Distribution of perfluorooctanesulfonate (PFOS) isomers in a Norwegian arctic food web

Perfluorooctanesulfonate (PFOS) is a global synthetic fluoroorganic compound and one of the most abundant per- and polyfluorinated alkylated substances (PFAS) in the arctic environment. PFAS are ubiquitously dispersed throughout the planet’s aquatic environments, soils and wildlife. Their environmental persistence, tendency to bioaccumulate and biomagnify in food webs coupled with negative health effects at elevated levels has resulted in them being commonly described as persistent organic pollutants. Although PFOS and other PFAS compounds have been subject to increasing scientific interest in the decades following their discovery, much remains unknown and uncertain in regards to their global and local transport mechanisms as well as their potential as environmental toxins. The objective of this study was to develop and validate an analytical method for the separation and determination of the individual PFOS isomers commonly found in environmental and technical samples, and attempt to quantitate them in biota samples from Svalbard, Norway. Collected samples from neighbouring levels of the food web at two different locations in the vicinity of Longyearbyen were analysed for the purpose of gaining insight into the levels of the individual PFOS-isomers, and changes happening to the isomer profile from one trophic level to the next. A new high performance liquid chromatography mass spectrometry (HPLC-MS/MS) analytical method was designed by combining elements from other published studies. The method was used to separate four groups of PFOS isomers from a mixture and was applied to quantitate PFOS isomers in the biota samples. It was found that the total PFOS concentrations and the relative concentrations of L-PFOS in the biota samples increased with increasing trophic levels, in agreement with previous reports on the isomer’s greater bioaccumulation tendency. Fish liver samples from a reference station without any known nearby local PFOS pollution sources were discovered to have higher total PFOS levels than fish liver samples from a station near a decommissioned fire-fighting station. However, a small sample size and uncertainty with regards to the quantitation made it hard to interpret the findings, as PFOS isomers at lower trophic levels were not detected due to insufficient sensitivity