²⁴¹Am in the bottom sediments of the southern Baltic Sea

Based on observations of ²⁴¹Am in dated sediments, we studied the history of isotope accumulation in these sediments and evaluated their contamination level and distribution in the sediment cores. The fieldwork and sampling collection in the presented project were performed during a cruise on the r/v Oceania, which belongs to the Polish Academy of Sciences (IO PAN). Sediment cores were collected from various locations in the southern Baltic Sea: the Bornholm Deep, the Gdansk Deep, and the Gotland Deep.

An analytical method for determining Am was adapted to analyse ²⁴¹Am in environmental and biological samples, which relies on the sequential use of ion exchange (Dowex 1x8) and extraction chromatography (UTEVA and TRU) to obtain a pure radioactive source of ²⁴¹Am. The procedure was developed using the tracer ²⁴³Am isotope and alpha spectrometry. The accuracy of the procedure was tested using the reference materials IAEA-300, IAEA-384 and IAEA-385.

The results showed that in bottom sediment samples taken in 2010, the activity concentrations of ²⁴¹Am in the Gdańsk Deep ranged from 0.009±0.003 (k=2) to 0.938±0.070 Bq∙kg^-1, and those in the Gotland Deep ranged from 0.024±0.004 to 2.57±0.19 Bq∙kg^-1. For bottom sediment samples collected in 2019, ²⁴¹Am activity concentrations in samples from the Bornholm Deep ranged from 0.030±0.012 to 0.85±0.06 Bq∙kg^-1, and those in the Gdańsk Deep ranged from 0.24±0.017 to 1.59±0.12 Bq∙kg^-1, while those in the Gotland Deep ranged from 0.017±0.002 to 2.25±0.16 Bq∙kg^-1.