广东东莞地区土壤-蔬菜系统重金属分布与富集特性分析

Distribution and Accumulation of Heavy Metals in Soil-Vegetable System of Dongguan Area,Guangdong Province

对东莞地区常见的7种叶菜类蔬菜及其相应的土壤样品中Cu、Zn、Cr、Ni、Pb等重金属元素的全量和稀盐酸可提取态进行了分析。结果表明,蔬菜存在明显的Pb、Ni超标问题,超标率分别为20.9%、7%,Cu、Zn含量较低,均没超出食品卫生标准限值。蔬菜重金属含量与土壤重金属总量和可提取态重金属含量均无显著的相关性,但基于可提取态含量的富集系数与蔬菜重金属含量具有显著相关性。因此,在评价土壤重金属污染对作物的影响时,仅仅用土壤重金属可提取态含量仍不足以有效反映土壤污染的生态危害性。不同品种蔬菜对同一重金属元素的富集不尽相同,总体而言,叶菜类蔬菜对金属元素的富集具有较强的选择性,对Cr的富集能力最强,其次为Zn、Cu、Ni,Pb最弱。但因土壤中Cr、Zn、Cu的可提取态含量及可提取态系数均较低,故作物未出现超标,蔬菜中Pb含量超标的成因较为复杂,以大气污染为主要来源。

Sixty-one soil samples and corresponding leafy vegetable samples were collected from Dongguan, a Township-Enterprise-Prosperity-Area of Guangdong Province, and the total content and extractable concentration of 5 heavy metal elements （Cu, Zn, Cr, Ni and Pb） for the samples were measured. The results show that the concentrations of Pb and Ni in vegetable samples are 20. 9% and 7.0% higher than the Chinese Food Hygienic Standards, respectively. The concentrations of Zn and Cu did not exceed the standard. The metal concentrations in leafy vegetable had no significant correlations with either the total or the extractable heavy metal concentrations in soil. The heavy metal concentrations in leafy vegetable were evidently related to the accumulation factors calculated from extractable heavy metal concentration, indicating the extractable heavy metals were not enough to reflect ecological system harm from soil pollution. The same type of vegetables have different absorbability to different heavy metals, different vegetables have different absorbability to the same heavy metal. Generally, the leaf vegetables have strong selective absorbability to heavy metals. Cr was easiest to be absorbed, Zn, Cu and Ni were the second easiest absorbed elements, and Pb was difficult to be absorbed. But the extractable content and the ratios of extractable content to total content of Cr, Zn, Cu in soils are low, the contents of Cr, Zn, Cu in vegetables did not exceed the national standard of food sanitation. The sources of excessive lead in vegetables are complicated and are possibly from air.