杭州地区农业土壤中重金属的分布特征及其环境意义

为了分析杭州地区农业土壤重金属的分布特征及其环境意义,通过现场采样和室内分析检测的方法,对杭州市各区县不同作物农业土壤表层土中的Hg、As、Cu、Pb、Cr、Cd 6种重金属元素进行检测,并对其分布特征进行了分析。结果表明,杭州地区农业土壤中除As外,其他5种重金属的平均含量均低于且接近浙江省土壤背景值,个别采样点的重金属含量超过了土壤环境质量国家二级标准。总体上,杭州地区农业土壤处于安全水平。通过重金属的区域分布特征分析表明,余杭区和富阳市农业土壤中重金属平均含量普遍高于其他区域。萧山区和建德市部分农业土壤则存在Cu和Hg含量较高的情况,而淳安县农业土壤中重金属含量差异较大,土壤中出现了As、Cr和Cd含量最大值。不同作物的农业土壤重金属含量存在一定的差异,但不明显。水稻田和蔬菜地的土壤中,重金属含量较其他作物种植类型的土壤中含量高;叶菜类(蔬菜、茶叶)作物土壤中的Cd含量要比根茎类(水稻)、茄果类(水果)及其他作物种植类型的土壤中的含量低。目前杭州地区土壤中6种重金属含量均对作物的直接危害不大,但由于萧山区个别采样点Cu含量严重超标,淳安县土壤中Cd受外源性来源影响也已较明显,需要相关部门加大监管力度,防止污染事件发生。同时,为防止农业土壤中重金属含量进一步升高,需要加大大气降尘监测与治理、废气污染监管与控制治理。

Characteristics of Heavy Metals Distribution in Agricultural Soils of Hangzhou and Its Environment Significances

In order to analyze the distribution of heavy metals in different agricultural soils of Hangzhou and its environmental significances, the auther analyzed the characteristics of six heavy metals (Hg, As, Cu, Pb, Cr, Cd) distributed in different agricultural soils of all districts of Hangzhou based on the methods of field sampling and interior analysis. The results showed the average contents of all the other five heavy metals, except for As, were all below or close to soil background values of Zhejiang Province, while the heavy metal contents at individual sampling points exceed the national secondary standards of soil environmental quality standard. This fact showed that the heavy metals under Hangzhou agricultural soils were at the safe level. While the heavy metals presented regional distribution characteristics. The average heavy metal contents distributed in agricultural soils of Yuhang district and Fuyang city were higher than the other districts, while the contents of Cu and Hg were averagely higher in Xiaoshan district and Jiande city, and the highest point of As, Cr and Cd happened in Chun'an county. Basically, the heavy metals under different crops agricultural soils were different, but they were not abvious.The heavy metal contents under rice paddies and vegetable fields were higher than other crop soils, while the content of Cd under Leafy vegetables crop soils (vegetables, tea ) was higher than rhizome (rice paddies) and tomato fruit (fruits) crop soils. At present, the threat from six heavy metals was not significant, but we still found that Cu content exceed the standard under some individual sampling point in Xiaoshan district, and Cd in Chun'an county was affected externally. So government should strenghen the monitoring and avoid the external pollutions. At the same time, atmospheric dust and exhaust pollution monitoring should be strenghened as well.