Per- and polyfluoroalkyl substances (PFAS) in the Hammarby groundwater reservoir : Evaluation of potential sources using particle tracking

Sammanfattning

High levels of per- and polyfluoroalkyl substances (PFAS) have been detected in the Hammarby aquifer in Norra Stockholmsåsen. These levels exceed the new regulations concencering drinking water from the Swedish National Food Agency (LVSFS 2022:22) that will become mandatory on January 1, 2026. The cause of these high levels is unknown. PFAS is an artificially made substance that is difficult to break down and therefore remains in the environment and in humans for a long time, where it has been shown to have harmful health effects. The purpose of this report is to evaluate the occurrence and potential sources of PFAS in the Hammarby groundwater reservoir in the Northern Stockholm Esker. The questions posed are: What sources contribute to the elevated PFAS concentrations observed in the groundwater reservoir? What additional information and data would be needed to confidently identify the primary sources responsible for PFAS contamination in the reservoir? To investigate this, groundwater analyses have been conducted, a literature review on activities that release PFAS has been performed, and the distribution of PFAS was evaluated using particle tracking from potential sources with the help of a groundwater model developed in FEFLOW. This information has then been compiled into a scoring system for the potential sources. The results indicate that it is difficult to definitively determine what contributes to the elevated levels of PFAS in the groundwater. A fire station and a landfill site located on the groundwater reservoir are important sources of PFAS. In particle tracking from these activities, the particles moved quickly to the groundwater reservoir and passed several of the observation wells where PFAS has been measured. The PFAS found in the groundwater can be connected to both landfill sites and fire stations in other studies. There are several other activities that are positioned such that the particles in the particle tracking quickly reach the groundwater reservoir and pass several of the locations where PFAS has been detected. These activities include engineering industries, metal surface treatment, electrical engineering industry, and intermediate storage and sorting stations for waste. However, there is a lack of information on what exact PFAS these activities release and in what quantities. It may also be historical usage that spreads further from soil contamination. Furthermore, the use and handling of PFAS in all these industries would need to be investigated to ensure whether they contribute to PFAS emissions to the groundwater.