Authors: Taki, G; Grierson, PF; Saini, N; Brand, HEA; Murphy, DV; Santini, TC

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Taki, G, Grierson, PF, Saini, N, Brand, HEA, Murphy, DV & Santini, TC 2022, 'Assessing the performance of blended byproduct caps for revegetation and closure of tailings storage facilities', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 941-948,

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Establishment of a vegetative cover during closure of tailings storage facilities is a critical component of the development of an environmentally sustainable landscape after mining. However, establishing vegetation on fresh bauxite residue (alumina refining tailings) is constrained by the high alkalinity, salinity, sodicity, elevated concentration of trace elements, and low plant available nutrients in residues. Currently, design of store and release vegetative covers for closure of tailings storage facilities in southwest Australia requires excavation of local soils and importing nutrients and mulch to apply on top of the tailings storage facility. Where the residues are mostly benign, in situ remediation (application of amendments directly into tailings to remediate the chemical and physical conditions) techniques may be a viable approach to create a plant growth medium for closure and revegetation. Nevertheless, using imported soils and blending products is expensive. Neutralisation of bauxite residue disposal areas (BRDAs) for capping offers a potential alternative and substantial cost savings, especially when coupled with incorporation of materials to develop an improved substrate for plant growth. In this study, a new technique called ‘blended byproduct capping’ was developed for closure of the South32 Worsley Alumina BRDA in southwest Australia. The blended byproduct cap uses bauxite processing residues that are blended with available byproducts readily and cheaply available onsite at the refinery. Three types of bauxite processing residue (bauxite residue fines, bauxite residue fines plus 10% bauxite residue sand, and bauxite residue sand) were blended with three byproducts (fly ash from power generation, eucalypt mulch from site clearing, and gypsum from other operations nearby) either alone or in combination to create 15 potential capping materials. These capping materials were leached under glasshouse conditions for 18 weeks (three wetting and drying cycles, three weeks each) to assess changes in pH, EC, total elements and nutrients. The three best performing capping materials in terms of chemo-physical properties were then selected for germination and growth experiments. Germination rates of barley (Hordeum vulgare), ryegrass (Lolium multiflorum) and clover (Trifolium spumosum) were assessed and then surviving plants grown for four weeks after the first visible leaf was observed. Root and shoot biomass were harvested at the end of the experiment. More than 90% of barley and ryegrass seeds germinated. Clover germination was less than 60% both blended byproduct caps and potting mix. However, biomass and growth rates were significantly lower in blended byproduct caps compared to potting mix for all three species. Overall, we conclude that blended byproducts caps show significant promise as a cost-effective alternative for BRDA closure and revegetation but require further optimisation.

Keywords: bauxite residue deposit area, red mud, bauxite residue sand, germination success, plant growth, annual grass, clover

