Assessment of potential land contamination around abandoned legacy mines in a selected region of South Africa

Abstract

Land contamination is recognised as an infrastructural challenge with unpredictable intensity and implications caused by historical industrial and waste disposal practices. South Africa accounts for approximately 6 000 legacy mines that generate mineral waste in the form of mine tailings, waste rock dumps and low-grade mineral discards that leach potentially toxic elements (PTEs) into the environment. This leads to unknown contamination of the land around these previous mining sites which strains the availability of land for alternative use. This study assessed potential land contamination around selected abandoned legacy mines located across three different provinces (Limpopo, Gauteng and Mpumalanga) to determine the state of the land. The study applied the mean hazard index assessment method to calculate land contamination indices using norms and standards contained in the National Framework for the Management of Contaminated Land. Remote sensing was used for land-use land-cover (LULC) classification to detect land-use change and determine factors which pose an environmental risk. The drivers, pressures, state, impacts and responses model was applied to identify sources (drivers), pathways and receptors within the study area by integrating different datasets. The study discovered that 11.03% of the land had low contamination and 54.60% had moderate contamination, with an index score of less than one which means that the land is suitable for a range of land uses. High contamination accounted for 25.84% and extreme contamination for 8.54% of the land, with an index score greater than one, indicating that the land was contaminated with one or more PTE concentrations above the permissible limit. Remote sensing satellite imagery LULC classification discovered that built-up, forested land, mines and quarries are driving land-use changes which expose risks of land contamination to humans and the environment. Surface water and groundwater were determined to be at risk of potential contamination in contaminated areas. Various receptors (e.g., humans, fauna, flora, wetlands, rivers, lakes, dams and cultivated land) were found to be vulnerable to land contamination.