基于内梅罗综合污染指数的农田耕层土壤重金属污染评价

Evaluation of Soil Heavy Metal Pollution in Farmland Soils Based on Nemero Comprehensive Pollution Index

为重金属污染防治提供科学依据,以石羊河流域武威平原区农田耕层土壤为研究对象,采集和测定了67个样点中重金属Cr、Ni、Cu、Cd、Pb、As、Hg的含量,在农田土壤重金属元素总量分布特征分析的基础上,分别以国标土壤污染风险筛选值和甘肃省土壤背景值为参评标准,采用单因子污染指数法和内梅罗综合指数法对重金属污染程度进行评价。结果表明,石羊河流域武威平原区农田耕层土壤中重金属Cd、Hg、Pb、Cr、Cu、As、Ni的含量,参比国标土壤污染风险筛选值,单因子污染指数均小于1,超标率为0,内梅罗综合污染指数为0.36,所有样点均处于安全无污染水平。参比甘肃省土壤背景值,内梅罗综合污染指数为2.16,轻度污染、中度污染和重度污染分别占56.7%、28.4%和14.9%;Cd、Hg污染最严重,平均含量分别达0.19、0.04mg/kg,分别是甘肃省土壤背景值的2.24倍和2.34倍,超标率分别达100.0%和92.54%,内梅罗综合污染指数分别达4.12和5.94,为重度污染;其余的Pb、Cr、Cu、As、Ni为轻度污染,超标率分别为56.72%、56.72%、53.73%、52.24%和40.30%。

To provide scientific basis for prevention and control of heavy metal pollution,taking farmland plough soil in Wuwei plain of Shiyang River as the research object,the contents of heavy metals such as Cr,Ni,Cu,Cd,Pb,As and Hg in 67 samples were collected and determined.Based on analysis of distribution characteristics of heavy metals in farmland soils,risk screening values for soil contamination of agricultural land and soil background value of Gansu Province were used as the reference standards,the pollution degree of heavy metals was evaluated by single factor pollution index method and Nemerow comprehensive index method.The result showed that the contents of heavy metal Cd,Hg,Pb,Cr,Cu,As and Ni in cultivated soil of Wuwei plain of Shiyang River Basin were all at the safe and non-pollution,compared with the national standard soil pollution risk screening value,the single factor pollution index was less than 1,the exceeding standard rate was 0,and the comprehensive pollution index of Nemero was 0.36.However,compared with the soil background values in Gansu Province,the Nemero comprehensive pollution index was 2.16.Slight pollution,moderate pollution and severe pollution accounted for 56.7%,28.4%and 14.9%,respectively.The most serious contaminants were Cd and Hg and the average contents were 0.19,0.04 mg/kg,respectively.It was 2.24 times and 2.34 times than the soil background value of Gansu Province,the rate of exceeding standard reached 100.0%and 92.54%,respectively.The comprehensive pollution index of Nemero reached 4.12 and 5.94,which belonged to serious pollution.Pb,Cr,Cu,As and Ni were slightly polluted,with exceeding standard rates of 56.72%,56.72%,53.73%,52.24%and 40.30%,respectively.