基于主成分分析法的高速公路土壤重金属污染研究

Study on heavy metal pollution in highway soil based on principal component analysis

为了解重金属Cr、Ni、Cu、Zn、As、Cd、Pb在高速公路旁土壤中污染状况,分析重金属可能来源,以成都绕城高速公路为例布设3个土壤采样断面,对其两侧土壤中7种重金属的质量比进行了测定,分析了其污染特征,并利用变异系数和地累积指数法对土壤重金属污染程度进行了评价。通过主成分分析法进一步研究了土壤样品中重金属可能来源。结果表明:土壤样品中重金属Cr、Ni、Cd受人为活动干扰的影响较大,重金属变异程度属于高变异;Cu、Zn、As和Pb受到人为活动干扰的影响较小,重金属变异程度属于低变异;7种重金属Cr、Ni、Cu、Zn、As、Cd、Pb地累积指数分别为-0.88、2.48、-0.02、0.36、-1.83、3.87、0.49,土壤样品中重金属Cu、Cr、As处于无污染状态,Pb、Zn处于轻度污染状态,Ni处于中度污染状态,Cd处于偏重度污染状态;与四川省土壤背景值相比较,土壤样品中重金属Ni、Cu、Zn、Cd、Pb存在富集现象但质量比未超过道路与交通设施用地筛选值,未构成污染风险;主成分因子分析表明土壤样品中重金属Cu、Zn、As、Pb、Cd可能为汽车尾气排放及汽车轮胎磨损等交通运输影响所致,表层土中Cr主要来自基岩原始含量的转化和迁移,交通运输对此有部分影响。

To comprehend the distribution and the pollution status-in-situ of Cr,Ni,Cu,Zn,As,Cd and Pb on the soil ground beside the highways,analyze possible sources of the heavy metal,we collected and analyzed the heavy metal contaminants at 0-20 cm soil layers along the Chengdu City Expressway by taking the three soil sampling sections as a case study sample.This article is concerned with an analysis of the features of the 7 heavy-metal pollutions in the roadside soil along the Chengdu City Expressway.For our work,we investigated and measured the contents of the 7 heavy-metal in the roadside soils along the expressway by using the ICP-MS and then analyzed their pollution features by using the coefficient of variation and the geo-accumulation index for assessing the pollution degree to the soil.The results of our investigation and analysis show that the geo-accumulation index of Cr,Ni,Cu,Zn,As,Cd and Pb was worked out at about-0.88,2.48,-0.02,0.36,-1.83,3.87 and 0.49 respectively,with the pollution degree being ordered in a sequence of Cu,Cr and As as“safe”,Pb and Zn ass“lightly polluted”,Ni as moderate and Cd as“heavy”.The contents of Cr,Ni and Cd were more severely affected by human activities and their variation degree were higher in comparison to Cu,Zn,As and Pb.Compared with the background values of the soil heavy metal contaminants in Sichuan Province,the enrichment phenomenon of Ni,Cu,Zn,Cd and Pb were found,but their mass ratio didn’t exceed the screening value of road and transportation facilities and pose a pollution risk.The heavy metal Cu,Zn,As,Pb and Cd in the soil samples may be caused by the traffic and transportation on the soil ground beside the expressway by principal component analysis,such as automobile exhaust emission and automobile tire wear.The heavy metal Cr mainly may be caused by the transfer of bedrock ingredients on the soil ground beside the expressway,the traffic and transportation have partial influence.