Natural attenuation of petroleum hydrocarbon contaminants in a shallow aquifer, Uiwang, Korea

Soil and groundwater in a shallow aquifer were contaminated with petroleum hydrocarbons, mostly comprised of toluene. Degrees of soil and groundwater contamination were closely correlated. The vertical profile of soil contamination showed an exponential or semi-linear decrease both upward and downward from the water table, and this was closely related to water table fluctuation. Vertical and seasonal variations in the concentrations of petroleum hydrocarbon contaminants and their degradation products were analysed in detail. Total natural attenuation rate and the contribution of biodegradation to that rate were estimated. Biodegradation was occurring at the study site but it was not sufficient for remediation of the site