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

Abstract

Per- and polyfluoroalkyl substances have the potential to leach into groundwater, particularly in areas with potential pollution sources, such as landfills. The composition and distribution of per- and polyfluoroalkyl substances, as well as soil characteristics, are particularly useful for identifying the sources of per- and polyfluoroalkyl substances. The objectives of the present study were to characterise per- and polyfluoroalkyl substance levels in groundwater in Thailand, identify their potential sources and highlight their spatial distribution. Groundwater samples were collected in areas hosting municipal and industrial waste disposal sites. Seven Per- and polyfluoroalkyl substances were extracted from the groundwater samples using the solid-phase extraction technique and analysed by high-performance liquid chromatography-tandem mass spectrometry. These samples contain mostly perfluorooctanoic acid and perfluorooctane sulfonate, with the highest concentrations of 34.96 and 25.88 ng L–1, respectively, obtained from industrial waste disposal site areas. The presence of perfluorohexane sulfonate in most samples from industrial waste disposal site areas suggests its usage as a substitute for perfluorooctane sulfonate-based products. In addition to waste disposal, hierarchical cluster analysis reveals that other sources likely influence the presence of per- and polyfluoroalkyl substances in groundwater in Thailand. Livestock farming and ponds near groundwater wells probably impact per- and polyfluoroalkyl substances levels in the associated groundwater. The spatial distribution of per- and polyfluoroalkyl substances shows that in addition to waste disposal sources, soil characteristics and interactions between their negatively charged components and cations in soils significantly influence the contamination of groundwater in the areas studied.