Spatiotemporal Assessment of CVOC Contamination in Karst Groundwater Sources and Exposure at Tap Water Point of Use

Abstract

Extensive historical contamination poses a potential threat to karst aquifer systems. Karst terrains are characterized by well-developed conduit porosity and highly transmissive zones. These characteristics make the karst aquifers highly productive but also highly vulnerable to contamination. As an important freshwater resource, groundwater systems in karst areas pose significant risk for exposure and lead to potential public health impacts. Of particular concern is the pollution with chlorinated volatile organic compounds (CVOCs) because they are ubiquitous in the environment and have been identified as potential precursors of preterm birth complications. The study aims at determining the link between contamination at karst groundwater source and pollution at the tap water point of use. GIS technology and statistical methods are used to perform spatiotemporal analysis of the collected data. The analysis incorporates data gathered from regulatory agencies and current groundwater and tap water samples collected from residential homes. Results show the presence of CVOC in groundwater and tap water. CVOCs, including carbon tetrachloride, tetrachloroethene, and trichloroethene, are found at higher frequencies and concentrations in groundwater than tap water. Chloroform is found at higher frequencies and concentrations in tap water than groundwater. Spatially, contamination is found throughout the study area, with some hot spot clusters in certain regions. Temporal analysis shows a decreasing concentration trend for CVOC in groundwater and high variability with no marked tendency in tap water. Spatiotemporal analysis suggests the pollution comes from multiple sources and extends beyond the demarked sites. Future work will assess additional sources of tap water contamination.