、镉的吸附能力最强,其次是黄壤,水稻土和红壤的吸附能力则较弱。除褐土对镉的吸附外,4种植烟土壤对铅、镉的吸附均可用Lang-muir及Freundlich方程拟合。在竞争吸附条件下,铅、镉的平均分配系数均下降,下降率分别为14%～34%和8%～25%,铅的存在明显抑制了土壤对镉的吸附,镉对铅的影响较小,铅、镉吸附量在水稻土和红壤中下降幅度更大。随土壤中铅、镉含量的增加,环境风险呈几何级数增加,4种土壤中,两元素在水稻土和红壤中的潜在环境风险更大。

Taking red, paddy, yellow and cinnamon soils, which are typical in major tobacco growing areas in China, as experimental material, the Pb and Cd adsorption-desorption behaviors of these soil samples were investigated with linear equilibrium method and the environmental risk of the presence of Pb and Cd in these soils was assessed with retention factors. The results showed that Pb and Cd adsorption differed significantly between the soil samples with highest adsorption capacity of cinnamon soil, followed by yellow soil, tailed by paddy soil and red soil. The Pb and Cd adsorption in tobacco growing soil could be well described by Langmuir and Freundlieh equation with the exception of Cd in cinnamon soil. The mean distribution＇ coefficient of Cd and Pb decreased by 14%-34% and 8%-25% , respectively, under a competitive condition, which means that the presence of Pb obviously inhibits Cd adsorption, while the presence of Cd imparts less effects on Pb adsorption; and Pb and Cd adsorption in paddy soil and red soil dropped more sharply. The environmental risk assessment indicated that the environmental risk was multiplied geometrically with the increase of Pb and Cd contents in soils, their presence in paddy soil and red soil was potentially more risky.