CONCENTRATION OF NATURAL RADIOACTIVITIES 226Ra, 232Th AND 40K IN RIVER SEDIMENTS AT PERAI INDUSTRIAL AREA, MALAYSIA AND THE ASSOCIATED RADIOLOGICAL RISK

Abstract

Sediment samples were collected from two rivers at the Perai Industrial area, which is one of the dense populated major industrial parks in Malaysia. The activity concentrations of the NORM members i.e. ²²⁶Ra, ²³²Th and ⁴⁰K were measured using HPGe gamma spectrometer after achieving 30 days secular equilibrium with their progenies. The radioactivity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 43.4 to 268.0 Bq kg^-1, from 69.4 to 312.0 Bq kg^-1 and from 181.8 to 777.2 Bq kg^-1, with an average value of 114.6±11.4 Bq kg^-1, 155.0±12.5 Bq kg^-1, and 504.6±59.7 Bq kg^-1, dry weight, respectively. Several radiation hazard indices were calculated to evaluate the radiological risk for the public. The average values of radium equivalent activity (Ra_eq) were 375.1 Bq kg^-1. Meanwhile, the average values for External (H_ex) and Internal (H_in) radiation hazard index were 1.0 and 1.3, respectively. Both Ra_eq and H_in were higher than the safety recommended value of 370 Bq kg^-1 and unity, respectively. Moreover, the average values of gamma absorbed dose rate (D) in the air were 167.6 nGy h^-1, which was also higher than the world average values reported by UNSCEAR but the average estimated annual effective dose (AED) values were only 205.6 μSv y^-1, that was below the annual public dose of 1,000 μSv y^-1 as recommended by ICRP for public radiological safety.