田间采样分析结果表明:在土壤pH值小于6.5(或5.8)条件下,土壤中交换态镉(或铅)占其全量的比例随土壤pH值的下降呈现明显的增加趋势,且交换态镉占其全量的比例增加更为明显;水稻糙米和叶菜中镉、铅的富集系数也随土壤pH值的下降而增加,且作物对镉的富集明显高于对铅的.模拟试验结果表明:土壤酸化可促使土壤镉、铅由稳定态向活性较高的形态转变,从而增加糙米中镉、铅的积累;当土壤pH值低于5.0时,土壤镉、铅的活化速度随酸度的变化明显加剧.因此土壤酸化是导致中轻度重金属污染农田农产品中镉、铅积累的重要原因.%Field sampling survey showed that: under the condition that soil pH-value was below 6.5 (or 5.8), the proportion of soil exchangeable cadmium (Cd) (or lead, Pb) content in their total content obviously increased with the decrease in soil pH-value, and the proportion of soil exchangeable Cd content in its total content increased more obviously.Meanwhile, the enrichment coefficients of Cd and Pb in both brown rice and leafy vegetable increased as soil pH-value decreased, and the enrichment amount of Cd in crops was apparently higher than that of Pb.The results of simulation experiment indicated that soil acidification could promote the transformation of soil Cd and Pb from stable form to available form, and could increase the accumulation of Cd and Pb in brown rice.The activation speed of soil Cd and Pb increased significantly with the increase in soil pH-value below 5.0.The above results confirmed that soil acidification was an important factor causing the accumulation of Cd and Pb in the agricultural products from the farmland which was polluted mildly or moderately by heavy metals.
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