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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor: Sasha Turchyn, Earth Sciences

This is a CASE project with Thermo Scientific

Brief summary: 
Investigating redox and other chemical and biological reactions in a range of environments using a novel analytical technique developed with Thermo Scientific.
Importance of the area of research concerned: 
The analysis of the oxygen isotopic composition of sulphate, phosphate, cellulose and other non-carbonate material has proved a powerful method for exploring processes from the oxidative weathering of pyrite, nutrient supply, microbial metabolism and the ecology of tree growth. This analysis is typically done by pyrolysis of the material coupled by continuous He flow to a mass spectrometer, and is limited by sample size. The ability to measure smaller samples will transform the range of questions that we can ask about redox processes in various environments. This can include better studies of the oxidation weathering of pyrite minerals (one of the key processes in the carbon cycle), the analysis of oxygen isotope ratios in sample-limited material from the geological record (e.g. carbonate-associated-sulfate or phosphate minerals), and a range of questions in the modern deep biosphere (how is sulphate coupled to methane oxidation in marine sediments?). Many of these studies are limited by the need for very large amounts of sample.
Project summary : 
The Godwin Laboratory for Paleoclimate research is acquiring a new Isolink - a peripheral that links to the gas source mass spectrometer. The Isolink has a stepped helium flow function which allows it to analyse orders-of-magnitude smaller samples for their carbon, nitrogen, and sulfur isotopic composition. It also has a second oven where samples, rather than being combusted, could be pyrolysed, allowing for the analysis of the oxygen isotopic composition of the material. Through method development with the manufacturer, this application will be developed. Then it will be applied to a range of smaller projects, based on the student's interest, that will use the new application to explore a new environmental or geological system.
What will the student do?: 
Working with Thermo Scientific (the maker of the Isolink) the student will develop the pyrolysis oven to leverage the stepped helium flow to allow for smaller samples sizes to be analysed. This will take the first year of the project and will involve some time in Bremen Germany working with the project engineers to understand and engineer the Isolink for the oxygen isotopic analysis of material and then returning to Cambridge to implement this. At this point the student can choose a range of subjects that suits their interest, to demonstrate and explore the new analytical capability. One high-profile possibility will be to develop a record of the oxygen isotopic composition of carbonate associate sulphate in foraminifera for the Cenozoic. A second possibility would involve fieldwork and sampling of river catchments to analyse in higher resolution the oxygen isotopic composition of river sulphate. A third possibility will be to explore the coupling of sulfate and methane during methane oxidation. The student will have autonomy to work with the supervisors and other advisers in the department to develop and implement the application that is of most interest to the student.
References - references should provide further reading about the project: 
Sequential measurement of δ15N, δ13C and δ34S values in archaeological bone collagen at the Scottish Universities Environmental Research Centre (SUERC …A new analytical frontier) KL Sayle, CR Brodie, GT Cook, WD Hamilton Rapid Communications in Mass Spectrometry 33 (15), 1258-1266
Isotope evidence for secondary sulfide precipitation along the Marsyandi River, Nepal, Himalayas AV Turchyn, ET Tipper, A Galy, JK Lo, M. Bickle- Earth and Planetary Science Letters, 2013 - Volume 374, 15 July 2013, Pages 36-46
The preservation of δSSO434 and δOSO418 in carbonate-associated sulfate during marine diagenesis: A 25 Myr test case using marine sediments VCF Rennie, AV Turchyn Earth and Planetary Science Letters 395, 13-23
Applying
You can find out about applying for this project on the Department of Earth Sciences page.
Dr Alexandra (Sasha) Turchyn
Department of Earth Sciences Graduate Administrator