Viability of natural attenuation in a petroleum-contaminated shallow sandy aquifer

This study focused on evaluating and quantifying the potential of natural attenuation of groundwater at a petroleum-contaminated site in an industrial area of a satellite city of Seoul, Korea. Groundwater at the study site was contaminated with toluene, ethylbenzene and xylene (TEX). Eight rounds of groundwater sampling and subsequent chemical analyses were performed over a period of 3 years. The groundwater quality data suggest that TEX concentrations at this site have been decreasing with time and that the TEX plume is at a quasi-steady state. Trend analysis, changes in mass flux and plume area also confirmed that the TEX plume has reached a quasi-steady state. The proportion of the total attenuation attributable to biodegradation has decreased over the monitoring period while contribution of other attenuation processes, such as dilution or dispersion, has increased. Based on the calculated attenuation rates, it would take more than 20 years to clean up the site by natural attenuation alone.