石油有机组分在包气带水土中残留和迁移差异

Residual and migration diversities of petroleum hydrocarbons in vadose zone

引言 石油作为主要的能源而被不断开采并广泛应用于各个领域，此过程中造成的石油有机物因意外事故或管理不当而散落于地表的情况在世界范围内频繁发生[1-3]。地表的污染物又可通过入渗的方式经过包气带土壤而最终进入到地下水中[4-6]。

Groundwater pollution of petroleum hydrocarbons is one of serious environment issues, which has potential great impact on human health and environment ecosystem.Although some efforts have been made to remove the petroleum contaminants, the results seem to be unsatisfied.There are a number of compounds in petroleum pollutants with different functional groups（chainalkanes： Chs,cycloalkanes：Cys,aromatics： Ars, and asphaltenes： Aps）, and their existence phases and migration pathways are various in vadose zone.However, these diversities are often ignored in prediction of environmental impacts and in design of remedial measures.So, in the present paper based on a survey for real contaminated sites the experimental study was conducted in a soil column to simulate, during leaching by contaminated water, the residue and migration of petroleum fraction #em/em#.e.Chs, Cys, Ars and Aps, in vadose zone when they penetrate into the soil and water.While the distinctions caused by both compounds characteristics and media properties was discussed.The results demonstrated that differences in solubility, fugacity and viscosity of the compounds and relative permeability of media were mainly factors leading to their migration diversity.Leaching factors of Chs, Cys, Ars and Aps in fined soil were 38.2,11.7,83.6 and 7.4×10-3 mg·L-1, respectively.Hence, the migration of Chs and Ars （volatilizing factor 43.9 mg·L-1） were significant and so they could be leached out of soil column.Especially, Ars （volatilizing factor up to 43.9 mg·L-1） was easier to leach out.Conversely, Aps was inclined to remain or be entrapped in soil due to its powerful viscosity.Because the permeability was the lowest for fine soil column, the components and amount of hydrocarbons pollutants accumulated were more and great, mainly on its upper layers, and decreased rapidly with depth of column.In contrast, for medium and coarse soil column, the residues were main Aps, and distributed in the whole column.At the end of leaching, soil samples of three columns were collected to determine the types and concentrations of compounds remained in soil.The analysis results showed that Chs and Aps could be remained in vadose zone for a long period, which is useful and helpful for risk assessment and remedial implements.