Study On Sorption And Transport Of Typical Gasoline Components In Porous Media Of Different Properties

Since the occurrence of underground storage tanks, pipeline leaks and otherincidents, a lot of oils enter into the underground environment. The study on sorptionand transport of organic contaminants in the underground environmental media is ofgreat importance. The gasoline additive methyl tertiary butyl ether (Methyl tert-butylether, MTBE) and typical gasoline components benzene and toluene are selected astarget organic compounds in this study. Batch experiments and column experimentswere conducted to investigate the sorption and transport of organic contaminants indifferent porous media. The conclusions are as follows.(1) The experimental results of toluene sorption in different porous media showed that:sorption of toluene was mainly influenced by organic carbon content and dissolvedorganic matter in porous media-water systems. The higher organic carbon content ofthe medium, the stronger the sorption of toluene. Conversely, dissolved organic matterincreased the solubility of toluene and blocked the sorption sites of sorbent, leading toa decrease of sorption of toluene to media.(2) In the column experiments filled with the standard soil, the influence of ionicstrength on transport of gasoline compounds in porous media was studied by choosing0.005M and0.05M CaCl2solutions as background solutions, respectively. Theresults showed that the effect of ionic strength on sorption and transport of MTBE,benzene and toluene in the standard soil was relatively insignificant.(3) Gasoline components transport processes in porous media is chemicallynon-equilibrium process. The sorption was a dynamic process but not absorption forMTBE in kaolin column and standard soil column. The sorption of gasolinecompounds to porous medium did not show a positive correlation with organic carboncontent. Organic carbon content of kaolin column was less than that of the standardsoil column. However, the sorption and migration of gasoline compounds in thekaolin column was consistent with that of the soil column, indicating that theinorganic mineral kaolinite played a certain role in the transport of gasolinecompounds. In artificial soil column, organic carbon played the main role in toluene sorption.(4) The transport of gasoline compounds in porous media was affected by coexistenceof other compound (s). Under the condition of coexistence of three gasolinecompounds, the sorption of gasoline compounds was closer to equilibrium than thatunder the condition of single-solute. The sorption of benzene and toluene weresmaller than that of single-solute. However, there was no significant effect ofcoexistence of solutes on MTBE sorption.(5) Organic carbon-water partition coefficient (Koc) of gasoline compoundsdetermines their sorption properties. When the soil organic carbon content is greaterthan0.1%, it dominates the sorption process. In the experiments, the sorption capacityof gasoline compounds follows the order of MTBE <benzene <toluene. The natureof gasoline compounds has a great effect on their sorption in porous medium. Organiccompounds having higher hydrophobicity are more likely to be sorbed.