Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730054
Title: Redox controls on Cr isotopes in natural waters
Author: Zhang, Qiong
ISNI:       0000 0004 6493 7740
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Abstract:
Shifts in Cr isotope fractionations due to microbial activity provide valuable insights into the mechanisms of its cycling, and can be used to quantify biogeochemically mediated redox processes in the environment. In my thesis, microbial Cr isotope fractionations were determined, with a broad range of experimental variables, including species, electron donors, Cr concentration, pH and respiration pathways, and the information can be used to understand the natural environment. Cr isotopes are found to be very sensitive to the types of electron donors and bacterial respiration pathways, indicating that the bacteria employed di erent metabolic pathways to reduce Cr under those conditions. These also suggest the potential to develop Cr isotopes as a new tool to probe speci c biological processes. Cr isotope fractionation in metal-microbe-mineral interactions is also studied. The addition of the minerals did not lead to a significant change on bacterial Cr isotope fractionations, though Cr reduction rates were significantly impacted. This indicates that although metabolic rates were altered by the interactions with the minerals, similar reduction pathways were still used by the bacteria. Based on these studies, the potential of combining a whole cell bioreporter, which can be used to assess the toxicity of Cr, and Cr isotope techniques, which can be applied in monitoring bio-reduction processes in contaminated sites, were explored. The whole cell bioreporter was found to be efficient in indicating Cr toxicity at different concentration levels and Cr isotopes were independent of toxicity levels. Therefore, it can be used to monitor bioremediation processes of Cr(VI) with different concentrations.
Supervisor: Thompson, Ian ; Porcelli, Don Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.730054  DOI: Not available
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