土壤气相抽提去除土壤中汽油烃污染物柱试验研究

原位处理土壤石油污染对于土壤和地下水的有机污染控制具有极其重要的现实意义.通过砂土柱试验研究了原位物理通风的主要工艺形式及运行参数,并初步分析了汽油烃在砂土柱中的迁移和通风去除机制.结果表明,顶部真空抽提与底部注气两种通风方式相比,顶部真空抽提效果较好,砂土柱汽油烃初始质量浓度为2.937 mg/g时,经过104.5 h通风,砂土柱中汽油烃去除率达80.49%.土壤汽油烃初始浓度影响其在土壤中的迁移和去除,土壤汽油烃初始浓度越大,相同通风条件下,物理通风方法去除土壤中挥发性有机物的效率越低.通风及通风方式对砂土中的汽油烃的去除影响很大,连续通风可在砂土柱中形成稳定的负压环境,在汽油烃初始质量浓度为35.730 mg/g时,连续真空抽提264 h,砂土柱中的汽油烃平均去除率达89.29%;间歇通风在砂土柱中形成的负压环境不稳定,但也可以去除砂土柱中的汽油烃.初步分析认为,汽油烃存在负压作用下的向上挥发和重力作用下的向下迁移两个过程,其综合作用的结果导致汽油烃在砂土柱中的分布状况.

Soil vapor extraction for removing gasoline hydrocarbons in a soil column

Soil vapor extraction experiments were performed in a soil column to determine the effects of initial gasoline hydrocarbons (HC) concentration and the venting method on HC removal and to propose mechanisms for HC movement and removal. Among the two extraction methods studied, air extraction was more effective than air injection. Starting from an initial HC of 2.937 mg/g, 104.5 h of air extraction removed 80.49% of HC in the soil column, soil vapor extraction efficiency decreased when the initial HC concentration increased. Continuous soil venting produced a steady vacuum environment and was more effective than the intermittent soil venting operated 12 h/day. At an initial HC concentration of 35.730 mg/g, 89.29% of HC in the column was removed after 264 h of continuous vapor extraction; only 41.82% HC was removed by the intermittent venting over the same period of time. The distribution and removal of HC in the soil column were results of both the upward movement caused by vacuum enhanced volatilization and the downward movement due to gravity.