Mass balance of perfluoroalkyl acids in the Baltic Sea

Abstract: Perfluoroalkyl acids (PFAAs) are man-made chemicals. Their unique properties make them beneficial for a wide range of industrial and consumer applications, such as constituents in fire fighting foams, hydraulic oils and food packaging materials.PFAAs have shown to be highly persistent in the environment, and the toxicological potential of long chain PFAA homologues is of a concern. International regulation and voluntary actions by the industry have been implemented and led to reduced primary emissions of PFAAs to the environment. However, the concentrations of some PFAAs in e.g. birds from the Baltic Sea are still very high and of ecotoxicological concern. Measures to reduce the PFAA contamination require an understanding of the sources and how the PFAAs are being transported in the environment.In this licentiate thesis a mass balance was assembled for perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDA) and perfluorooctane sulfonic acid (PFOS) in the Baltic Sea. A one-box model was used including the input pathways river inflow, atmospheric deposition, wastewater discharges and inflow from the North Sea via the Danish Straits, while the loss processes considered were sediment burial, transformation of the chemicals and outflow to the North Sea via the Danish Straits. Additionally, the inventories of the four target PFAAs in the Baltic Sea were estimated. Both chemical fluxes and inventories were estimated using recently published monitoring data (2005-2010).In order to obtain a detailed perspective on the current knowledge regarding PFAAs in the Baltic Sea, challenges and uncertainties in data selection were discussed for the most dominant input pathways. This included WWTP emissions and calculation of emission factors (EFs), atmospheric deposition and riverine inflow.River inflow and atmospheric deposition were the dominant inputs, while wastewater treatment plant (WWTP) effluents made a minor contribution. The input to the Baltic Sea exceeded the output for all 4 PFAAs, suggesting that inputs were higher during 2005-2010 than during the previous 20 years despite efforts to reduce emissions of PFAAs. Comparing the difference between PFAA input and output with the PFAA inventory, the doubling time for the concentration in the Baltic Sea was estimated to be 8-94 yr for PFHxA, 12-16 yr for PFOA, 3-5 yr for PFDA and 4 yr for PFOS. The surplus of the input can be an effect of retention and delayed release of PFAAs from atmospheric deposition in the soils and groundwater of the watershed.The licentiate thesis contributes to a holistic understanding of the major input and output pathways and inventories of PFAAs in the Baltic Sea. Furthermore, it points out current knowledge gaps in our understanding of sources and fate of PFAAs in the aquatic environment.