Evaluation of Radiological Risk Hazards in Sediments and Selected Streams Around Kalulushi and Kitwe Towns

Author(s): P. Shaba, KK Maseka, P Hayumbu

Mining operations in the uraniferous Copperbelt Province of the Katanga Basin have raised significant environmental and health concerns, primarily due to the generation of waste during copper and cobalt extraction processes. Kitwe town heavily relies on the Kafue River for its domestic water supply. However, studies measuring the levels of natural radionuclides in several tributaries of the Kafue River, namely, the Fikondo Stream, Mindolo Stream, Kitwe Stream, and Mwambashi River, are lacking. This study utilized gamma-ray spectrometry to assess the presence of radionuclides, specifically radium-226, thorium-232, and potassium-40, in sediments and water near Kitwe and Kalulushi. The radionuclide concentrations varied, with sediments showing 51.8 to 104.6 Bq/kg and 43.1 to 72.2 Bq/kg and water showing 1.7 to 28.5 Bq/l and 0 to 1.3 Bq/l. These concentrations were compared to permissible limits set by the UNSCEAR and WHO. Sediment samples had higher radionuclide activity than water with 226Ra often exceeding the WHO limits, while 232Th and 40K were generally greater in all stream samples. To assess the radiological hazard, parameters, such as the radius equivalent, absorbed dose rate, absorbed equivalent dose, internal hazard index, external hazard index, and excess lifetime cancer risk, were calculated.