PCB remobilisation from soils as contamination pathway for fish in the NE Atlantic and the Baltic Sea

We studied potential pathways of PCB transport from source countries that may have caused contamination of marine fish in the Northeast Atlantic and the Baltic Sea. Using the relative fractions of ICES-7-PCB concentrations as profiles, we matched observed profiles from fish caught between 1982 and 2020 with predicted profiles, referred to as 'shadow profiles', reflecting potential contamination pathways from PCB consuming and emitting countries into marine fish. While shadow profiles directly associated with emissions from major European industrial nations showed the closest match to contamination profiles of marine fish, modelling a transient degradation of PCB in soils and a subsequent remobilisation revealed an additional plausible pathway of contamination. Shadow profiles from this plausible pathway matched published median soil profiles from selected European countries and significantly improved the explanation of congener profiles observed in marine fish. For PCB in fish, both emissions from Germany and degraded but remobilised contamination of soils in former USSR appeared to be particularly important. Unexplained observed fish profiles may be related to a mix of contamination pathways from different source countries. Overall, our results highlight the important role of soils as secondary sources of PCB contamination for marine fish.