The training program is designed for Annika Jahnke, a very talented young researcher who has successfully completed her doctoral studies on polyfluorinated alkyl substances in the marine atmosphere. The proposed 24-month project seeks to extend her competencies to internal exposure, bioaccumulation and bioavailability of organic contaminants. The missing link between external concentrations of persistent organic pollutants (POPs) and their levels at target sites in organisms where adverse effects occur will be investigated. This research issue is fundamental for risk assessment of contaminants. The training program consists of three research objectives: (1) Internal exposure: Develop equilibrium sampling methods to measure chemical activity / fugacity of POPs in biota; use them to test the hypothesis that POP fugacity is the same in different tissues throughout a given organism. (2) Bioaccumulation: Explore bioaccumulation in marine food webs from the Baltic Sea by measuring the fugacity of a given POP at different trophic levels. (3) Bioavailability: Develop methods to measure the freely dissolved concentration of POPs in water and sediment, which is equivalent to the chemical activity / fugacity. Use them together with the above methods to explore bioavailability effects on bioaccumulation, and to determine differences in POP fugacity between benthic and pelagic organisms as well as their respective environments. An additional component of the training program will provide the applicant with important complementary competencies including research supervision and project management. This completes a program which is carefully matched to the applicant´s needs and exploits the unique possibilities at Stockholm University and the Danish National Environmental Research Institute. With the experience gained in this project, the talented applicant will be well prepared for a successful independent research career.