Hazards index analysis of gamma emitting radionuclides in selected areas around the uranium mine sites at Erongo Region, Namibia

Abstract

This study measures the 226Ra, 232Th and 40K activity concentrations using gamma spectrometry to asses first order exposure risks for the persons residing in Walvis Bay and Swakopmund towns in Erongo Region, Namibia. The concentrations of 226Ra, 232Th and 40K in the soil samples vary from 14.94 Bq kg-1 to 48.24 Bq kg-1, 17.68 Bq kg-1 to 52.51 Bq kg-1 and 162.58 Bq kg-1 to 259.35 Bq kg-1, respectively, with average values of 30.38 ± 11.28 Bq kg-1, 32.58 ± 10.09 Bq kg-1 and 203.62 ± 27.00 Bq kg-1 in Walvis Bay town. For Swakopmund town, the concentrations vary from 71.38 Bq kg-1 to 155.80 Bq kg-1, 41.63 Bq kg-1 to 131.58 Bq kg-1 and 360.82 Bq kg-1 to 761.76 Bq kg-1, respectively, with average values of 99.59 ± 24.39 Bq kg-1 90.90 ± 31.99 Bq kg-1 and 553.07 ± 107.17 Bq kg-1. The radium equivalent activity (Raeq) calculated for the same composite soil samples varies from 62.14 Bq kg-1 to 126.69 Bq kg-1 with an average value of 92.64 Bq kg-1 in Walvis Bay town. In Swakopmund town, it varies from 172.32 Bq kg-1 to 332.66 Bq kg-1 with an average value of 273.43 Bq kg-1. The average values of absorbed dose and annual effective dose (outdoors) are found to be 42.20 nGy h-1 and 123.98 nGy h-1, 0.05 mSv y-1 and 0.15 mSv y-1 in Walvis Bay and Swakopmund towns, respectively. The average excess lifetime risks of cancer (ELRC) in Walvis Bay and Swakopmund towns were 1.81 × 10-4 and 5.33 x 10-4, respectively. This implies that 1 person out of 5555 persons in Walvis Bay town and 1 person out of 1876 persons in Swakopmund town may be affected of cancer related diseases.