Evaluation of Indoor Radon Activity Concentrations and Controls in Dwellings Surrounding the Gold Mine Tailings in Gauteng Province of South Africa.

Radon in dwellings is recognized as the primary source of natural radiation exposure to members of the public. In the West Rand District and Soweto in the Gauteng Province (South Africa), indoor radon (222Rn) mapping was carried out to assess the exposure levels of radon in dwellings around gold and uranium mining tailings dams. This study was conducted predominately during warm and cold seasons, using the solid-state nuclear track detectors. In summer months, the indoor radon levels measured in all areas ranged from below the lower limit of detection to 71 Bq/m3, with a mean value of 29 Bq/m3, whereas in winter, the levels ranged between 11 and 124 Bq/m3, with a mean value of 46 Bq/m3. Higher indoor radon levels are found in colder months (winter season) than warmer months (summer season). However, no dwellings with indoor radon levels that exceed the WHO (2009) recommended reference level of 100 Bq/m3 were found, except for one that was constructed directly on soil mixed with tailings material. It is recommended that residents should keep their indoor radon levels low through continuous ventilation so as to minimize the buildup of radon and the likelihood of increased health hazards associated with radon exposure.

Surface water and groundwater interaction in the Vredefort Dome, South Africa: a stable isotope and multivariate statistical approach.

The growing importance of groundwater as a freshwater supply in semi-arid areas such as the Vredefort Dome World Heritage Site (VDWHS) demands the judicious management and development of this vital resource. The increased demand for groundwater due to the contamination of surface water, coupled with the lack of information on hydrological interaction and associated water quality implications, present difficulties in establishing management strategies. An integrated study based on hydrochemistry and multivariate statistical techniques supplemented by environmental isotopes delineated discrete areas of surface water and groundwater interaction in a fractured-rock terrain. Surface water loss was observed in sections that exhibited declining groundwater levels, whereas limited baseflow was restricted to zones with stable groundwater levels. The multivariate statistical analysis revealed the combined effect of natural hydrochemical processes and anthropogenic sources as controlling factors of water composition, and highlighted zones of aquifer-river water mixing, where certain areas were found to be additionally polluted by human-derived contaminants. The stable isotope (18O and 2H) ratios confirm mixing between depleted groundwater and enriched river water, producing a composition that reflected an integration of the isotopic variations. The continuous wastewater discharge into the Vaal River combined with the increased groundwater exploitation may be prompting induced recharge conditions. The results suggest compartmentalization of the groundwater systems, where certain areas within 1 km of the channel were not influenced by river-induced contamination. This indicates that hydrological connectivity is governed by site-specific hydraulic properties. This study shows the usefulness of a multi-method approach by combining environmental isotopes, hydrochemistry, and multivariate statistics to characterize hydrological linkage in semi-arid regions.

Natural radioactivity and metal concentration in the Thyspunt area, Eastern Cape Province, South Africa.

Naturally occurring radionuclides and metals have adverse human health impacts when they occur at higher activity and concentration above the threshold value, respectively, in the water supply system. This study aimed to establish the baseline radionuclide and metal content in rocks, soils, and water in the Thyspunt area of the Eastern Cape Province, South Africa, which is selected as a potential site for the development of a nuclear power plant. Extensive sampling of rocks, soils, groundwater, and surface water was conducted in the area. The employed methods of sample analyses include ICP-MS, gamma-ray spectrometery (RS 230), and accelerator mass spectrometry. The results indicate that the Ceres Subgroup shale and the Skurwerburg formation quartzite of the Table Mountain Group (TMG) contain the highest activity of most radionuclides, including 238U, 235U, 234U, 226Ra, 232Th, and 210Pb; these are linked to the natural geochemistry of the rocks that have been facilitated by the low-grade metamorphism to which the local geology was subjected. The metamorphism-related radionuclide enrichment is also apparent in the soils and groundwater associated with these rocks. The activity of the radiotoxic and carcinogenic uranium (238U and 235U) and radium (226Ra and 224Ra) isotopes in water was found to be well above the WHO guideline of 0.03 and 1 Bq/L, respectively. The exposure dose rate was the highest in the Ceres Subgroup shales (185.7 nS/h), and this is linked to the elevated natural radioactivity in the rocks. The estimate of the ingestion-related effective dose indicates high doses associated with the uranium and radium isotopes, thus signifying the potential adverse impact on human health associated with the ingestion of the widely used groundwater in the area.

Physicochemical and metal composition of rainfall in the Johannesburg region, South Africa.

The change in the water quality of rainfall impacts water supply through the contamination of surface water and groundwater. The presence of potential sources for metals in the form of aerosol through atmospheric transportation from gold tailings dams, coal mines, and coal-fired power stations increases the risk of water quality deterioration in the Johannesburg region. Rainfall monitoring was conducted for one hydrological year. Rainfall amount was measured, and samples were collected for stable isotope and metal analysis. Some metals show very high concentration in the rainfall with a decreasing order from zinc, cadmium, copper to lead. Their presence in the water is not desirable, as a result of favourable pH and Eh conditions in the rainfall with contaminant inputs from the gold tailing dams, coal mines, and coal-fired power stations. Therefore, the Johannesburg rainfall can be considered as potentially toxic due to the constant input of meals into water supply dams and aquifers recharged by the rainfall.