Impact of seasonal variations in hydrological stresses and spatial variations in geologic conditions on a TCE plume at an industrial complex in Wonju, Korea

摘要

Spatial and temporal variations in a trichloroethylene (TCE) plume at an industrial complex in Wonju, Korea, were examinednbased on hydrogeological data and seven rounds of groundwater quality data collected over a year. The site has considerablenvertical heterogeneities; the top layer of soil is covered by impermeable paving material at several locations, followed by anseries of reclaimed or residual soil layers, and with weathered rocks to the crystalline biotite granite at the bottom. Arealnheterogeneity in the surface conditions plays an important role in controlling groundwater recharge. The heterogeneity structurenis influenced by complex surface conditions paved with asphalt and concrete. Owing to the presence of limited recharge areanand concentrated summer precipitation events, the effects of seasonal variations on groundwater hydraulics tend to diminishnwith distance from the recharge area. This result was established by analysing the influence of the contrasting surface rechargenconditions between the near-source zone and the far zone, and the seasonally concentrated precipitation on the transport patternsnof a TCE plume. In addition, variations in the plume’s downstream contaminant flux levels were also analysed along a transectnline near the source zone. The results show that the general tendency of the TCE plume contaminant concentration and massndischarges were reproducible if we account for seasonal recharge variations and the associated changes in the groundwaternlevel. During recharge events, the TCE concentration variations appear to be influenced by leaching of the residual dense nonaqueous-nphase liquid (DNAPL) TCE trapped in the unsaturated zone. This result shows that seasonal variations in contaminantnplume near the source zone is inevitable at this site, and that these variations indicate the presence of residual DNAPL at ornabove the water table, at least in some isolated locations. Copyright  2011 John Wiley & Sons, Ltd.