TRICHLOROETHYLENE (TCE) IN TREE CORES COLLECTED AT A CONTAMINATED SPRING COMPLEX IN ASHEVILLE, NC

CTS of Asheville is a former electroplating facility and a proposed EPA Superfund site. In 1999, residents living near the site noticed an oily substance in springs they had been using as a drinking-water source. Subsequent sampling of the springs revealed concentrations of trichloroethylene (TCE; 21,000 ppb) well above the federal drinking-water standard (5 ppb). Much of the TCE volatilizes as it discharges at the springs, raising concerns about air quality and vapor intrusion near the site. Several other volatile organic compounds (VOCs) and heavy metals have since been detected in soil, surface water, and groundwater beneath and near the CTS facility.

In this study, we cored trees at the contaminated spring complex and developed a semi-quantitative method for analyzing TCE in the tree cores with purge-and-trap gas chromatography-mass spectrometry. The detection limit for the method is approximately 20 ng/g (dried tree core weight) and measured concentrations have ranged from 60 to 800 ng/g. To date, TCE detections have been limited to trees growing above or immediately adjacent to the 4 main springs within the spring complex. This suggests the springs are a local discharge phenomenon, and contamination of shallow groundwater is not widespread. Instead, TCE that does not discharge in the springs likely migrates downward to the fractured bedrock aquifer below. This interpretation is consistent with borehole logging and imaging data collected by the USGS, which indicate a preferred orientation of bedrock foliation and fractures away from the spring complex and toward a residential area where TCE has been detected in both monitoring and private wells.