Distribution of gamma-ray radionuclides in surface sediments of the Kongsfjorden, Arctic: Implications for sediment provenance

The Kongsfjorden is highly sensitive region to climate variability, however, the study of gamma-ray radionuclides in related areas is relatively scarce. In this study, the grain size, total organic carbon (TOC), ¹³C_org isotopes, and specific activities of seven gamma nuclides were analysed in surface sediments of the Kongsfjorden in the Arctic during the summer of 2017. The specific activities of ²¹⁰Pb_ex, ¹³⁷Cs, ²³⁸U, ²²⁶Ra, ²²⁸Ra, ²²⁸Th, and ⁴⁰K were 12–256 Bq/kg, 0–3.8 Bq/kg, 25–42 Bq/kg, 24–38 Bq/kg, 22–40 Bq/kg, 22–40 Bq/kg, and 354–738 Bq/kg, respectively, with average values of (121±94) Bq/kg, (2.0±1.2) Bq/kg, (34±6) Bq/kg, (32±4) Bq/kg, (32±6) Bq/kg, (33±6) Bq/kg, and (611±119) Bq/kg. This study observed a significant positive correlation (r=0.845, p<0.05) between TOC and ²¹⁰Pb_ex, highlighting the strong influence of organic matter on the distribution of ²¹⁰Pb_ex. The boundary scavenging of ²¹⁰Pb from the open sea contributed 27.5%–46.2% to the total ²¹⁰Pb_ex in the sediments of the outer Kongsfjorden. The grain size was an important factor affecting the activity distribution of several radionuclides (²³⁸U, ²²⁸Ra, ²²⁸Th, ²²⁶Ra, and ⁴⁰K). The specific activity of ¹³⁷Cs indicated the transport of terrestrial materials from the exposed area of the Kongsfjorden. The sediments in the Kongsfjorden were derived from various material contributions of glacial meltwater debris, glacial rivers, bare soil, atmospheric deposition, and marine sources. This study explains the source of the Kongsfjorden sediment and the distribution characteristics of radionuclides, and illustrateas the main factors affecting the distribution of radionuclides, which provides a reference for the behavior of polar radionuclides in future research.