基于改进物元可拓模型的鄱阳湖区耕地土壤重金属污染评价

Assessment of heavy metal pollution in arable soils in the Poyang Lake area based on the improved matter-element extension method

为了解鄱阳湖区耕地土壤重金属污染状况,采集252个耕地表层土壤样品,分析测定了Hg、As、Pb、Cd、Cu、Cr、Zn7种重金属元素的含量。鉴于土壤重金属污染的模糊性和不确定性,尝试运用物元可拓模型并对其进行改进,同时引入Hakanson毒性响应系数修正传统超标倍数赋权法权重,建立了基于改进物元可拓模型的耕地土壤重金属污染评价模型,并将其评价结果与传统评价方法结果进行对比。结果表明:样品中7种重金属的平均含量均超过当地背景值,并有不同程度累积,超标率Cr>Cu>Cd>Hg>Zn>Pb>As;运用改进后的物元可拓模型得到的鄱阳湖区耕地土壤重金属总体污染情况为尚清洁状态,都昌县、湖口县、共青城市的污染等级均为清洁级,其余地区均为尚清洁状态;改进物元可拓法与传统评价方法得到的评价结果基本一致,表明改进物元可拓模型在土壤重金属污染评价中同样适用,且更为合理。

To examine the contamination status of heavy metals in arable soils in the Poyang Lake area, a total of 252 top soil samples were collected from this area. Contents of the heavy metals Hg, As, Pb, Cd, Cu, Cr and Zn were determined using standard methods. Taking into consideration the fuzziness and uncertainty of soil heavy metal pollution, we used the improved matter-element extension model to assess soil heavy metal pollution. We also applied Hakanson toxic response coefficients to modify the weights determined by the traditional multiple super-scale weighting method. Having thus established an assessment model for heavy metal pollution in arable soils based on the improved matter-element extension model, we compared the evaluation results with the results obtained using traditional evaluation methods.We accordingly found that the average contents of the seven examined heavy metals in soil samples exceeded the local background values,and accumulated to different degrees, with the order of over-standard rates being Cr > Cu > Cd > Hg > Zn > Pb > As. On the basis of the results obtained using the improved matter-element extension model, we could conclude that the heavy metal contamination of soil in the Poyang Lake area was generally at a safe level. The heavy metal content in soils from Duchang County, Hukou County, and Gongqingcheng City was at a safe level, whereas that of soils from other areas was at alert level. The evaluation results obtained using the improved matter-element extension model were essentially consistent with those obtained using the traditional evaluation methods, thereby indicating that the improved matter-element extension model can be applied for the evaluation of soil heavy metal pollution and yields reliable results.