基于标准化方法和统计分析法的土壤重金属环境基线值分析比较

通过监测研究区域208个监测点位表层土壤重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn的含量,并以此为基础获得区域表层土壤重金属环境基线值,以及区域表层土壤重金属环境基线值相对于本底值的变化累积情况,以此来判断区域表层土壤重金属受人为活动的扰动程度。采用标准化方法和相对累积频率统计方法,分别获得基于这两种方法的重金属环境基线值及偏差,以两者的平均值作为研究区域表层土壤重金属环境基线值。结果显示:研究区域监测点位表层土壤重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn分别有17.3%、1.0%、4.3%、0.0%、2.4%、3.8%、1.9%、0.0%的监测点位超出了农用地土壤污染风险筛选值限值,分别有26.9%、26.0%、29.8%、17.3%、16.8%,20.2%、28.4%、21.6%的监测点位较区域本底值均有不同程度累积;基于标准化方法和相对累积频率统计方法两种方法获得的重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn的环境基线值平均值分别为0.22、0.09、13.34、30.7、82.0、29.7、38.0、89.1 mg/kg,相对偏差为0.5%～12.0%;土壤中重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn的环境基线值较区域本底值的累积指数分别为1.5、1.2、1.0、1.1、1.0、1.0、1.0、1.0、1.0,重金属Cd的环境基线值较区域本底值有轻度累积,说明土壤重金属Cd已经受到一定程度的人为因素干扰,但影响程度较小,Hg有轻度累积的风险,As、Pb、Cr、Cu、Ni、Zn无明显累积。

Analyzing and comparing environmental baseline values of heavy metals in soil based on standardized method and statistical method

The contents of heavy metals Cd,Hg,As,Pb,Cr,Cu,Ni and Zn were monitored in the surface soils at 208 monitoring points in the area studied. The environmental baseline values of heavy metals and the cumulative changes of the baseline value relative to the background value were obtained. Based on this,the degree of disturbance of heavy metals in the regional surface soil by human activities can be judged. Standardized methods and relative cumulative frequency statistics were used to acquire the environmental baseline value and deviation of heavy metals in regional surface soil. The average environmental baseline values obtained by these two methods were used as the environmental baseline values of heavy metals in the surface soil of the area studied. The contents of heavy metals Cd,Hg,As,Pb,Cr,Cu,Ni,Zn exceeded the risk screening values for soil contamination of agricultural land of monitoring points in regional surface soil. The ratio of monitoring points was 17.3%,1.0%,4.3%,0.0%,2.4%,3.8%,1.9%,E95and 0.0%,respectively. Compared to the regional background values,the heavy metals had accumulated to different degrees of monitoring points in regional surface soil,and the ratio of monitoring points was 26.9%,26.0%,29.8%,17.3%,16.8%,20.2%,28.4%,and 21.6%,respectively. The mean environmental baseline value of heavy metals Cd,Hg,As,Pb,Cr,Cu,Ni and Zn obtained by the standardized method and the relative cumulative frequency statistics was 0.22 mg/kg,0.09 mg/kg,13.34 mg/kg,30.7 mg/kg,82.0 mg/kg,29.7 mg/kg,38.0 mg/kg and 89.1 mg/kg,with the relative deviation ranged from 0.5% to 12.0%. According to accumulation index of heavy metal,the environmental baseline values of heavy metals Cd,Hg,As,Pb,Cr,Cu,Ni,Zn increased to different degrees relative to the regional background values of the monitoring points in regional surface soil. The increasing change rate was less than 50%,which was not significant. The cumulative index of environmental baseline value of heavy metals Cd,Hg,As,Pb,Cr,Cu,Ni and Zn was 1.5,1.2,1.0,1.1,1.0,1.0,1.0,and 1.0,respectively. Among them,the environmental baseline value of heavy metal Cd is slightly accumulated compared to the regional background value,indicating that the soil heavy metal Cd has been disturbed by a certain degree of human factors,but the impact is small. The heavy metal Hg had slight risk of accumulation,and the heavy metals As,Pb,Cr,Cu,Ni,Zn had no obvious accumulation.