Epsilon Open Archive

Abstract

Persistent organic pollutants (POPs) are bioaccumulative chemicals that are ubiquitously and globally distributed in the environment. Several species of POPs have been studied extensively and are continuously being monitored in various environmental matrices for decades. However, with the increasing amounts of chemicals produced and made commercially available, potential emerging POPs are receiving more attention. Per- and polyfluoroalkyl substances (PFASs) and polycyclic aromatic compounds (PACs) are two groups of emerging substances that are currently of great concern due to their potential toxicity and high mobility in terrestrial and aquatic ecosystems. The overall objective of this thesis was to improve our understanding on the impact of various pollution sources, environmental pathways, transport and fate of both legacy and emerging PFASs and PACs in pristine and polluted boreal catchments.
In Paper I, population density was found to be significantly correlated with PFAS levels in rivers. Ten rivers with distinctly higher ƩPFAS concentrations and with a common compositional profile (higher fraction of perfluoroalkane sulfonic acids) were identified, suggesting a major impact from a similar kind of point source(s) in these rivers. Significant positive relationships between several PFASs and dissolved organic carbon were detected in river and sea water, indicating chemical binding and co-transport in aquatic ecosystems. The findings in Paper II show that levels and compositional profiles of PFASs in river water were highly impacted by point sources and hydrological conditions. Seasonal trends of PFASs were impacted by river flow probably caused by mobilization of PFASs from contaminated soil and groundwater. In Paper III, fluxes of PACs in atmospheric deposition showed that they were higher during the cold season, both for PAHs and PAH-derivatives. The deposited PACs were found to be largely retained in the terrestrial environment of the boreal forest catchment or lost by other processes with <2% of the total deposited amount of ƩPACs exported via the outlet of the headwater on average over a year. During spring flood, the concentrations of PACs were found to be significantly higher than levels during the preceding snow-covered and snow-free seasons (Paper IV). Besides seasonal changes, landscape type (forest or mire) was found to have an impact on terrestrial export of PACs, with higher levels of PACs in a mire stream than in stream water in a forested sub-catchment.