Gasoline type contaminants are a serious threat to soil and groundwater quality as well as health and welfare of general public. Most constituents of gasoline are volatile organic compounds. Soil vapor extraction and air sparging (SVE/AS) are the most efficient techniques to remediate soils and groundwater contaminated with volatile organic compounds. Hence in this state-of-the-art review paper the transport of gasoline-type contaminants in subsurface system and subsequent remediation process are introduced, discussed and summarized. First the mechanism of contaminant transport in subsurface system is briefly introduced, and the mass transport equations, fluid flow equations, and the constitutive model of relative permeability - saturation - capillary pressure are discussed. Then the numerical method is introduced to simulate the process of multiphase flow and contaminate transport in porous media, and the tempo-spatial distribution of contaminants. Then the geotechnical centrifuge modeling, a convenient and efficient physical modeling technique is introduced.Centrifuge model tests were conducted to study transport behavior of gasoline during contamination and remediation process, as well as air flow patterns during sparging process. The test results showed that gasoline infiltrated the vadose zone and moved downwards, forming a high concentration zone above the water table and then spreading out laterally. The water solubility and soil property influence gasoline transport behavior. The vapor pressure of contaminant seems to be an important factor affecting the efficiency of SVE. The zone of influence (ZOI) for air sparging is cone-shaped, and a stable ZOI can be maintained by the sparging pressure higher that a critical value. Based in the presentation it can be concluded that a combination of numerical simulation and centrifuge modeling can be a used to understand the subsurface transport of LNAPLs and their remediation.
Li-Ming HU Jay N.MEEGODA Irene M.C.LO Yan LIU Sheng-Yan GAO Zhao-Qun WU
Department of Hydraulic Engineering, State Key Laboratory of Hydro Science and Engineering, Tsinghua Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07 Department of Civil Engineering, Hong Kong University of Science and Technology, HKSAR, China State Key Laboratory of Hydro Science and Engineering, Tsinghua University, China Department of Civil and Environmental Eng., New Jersey Institute of Technology, Newark, NJ 07102, US