Assessment of heavy metals and natural occurring radioactive materials from historical mine wastelands: A case study of Brakpan, South Africa

Mining has contributed to South Africa’s development, but its legacy has left more than 6 000 abandoned sites, with Brakpan among the most affected areas. This study assessed heavy metals and Naturally Occurring Radioactive Materials (NORMs) in the Brakpan mine wasteland in Gauteng province, South Africa. Soil and water samples from the area were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for heavy metals and High-Purity Germanium gamma spectrometry was used for NORMs analysis. The results showed elevated concentrations of several contaminants. In soils, chromium (103.98 mg/kg) and arsenic (47.75 mg/kg) were notably enriched, while uranium exhibited the highest mean concentration (7.14 mg/kg), exceeding the South African soil quality guidelines for contaminated land. Water samples showed high uranium (mean: 1.64 mg/L) and nickel (12.78 mg/L) concentrations, surpassing guideline values for agricultural and aquatic ecosystem protection value of 0.03 mg/L and 0.04 mg/L, respectively. Suggesting potential risks to downstream water users and ecological receptors. NORMs analysis revealed activity concentrations of ²³⁸ U ranging from 12.78 to 409.73 Bq/kg (mean: 160 Bq/kg), with mean activities of ²³² Th and ⁴⁰ K of 19.65 Bq/kg and 376 Bq/kg, respectively. Absorbed dose rate averaged 108.19 nGy/h exceeded UNSCEAR global background levels (59 nGy/h). Localised hotspots exhibited radium equivalent activity of up to 492.49 Bq/kg and an external hazard index of 1.33, indicating elevated radiological risk near residential settlements. Overall, the findings highlight combined geochemical and radiological hazards, underscoring the need for integrated remediation and management strategies to protect affected communities.