湘江中下游农田土壤和蔬菜的重金属污染

从湖南省湘江中下游衡阳-长沙段沿岸采集219个农田土壤样品和48个蔬菜样品,测试其中As、Cd、Cr、Cu、Ni、Pb、Zn等7种重金属元素的含量,并结合GIS作图与数据统计,对农田土壤中重金属空间分布、土壤和蔬菜中重金属富集特征以及其潜在风险进行分析.结果表明,农田土壤中As、Cd、Cu、Ni、Pb和Zn含量均大于湖南省相应土壤重金属含量背景值,Cd(2.44 mg kg-1)、Pb(65.00 mg kg-1)、Zn(144.13 mg kg-1)含量分别超标7.97、3.69和1.63倍.与我国《土壤环境质量标准》(GB15618-1995)中Ⅱ级标准(pH 6.5～7.5)比较,土壤As、Cd、Cu、Ni、Pb和Zn含量的超标率分别为13.2%、68.5%、2.7%、2.7%、8.7%和15.1%,表现为以Cd为主的多种重金属混合污染.菜地土壤中As、Cd、Cu、Pb和Zn的含量(几何均值)分别高于水稻土As、Cd、Cu、Pb和Zn含量.与《食品中污染物限量》(GB2762-2005)等标准比较,蔬菜As、Cd、Ni、Pb含量的样本超标率分别为95.8%、68.8%、10.4%和95.8%;蔬菜Cd、Pb、Zn含量与相应土壤的Cd、Pb、Zn含量存在极显著的相关性(P＜0.01).湘江中下游的农田土壤和蔬菜中重金属污染的潜在风险值得关注.

Heavy Metal Pollution of Soils and Vegetables from Midstream and Downstream of Xiangjiang River

A total of 219 of agricultural soil and 48 of vegetable samples were collected from the midstream and downstream, Hengyang to Changsha, of Xiangjiang River of Hunan Province. The spatial distribution, accumulation characteristics and potential risk of heavy metals in the agricultural soils and vegetables were depicted in details by three different approaches, including total contents of 7 metal elements in soils and vegetables, GIS map of heavy metals in soils, and multi-analysis of the relationship between metals content of soils and egetables in this study. The results show that there are higher accumulations of heavy metals such as As, Cd, Cu, Ni, Pb and Zn in agricultural soils, and the contents of Cd (2.44 mg kg-1), Pb (65.00 mg kg-1) and Zn (144.13 mg kg-1) are 7.97, 3.69 and 1.63 times of background contents of the corresponding heavy metals in soils of Hunan Province, respectively. There are about 13.2% of As, 68.5% of Cd, 2.7% of Cu, 2.7% of Ni, 8.7% of Pb and 15.1% of Zn in all the collected soil samples from the investigated sites which have overran the contents for heavy metal of China Environmental Quality Standard for Soils (GB15618-1995, Grade II). The pollution characteristics of multi-metals in soils are mainly reflected by Cd. Contents of As, Cd, Cu, Pb and Zn in vegetable soils are significantly higher than those in paddy soils, respectively. The ratios of vegetable samples which As, Cd, Ni and Pb concentrations are higher than the Maximum Levels of Contaminants in Foods (GB2762-2005) are 95.8%, 68.8%, 10.4% and 95.8%, respectively. There are significantly positive correlations between the concentrations of Cd, Pb and Zn in vegetables and the content of them in vegetable soils (P < 0.01). It is very necessary to focus on potential risk of heavy metals for food safety and human's health in agricultural soils and vegetables in the midstream and downstream of Xiangjiang River, Hunan Province of China.