包气带土壤对石油烃的截留作用研究

Retention capacity of petroleum contamination in vadose zone

包气带土壤对地表污染物的截留作用是地下水免受污染的一道天然屏障。土壤截留污染物的能力对地下水石油烃污染的治理起着关键作用。在对实际污染场地进行调查研究的基础上,采用土柱淋滤、吸附/解吸、石油挥发等室内模拟实验,研究包气带土壤对石油烃的截留作用及其影响因素。结果表明,细砂、中砂和粗砂3种土壤对石油烃的截留率分别为81.0%、75.2%和70.2%,土壤对石油烃的截留作用很强;土壤深度与总石油烃浓度之间呈负指数关系;不同土层厚度与其对石油烃截留率之间呈对数增长关系。吸附/解吸实验得出,细砂、中砂和粗砂的阻滞系数分别为2 020 554、1 791 444和1 295 855,阻滞系数越大,对石油烃的截留能力也就越强。挥发实验表明,细砂、中砂和粗砂中石油的挥发率分别为1.66%、3.67%和7.34%,石油的挥发作用较小。根据实验结果可知,当土壤表层石油烃进入包气带过程中,吸附/解吸对土壤的截留能力起着主导作用。实验结果为石油烃污染场地土壤及地下水石油烃污染修复治理提供了科学依据。

The vadose soil as a natural barrier could protect groundwater against pollutants from earth surface,so the retention capacity of vadose soil was a significant factor for groundwater petroleum pollution control.Based on the field investigation in petroleum contaminated site,combined with the results of soil column leaching,adsorption/desorption and volatilization experiment,this paper investigated the actual fate and transport of petroleum in vadose zone.Results showed that the vadose soil presented perfect retention capacity,PHCs retentate rate of fined sand,medium sand and coarse sand were 81.0%,75.2% and 70.2% respectively.The relationship between PHCs concentration and the depth of soil can be expressed by a negative exponential equation c=ae^-bd.The retardation factors of fined sand,medium sand and coarse sand were 2 020 554,1 791 444 and 1 295 855.The volatilized amount of crude oil in fined sand,medium sand and coarse sand were 1.66%,3.67% 7.34%,which indicated that the volatilization of petroleum in vadose zone was relatively weak,and adsorption/desorption was main factor impacted the retention capacity.This study could provide scientific basis for remediation the petroleum contaminated soil and groundwater pollution control.