菜园土铅的形态分布及吸持-解吸特性的研究

菜园土原有的铅以残留态为主,交换态的比例很小,新鲜吸持的铅,占残留态的比例较小,但其中交换态铅的比例是酸性菜园土明显高于中性和碱性菜园土,菜园土对铅吸持量大小顺序为:碱性菜园土>中性菜园土>酸性菜园土;与解吸率恰好相反,提高土壤pH可提高吸铅量,降低解吸率,除去土壤有机质可降低吸铅量,提高解吸率。

FRACTIONAL DISTRIBUTIONS AND SORPTION -DESORPTION CHARACTERISTICS OF LEAD IN VEGETABLE SOILS

Soils from five vegetable gardens with different pH values werestudied. The study shows that the majority of the soil native Pb exists in theform of residual fraction and only a small amount in the form of exchangeablePb. But in the freshly retained Pb, residual fraction amounts to very little,and exchangeable Pb contents are different in different soils, with acidic soilranking first, then neutral soil and then alkaline soil. Soil with higher pHvalue retains and fixes more Pb than acidic soil, and their desorption order isjust opposite to that of retention. Increasing soil pH can promote Pb retentionand restrain Pb desorption, and the reverse is true after H_2O_2 treatment. Theseresults may indicate that the soil pH and organic content play a decisive rolein the Pb accumulation in plants. Practical agricultural measures to decreasePb toxicity of acidic and high Pb soils consist of liming and other manures.