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Geochemical sources and long-term implications of mine waste weathering, Cwmystwyth Mine, Wales

Marquinez, Yulieth, Bowell, Robert, Jones, Timothy and Brabham, Peter 2021. Geochemical sources and long-term implications of mine waste weathering, Cwmystwyth Mine, Wales. Presented at: 14th International Mine Water Association Congress, Online, 12-16 July 2021.

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Abstract

Evaluation of the distribution and leaching potential of lead, cadmium, and zinc from the Cwmystwyth Mine has been undertaken along with surface grab sample mineralogy. Metal concentrations and pH were evaluated respectively, in which a general weak association between these two factors was found. Using these two parameters, a Ficklin diagram was created to assess the type of drainage being produced at the Cwmystwyth Mine, which indicated that metal leaching neutral mine drainage is being generated. Discharge water from mine workings, waste materials and outcrop generated some variations in terms of pH and metal concentration, with most samples showing alkaline results but higher metals from water that flows through the mine (Nant y Gwaith). Given the extensive mining history at Cwmystwyth, it is no wonder that metals are finding their way through the environment, heavily exceeding the EQS set out by the European Commission. Lead concentrations in all samples but one exceeded the EQS range, and dissolved metal concentrations in the water samples significantly increased downstream. Zinc concentrations are uniformly high, reflecting the higher mobility of zinc over lead and secondary zinc minerals are much rarer than lead sulfate or lead carbonate phases. Cadmium geochemistry appears controlled by zinc mobility and secondary phases. In summary, the mine is heavily contaminating the Ystwyth catchment, with high levels of Pb, Zn, Cd, and other transition metal(loids) are contributing to this contamination such as Mn and As. As proved to be leaching, but it still meets the EQS. Contamination in the river is attributed to the water discharge and perhaps seepage from different mine tailings, adits and underground workings. It is very unlikely that the site will be remediated by cover or removal of mine waste or by using passive treatment due to its topographical complexity, and the sensitive nature of the site, being within a protected Site of Special Scientific Interest (SSSI). Moreover, the data suggests that there have not been any improvements in terms of dissolved metals in the water when data was compared to historic values; hence the mine remains a potential source of metals to the catchment

Item Type: Conference or Workshop Item (Poster)
Date Type: Publication
Status: Unpublished
Schools: Earth and Environmental Sciences
Subjects: Q Science > QE Geology
Date of Acceptance: 21 June 2021
Last Modified: 26 Jul 2021 10:00
URI: http://orca.cardiff.ac.uk/id/eprint/142600

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