The Biogeochemistry of Vanadium
Supervisors: Vicky Coker, Kath Morris, Jon Lloyd and Richard Pattrick University of Manchester: Earth, Atmospheric and Environmental Sciences Background
Vanadium(V) is a common environmental contaminant associated with mining activity and fossil fuel combustion, while vanadium metal is an important ferroalloy in the steel industry. The most common and economically important natural occurrence of vanadium is as a substituting element in magnetite (Fe3O4) in layered mafic intrusions such as the Bushveld Complex, South Africa and at Panzhihua, China, although it is present in a range of mineral phases including uranium-vanadium minerals found in Cu-V-U ores of the Western, USA (Figure 1). Vanadium is redox active and can occur naturally in three different states oxidation states, V(III), V(IV) as vanadyl conditions. Vanadate is the most soluble and toxic, however, both V(V) and V(IV) are often associated with mining and petroleum exploitation. Vanadium is toxic to animals at vanishingly small (nano-molar) concentrations, and is a co-contaminant with uranium mining sites in many parts of the world. However, very little is known about the environmental subsurface processes and interactions involving the V-bearing mineral species and microorganisms that influence the behavior and bioavailability of this element. Naturally occurring anaerobic Fe(III)-reducing bacteria are able to directly respire many different oxidized metal species such as Fe(III), Mn(VI) and V(V) by coupling metal reduction to oxidation of naturally occurring organic compounds. Previous work on the interaction of metal- reducing bacteria with vanadium found that G. metallireducens and S.oneidensis MR-1 were both able to couple growth to the direct enzymatic reduction of V(V), subsequently precipitating V(IV) compounds. Reduction of oxidized minerals can lead to the capture and, therefore, remediation of toxic metals, such as the conversion of Fe(III)-oxyhydroxides to magnetite (Fe3O4), a reduced Fe(II)-bearing mineral, which is able to hold vanadium within the mineral structure. Recent work has shown that vanadium is recalcitrant to re-oxidation in natural systems compared to other redox active contaminants such as uranium, although the detailed biogeochemical and mineralogical The subsurface processes governing vanadium redox behaviour will be investigated in both natural samples and pure mineral systems. Vanadium-rich sediment samples, natural and anthropogenic, will be collected from the UK and N. America. Using techniques detailed below, the student will use microcosm and pure culture approaches to create a model of the interplay between microbes and mineral structures and how these interactions govern vanadium mobility, and thus control contamination and remediation. In addition, vanadium is often a co-contaminant with uranium, itself a redox active contaminant, and where appropriate we will investigate the behavior of both V and U in these systems which is likely to be interlinked. Training
The student will join a vibrant research group of 20+ researchers environmental sciences. Training will be provided in state-of-the- art biogeochemical techniques such as geomicrobiological laboratory methods including wet chemical and metagenomic analyses, mineralogical analysis including microscopy and investigations. This combination of advanced training will provide a broad portfolio of skills that are required for future employment in the academic, environmental and industrial sectors and with clear links to the mining and nuclear industrial sectors. References and reading
 Begg, J.D.C. et al. (2011). Bioreduction behavior of U(VI) sorbed to sediments.  Coker, V. S., et al. (2008) Probing the Site Occupancies of Co, Ni and Mn Substituted Biogenic Magnetite Using XAS and XMCD. Am. Mineral. 93, 1119-1132.French et al.
(2013) Changes in Shewanella putrefaciens CN32 membrane stability upon growth in the presence of soluable Mn(II), V(IV), and U(VI). Geomicro J., 30, 245-254  Yelton et al. (2013) Vanadate and acetate biostimulation of contaminated sediments decreases diversity, selects for specific taxa, and decreases aqueous V5+ concentration.  Coker et al. (2013) Vanadium capture by biogenic magnetite, in prep


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