成渝高速公路旁土壤铅污染分布及评价

Distribution and Environmental Quality Assessment of Lead Polution in Soil along Chengyu Highway

为研究公路交通尾气排放对路边土壤铅累积和分布的影响,并评价其污染程度,在成渝高速公路某段下风侧3个断面内分别采集了水平和垂直土壤样品,用碘化钾-甲基异丁基甲酮萃取火焰原子吸收法测定土壤样品中的铅含量.结果表明水平方向距离公路4 m处土壤铅含量最高,总体分布呈先增后减趋势,128 m处铅含量已接近背景浓度;垂直方向上0-5 cm表层土壤铅含量平均值显著高于以下各层,0-20 cm范围内铅含量向下逐渐减少,20 cm以下趋于稳定.采用地质累积指数分析表明,该地区表层土壤个别采样点处受到轻微或中等铅污染,其余采样处未受铅污染.

To study the distribution and accumulation of lead in soil along the road polluted by vehicle exhaust and to assess the pollution, some samples collected at the leeward along Chengyu Highway and in referential areas were determined by flame atomic absorption spectrophotometry combined with extraction by potassium iodine-methyl isobutyl ketone （KI-MIBK） system. The results show that the lead concentrations in topsoils increase with the increase of vertical distance from highway and then after reaching a maximum value, at 4 m, they decrease gradually with the increasing distance. The results also show that the topsoil, with depth between 0 and 5 cm, is polluted by lead from gasoline combustion and the lead concentrations in soil decrease with the sampling depth increase from 0 to 20 cm, and then reach a steady concentration. The contamination of the topsoil is assessed on the basis of geoaccumulation index. The tests reveal that only two sampling sites are polluted mildly or moderately, the rest sites are non-polluted.