农作物体内铅、镉、铜的化学形态研究

Chemical forms of Pb, Cd and Cu in crops

本文报道了农作物体内重金属存在的化学形态。用逐步提取法分析了生长在污染土壤上的水稻、小麦的根与叶。结果表明,在两种作物中,根部的铅以活性较低的醋酸可提取态与盐酸可提取态占优势,而叶中的铅以盐酸可提取态占优势。不论根部或叶部,在各种形态镉中,以氯化钠可提取镉所占比例较高,作用较重要。作物体内的铜活性较强,根部以乙醇可提取态占优势,叶中以水提取态占优势。各种结合形态的重金属迁移能力、毒性效应有显著差异。作物体内重金属化学形态特征与其表观毒性效应有密切联系。

In order to study the chemical forms of heavy metals in crops growing on polluted soil, sequential extraction method has been applied to analyze the roots and leaves of both wheat and rice growing in pots. The results revealed that acetic acid extractable Pb and HCl extractable Pb are the main forms in roots whereas the latter is the main form in leaves as well. Moreover, NaCl extractable Cd predominates in both crops, whereas ethanol extractable Cu and water extractable Cu predominates in roots and leaves respectively. Chemical forms significantly influence the characteristics of migration and accumulation as well as the degree of toxicity of these elements in plants. Pb is generally concentrated and fixed in roots which results in relatively weak accumulation in grains and insignificant retardation effect on the growth of plants. Cd may combine with protein and disturb the activity of enzymes. The existence of low molecular organic complex of Cu results in relatively high accumulation in grain and retardation effect on plant growth when the content is high.