M.Sc. in environmental chemistry

Multicore.

She has analysed eight sediment cores from the Barents Sea and the Norwegian Sea for cesium-137 (137Cs) (half-life 30.1 years). This radionuclide is anthropogenic and originates from e.g. nuclear weapons testing in the 1950s and 1960s, discharges from nuclear power plants as Sellafield (UK) and La Hague (France) and the Chernobyl accident in 1986. Furthermore, she has dated the sediment cores using lead-210 (210Pb) (half-life 22.2 years). The results from the 210Pb-dating were compared with dating results obtained at the Danish Hydraulic Institute (DHI), in order to quality assure a dating method recently implemented at IMR.

The concentrations of 137Cs in the surface samples ranged from 3.9 to 31.7 Bq/kg dry weight. In 3 cores, the concentrations increased somewhat below the surface (to a maximum of 55.3 Bq/kg dry weight). The surface concentrations are alike to or slightly higher than concentrations found in other monitoring programs in the same areas. There was a consistency between the 137Cs concentrations and sediment grain sizes. Further, there was a consistency between the 137Cs concentrations and  the levels of polycyclic aromatic hydrocarbons (PAHs), represented by the PAH-16 parameter. A reason for this might be that both 137Cs and PAH-16 compounds tend to adsorb to fine-grained sediments. The 210Pb dating results obtained by the DHI were within the estimated uncertainty for most of the samples dated at IMR, which indicates that the 210Pb dating method implemented at IMR is of appropriate quality.