施用磷酸盐和沸石对土壤镉形态转化的影响

本试验在室内模拟外源Cd污染土壤,研究了磷酸二氢钾、磷酸氢二铵和沸石单独施用,以及沸石和磷酸氢二钾、沸石和磷酸氢二铵二者配施,对Cd污染土壤形态变化的影响.结果表明,施用不同改良剂后,土壤交换态Cd含量出现不同程度降低,而碳酸盐结合态、铁锰氧化物结合态、有机结合态和残渣态Cd含量增加.与对照相比,单独施用磷酸二氢钾、磷酸氢二铵和沸石,以及沸石和磷酸氢二钾配施、沸石和磷酸氢二铵配施分别使土壤有效Cd含量降低25.2%~51.7%、21.6%~46.8%、6.4%~23.2%、38.6%~61.4%和34.1%~56.4%.各处理均能提高土壤速效磷含量,且土壤速效磷含量与有效态Cd含量呈极显著负相关,相关系数r=-0.902 6,各处理之间土壤p H值与有效态Cd含量存在负相关关系.由此可知,在施用磷酸盐和天然沸石条件下,土壤速效磷含量的变化是降低土壤镉有效性的主要因素.

Effects of Phosphate and Zeolite on the Transformation of Cd Speciation in Soil

The test simulated exogenous Cd contaminated soil indoors, and studied separate application of potassium dihydrogen phosphate, diammonium hydrogen phosphate and zeolite, and combined application of zeolite and dipotassium hydrogen phosphate, zeolite and diammonium hydrogen phosphate, as well as the effect on the morphological changes of Cd contaminated soil. The results showed that soil exchangeable Cd contents were reduced in different degrees after the application of different modifiers, and the carbonate bound and Fe-Mn oxide bound, organic bound and residual Cd contents increased. By comparison, the separate application of potassium dihydrogen phosphate, diammonium hydrogen phosphate and zeolite, and the combined application of zeolite and dipotassium hydrogen phosphate, zeolite and diammonium hydrogen phosphate respectively reduced the soil available Cd contents at 25.2%-51.7%, 21.6%-46.8%, 6.4%-23.2%, 38.6%-61.4%, and 34.1%-56.4%. All treatments could increase the soil available phosphorus contents, making the soil available phosphorus contents negatively correlated with the available Cd contents significantly, with the correlation coefficient r=-0.9026, and the soil pH values had a negative correlation with the available Cd content during the treatments. Therefore, it could be known that the changes of soil available phosphorus contents were the major factor in reducing the availability of soil cadmium under the conditions of the application of phosphate and natural zeolite.