重金属在矿区土壤——蔬菜系统的吸收与迁移特性研究

Absorption and Migration of Heavy Metals in Soil-Vegetable System in Mining Area

重金属污染土壤的农产品安全倍受大家的关注。研究选择某铅锌矿区周边的蔬菜地,采集叶菜类蔬菜及土壤样品,研究Cd、Pb、Cu、Zn在土壤中的赋存形态及其在土壤-蔬菜系统中的迁移特性。结果表明,污染土壤中Cd、Pb、Zn超标,分别为国家标准限值的1.44~6.44倍、2.97~3.88倍和1.30~2.30倍。BCR连续提取结果显示,Cd、Pb以可还原态为主,Cu、Zn以可还原态和残渣态为主,可还原态Cd、Pb、Cu、Zn分别占总量的70.6%、79.0%、34.4%和38.1%;残渣态Cu、Zn分别占总量的34.6%和30.2%。酸可提取态Zn、Cd分别达13.2%和6.3%。供试蔬菜茎叶中Pb含量超标,为国家标准限值的1.50~5.83倍。蔬菜茎叶中Cd、Pb含量与其土壤中可还原态含量显著正相关,Cd含量与土壤酸可提取态Cd含量显著正相关。蔬菜Cd的富集系数(BCF)相对较高(0.61~3.34),其中水芹和香芹Cd、Pb、Zn的BCF值显著高于其他蔬菜。蔬菜中Zn的迁移系数(TF)较高(0.54~2.07)。叶用芥菜中Cd、Pb、Zn的TF值较高,分别为1.02、2.25、1.62。因此,在污染土壤蔬菜风险评价中需要考虑不同蔬菜品种对重金属吸的吸收迁移特性的差异。

Agricultural product safety in heavy metal polluted soil has drawn increasing attentions. Leafy vegetables and soil samples were collected from the vegetable fields around a lead(Pb)-zinc(Zn) mining area. And the existing fractions of cadmium(Cd), Pb, copper(Cu), and Zn in soil and their transform properties in the soil-vegetable system were analyzed. Sequential extraction procedure proposed by The European Community Bureau of Reference(BCR) was used to measure different fractions(acid soluble, reducible, oxidizable and residual) of heavy metals in soil. The concentrations of Cd, Pb and Zn in the contaminated soil were 1.44-6.44 times, 2.97-3.88 times and 1.30-2.30 times higher than the national standard limitations, respectively. Cd and Pb were mainly composed of the reducible fraction, while Cu and Zn mainly existed as reducible and residual fractions. The concentrations of reducible fractions of Cd, Pb, Cu and Zn were 70.6%, 79.0%, 34.4% and 38.1%, respectively. The residual fractions of Cu and Zn accounted for 34.6% and 30.2%, while the acid-extractable fractions of Zn and Cd were 13.2% and 6.3%,respectively. The concentrations of Pb uptake by vegetables were 1.50-5.83 times higher than the limitation.Furthermore, the concentrations of Cd and Pb in vegetables were significantly correlated with the concentrations of reducible fractions of Cd and Pb. The bioconcentration factor(BCF) of Cd ranged from 0.61 to 3.34, and the BCF values of Cd, Pb and Zn in cress and parsley were significantly higher than those in other vegetables. The transfer factor(TF) of Zn varied from 0.54 to 2.07. The TFs of Cd, Pb and Zn in leaf mustard reached at 1.00, 2.25 and 1.62,respectively. Therefore, when assessing the risk of vegetables in contaminated soils, it is necessary to pay more attention to the differences in the absorption and transporting characteristics of heavy metals among different vegetable types.