为了研究崇明岛公路两侧土壤和蔬菜重金属污染状况,采集陈海、北沿公路两侧蔬菜地土壤、蔬菜和路面灰尘样品,测定重金属Pb、Cd、Cu、Zn含量。结果表明,以上海市土壤环境背景值上限值为评价标准,所有土壤样品Pb、Cd、Cu和Zn的超标率分别为10.1%、25.4%、6.5%和8.7%;以HJ332-2006食用农产品产地环境质量评价标准中蔬菜地土壤环境质量评价指标限值(pH值6.5~7.5)为标准,Cd超标率在21.0%,仅有不到3%样品Pb含量超标,而没有样品Cu、Zn含量超标。以国家食品卫生标准中规定的重金属限量为标准,路侧蔬菜样品Pb含量超标率为43.2%,Cd为18.6%,Zn和Cu则小于5%。由此可见,崇明岛主要公路两侧土壤污染以cd为主,而蔬菜污染则以Pb为主。在长期运营的前提下,低交通量公路两侧50m范围内耕作层土壤和两侧作物会发生一定程度的重金属污染,路面灰尘是路侧土壤和蔬菜的潜在污染源。
To study heavy metals ( lead, cadmium, copper and zinc) contamination of soils and vegetables on roadsides, samples of soils, vegetables and dust were collected alongside the Chenhai and Beiyan highways on the Chongming Island for analysis of Pb, Cd, Cu and Zn contents. With the upper limit of the background values of Shanghai set as criterion for evaluation, 10.1% ,25.4% ,6.5% and 8.7% of the soil samples exceeded the criterion for Pb, Cd, Cu and Zn, respectively. When the evaluation was based on the criteria in the farmland environmental quality evaluation standards for edible agricultural products ( HJ 332-2006), 21.0% of the soil samples were beyond the criterion for Cd, less than 3% beyond the criterion for Pb, but none beyond the criterion for the other two. And when the vegetable samples were evaluated based on the national tolerance limit of heavy metals in foods, 43.2% exceeded the criterion for Pb, 18.6% for Cd and less than 5% for Zn and Cu. All the findings suggest that the soils and vegetables, within 50 m, alongside the roads low in traffic load will get contaminated with heavy metals after long terms of road service. Flying dust is an important potential source of heavy metal contamination in the roadside environment.