A gas monitoring approach to estimate the residual TCE location in the unsaturated zone of Woosan Industrial Complex (WIC)

Abstract

An area accommodating various industrial facilities has fairly high probability of groundwater contamination with multiple chlorinated solvents such as trichloroethene (TCE), carbon tetrachloride (CT), and chloroform (CF). Source tracing of chlorinated solvents in the unsaturated zone is an essential procedure for the management and remediation of contaminated area. From the previous study on seasonal variations in hydrological stresses and spatial variations in geologic conditions on a TCE plume, the existence of residual DNAPLs at or above the water table has indicated. Since TCE is one of the frequently detected VOCs (Volatile Organic Compounds) in groundwater, residual TCE can be detected by gas monitoring. Therefore, monitoring of temporal and spatial variations in the gas phase TCE contaminant at an industrial complex in Wonju, Korea, were used to find the residual TCE locations. In each field test, TCE gas samples were collected at 4 different depths above the water table from the well, KDPW-2, with/without a packer and were analyzed using SPME (Solid Phase MicroExtraction) fiber and Gas Chromatography (GC). The results showed that the highest TCE concentration appeared near at 12 m depths in each test and the range of TCE concentration decreased as the sampling period went from May to November. With these concentration data, the radius of influence (ROI) was calculated and applied on the real scale map of WIC. Therefore, this gas monitoring approach could be used as a method to find the approximate location of residual DNAPLs in the unsaturated zone. Moreover, it will be helpful for the efficient remediation of groundwater by giving the idea of the sources location.