IAP2-23-053

Mineral-microbe transformations in carbon critical environments

Carbon cycling is a crucial component of our global climate. Nanoparticles of reactive iron minerals are essential for the long-term drawdown and storage of atmospheric carbon dioxide in soils and sediments; a process which is driven by microorganisms. The specific microbe-mineral mechanisms that facilitate these relationships across different environments are currently unknown, owing to the challenges of characterising such small components. In order to build a more robust global profile of current and future microbial carbon cycling hotspots, we need to better understand the pairing of iron mineral species to carbon cycling processes across different environments.

This project will target peatland and glacial environments; both known to be globally important in terms of their carbon and iron content, and their climate sensitivity, yet both contrasting in their geochemical compositions. Microbe-mineral interactions will be investigated on scales never targeted before, using cutting edge technologies to speciate nanoparticulate iron minerals, paired with metagenomic microbial community sequencing to profile associated microbes. Iron mineralogy will be analysed using the European Synchrotron Radiation Facility (ESRF), offering unparalleled x-ray energy – 10 trillion times brighter than medical x-rays – to identify individual iron nanoparticles, while metagenomics will allow both microbial community composition, as well as community function, to be investigated in parallel. Standard geochemical analyses will be simultaneously performed to investigate interactions between the major nutrient cycles, and their impact on the overall extent and pathway of carbon cycling.

This is a highly interdisciplinary project that uses a holistic approach to understand the
intertwined biogeochemical iron and carbon cycling processes in climate-sensitive environments: the student will receive training that spans geochemical, microbiological, and physical science disciplines.

In the first year, the student will carry out an initial fieldwork programme to sample sediment cores from the main natural peatland habitats across Scotland (including blanket bogs, raised bogs, fens and bog woodlands), with a further opportunity for supported fieldwork from outlet glaciers of the Greenland Ice Sheet in the second year.

Each type of peatland and glacial habitat supports a unique biological niche; using conventional (including scanning electron microscopy, inductively coupled plasmas mass spectrometry and optical emission spectrometry, and wet chemistry) and isotopic (δ18O, δD, δ34S) geochemical techniques, combined with microbial metagenomic analyses, the student will gain significant experience in understanding how carbon cycling specific to each of these systems functions currently, and how this function may be affected by future climate change. The student will gain training in conventional (at the University of Stirling, UoS) and synchrotron source Mössbauer spectroscopy (at the ESRF), to probe the critical function of environmental iron nanoparticles in carbon cycling within each distinct environment.

Year 1

All peatland fieldwork will be completed in year 1, and preparations for the glacial fieldwork programmes will begin. After collection of core samples at the beginning of the studentship, most of this year will be spent developing the laboratory skills required for geochemical and isotopic analyses of the sediment solid phase and interstitial porewater at the Scottish Universities Environment Research Centre (SUERC), East Kilbride and the School of Geographical and Earth Sciences (GES), Glasgow. Specifically, the student will learn a variety of chemical digestion and sequential extraction techniques, to better understand iron speciation within the diagenetic sediment sequence. By the end of Year 1, all geochemical analyses will be completed for the Scottish peatland sediment samples. Mid-way through Year 1, the student will begin training in Mössbauer spectroscopy at the UoS, where they will also complete the initial mineralogical characterisation of the peatland sediments. The student will also have the opportunity to register for the online Hyperfine Interactions course run by Ghent University, Belgium that explains the theoretical physics behind, and experimental methods based upon, hyperfine interactions, which form the basis of Mössbauer theory. Similarly, the student will have open access to all online training materials across the Geo-Biosciences Advanced E-Learning Academy (GAEA) platform, which explains detailed isotope systematics and the theory behind mass spectrometry. By the end of the year, the student will have completed a literature review featuring the latest research in the field, which will be incorporated into the thesis introduction.

Throughout the first year, the student will also prepare their first application for beamtime at the ESRF, and application to the supported by Hepburn and Schröder; and their first NEIF application for isotope analysis at SUERC, supported by Hepburn.

Year 2

The building and sequencing of microbial metagenomic libraries will occupy the beginning of Year 2, supervised by Cameron at GES. Fieldwork techniques and laboratory skills acquired in Year 1 will be employed by the student during a summer fieldwork season of at least 3 weeks, and subsequent geochemical processing of these samples at SUERC, GES, and UoS. The student will also begin training in the isotopic analysis of oxygen and sulfur in the sediment solid phase and porewater, using custom built vacuum extraction lines and dual-inlet isotope ratio mass spectrometry at SUERC. The student will aim to have completed most of the conventional sediment geochemical analyses by the end of Year 2.

The first round of beamtime will commence in the Spring of Year 2 for SMS analysis of porewater-suspended iron nanoparticles. The preparation of all samples for SMS will be carried out between SUERC and UoS.

In Year 2, the student will begin writing the PhD thesis, specifically focussing on the sampling areas, methodology, and initial geochemical results. The presentation of these initial results will be encouraged at an international workshop in the summer of Year 2.

Year 3

Most of this year will be dedicated to completing the microbial metagenomic analysis of the glacial samples, and any remaining sediment geochemistry, including conventional Mössbauer spectroscopy work at the UoS. The student will conduct their second and final visit to the ESRF to carry out all remaining SMS analysis of the glacial sediment samples.

The student will continue writing the PhD thesis, and associated publications, with the opportunity to gain further support through the University of Glasgow’s thesis writing mentorship scheme.

Year 3.5

The final section of the studentship will be dedicated to writing up the thesis and associated publications.

This studentship will provide multidisciplinary training across multiple research institutes at the University of Glasgow (SUERC and GES) and the University of Stirling, presenting an excellent opportunity to gain training and expertise in geochemistry and microbial ecology, and to experience environmental and climate change research. Skills in fieldwork, sample collection, and sample processing, will also be gained. An application will be submitted to the ESRF, to use The European Synchrotron in Grenoble, the world’s brightest x-ray source, presenting the student with a unique opportunity to experience this international Centre of Excellence. Applications for beamtime at the ESRF and isotopic analyses at SUERC via NEIF, will add valuable skills in grant capture for the successful student. After completion of their PhD, students may wish to consider careers such as analytical geochemistry, exploratory geology, particle accelerator science and technology, academia or environmental surveying.