Baseline status of microbial activity on gold tailings facilities in South Africa

Abstract

In many ways, South Africa’s landscape has been dominated by mining, given that, for so many years this sector has been the mainstay of the South African economy. As such the environmental impacts of these mining activities are one of the greatest globally. These environmental impacts need to be addressed during each phase of environmental planning, especially during mine closure. By investigating the microbial enzymatic activity of tailings associated with different gold mine waste disposal environments in order to distinguish the effects of gold mining on associated ecosystems. This research will exemplify the importance of microbiological enzymatic characteristics as part of rehabilitation assessment criteria. Soil enzymatic and physicochemical analysis were analysed by standard methods and the result emphasised that the tailings materials possess poor microbial enzymatic activities. The baseline soil microbial activity levels of the tailings are dependent on the specific chemical, physical and biological parameters of the tailings materials. The microbial activity of the different gold tailings storage facilities varied greatly. Generally, the microbial enzymatic activity was greater on the surface/rhizosphere zone in the partially revegetated tailings sites. In contrast, the barren tailings had the lowest microbial enzymatic activity, which also had the lowest acidic pH. The low dehydrogenase, β-glucosidase, urease, acid and alkaline phosphatase enzymatic activities observed at these mining sites signifies that tailings materials possess poor microbiological enzymatic characteristics. Consequently, it can be assumed that the soil quality and fertility of these sites are lower because of decreased microbial activity due to the deficit of biodegradable organic matter and limited nutrient cycling. The mine waste disposal environment is devoid of true soil character deprived of macro and micro-nutrients, acidic pH with elevated concentrations of trace metals. Thus, indicating a high degree of soil degradation and poor soil health that affects not only the chemical and physical characteristic of the tailings material but also the microbiological properties. As such, it is clear that the contribution that microbes make to the ecosystems functioning in extreme environments, such as mine waste disposal environments is vastly underrated. Subsequently, microbial processes need to be included into mine rehabilitation practices, hypotheses, models, and interpretation of rehabilitation findings. To conclude, the study provided a microbial baseline status of different gold tailings storage facilities that will provide a platform for future investigations.