Assessment of radioactivity levels in shore sediments along the coastline of the Orange River, Oranjemund, Namibia

Abstract

The objective of present study was to evaluate the activity concentrations of 238U, 232Th and 40K and radiological hazards due to gamma exposure of shore sediment along the coastline of the Orange River, Oranjemund, Namibia. A total of 20 shore sediment samples were collected along the coastline of the Orange River. Shore sediment samples were analyzed using a Canberra Gamma Spectrometric detector inter phased with a multichannel analyzer (MCA) that was well calibrated for energy and efficiency respectively. The mean activity concentrations of 238U, 232Th and 40K for the shore sediment samples were 63.46 ± 9.83 Bqkg−1, 54.88 ± 5.03 Bqkg−1 and 416.99 ± 57.85 Bqkg−1 respectively. The mean activity concentrations of 238U, 232Th and 40K in the shore sediment samples were slightly higher than world reference levels. Also, the radiological hazards parameters of absorbed dose rates, annual effective dose equivalent (outdoor) and the excess lifetime cancer risk for the Orange River shore sediment samples were calculated. The mean values calculated for absorbed dose rates (63.98 nGy/h), annual effective dose equivalent (outdoor) (0.78 mSv/y) and excess lifetime cancer risk (2.73) were higher than the recommended limits, therefore long term radiation exposure of the local population along the coastline of the Orange River may pose significant health threat from radiological point of view.