Study On Remediation Of Contaminated Gasoline Station By Petroleum

The soil and groundwater have become more contaminated gradually in our country because of the long-term lack of attention and effective protection due to the concealing of the contaminants in the subsurface. As the typical facility of petroleum storage, the gasoline station is one of the main sources of organic contaminants in the soil and groundwater. The seepage of petroleum in the soil and groundwater can be caused by the breakage of petroleum pipelines or tanks which are buried in the subsurface, and the human's health is threatened by the toxic petroleum hydrocarbons. Fewer studies have focused on the remediation of the contaminated gasoline station by petroleum presently in our country, so there is less practical experience and inperfect technology system. Regarding a gasoline station in Beijing and the BTEX (benzene, toluene, ethylbenzene and xylene) which are common volatile organic contaminants in the petroleum hydrocarbons as the study object and the typical contaminants respectly, this study has established an entire treating procedure for the contaminated gasoline station from the field monitoring to the design of remediation technology. This study has set a technical demonstration for the monitoring and the remediation of a contaminated site by petroleum.This study has amended the conventional technology of soil gas sampling in the subsurface, conducted the field monitoring in the gasoline station and obtained the BTEX gas phase concentrations of the sampling locations in the unsaturated zone. Because the 4 phases of BTEX which are gas phase, adsorbed phase, NAPL phase and dissolved phase usually coexist in the unsaturated zone, this study has calculated the multi-phases equilibrium concentrations. Based on the environmental quality standards for soils at home and abroad, this study has concluded that the gasoline station has been slightly contaminated and the region nearby G3 location should be the major remediation site. This study has also implied the limitation of such a soil environmental quality assessment.This study has surveyed the mechanism of monitored natural attenuation (MNA) overall, and analyzed all kinds of major abiotic processes and biotic processes. This study has also indicated the specialty of the biodegradation of the organic contaminants in the unsaturated zone, that is, the aerobic respiration is the major biodegradation form and the process accords with the first-order decay law 0C = C e?kt. Then the trend of the biodegradation of the organic contaminants in the unsaturated zone of the site has been evaluated by the first-order law. Soil vapor extraction can restore the unsaturated zone which has been contaminated by petroleum effectively. According to the site conditions and contaminated situation, this study has utilized the software AIR3D which can simulate the soil gas flow in the unsaturated zone to set up a single well, homogeneity and steady state model. Considering both the extraction influence area and the cost, this study has designed the extraction vacuum and the screen length, which are the major parameters of a SVE system, based on the results of the numerical simulations.