Alhar, Maysaa Abdulrudha Majeed (2021) Applying analytical chemistry techniques to the characterisation of mine spoils and assessing treatments for minimising their environmental impacts. Doctoral thesis, Keele University.

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Abstract

Mining activities can leave a legacy of contamination with the potential to threaten the wider environment and human health. This is particularly so with historic mines that pre-date modern restoration and environmental protection measures. This study aimed to characterise mine spoil materials from five historic abandoned mine sites around the UK and assess them for risks they might pose. The sites were Glendinning, Wanlockhead, and Greendykes Bing in Scotland, Nenthead in England and Parys Mountain in Wales. Characterisation of elemental contents was achieved using different analytical techniques, including non-destructive methods of SEM/EDX, XRD and XRF techniques, as well as destructive techniques of digestions in mineral acid followed by ICP-OES analysis. Mobility and internal distribution (partitioning) of these elements was determined via single (CaCl2 solution) and sequential (BCR) extraction methods. Human health risk aspects were assessed by exposing the finest size fraction of the spoils to simulated lung fluid (Gamble’s solution) to estimate how readily elements from dusts could be assimilated into the body. Finally, this present study assessed remediation potential of the spoil heaps by assessing whether incorporation of rice husk and wheat straw biochar could promote plant growth (ryegrass, Lolium perenne) and thus reduce risks of erosion, leaching and redistribution of spoil materials into the wider environment.
SEM results indicate Si, Fe and Al were dominant elements across all spoils and this was supported by XRD results indicating mineral forms. Glendinning, Wanlockhead, and Parys Mountain were each dominated by muscovite and quartz even though the main target for extraction (Sb, Pb/Zn and Cu, respectively) was quite different at the locations. In contrast to SEM/EDX, XRF and digestion followed by ICP OES/MS analysis quantified more elements. Nenthead, Glendinning and Wanlockhead showed particularly high concentrations of Ba, Cd, Mg, Mn, Ni, Pb, Zn, As and Sb. The ICP methods (OES and MS) were very efficient at detecting and quantifying elements in mine spoil digests. The ability to detect very low concentrations and a wide range of elements is one of important characterisation of these techniques for example ICP-MS can detect 10-50 ppt of Ag, Be, Cd and Au. However, the preparation for these methods, which includes multiple steps and using strong acidic solutions, is a factor to consider when selecting a method to use.
The CaCl2 extractions revealed that when pH is decreased to low level (≤2), elements in the spoils are readily mobilised. BCR results revealed that all elements had the highest concentrations in the residual phase, with the exception of the following: Al, Mg, Zn in the reducible fraction (BCR2) at Greendykes Bing; Mn, Ni on the exchangeable fraction (BCR1) in Nenthead and Parys Mountain; and finally, Sb on the exchangeable fraction in Glendinning, Wanlockhead and Greendykes Bing. Bioaccessible As was very low at 24 h of simulated exposure of Gamble’s solution, but rose greatly at 72 h in the case of Glendinning (>1800 mg/kg), Wanlockhead (>1300 mg/kg) and Greendykes (~600 mg/kg). Addition of biochar decreased element (As, Cd, Cr, Pb, Sb and Zn) mobility in porewater and assimilation into plants and increased plant growth, indicating potential for using biochar in spoil stabilisation and remediation.
The study provides a basis for selecting an analytical approach to characterising elemental and mineral structures of mine spoils (e.g. for purposes of environmental risk assessment or resource recovery potential). It shows that if subjected to acidic inputs the spoils examined can readily leach potentially toxic elements (PTEs) to the wider environment but that otherwise their potential to leach PTEs in neutral solutions is much more limited. The study found that dust release from 3 of the examined spoils could potentially disperse lung bioaccessible forms of PTEs and therefore, together with their capacity to leach PTEs, remediation via covering with vegetation growth would be advisable. The study demonstrated that vegetation growth can be enhanced on the spoils through incorporation of biochar and therefore this should be considered as a low-cost management option.

Item Type: Thesis (Doctoral)
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions: Faculty of Natural Sciences > School of Geography, Geology and the Environment
Contributors: Oliver, IW (Thesis advisor)
Depositing User: Lisa Bailey
Date Deposited: 18 Oct 2021 09:09
Last Modified: 18 Oct 2021 09:09
URI: https://eprints.keele.ac.uk/id/eprint/10146

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