Radionuclides in sediments of Beibu Gulf: activity levels, distribution patterns and implications

Marine sediments are the final destinations of radionuclides. We used a high purity germanium γ spectrometry to measure natural radionuclides and explore the spatial distribution characteristics of nuclides in the surface sediments of Beibu Gulf. The mean activities of ²³⁸U, ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ²¹⁰Pb are (29.5±14.6) Bq/kg, (22.0±12.2) Bq/kg, (37.0±20.2) Bq/kg, (302±195) Bq/kg, and (34.4±19.9) Bq/kg, respectively. In the horizontal direction, ²²⁸Ra, ⁴⁰K and total activity（A_T）show an increasing pattern from nearshore to far offshore. Fingerprints of ²³²Th/²³⁸U and ²²⁸Ra/²²⁶Ra activity ratios in sediments are 1.2 and 1.5, respectively. In addition, the ⁴⁰K low activity area in Beibu Gulf is highly consistent with the distribution of marine sands, suggesting that ⁴⁰K may be a potential indicator of marine sands. This study systematically quantifies sediment radioactivity levels in Beibu Gulf, which not only provides a background baseline for future assessment of the radiological environmental impacts of coastal nuclear power in Beibu Gulf, but also may provide some reference value for the future on-line travelling and efficient exploration of sea sand resources in Beibu Gulf.