Polybrominated Diphenyl Ethers (PBDEs) as a Potential Groundwater Contaminant

Polybrominated diphenyl ethers (PBDEs) are ubiquitous contaminants that are found in numerous matrices including human milk, wildlife, air, sediment, rivers, landfill leachate and sewage. Although previous research is extensive with respect to biotic matrices and some abiotic strata, no known published studies have been conducted to investigate PBDE concentrations in groundwater. Hydrogeological settings, such as fractured rock aquifers with minimal overburden cover, may be particularly vulnerable to PDBE contamination from land surface or airborne sources. To explore this, PBDE concentrations were measured at a field site located near Perth, Ontario, Canada, where the gneissic fractured bedrock aquifer is overlain by a thin veneer of unconsolidated glacial material (0 to 4 m thick). Land use in the area is predominantly agricultural. Water samples were collected from multilevel wells (up to 45 m deep) for PBDE analysis on four occasions (26 samples from 16 multilevel intervals). Wells were purged and sampled using a submersible pump with polyethylene tubing or via dedicated polyethylene tubing equipped with foot valves. The concentrations of 17 congeners were determined by gas chromatography-high resolution mass spectrometry. Of the 26 samples, 13 showed detectable PBDE concentrations, with various congeners present. The maximum total concentration (for the 17 measured congeners) was 93.5 ng/L, with an average of 13.3 ng/L for the 13 positive samples. The most frequently detected congeners were BDE-209 (9 instances), BDE-138 (6 instances), and BDE-183 (4 instances). Potential PBDE sources include point (septic tanks, landfills) and more disperse (atmospheric transport, manure) sources. This study illustrates the need for further investigation into the fate and transport of PBDEs in groundwater settings. Future research should focus on: 1) more widespread investigation of the presence and extent of PBDEs in groundwater (in particularly vulnerable hydrogeological settings); and 2) the determination of potential pathways of PBDEs from source to water supply.