小安溪河流域污水灌区重金属的污染特征

The Pollution Characteristic of Heavy Metals of Sewage Irrigated Region in Xiao Anqi River

小安溪河流域沿河从下游到上游土壤重金属Pb的含量变化幅度较大,Cd含量有升高趋势,Cu、Zn、As、Hg的含量较平稳;小麦中Hg、Pb的含量有升高趋势;水稻中Cd的含量有升高趋势;莴笋和包白菜的Cd含量有升高趋势。不同污灌段土壤和农作物重金属含量差异明显。土壤重金属Cu低于背景值,Zn、Cd、As同背景值接近,Pb、Hg高于背景值;土壤重金属含量均低于国家土壤二级质量标准。全流域水稻、小麦、蔬菜重金属含量均低于国家食品卫生限量标准,农作物没受到重金属污染。但土壤重金属Cd同蔬菜具有显著正相关,因此在污灌的时候,不能简单从重金属绝对含量的大小考虑,还应综合考虑其影响程度。

From lower reaches to upper reaches of the Xiao anqi river the Pb content in soil ranges more widely, and the Cd content has a tendency to ascend, while the contents of Cu, Zn, As and Hg are stable. The contents of Hg and Pb in wheat and the Cd content in rice, lettuce and cabbage also have tendency to go up. In different sewage irrigated sections, the contents of heavy metals in soil and crops have obvious differences. Compared to the background values, the Cu content in soil is lower, while the contents of Pb and Hg are higher, and the contents of Zn, Cd and As are close to the responding background values. All the contents of heavy metals in soil are lower than the nation second grade quality standards. In the whole valley, the contents of heavy metals in rice and wheat and vegetable are all lower than the national limited standard of food hygiene, therefore, the crops aren't polluted by heavy metals. However, Cd content in soil has obvious positive correlation with vegetables. So when sewage irrigating, we should not only think about the absolute contents of heavy metals, but also synthesize its effect degree.