An In Toto Approach to Radon Dispersion Modelling from a South African Gold Mine Tailings

Abstract

The USA Environmental Protection Agency’s (EPA) Industrial Source Complex Short Term 3 (ISCST3) dispersion modelling code was used to evaluate radon transport and the effects of local variations around tailings dam using a Gaussian plume model. The tailings dam was modelled as point, flat ground and top level, total emitting surface area (true geometry) and volume source geometries. The true area geometry was considered as the baseline source geometry. To improve the accuracy of the model predictions as compared to traditional approaches, the true geometry area source term was corrected to account for cracks and fissures on the tailings and the geometry of tailings dam was modelled by considering all emitting surfaces as sources. Compared to the baseline, the model overpredicted the flat ground area source by up to 274% and underpredicted the top-level area source by up to 50%. The volume emission source was overpredicted by up to 300% in 60% of the modelling runs and underpredicted by 55% in 40% of the volume model runs. While the top-level area source term produced lower concentrations at near-field ground-level receptors, accounting for the wakes effect increased the radon concentrations from the top-level area source of the tailings dam by up to 239%. From the modelling results, the highest concentration predicted by the model from the true geometry source was found to be 0.843 Bq m−3, which corresponds to the dose of 0.012 mSv/y to the public due to radon from the tailings. This value is less than the 1 mSv/y dose constraint stipulated by the National Nuclear Regulator.

Radon exposure risks among residents proximal to gold mine tailings in Gauteng Province, South Africa: a cross-sectional preliminary study protocol

“…The majority of the exposed communities are of lower socioeconomic status, marginalized ethnic groups living in governmentfunded houses, and informal settlements (1,2,(8)(9)(10). Residents residing in proximity to Gold mine tailings experience elevated radiation exposure owing to the presence of significant quantities of uranium and its decay products, notably radon, within the tailings (15,16). This exposure frequently surpasses the annual safety threshold of 1 Millisievert (mSv) established by the World Health Organization (WHO) and the National Nuclear Regulator (NNR) (15,17,18).…”

“…Residents residing in proximity to Gold mine tailings experience elevated radiation exposure owing to the presence of significant quantities of uranium and its decay products, notably radon, within the tailings (15,16). This exposure frequently surpasses the annual safety threshold of 1 Millisievert (mSv) established by the World Health Organization (WHO) and the National Nuclear Regulator (NNR) (15,17,18). Radiometric surveys have played a crucial role in assessing environmental safety and preventing unknowingly exposure to excessive background radiation (15,16).…”

“…This exposure frequently surpasses the annual safety threshold of 1 Millisievert (mSv) established by the World Health Organization (WHO) and the National Nuclear Regulator (NNR) (15,17,18). Radiometric surveys have played a crucial role in assessing environmental safety and preventing unknowingly exposure to excessive background radiation (15,16). Natural radioactivity permeates rocks, water, soil, and living organisms, with decaying elements like uranium, influencing radiation levels.…”

“…Several large-scale epidemiological studies found a statistically significant linear relationship between lung cancer risk and cumulative radon exposure (24,27,28). According to WHO, radon is considered the second leading cause of lung cancer among smokers and the leading cause of lung cancer among non-smokers (11,15,19,(25)(26)(27). Furthermore, radon is responsible for 3-14% of lung cancer cases (28)(29)(30)(31)(32)(33)(34).…”

“…Unlike other countries (mostly developed), South Africa lacks government monitoring of indoor radon levels, leaving residents unaware of their exposure. Therefore, it is in the public's interest to establish the health implication of everyday indoor radon exposure, particularly among people residing proximal radioactive sites (i.e., gold mine tailings) (15,18,26,30,50).…”