土壤pH对镉存在形态影响的模拟实验研究

通过模拟实验,研究了土壤pH对水稻土、紫色土和黄壤的水溶态、可交换态、碳酸盐态、铁锰氧化态、有机结合态和残渣态Cd含量的影响。结果表明:在中碱性条件下,水溶态Cd质量分数比值小于3%,但pH<6.5时,水溶态Cd含量随着pH 减小迅速增加, pH 为4. 57 时,水稻土水溶态Cd 质量分数比值最高达48 39%;可交换态Cd含量在碱性条件下,随着土壤pH值增大迅速下降,在酸性区域内,可交换态Cd含量随pH增加呈上升趋势;碳酸盐态和铁锰氧化态Cd含量随土壤pH增大而增加;有机结合态Cd含量随土壤pH增加而增大,但变化幅度不大。对Cd污染的土壤进行治理时,控制土壤pH大于6.5以及增施有机肥等是减少Cd对生态系统危害的关键。

A study of the effect of soil pH on chemical species of cadmium by simulated experiments

The effect of soil pH on various chemical species of cadmium in paddy soil, purple soil and yellow soil was studied by a series of simulated experiments. The results show that 1 under alkali condition the percentage of dissolvable Cd is less than 3% but it increases significantly with a decrease in pH value when pH value is less than 6.5, and it reaches 48.39% when the pH value is 4.57 in paddy soil; 2 the percentage of exchangeable Cd decreases rapidly with the increase of pH value under basic condition but displays an increasing trend under acid condition; 3 the percentages of Cd bound to carbonates and bound to Fe-Mn oxides increase with the increase of pH; and (4) the percentage of Cd bound to organic matters mildly increases with the increase of the pH. From this study, we suggest that an efficient way to reduce the harmful effects of Cd to the ecosystem is to hold the pH value of soils at greater than 6.5 and/or to fertilize soil by organic manure.