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Title: Microbial geochemistry of a lead-zinc mine
Author: Langford, Emma
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2013
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Frongoch is a disused Pb-Zn mine situated approximately 16 km SE of Aberystwyth in central Wales. Despite being disused for over 100 years, the site is leaching heavy metals (Zn and Pb) into the Nant Cwmnewydion and ultimately Ystwyth rivers. The prevalence of heavy metal salts in the River Ystwyth was first reported by Carpenter in 1924 but remains a problem today. In 2002, the Environment Agency released a report ranking Frongoch in the top 50 mine sites impacting surface waters, and in 2010 work commenced to remediate the site. The British Geological Survey (BGS) and Environment Agency have been characterising the geochemistry and hydrology of the site. This study aimed to complement BGS studies by elucidating the total microbial population of tailings, peat and water samples from Frongoch and determining if the microbial population was accelerating leaching of heavy metals from the tailings. Culture dependant and independent methods were used to elucidate the microbial (predominantly Bacterial but also Archaeal and Eukaryotic) populations from a range of samples from Frongoch. However, an emphasis was made on determining the presence of sulphur oxidising bacteria (SOB), as they are known to cause dissolution of Zn and Pb by degradation of sphalerite (Zn5) and galena (PbS). In addition, a microcosm experiment was used to monitor chemical changes over time both in the presence and absence of microorganisms. • A number of known SOB were identified using 165 rDNA PCR DGGE. Subsequent analysis using selective cultures for Suljobacillus and PCR probes specific to Acidithiobacillus errooxidans (a known sulphur- and iron-oxidising species) and the soxB gene of the sulphur oxidase operon ubiquitous to many SOB gave further evidence for the presence of SOB in Frongoch tailings. However, no geochemically significant organisms were detected from water samples. Furthermore, reported microbial communities were diminutive in peat samples when compared to tailings samples with equivalent heavy metal concentrations. During the course of microcosm experiments, dissolution of heavy metals (Zn, Pb and Fe) by a consortium of cultured microorganisms native to Frongoch was detected. However, the pH increased to approximately pH 8.1 over time for all treatments, thus Acid Mine Drainage (AMD) was not generated. In addition, the inclusion of 10 mM ZnS in the growth medium decreased the lag time of the microbial growth curve when compared to cultures from un-spiked growth medium. This means that an increase in ZnS concentration stimulated the growth of microorganisms, suggesting that the culturable microbial population of Frongoch has adapted to use ZnS as a growth substrate .
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available