东莞市农田土壤和蔬菜重金属的含量特征分析

从东莞市采集118 个农田土壤样品和43 个蔬菜样品, 测试其中Cu、Zn、Ni、Cr、Pb、 Cd、As 和Hg 等8 种重金属元素的含量, 并结合GIS 制图和数据统计, 对农田土壤中重金属 的空间分布和来源、土壤和蔬菜中重金属的富集特征及其潜在风险进行了分析。结果表明, 农田土壤中Cu、Zn、Ni、Pb、Cd 和Hg 等元素含量均高于相应元素的广东省土壤背景值, 其中, Pb (65.38 mg kg^-1) 和Hg (0.24 mg kg^-1) 含量分别为其对应背景值的1.82 和2.82 倍。与我国《土壤环境质量标准》中II 级标准(pH < 6.5) 相比, 土壤中Cu、Ni、Cd 和Hg 含量样本超标率分别为3.4%、5.9%、1.7%和28%, 表现为以Hg 为主的多种重金属共同污染。土壤 中8 种重金属中Cu、Zn、Ni、Cr 和As 等元素主要来源于成土母质, Pb、Hg 和Cd 等元素主要与人类活动有关。空间分布上, Cu、Zn、Ni、Cr、Pb、As 和Hg 等7 种重金属含量呈现出西部高、东部低的特点, Cd 含量在西北部和东南部较高, 西南部较低。与《食品中污染物限量》(GB2762-2005) 等相关标准比较, 蔬菜中Ni、Pb 和As 含量的样本超标率分别为4.7%、16.3%和48.8%。蔬菜中重金属富集系数的顺序为: Cd > Zn > Cu > As > Ni > Hg > Cr > Pb。

Heavy Metal Concentr ations of Agr icultur al Soils and Vegetables from Dongguan, Guangdong Province, China

A total of 118 of agricultural soil and 43 of vegetable samples were collected from Dongguan, Guangdong Province. The spatial distribution, sources, 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 8 metal elements in soils and vegetables, GIS maps and multivariate analysis of heavy metals in soils in the study. The results show that there are higher accumulation of heavy metals such as Cu, Zn, Ni, Pb, Cd and Hg in agricultural soils, and the contents of Pb (65.38 mg kg^-1) and Hg (0.24 mg kg^-1) are 1.82 and 2.82 times of background contents of the corresponding heavy metals in soils of Guangdong Province, respectively. There are about 3.4% of Cu, 5.9% of Ni, 1.7% of Cd and 28% of Hg in all collected soil samples from all investigated sites which have overran the contents for heavy metals of China Environmental Quality Standard for Soils (GB15618-1995, Grade II). The pollution characteristics of multi-metals in soils are mainly reflected by Hg. There are different sources to 8 metal elements in soils, Cu, Zn, Ni, Cr and As are predominantly derived from parent materials, and Pb, Hg and Cd are affected by anthropogenic activity. The spatial distribution shows that Cu, Zn, Ni, Cr, Pb, As and Hg contents of agricultural soils are high in west and low in east, and Cd contents are high in northwest, southeast and low in southwest in Dongguan. The ratios of vegetable samples with Ni, Pb and As concentrations higher than the Maximum Levels of Contaminants in Foods (GB2762-2005) are 4.7% , 16.3% and 48.8% , respectively. The order of bioconcentration factors (BCF) of heavy metals in vegetables is: Cd > Zn > Cu > As > Ni > Hg > Cr > Pb.