基于地球化学基线的内蒙古东来地区土壤重金属污染评价

Assessment of Soil Heavy Metal Pollution in Donglai area of Inner Mongolia Based on Geochemical Baseline

目前,在中、小尺度上确定环境地球化学基线并准确实现重金属元素的空间分布是研究陆表环境变化过程的基础性工作,仍需深入研究。在野外样品采集、实验室分析及取得内蒙古东来地区土壤重金属数据的基础上,采用标准化法确定了内蒙东来地区的表层土壤中8种重金属元素Cu、Cr、Ni、Pb、Zn、Hg、As、Cd的地球化学基线值,分别以研究区土壤背景值及地球化学基线值为参照,使用地累积指数法和潜在生态污染指数法对研究区土壤质量进行了评价,并对几种重金属元素空间分布特征进行了研究。结果表明,由地累积指数法确定研究区土壤Ni、Zn、Pb、As、Hg、Cd元素达到轻-中度污染水平的样品占比分别为4.9%、3.4%、3.8%、7.9%、6.0%、6.2%,其它元素未达到污染水平;由潜在生态风险指数法评价结果可知,Hg和Cd元素具有较重潜在生态风险,达到较重及以上潜在生态风险等级的样品占比依次为9.1%和2.1%,其它元素风险较低;不同参比值的选取对评价结果有一定的影响,整体看来以地球化学基线值为参比值的评价效果较好于以土壤背景值的评价效果。达到一定污染等级的元素集中分布在东来镇东北部及西部地区,其原因可能与人口分布及通过该区的铁路、公路有关。研究区土壤环境质量总体较好,但个别元素潜在生态风险指数较高,应加强管控及预防重金属污染。

At present,determining the environmental geochemical baseline and accurately realizing the spatial distribution of heavy metal elements at the medium and small scales is a basic work to study the process of land surface environmental change,which still needs further research.On the basis of field sample collection,laboratory analysis and obtaining soil heavy metal data in Donglai area of Inner Mongolia,the geochemical baseline values of 8 heavy metal elements(Cu,Cr,Ni,Pb,Zn,Hg,As and Cd)in the surface soil in Donglai area of Inner Mongolia were determined by standardization method.The soil background value and geochemical baseline value were selected as the reference values,and the soil quality in the study area was evaluated by the methods of geoaccumulation index and potential ecological pollution index,and the spatial distribution characteristics of several heavy metal elements were studied.The results showed that the percentages of samples Ni,Zn,Pb,As,Hg and Cd elements in the study area that reached the light-moderate pollution level determined by the geoaccumulation index method was 4.9%,3.4%,3.8%,7.9%,6.0%and 6.2%,respectively,and the other elements did not reach the pollution level.According to the evaluation results of potential ecological risk index method,Hg and Cd elements have heavy potential ecological risk,and the proportion of samples with heavier and above potential ecological risk grade is 9.1%and 2.1%respectively,and the risk of other elements is lower.The selection of different reference values has a certain impact on the evaluation results.On the whole,the evaluation effect of geochemical baseline value is better than that of soil background value.The elements that reach a certain pollution level were mainly distributed in the northeast and west of Donglai,which might be due to the population distribution and the railway and highway passing through the area.The soil environmental quality in the study area is generally good,but the potential ecological risk index of individual elements is higher,so the control and prevention of heavy metal pollution should be strengthened.The soil environmental quality in the study area was generally good,but the potential ecological risk index of individual elements was higher,so the control and prevention of heavy metal pollution should be strengthened.