Anderson, JD, Bell, RW & Phillips, IR 2011, ‘Bauxite residue fines as an amendment to residue sands to enhance plant growth potential—a glasshouse study’, Journal of Soils and Sediments, vol. 11, pp. 889–902.
Bray, AW, Stewart, DI, Courtney, R, Rout, SP, Humphreys, PN, Mayes, WM & Burke, IT 2018, ‘Sustained bauxite residue rehabilitation with gypsum and organic matter 16 years after initial treatment’, Environmental Science & Technology, vol. 52, no. 1,
pp. 152–161.
Chalker-Scott, L 2007, ‘Impact of mulches on landscape plants and the environment — a review’, Journal of Environmental Horticulture, vol. 25, no. 4, pp. 239–249.
Courtney, R, Timpson, JP & Grennan, E 2003, ‘Growth of Trifolium pratense in red mud amended with process sand, gypsum and thermally dried sewage sludge’, International Journal of Mining, Reclamation and Environment, vol. 17, no. 4, pp. 227–233.
Courtney, R & Mullen, G 2009, ‘Use of Germination and Seedling Performance Bioassays for Assessing Revegetation Strategies on Bauxite Residue’, Water, Air, & Soil Pollution, vol. 197, pp. 15–22.
Courtney, R & Kirwan, L 2012, ‘Gypsum amendment of alkaline bauxite residue – plant available aluminium and implications for grassland restoration’, Ecological Engineering, vol. 42, pp. 279–282.
Di Carlo, E, Boullemant, A & Courtney, R 2019, ‘A field assessment of bauxite residue rehabilitation strategies’, Science of The Total Environment, vol. 663, pp. 915–926.
Di Carlo, E, Boullemant, A & Courtney, R 2020, ‘Ecotoxicological risk assessment of revegetated bauxite residue: Implications for future rehabilitation programmes’, Science of The Total Environment, vol. 698.
Fourrier, C, Luglia, M, Keller, C, Hennebert, P, Foulon, J, Ambrosi, JP, … Criquet, S 2021, ‘How Raw and Gypsum Modified Bauxite Residues Affect Seed Germination, Enzyme Activities, and Root Development of Sinapis alba’, Water, Air, & Soil Pollution, vol. 232, p. 309.
Hazelton, P & Murphy, B 2007, Interpreting Soil Test Results: What do all the Numbers mean?, CSIRO Publishing, Melbourne.
Hudson, AR, Ayre, DJ & Ooi, MK 2015, ‘Physical dormancy in a changing climate’, Seed Science Research, vol. 25, no. 2, pp. 66–81.
Ippolito, JA, Redente, EF & Barbarick, KA 2005, ‘Amendment effects on pH and salt content of bauxite residue’, Soil Science, vol. 170, no. 10, pp. 832–841.
Jones, BEH, Haynes, RJ & Phillips, IR 2015, ‘Addition of an organic amendment and/or residue mud to bauxite residue sand in order to improve its properties as a growth medium’, Journal of Environmental Management, vol. 95, no. 1, pp. 29–38.
Kossoff, D, Dubbin, WE, Alfredsson, M, Edwards, SJ, Macklin, MG & Hudson-Edwards, KA 2014, ‘Mine tailings dams: characteristics, failure, environmental impacts, and remediation’, Applied Geochemistry, vol. 51, pp. 229–245.
Khaitan, S, Dzombak, DA & Lowry, GV 2008, ‘Neutralization of bauxite residue with acidic fly ash’, Environmental Engineering Science, vol. 26, no. 2, pp. 431–440.
Li, GK, Fischer, WW, Lamb, MP, West, AJ, Zhang, T, Galy, V,... Ji, J 2021, ‘Coal fly ash is a major carbon flux in the chang jiang (yangtze river) basin’, Proceedings of the National Academy of Sciences, vol. 118, no. 21.
Mupangwa, W, Twomlow, S & Walker, S 2013, ‘Cumulative effects of reduced tillage and mulching on soil properties under semi-arid conditions’, Journal of Arid Environment, vol. 91, pp. 45–52.
Pathan, SM, Aylmore, LAG & Colmer, TD 2003, ‘Properties of several fly ash materials in relation to use as soil amendments’, Journal of Environmental Quality, vol. 32 no. 2, pp. 687–693.
Power, G, Gräfe, M & Klauber, C 2011, ‘Bauxite residue issues: I. Current management, disposal, and storage practices’, Hydrometallurgy, vol. 108, no. 1–2, pp. 33−45.
Santini, TC & Fey, MV 2015, ‘Fly ash as a permeable cap for tailings management: Pedogenesis in bauxite residue tailings’, Journal of Soils and Sediments, vol. 15, no. 3, pp. 552–564.
Santini, TC & Banning, NC 2016, ‘Alkaline tailings as novel soil forming substrates: reframing perspectives on mining and refining wastes’, Hydrometallurgy, vol. 164, pp. 38−47.
Santini, TC, Wang, JC, Warren, KL, Pickering, G & Raudsepp, MJ 2021, ‘Simple organic carbon sources and high diversity inocula enhance microbial bioneutralization of alkaline bauxite residues’, Environmental Science & Technology, vol. 55, no. 6, pp. 3929–3939.
Wehr, JB, Fulton, I & Menzies, NW 2006, ‘Revegetation strategies for bauxite refinery residue: A case study of Alcan Gove in northern territory, Australia’, Journal of Environmental Management, vol. 37, no. 3, pp. 297–306.
Zhang, H, Li, X, Nan, X, Sun, G, Sun, M, Cai, D & Gu, S 2017, ‘Alkalinity and salinity tolerance during seed germination and early seedling stages of three alfalfa (Medicago sativa L.) cultivars’, Legume Research, vol. 40, no. 5, pp. 853–858.

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