太湖流域某典型农业区不同形态土壤重金属的生物有效性研究

摘要

[Objective] The research aimed to explore the content of five heavy metals (Cu, Cd , Zn, Fe and Cr ) in the soil, and the bioavailability of heavy metals were evaluated. [Method] A typical agricultural soil of Taihu Lake Basin was selected as the study area. 15 soil samples and 17 vegetable samples were collected. The concentrations of five heavy metals in soil samples and vegetable samples were detected , and the distribution characteristics of different forms of heavy metals were studied to evaluate the bioavailability of heavy metals. [Result] The surface layer, middle layer and deeper layer of the soil were polluted with Cr (the content in the deeper layer wasn' t exceeded), Cu and Cd, in which Cd was exceeded seriously with the rate of 97. 8% , the content of Zn was lower than the soil standard limits of Class H , and the content of Fe was lower than the soil background value of China and the medium value of the world. There was a downward trend of the content of Cr, Cu, Cd and Zn with the increasing of soil depth, and there was a certain degree of vertical migration of heavy metals in soil of the study area. In soil, Cr, Cu, Fe and Zn were mainly existed with residual form, and Cd was existed with ion exchange state. In the vegetables, Zn, Fe and Cr were mainly existed with sodium chloride state, and Cu and Cd were mainly existed with ethanol state. In five vegetables, Cr ( except bulb vegetable) and Cd were seriously exceeded, which were correlative with the exceed of Cr and Cd in soil. There was biological concentration of five vegetables to Cr and Cd, and were significantly concentrated with WS-Cd, WS-Cr, EXC-Cd and EXC-Cr. [Conclusion] The study provided the scientific basis for the study of heavy metals compound pollution on the risk of human health in agricultural area and the promulgation of standards and management regulations to prevent and control the heavy metals compound pollution of cultivated land.%[目的]为了探讨土壤中5种重金属(Cu、Cd、Zn、Fe、Cr)含量,评价重金属的生物有效性.[方法]以太湖流域某农业区为研究区域,采集土壤样品15组、蔬菜样品17组,检测土壤样品和蔬菜样品中5种重金属含量.通过研究蔬菜中不同形态重金属含量的分布特征,对重金属的生物有效性进行评价.[结果]研究区表-中-底层土壤均存在一定程度的Cr(底层未超标)、Cu和Cd污染,其中Cd含量严重超标,超标率达97.8％,Zn含量比Ⅱ类土壤标准限值低,Fe含量远远低于中国土壤背景值、世界土壤中值.Cr、Cu、Cd和Zn含量随土壤深度的增加呈现下降趋势,研究区土壤重金属存在一定程度的垂直迁移.土壤Cr、Cu、Fe、Zn以残渣态为主,而Cd以离子交换态存在,蔬菜Zn、Fe、Cr以氯化钠态为主存在,Cu、Cd以乙醇态为主存在.5类蔬菜中,Cr(葱蒜类除外)和Cd含量均严重超标,5类蔬菜对土壤Cr、Cd存在生物富集,对WS-Cd、WS-Cr,EXC-Cd、EXC-Cr有明显的富集.[结论]该研究为农业活动区重金属复合污染对人体健康风险的研究以及防治耕地土壤重金属复合污染的相关标准和管理法规的制定提供了科学依据.