Measurement of radioactivity concentration in soil samples around phosphate rock storage facility in Richards Bay, South Africa

Abstract Mining, mineral processing and industrial activities have long been linked to increased levels of radioanuclides in soil in their vicinity. In this work, concentrations of naturally occurring radionuclides in soil samples collected around a rock phosphate storage facility in Richards Bay in South Africa were determined. A total of 90 soil samples were collected and analyzed for 238 U and 232 Th using neutron activation analysis and 226 Ra and 4  K using a HPGe detector. The results revealed the average radioactivity concentrations of 238 U, 232 Th, 226 Ra and 4  K in soil samples collected around the rock phosphate storage area were 28.26 ± 11.40, 29.64 ± 11.50, 32.18 ± 11.50 and 146.77 ± 63.30 Bq. kg −1 , respectively, which are higher than the corresponding values of 22.26 ± 8.60, 23.09 ± 9.80, 26.52 ± 11.50 and 117.82 ± 10.04 Bq. kg −1 in soil samples from the control area about 2.0 km–4.5 km away from the rock phosphate storage facility. Furthermore, the all radiological hazard parameters (i.e annual effective dose equivalent, annual gonadal dose equivalent, the absorbed dose rate in air, the radium equivalent activity and the external Hazard Index) investigated in this study were below the maximum recommended safety limit. The observed 238 U, 232 Th, 226Ra and 4  K levels indicate contributions from anthropogenic activities with no significant health risks to humans or to the environment. Hence, in terms of terrestrial gamma radiation from soil, rock phosphate storage within this area does not pose any significant radiation hazard to the workers and dwellers.