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Abstract Carbon-14 ( 14 C) is an important contributor to the collective effective dose to the public due to releases from nuclear power plants (NPPs). In Sweden, only airborne emissions of 14 C from NPPs are currently routinely monitored, and the existing data on waterborne 14 C discharges are limited. A recent study of 14 C in brown algae ( Fucus spp.) in Swedish coastal waters showed higher F 14 C values collected at Ringhals NPP, on the Swedish west coast, than expected. Therefore, this study aimed at assessing if blue mussels ( Mytilus edulis ) could be used to retrospectively estimate the 14 C concentration of dissolved inorganic carbon (DIC) in seawater at three sites. A method was developed to extract the fibrous layer that forms visible annual structures in the shells. All samples were analyzed with accelerator mass spectrometry and the results compared with 14 C data from Fucus spp. For one of the analyzed shells (structures from 1974–1978), from the site Särdal, F 14 C in Fucus spp. and M. edulis agreed very well. For another shell (1972–1978), shell structures from some of the earlier years displayed up to 6% lower F 14 C than Fucus spp. F 14 C in one shell from a remote site, Båteviken, only had small annual variations (2017–2022: F 14 C = 1.070 ± 0.015 (1 σ)). Two shells from Ringhals NPP had higher average F 14 C, and a significant temporal variability (2014–2022: F 14 C = 1.427 ± 0.268 (1 σ)). Difficulties in unambiguous identification of the annual structures in the shells, as well as the future potential of this method, are discussed.
Bjarheim et al. (Thu,) studied this question.