乡镇企业密集区菜地土壤重金属含量分布特征及生态效应——以东莞市为例

Distribution Characteristics and Ecological Effects of Heavy Metals in Vegetable Soils from Township-enterprise Prosperity Area: A Case Study of Dongguan

采用现场采样及室内分析方法,研究了东莞市乡镇企业密集区菜地土壤重金属含量分布特征及生态效应。结果表明,与广东省土壤背景值相比,该地区菜地表层土壤Hg、Pb和Cd发生明显累积,西部平原区和中部过渡区污染最为严重,呈现出产业依赖和地域特征。因子分析和聚类分析结果指示,研究区菜地表层土壤中的8种重金属主要有3种不同来源:Ni、Cr、As和Zn以自然源为主,Hg和Pb主要来源于工业及交通运输,农业生产活动对Cu和Cd贡献最大。土壤重金属污染产生的生态效应明显,近40%的蔬菜样品Pb、Cd、Ni、As含量超过国家食品卫生标准。同种蔬菜对不同重金属以及不同品种蔬菜对同一重金属都具有不同的生态效应。生菜、油麦菜和白菜易受Pb污染影响;油麦菜和白菜易受Cd污染影响;菜薹易受As、Ni污染影响。蔬菜Cd、Ni、As超标与土壤重金属污染关系密切,而Pb含量超标以大气污染为主要来源。

The township enterprise in Dongguan city of Guangdong province is extremely prosperous. According to the distribution characteristics and concentrations of heavy metals（ Hg,Cd, Pb,Cu, Zn, Ni, Cr, As） in vegetables and top soil from Dongguan, Hg, Pb and Cd cumulated remarkably compared with the soil background contents of metal elements in Guangdong province. Pollution is more serious in western plain area and central transition region controlled by the distribution of industries and river. Results of multivariate statistic show that there are three categories of sources of the eight heavy metals mentioned above. The first category consists of Ni, Cr, As and Zn which are predominantly derived from natural sources. The second includes Hg and Pb as a result of the influence of industries and transportation. The last includes Cu and Cd mainly from agricultural activities. Ecological effect of soil pollution with heavy metals is extraordinarily serious; almost 40% vegetable samples are polluted with Pb, Cd, Ni and As based on national standard of food sanitation. The same type of vegetables have different ecological response to different heavy metals, different vegetables have different ecological response to the same heavy metal. Romaine lettuce, Youmei lettuce and Chinese cabbage have strong absorbability to Pb. Youmei lettuce and Chinese cabbage can strongly accumulate Cd. Flowering Chinese cabbage could easily accumulate As and Ni. Cd, Ni and As in vegetable is closely related to the corresponding polluted elements in soil, but excessive lead in vegetable is mostly originated from air polluted with lead.