Sources and controls of greenhouse gases and heavy metals in mine water: A continuing climate legacy

Brown, A. M., Bass, A. M. , Garnett, M. H. , Skiba, U., Macdonald, J. M. and Pickard, A. E. (2024) Sources and controls of greenhouse gases and heavy metals in mine water: A continuing climate legacy. Science of the Total Environment, 906, 167371. (doi: 10.1016/j.scitotenv.2023.167371) (PMID:37758145)

Abstract

Water pollution arising from abandoned coal mines, is second only to sewage as a source of freshwater pollution and in coalfield catchments mine water can be the dominant pollutant, with oxidised iron smothering the bed of receiving rivers. This study measured greenhouse gases in mine water outflows from sixteen sites across the Midland Valley in Scotland. Radiogenic and stable carbon isotopes measurements (Δ 14C and δ13C) were used to determine the sources of both methane (CH4) and carbon dioxide (CO2) produced within the flooded mine environment. Concentrations of CH4-C ranged from 20 to 215 μg l−1 and CO2-C from 30 to 120 mg l−1, with CO2 accounting for 97 % of the mine water global warming potential. Methane origins included 51 % modern biogenic, 41 % thermogenic and 8 % from hydrogenotrophic methanogenesis of coal. The most significant inverse impact on biogenic CH4 concentrations was sulphate, most likely due to sulphate reducing bacteria outcompeting methanogens. Carbon dioxide origins included 64 % from the dissolution of limestone, 21 % from terrestrial organic carbon and 15 % from coal. The limestone derived CO2 was positively correlated with high sulphate concentrations, which resulted in sulphuric acid and caused the dissolution of carbonate from limestone. The mine waters experienced significant carbonate buffering becoming only slightly acidic (pH 6–7), but with significant loss of inorganic carbon. The mine waters had low dissolved oxygen (6–25 %) and high dissolved iron (2 to 65 mg l−1) and manganese (0.5 to 5 mg l−1) concentrations. Dissolved greenhouse gases from abandoned mines were estimated as 0.27 +0.31 -0.18% of Scotland's global warming potential. This novel work has contributed information about the sources and controls of greenhouse gas fluxes in mine waters and identified the need to quantify and report this emissions term.

• Item Type: Articles
• Additional Information: This work was financially supported by Natural Environment Research Council (NERC) studentship through the IAPETUS 2 Doctoral Training Partnership Grant No. NE/S007431/1. The radiogenic and stable carbon isotope analysis was financially supported by a National Environmental Isotope Facility (Part of the Natural Environmental Research Council), Grant Number 2513.0422 and samples were measured by the NEIF Radiocarbon Laboratory in East Kilbride.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Brown, Alison and MacDonald, Dr John and Garnett, Dr Mark and Bass, Dr Adrian

Creator Roles

Brown, A. M.: Conceptualization, Funding acquisition, Methodology, Investigation, Data curation, Formal analysis, Writing – original draft, Visualization, Project administration
Bass, A.: Conceptualization, Funding acquisition, Supervision, Writing – review and editing
Garnett, M.: Conceptualization, Funding acquisition, Investigation, Writing – review and editing
MacDonald, J.: Supervision, Writing – review and editing

• Authors: Brown, A. M., Bass, A. M., Garnett, M. H., Skiba, U., Macdonald, J. M., and Pickard, A. E.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences; College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Science of the Total Environment
• Publisher: Elsevier
• ISSN: 0048-9697
• ISSN (Online): 1879-1026
• Published Online: 25 September 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Science of the Total Environment 906: 167371
• Publisher Policy: Reproduced under a Creative Commons License