Leakage Contamination Of Underground Oil Storage Tank In South Jiangsu Province

The leakage of underground oil storage tank leads to the contamination of soil and groundwater. There is no high concentration on the phenomenon and no high efficiency method to detect the leakage contamination. Ground penetrating radar(GPR),has been used as a geophysic method in environment geology investigation for several years, but it hasn't been reported in china as a method in groundwater and soil organic contamination investigation especially the petroleum-derived hydrocarbons contamination.As a trying, the author investigated several gas station in South Jiangsu province by GPR and analysis the conditions which affect the probability of leakage and diffiusion. The applicability of the GPR in south Jiangsu province were certified, which provide the experience to the popularilize the GPR and research the problem further. The situation and the trend of the leakage contamination of gas station in South Jiangsu province were also estimated, which provide the government imformations and basis to make dicision and administrate.The research shows that most of the old gas station has the problem of leakage. Leakage was detected in 21gas station. It means 72.4% of the 29 gas station which was investigated were detected to leak. Typical leakage character were found in 18 gas station and these station dominate 62.1% of all the 34 cases.12 gas station which have typical leakage character are older than 15 years age. It means that 2/3 of those gas station with typical leakage character are old ones. That is to say the probability of leakage in old gas station is 60%.The result of GPR survey shows that GPR can detect the organic contaminant disributing from 0.5 meter to 15 meter beaneth the ground under the conditions of sand-water interlayer. High electronical conductivity of clay can reduce dephth of the GPR detection but can increase the difference of the conductivity between the background and organic contaminant, which can increase the accuracy of the GPR. The analysis to the sample from the ground in which contamination were deteced certified the result of GPR survey. Strong reflection character indicated high electronical resistance were observed in the GPR image of contamination plume, which indicates that the contaminant exist in liquid state.The analysis to the environment and geology conditions of these gas stations shows that the history, the lithology of the unsaturated zone, the permittivity of the acquifer, the water table, capacity of the UST, the load to the ground, and the cover of the ground can affect the probability of the leakage and the speed of expansion of the contaminants. These facters are also affect each other. In all these facters history is the main facter to the leakage probability. In the other hand the lithology of the unsaturated zone and the permittivity of the acquifer dorminant the speed of contaminant's expansion. The older the gas station is, the high leakage probability will be and the high the permittivity of unsaturated zone and the acquifer is, the high the speed of contaminant's expansion will be.It is worthile to attention that the variety of the contaminant concentration will lead the variety of the Character of the GPR image. It is necessary to relate the variety of the concentration to the data of the GPR quantificaitonally, which is hepful to surpervise the process of the attenuation and biodegradation of the contaminants.