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Diffusive Gradients in Thin-Films to Assess the Processes Influencing the Flux of Trace Metals From Mine Spoil to a River System

Carney, L (2022) Diffusive Gradients in Thin-Films to Assess the Processes Influencing the Flux of Trace Metals From Mine Spoil to a River System. Other thesis, Liverpool John Moores University.

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The mobility of trace metals within mine wastes can be affected by different geochemical and hydrological processes. Climate change is expected to alter the severity and frequency of extreme weather conditions, which in turn will affect the hydrological conditions at mine sites and within the river systems that flow through them. Wetting and drying cycles alter the exposure and submergence times of river sediment, causing shifts in the redox conditions and potential mobility of trace metals. This project utilized river water sampling, diffusive gradients in thin films (DGT), and a laboratory-based mesocosm experiment to quantify seasonal variability in metal concentrations as well as identify the geochemical processes that control metal speciation at Wemyss mine, in central Wales. Zinc and Pb were the main contaminants identified within both river and sediment pore water, constantly exceeding environment quality standards. Higher metal concentrations were observed during the summer, when dry conditions were more common, allowing for an increase in oxidation of sulphides and the deposition of fine sediment. Initial wetting following lengthy dry periods led to metal release, most likely from mineral salts that may have formed. High flows and increased submergence facilitates a shift towards anoxic conditions, whereby Fe/Mn oxides and, more commonly at this site, sulphates become reduced. Dilution, sulphide formation and the removal of fine sediment as a result of higher flow rates leads to a decrease in metal concentrations within river water. A conceptual model is proposed to outline the various hydrological and geochemical processes that influence sediment metal pore water concentrations and release. A better understanding of these processes and the conditions that influence them is essential for future management of abandoned mine wastes.

Item Type: Thesis (Other)
Uncontrolled Keywords: DGT; Trace metals; Sediment; Mining; Pollution
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions: Biological & Environmental Sciences (from Sep 19)
SWORD Depositor: A Symplectic
Date Deposited: 27 May 2022 07:59
Last Modified: 13 Sep 2022 12:55
DOI or ID number: 10.24377/LJMU.t.00016897
Supervisors: Byrne, P, Kiriakoulakis, K and Dick, J
URI: https://researchonline.ljmu.ac.uk/id/eprint/16897
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