Environmental radioactivity assessment of the Brunei Darussalam coastline of the South China Sea

Abstract

Radioactivity levels of naturally occurring radionuclides at the coast of Brunei Darussalam were evaluated along with their dose rates. Twenty-six berm and intertidal sediment samples were measured using gamma-ray spectrometry. The mean activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in berm sediments were 10.07 ± 1.02 Bq/kg, below the minimum detectable activity, and 21.44 ± 1.23 Bq/kg, respectively, whereas for intertidal sediments they were 7.01 ± 0.87, 1.67 ± 0.15 and 4.99 ± 0.42 Bq/kg, respectively. With respect to the radiological health risk, the average hazard indices, absorbed gamma dose rate, effective dose equivalent, and excess lifetime cancer risk were found to be less than the global average. Calculation of the activity ratio showed that ⁴⁰K is the main source of radiation in the coastal sediments. Furthermore, the difference in radioactivity levels between the berm sediments and intertidal sediments collected at the same location was investigated. Finally, a standard geological terminology of the littoral zone profile is proposed for describing coastal samples for universal communication among researchers.

Keywords: Activity ratio; Berm sediment; Brunei Darussalam; Intertidal sediment; Natural radionuclides; South China Sea.