pH和有机质对铬渣污染土壤中Cr赋存形态的影响

选用3种不同的铬渣污染土壤作为试验样,通过调节其pH和有机质含量,并采用碱消解-共沉淀法和改良BCR顺序提取法,研究了pH和有机质含量对土壤中铬的价态及形态的影响。结果表明,总体上Cr(Ⅵ)含量随pH降低和有机质投加量增大而减小,Cr(Ⅲ)则增加,但土1各水平间差异均显著(F8.89),土2和土3只有部分水平间差异显著。同时,随pH降低和有机质投加量增大,酸可提取态Cr含量减小,可氧化态Cr增加,可还原态略有增加,表明酸性条件和有机质有利于Cr(Ⅵ)的还原和酸可提取态Cr向可还原态和可氧化态Cr的转化。

Potential influences of pH and organic matter on the occurrence forms of chromium in chromium-contaminated soils

Variations in concentrations of different occurrence forms of chromium were evaluated in three chromium-contaminated soils with different properties, and the pH and organic matter content were tested to explore their potential influence on the different valence states and different fractionations of chromium in soils using acid digestion, alkaline digestion coprecipitation, and modified BCR. The main findings were as follows. As the pH decreased and the organic matter content increased, the concentration of hexavalent chromium decreased in general, and trivalent chromium inversely increased. However, there were significant differences among all the treatments of soil 1, while the differences among some treatments of soil 2 and soil 3 were not significant. Simultaneously, the concentration of exchangeable and acid soluble fractionation declined opposite to oxidizable fractionation and reducible fractionation with the drop of pH and the rise of organic matter content. The findings indicated that the lower pH, especially under acidic condition, and the higher organic carbon might enhance the deoxidization process of hexavalent chromium into trivalent chromium and the transformation process of exchangeable and acid soluble fractionation chromium into oxidizable and reducible fractionations chromium.