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

Highlights: • 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. 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.