Hydrodynamic modelling of current and future spread of PFOS in Lake Ekoln - Impacts of Climate Change and Socioeconomic Development

Abstract

The spread of Per- and polyfluoroalkyl substances (PFAS) is a global issue since it has been detected in aquatic environments all around the world and may have adverse effects on human health. The major exposure pathway for humans is drinking water. High levels of PFOS, one of the most harmful PFAS, have been detected in Lake Ekoln - a sub basin to Mälaren, and its surrounding environment. The aim of this study was to analyse current and future spread of PFOS in Lake Ekoln. Sources to PFOS in the area, and processes affecting fate and transport of PFOS were investigated. Hydrodynamic modelling in MIKE 3FM was applied to simulate the current spread of PFOS in the lake, but also to investigate future conditions in regards to climate change and socioeconomic development. Future scenarios were set up for 2050 where climate change was described by Representative Concentration Pathways (RCPs) and socioeconomic development by Shared Socioeconomic Pathways (SSPs). Major sources of PFOS in Lake Ekoln are firefighting training sites where firefighting foam containing PFOS historically have been used, and the Wastewater Treatment Plant (WWTP) Kungsängsverket. Fyrisån receives water from both of these sources and is considered to be the major pathway for PFOS entering Lake Ekoln. Other possible sources are landfills, industrial activities and On-site Wastewater Treatment Systems (OWTS), and other pathways are Uppsalaåsen, precipitation and other rivers. Processes affecting the fate and transport of PFOS are sedimentation and bioaccumulation, however, these were not included in the modelling. Climate change will not affect the situation with PFOS remarkably until 2050 while socioeconomic development will have a larger impact; the concentration of PFOS is assumed to decrease, however the extent of the decrease varies a lot between the different SSPs. Considering the possibilities to use Lake Ekoln as drinking water source in regard to PFOS, the quality is good and will remain so in 2050, according to the current regulations. However, other kinds of PFAS could be as harmful as PFOS why research regarding the spread of PFAS in the area needs to proceed.