Authors: van Wyk, SJ; Haagner, ASH

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van Wyk, SJ & Haagner, ASH 2023, 'Soil Microbial Enzymatic Activity in 20-year-old rehabilitated platinum tailings substrates in South Africa', in B Abbasi, J Parshley, A Fourie & M Tibbett (eds), Mine Closure 2023: Proceedings of the 16th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth,

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Soil microbial health has become a key rehabilitation requirement to achieve more sustainable ecosystems on reconstructed mined landscapes. The status of soil microbial activity in rehabilitated tailings substrates are not well understood since the rehabilitation performance appraisal methodologies mainly focus on soil nutrition and revegetation success. Furthermore, rehabilitation amelioration specifications mainly consider soil physical and chemical improvements and the achievement of floristic biodiversity, rather incorporating microbial success criteria and therefore a complete lack of information exist about the progression of microbial activity and its role in pedogenesis in restored tailings materials. Rehabilitation programs usually aims at indirect improvement of soil organic status through soil nutrient amendment and rapid root mass development without sustainable soil rhizome reconstruction, final closure attempts will be compromised. This study presents Soil Microbial Enzymatic Activity (SMEA) progress on a rehabilitation trial conducted on platinum tailings 20 years ago (January 2003)- which has not received any maintenance since - and the microbial status were evaluated in 2009, 20013 and 2023 since. The 8 treatments included amelioration with different organic amendments, organic covers, as well as rock armouring and organic fertilizers, which is aligned with general tailings rehabilitation methodologies. An untreated control sample and the reference activity for natural surrounding area was also considered. Composite samples of the 9 treatments of the platinum tailings were analysed by means of the Soil Dehydrogenase Activity methodology. Microbial enzymatic status is analysed for by determining the concentration of Iodonitrotetrazolium Violet-formazan (INF), which is a reaction product of soil enzyme activity. It was clear that after 20 years, the soil microbial status is still in a distressed state. Although soil enzyme activity on average increased from 0 INF µg g-1 h-1 to 15INF µg g-1 h-1 on average per treatment, it still lacks significantly behind the activity within natural reference area of >45 INF µg g-1 h-1. It was evident that the originally treated sewage and grass mulch covered treatments presented the most improved microbial status over time. Values of 28 INF µg/g/h were achieved which may be explained by higher original root mass and biomass development in the first years after the inception of the project. Considering the average 5-year enzymatic activity improvement trajectory, another 20 years would be required for the system to achieve naturally comparable microbial activity rates. The lack of a restored system to produce required levels of soil organic matter is an inhibiting factor for soil ecosystem development which not only delay sustainability of rhizosphere but starve the above-ground vegetation layer. Therefore, initial enablement of root biomass through increased rates of organic matter, and annual additions through dedicated maintenance may be achieve sustainable ecosystems on platinum tailings materials.

Keywords: platinum tailings, microbial activity, dehydrogenase analysis, soil health, tailings rehabilitation.

Bruneel, O, Mghazli, N, Sbabou, L, Hery, M, Casiot, C, & Filali-Maltouf, A 2019, Role of microorganisms in rehabilitation of mining sites, focus on Sub Saharan African countries. Journal of Geochemical Exploration. Vol 205, pp. 1016-1024.
Campbell, G 2006, High resolution aeromagnetic mapping of “loss-of-ground” features at platinum and coal mines in South Africa. South African Journal of Geology, Vol 109, no. 4, pp 439-458p
Glaister, BJ & Mudd, GM 2010, The environmental costs of platinum PGM mining and sustainability: is the glass half-full or half-empty?, Minerals Engineering, Vol 23, no. 5, pp.438-450.
Huang, L, Baumgartl, T & Mulligan, D 2012, Is rhizosphere remediation sufficient for sustainable revegetation of mine tailings?, Annals of botany Vol 110, pp. 223-238.
Mbendi, M 2004, South Africa Mining: Platinum Group Element Mining – Overview, Viewed 25 January 2004, .
PricewaterhouseCoopers, November 2010. SA Mine: Review of Trends in the South African Mining Industry, p. 11.
Maboeta, MS, van Rensburg, L, & Jansen van Rensburg, P 2007, Earthworm (Eisenia fetida) bioassay to assess the possible effects of platinum tailings disposal facilities on the environment along a gradient, Applied ecology and environmental research, Vol 6, no. 2, pp. 13-19.
Rauwane ME 2008, Microbial diversity and metal pollution from a platinum mine tailings dam in the North-West Province (RSA). Dissertation Master of Science, School of Environmental Science and Development: Microbiology Faculty of Natural Science North-West University (Potchefstroom Campus).
van der Walt, L, Cilliers, SS, Kellner, K, Tongway, D, & van Rensburg, L 2012, Landscape functionality of plant communities in the Impala Platinum mining area, Rustenburg, Journal of Environmental Management, Vol 113, pp. 116-131.
van der Merwe, AJ & Vosloo, JI 1992, Soil pollution - Action required. – In “Proceedings of the Natural Veld Trust Jubilee Congress”, Pretoria.
Van Deventer, PW & Hatting JM. 2001. Characterising soil physical properties of platinum tailings for dust risk. Scientific report for Anglo American Platinum by Envirogreen. 28p.
van Deventer, PW, Hatting JM & Van Wyk, S.J. 2003. Rehabilitation of platinum tailings material. Scientific report prepared for Anglo American Platinum by Envirogreen. 54p.
van Wyk, S.J. 2009. Grassing techniques for surface stabilisation of platinum tailings storage facilities in South Africa, In Proceedings of the Mine Closure Conference, Australian Centre for Geomechanics, Perth, Western Australia.
van Rensburg, L & Morgenthal, T 2004, The effect of woodchip waste on vegetation establishment during platinum tailings rehabilitation, South African Journal of Science, Vol 100, pp. 294-300.
von Mersi W & Schinner, F 1991, An improved and accurate method for determining the dehydrogenase activity of soils with iodonitrotetrazolium chloride, Biology and Fertility of Soils, Vol 11, pp. 216–220.
Winde, F. and Sandham, L 2004, Uranium pollution of South African streams – An overview of the situation in gold mining areas of the Witwatersrand. GeoJournal, Vol 61, pp 131-149.
Xie, L & van Zyl, D 2020. Distinguishing reclamation, revegetation and phytoremediation, and the importance of geochemical processes in the reclamation of sulfidic mine tailings: A review. Chemosphere. pp. 252-265.

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