| Summary: | 碩士 === 國立臺灣大學 === 環境工程與科學系 === 81 === Soil gas monitoring method is used to locate the VOCs polluted region of groundwater and soils, and to screen the sites of groundwater monitoring wells. The objectives of this thesis are to study the VOCs transportation in the vadose zone, to establish a pollutant transport model and to evaluate the relationship among the concentration of the pollutants in soil gas, the concentration of the source and the pollutant evaporating rate from soil surface. Further soil column experiments were performed to verify the transport model. In the other hand, sorption kinetics experiments were conducted to establish a first-order sorption model, and to get the sorption rate constant and the factors affecting non-equilibrium sorption.
Because of biodegradation, there is no significant relationship between toluene concentration in soil gas and that in polluting source in the soil column experiments. And the toluene concentration is smaller than that in polluting source by 2 to 4 orders. It was found that the concentration of soil gas at sampling point closest to the source is larger than the next point by one hundred times. When the soil gas technique is used to study biodegradable pollutants, the distance between the sampling site and polluting source must be considered to get the representative samples and reasonable explanations.
For the sorption kinetic experiments, it was found that the pollutant concentration and the flow rate of mobile phase would affect the sorption of pollutants by soil. Naphthalene is much more affected than toluene. The fitting results of the first-order sorption model were not affected by the concentration and the flow rate. So, uniform sorption rate constant was obtain. From the rate constant and with calculation by SKIT method, it was observed that the transport of toluene and naphthalene in groundwater is not affected by the non-equilibrium sorption under nature groundwater flow conditions.
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