Sorption And Transport Of Typical Gasoline Components In Saturated Porous Media

Gasoline contaminants have caused serious pollution problems in soil andgroundwater. It is of significance to study the sorption and migration of oragnicpollutants in different components of the soil, because soil is a main sink of pollutants.Inthis thesis, benzene, toluene and methyl tert-butyl ether ( MTBE ) were selected as thetarget pollutants. Batch experiments and column experiments were used to study theadsorption and transport of organic pollutants in typical saturated porous media.Conclusions were summarized as follows:(1) Batch experiments were carried out to investigate the sorption and competitivesorption between benzene and toluene to soils of different organic carbon content.Single-solute solution experiments showed that sorption of single compound to soils canbe described by a linear sorption isotherm, and the sorption capacity is proportional tosoil organic carbon content. In bi-solute solution experiments, competitive sorption ofsolutes was observed and caused a decrease of sorption capacity of target compoundwhen compared to that of single-solute cases. The competitive sorption results indicatedthat sorption of organic compounds to specific sites on the solid surface probably playedan important role.(2) Column experiments were carried out to investigate the sorption and migrationin kaoline and Cihe soil columns. The breakthrough curves ( BTCs ) of MTBE showedthe symmetrical phenomenon. But in Cihe soil, the BTCs of MTBE slowly declined indesorption stage, with a long tail in the desorption stage, so the mainly adsorptionmechanism is chemical adsorption, because there are soil organic carbons in soil.(3) The order of typical gasoline components reaching the peak time of BTCs isMTBE, benzene and toluene. Due to the large molecular weight and low solubility ofbenzene and toluene, the desorption hysteresis of benzene and toluene in porous media ismore obvious. (4) With the increase of the concentration of CaCl2, kaoline crystals within the filmlayer spacing increases, adsorption point increase, the adsorption capacity increases. InCihe soil, complexation organic matter with Ca2+, hinders pollutants contacting withCihe soil. Therefore, the leaching rate of benzene and toluene became faster, and theleaching concentration increased if the CaCl2concentration increased in the solution.(5) The transport of typical gasoline components in saturated porous media can bewell simulated by the Freundlich model. The transport of typical gasoline components inCihe soil can be better simulated by the two-site model with CXTFIT than in kaoline.Therefore, the adsorption of the organic pollutants in the saturated porous mediumtransport processes was affected by nonlinear adsorption. With the soil organic carboncontent increases, the organic pollutants were also affected by chemical non-equilibriumadsorption.