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

Abstract 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, there has been a lack of 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. 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 in the Copperbelt Province. The results indicated varying concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in sediments and water, ranging from 51.8 to 104.6 Bq/kg and 1.7 to 28.5 Bq/l, respectively, in sediments, and 43.1 to 72.2 Bq/kg and 0 to 1.3 Bq/l, respectively, in water. These concentrations were compared to permissible limits set by the UNSCEAR and WHO. The study revealed that all three primordial radionuclides exhibited greater activity in sediment samples than in water samples, except for specific instances. The activity of ²²⁶Ra exceeded the WHO limits in most cases, while ²³²Th and ⁴⁰K were generally greater in all stream samples. To assess the radiological hazard posed by natural radioactivity, various 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 for the study sites and materials.