Distribution of natural and anthropogenic radionuclides in sediments from the Vefsnfjord, Norway

Areas in central Norway were heavily contaminated with fallout from the Chernobyl accident in 1986. In this study, we assess 137Cs in surface sediments and sediment cores collected in the Vefsnfjord in Nordland county. Concentrations of 137Cs in surface sediments ranged from 159 to 191 Bq kg−1 dry weight (d.w.). Sub-surface peaks of 137Cs were observed in all cores, with a maximum concentration of 432 Bq kg−1 d.w. Given that little is known about the distribution of naturally occurring radionuclides in Norwegian fjords and coastal areas, a better understanding of the total burden of radioactivity is important for the Norwegian fishing and aquaculture industries. Therefore, analyses of the natural radionuclides 40K, 226Ra, 228Ra and 210Pb were included in the study. Analyses of total sulphur (TS), total carbon (TC), total organic carbon (TOC) and grain size distribution have been performed to provide a sedimentologic context for interpreting the radionuclide results. •Vefsnfjord is heavily affected by 137Cs contamination from the Chernobyl accident.•Vefsnfjord is suitable for terrestrial-marine transfer studies of 137Cs.•Potential health risks caused by 137Cs contamination in Vefsnfjord are very low.•Levels of natural radionuclides are comparable to other Norwegian sea areas.•The natural radionuclide 40K exhibits the highest activity concentrations.