不同标准对城市土壤重金属质量分数的评价

Discussion of Different Heavy Metal Quality Assessment Standards of Urban Soil

对广州市某区城市土壤重金属污染现状进行调查,共采集土壤样品34个,分析样品中As,Hg,Cr,Cd,Ni和Pb的全量及有效态质量分数,探讨重金属元素全量和有效态质量分数之间的关系,并采用4种不同标准对结果进行了评价.结果表明:研究区工业用地、城区和农村居住区的土壤已受到一定程度的重金属污染,且为2种或3种重金属元素的复合污染;As,Hg,Cr,Cd,Ni和Pb有效态质量分数平均值分别为0.09,0.004,0.09,0.18,0.40和32.80 mg/kg,Cd和Pb的有效态质量分数占全量的比例较高.4种标准综合评价结果中,轻度、中度和重度污染样点数占样点总数的比例依次为国标(GB15618—1995)二级标准评价(62%)>有效态污染起始值评价(29%)>全量污染起始值评价(24%)>国标三级标准评价(21%).

The heavy metal contents of soil in one district of Guangzhou City were investigated. The total contents and available contents of As, Hg, Cr, Cd, Ni and Pb in 34 soil samples collected from the study area were analysed. The relationship between the total contents＇and available contents was discussed and evaluated using 4 kinds of soil quality standards. The results showed that the sods in the industrial, downtown and suburban residential zones of the study area were simultaneously contaminated by two or three heavy metal elements to some extent. The average available contents of As, Hg, Cr, Cd, Ni and Pb in the soils were 0.09, 0.004, 0.09, 0.18, 0.40, and 32.80 mg/kg, respectively. In addition, the ratio of available content to total content of Cd and Pb were higher than that of others. Using the second class of Soil Environment Quality Standard （SEQS）（ GB15618-1995 ）, the available content background values, the total content background values and the third class of SEQS as the indexes for evaluation, about 62%, 29%, 24%, and 21% of the soil samples exceeded the upper limit values of soil content, respectively. Therefore, using the available content background values to evaluate the heavy metal contamination of urban soil is feasible.