Phytoremediation: an assessment of the potential of Casuarina equisetifolia in environmental rehabilitation in the mining industry of South Africa

James, Lucien
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For more than a century, mining has played an important role in the development of South Africa. At the same time, mining has also been instrumental in the degradation of the country’s environment. It has become a priority that the mining industry of South Africa adopts a more sustainable approach to mining by practicing environmental rehabilitation. However, as the rehabilitation of mining sites can be approached using several methods with some being more effective than others. Asa biological method, the use of plants for rehabilitation and phytoremediation has become an area of world-wide academic interest as an effective means to address environmental issues, even leading to the complete ecological restoration of degraded areas. It was the aim of this study to assess Casuarina equisetifolia as a potential phytoremediation or rehabilitation tool for the mining industry of South Africa. A three-step data collection process was followed to investigate how mining companies in South Africa address rehabilitation. This included (1) a desktop study of large mining companies’ ESG reports, (2) engagement with various professionals and (3) field visits to two mining sites. The specific methods used by the industry as well as their associated challenges and opportunities were assessed. Finally, through further engagement with professionals and a rapid appraisal of literature that considered past studies on Casuarina equisetifolia, the potential of the plant in the context of what was learned about rehabilitation in the mining industry was established. It was learned that mining companies practice revegetation as their overarching rehabilitation strategy. Mining companies use a mix of different physical, chemical, and biological methods to prepare a site before planting indigenous trees for revegetation. As a resilient plant species able to withstand the conditions of raw mining tailings, Casuarina equisetifolia has the potential to be used as a direct revegetation method requiring little to no preparation of land before planting. Secondly, the plant is capable of fixing atmospheric nitrogen, encouraging the growth of indigenous plant species, and the subsequent re-establishment of plant communities. The plant is a hyperaccumulator of eight heavy metal contaminants and can be used for phytoremediation at gold and platinum mining sites. Through this study, it has been established that Casuarina equisetifolia has the potential to be used by the mining industry to kickstart revegetation projects. Further experimentation is therefore encouraged to study the plant through long-term trials in practical situations
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science, 2021