Per- and polyfluoroalkyl substances in groundwater of Thailand: Occurrence, source identification and spatial distribution

Abstract

Per- and polyfluoroalkyl (PFAS) have the potential to leach down to the groundwater particularly in areas with potential source pollution such as landfills. The composition patterns of PFAS, distribution and soil characteristics significantly contribute to their source identification. The objectives of this study were: (1) to examine the levels of PFAS in Thailand groundwater, (2) to identify potential sources, and (3) to study the spatial distribution of PFAS. Groundwater samples were collected around municipal waste disposal sites (MWDS) and industrial waste disposal sites (IWDS). Seven PFAS were extracted by solid phase extraction technique and analyzed by high-performance liquid chromatography tandem mass spectrometer. Total PFAS in groundwater around the MWDSs varied from 1.68 to 7.75 ng L− 1. The total PFAS in groundwater around the IWDS varied from 2.64 to 42.01 ng L− 1. PFOA and PFOS were the most dominant compounds around the MWDS and IWDS areas. PFHxS was frequently observed in the groundwater around the IWDSs, suggesting that it has been used as a substitution of PFOS-based compounds due to it having a shorter chain length or resulting from degradation of fluorotelomers. In addition to source identification, the hierarchical cluster analysis showed that other than the waste disposal site, other factors or activities could have been involved. It was found that livestock farming and an abandoned pond very close to the groundwater well could have affected the levels of PFAS in the groundwater. Moreover, spatial distribution showed that besides the impact of waste sources, soil characteristics and interaction between negative charged PFAS and cation in the soil played an important role in the PFAS contamination in groundwater.