深圳市农林土壤重金属累积现状及风险评价研究

Heavy Metal Accumulation Characters and Risk Assessment in the Soil of Agriculture and Forest of Shenzhen Area

为探讨深圳市农林土壤重金属的污染现状,系统采集了深圳市菜地、果园、林地和荒地4种土地利用的52个土壤样品,测定了Cu、Pb、Cd、Zn、Cr、Ni6种重金属的全量,对深圳市农林土壤重金属20余年来的累积状况进行了分析并进行了初步的风险评价.结果发现,深圳农林土壤均存在不同程度的重金属累积,总体而言,Cu、Pb、Zn、Cr和Ni的累积较轻,Zn的最大含量尚未超过其80年代末背景值的最大值;Cd的累积最为严重,其最大含量已为背景最大值的16倍.以GB15618-1995为标准,对深圳农林土壤的重金属风险进行评价后发现,Cu的污染最轻,仅20%的菜地土壤超过国家一级标准,Pb50%超过国家一级标准,但尚未超过二级标准;Zn、Cr和Ni均有一定比例的样点超过二级标准,最少4%,最高50%,但未有超过三级标准的样点;Cd的风险最大,不仅有大量超过一、二级标准的样点,而且超过三级标准的样点也占有一定的比例(菜地、果园、林地和荒地土壤中Cd含量超过三级标准的比例分别为10%、23%、29%和50%).深圳农林土壤中的Cd污染应该引起相关部门的重视.

In order to explore the pollution situation in Shenzhen agriculture and forest soils, fifty -two soil samples in vegetable land, fruit land, woodland and barren land in Shenzhen were collected and the concentrations of copper, lead, cadmium, zinc, chromium, and nickel were determined. Results showed that the six heavy metals have a degree of accumulation in vegetable land, fruit land, woodland, and barren land. In general, the accumulation of copper, lead, zinc, chromium, and nickel is relative light, and the accumulation of cadmium is relative serious. The maximum concentration of zinc is lower than the maximum of Shenzhen zinc background concentration of the late 1980s. The maximum of cadmium is 16 times of the maximum background concentration. Based on the soil environmental criterion of Chinese （GB15618 - 1995）, we assessed the risk of the former six heavy metals in soil. Results showed that the accumulation of copper is lightest. In only 20% sample sites of vegetable soil, copper concentrations exceed the criterion I. In at least 50% sample sites of all the four soils, lead concentrations exceed the criterion I and no sample site exceeds the criterion Ⅱ. There are different proportions of sample sites in which zinc, chromium, and nickel concentrations exceed criterion Ⅱ and no sample site exceeds criterion Ⅲ . The minimum and maximum sample proportion of surpass criterion Ⅱ are 4% and 50% , respectively. The risk of cadmium is highest among the six heavy metals in Shenzhen soil. In 10%、23%、29% and 50% sample sites of vegetable land, fruit land, woodland and barren land, respectively, cadmium concentrations exceed the criterion Ⅲ.