Evaluation of trace metal concentration and health impacts in abandoned gold mine tailings in Johannesburg, South Africa and their environmental impacts

Abstract: Environmental pollution by major and trace metals is one of the critical concerns facing the world because of health-related issues. Hence, it is important to determine their concentration in various environmental matrices (such as soil, water, sediments, and plants) as they introduce metals into the food chain. It is therefore important to obtain information about the level of major and trace metals in soils, water, and vegetables around mine tailings as well as their available fractions to estimate their potential toxicity and mobility. Therefore, the aims of this study were: (1) to determine the physical and mineralogical properties of tailing soil samples; (2) To determine the concentration of major and trace metals in soil and plants collected from two gold mine tailings (Princess and Struisbult) located in the Johannesburg area (Gauteng, South Africa). (3) To assess the availability and mobility of trace metals modified ultrasound-assisted sequential Community Bureau of Reference (BCR) and single extraction procedures. (4) To validate the results obtained using pseudo total digestion, single and sequential extraction procedures using certified reference materials (CRMs). (5) To estimate environmental pollution of the study area various indices such as geo-accumulation index, ecological risks, pollution index, among others. (6) To assess the extent of trace metal accumulation in leafy vegetables growing in the study areas. Major and trace cations were determined using inductively coupled plasma optical emission spectrometry (ICP-OES) and mineralogical phases were determined using X-ray diffraction (XRD) spectroscopy. The subsequent paragraphs summarize the research findings. Physicochemical properties such as pH, soil organic matter (SOM), cation exchange capacity (CEC), and conductivity were assessed at both Struisbult and Princess gold mine tailings samples to understand the soil quality. The soil sample were found to be extremely (pH = 3.02-4.9) to moderately (pH = 5.0-6.6) acidic in nature. This suggested that the solubility of trace metals is high especially in strongly acidic soil samples. The analysis of variance at 95% confidence level for all the soil properties between Princess and Struisbult gold mine dump revealed that there is no significant difference since the p-value was more than 5%. The mineralogical composition of tailing samples was assessed in both study areas. Analysis of samples using XRD was done to determine the mineralogical compositions of the samples collected from the study area. XRD analysis was also conducted to determine whether there is a possibility that the geology of the study areas plays a role in the concentrations of trace metals. The results showed that the samples were composed of more than 70% quartz (SiO2) mineral was present in both mine tailings...Ph.D. (Chemistry