Radioactive soil contamination from the coastal towns of Walvis Bay and Swakopmund in the vicinity of uranium mine sites of Erongo region, Namibia

Abstract

Radioactive soil contamination is one of the major causes of external gamma rays exposure in many places including the coastal towns of Walvis Bay and Swakopmund in the Erongo region of Namibia. Gamma radiation emitted from natural occurring radioisotopes such as 238U, 232Th and 4°K series and their decay products are present in all ground formations and these represent the main external source of irradiation to the human body. The levels of radioactive soil contamination due to naturally occurring rad ioactive materials (NORM) were investigated, followed by assessment of the radiological hazard to both the public and the environment using a well calibrated HPGe gamma ray-spectrometry setup. The activity concentration in the two coastal towns was found to vary from 14.94±3.81 to 289± 76 Bq kg- 1for 238U, 17.68±4.62 to 131.58 ±19.26 Bq kg -1for 232Th and 162±54 to 581±194 Bq kg-1for 4°K. The mean values of radium equivalent index (Raeq ), radiation hazard index (H ex) and total annual external gamma radiation dose were found to be 205 Bq kg-1, 0.56 and 0.11 mSvy(1respectively. Since the estimated radiological impact assessment factors are lower than the world permissible United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR), there seems to be no potential radiological health hazard associated with the soils of Walvis Bay and Swakopmund towns. This shows that the risk due to radiation contamination in Erongo region is low.