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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 
Importance of the area of research concerned: 
The information about how the oxidizing capacity of the atmosphere responds to human activity and natural phenomena is of key interest for air pollution concerns. The oxidizing capacity of the atmosphere is defined as the global mean tropospheric abundance of the hydroxyl radical (·OH). Other oxidants are also present in the atmosphere (e.g., O3, H2O2, ·NO3) and each of them is interlinked with the others through highly complex non-linear cycling reactions [1,2]. The oxidizing capacity of the atmosphere determines the lifetime of emitted gas-phase pollutants and volatile organic compounds emitted by the marine and terrestrial biosphere and plays a key role in particulate matter formation in the atmosphere. All these phenomena influence the Earth’s climate through direct and indirect forcing, thus having global importance. While ice-core measurements of long-lived gases and many inorganic compounds have provided environmental information on the past atmosphere, oxidants are not preserved in the ice archives. A combined modelling and analytical approach is therefore necessary to tackle the challenge of unveiling past changes in the oxidizing capacity of the atmosphere.
Project summary : 
Organic compounds emitted by the terrestrial biosphere are a major control on ·OH concentration in the atmosphere [3]. This project will start with a modelling study to monitor how ratios between different oxidation products of isoprene, monoterpenes and sesquiterpenes change depending on different exposure to atmospheric oxidants during their atmospheric lifetime and transport before they get incorporated into the ice. Measurements of such compounds for ice cores from alpine and polar regions will be done using advanced mass spectrometry techniques. The data will be evaluated against other species measured in the ice samples, then used to infer information on the average concentration of oxidants to be compared with nineteenth-century observations. The goal is to validate a modelling/analytical approach to infer past changes in the oxidative capacity of the atmosphere.
What will the student do?: 
The student will be based at the Department of Chemistry, where the supervisory team will assist the student in the chemical-and-transport modelling and analytical work from the sample preparation to the mass spectrometry measurements and data analysis. The samples, from pre-collected polar and alpine ice cores, will be pre-concentrated and analysed following a proven method developed by the project team. The analytical work may include optimisation and validation to reach the maximum instrumental performances and ensure adequate detection limits. The student will also work in the -20 cold laboratories and a class-100 cleanroom at the British Antarctic Survey (BAS). The project is not dependent on the collection of new ice cores; however, we endeavour to include the student in future drilling projects. The student will have a chance to interact with an international network of collaborations and to present the results in national and international conferences.
References: 
[1] Thompson, A.M. 1992. The oxidizing capacity of the Earth’s atmosphere: Probable past and future changes. Science, vol. 256, pp. 1157–1165., DOI: 10.1126/science.256.5060.1157
[2] Alexander, B., & Mickley, L.J. 2015. Paleo-Perspectives on Potential Future Changes in the Oxidative Capacity of the Atmosphere Due to Climate Change and Anthropogenic Emissions. Current Pollution Reports, vol. 1, pp. 57–69., DOI: 10.1007/s40726-015-0006-0
[3] Giorio, C., Kehrwald, N., Barbante, C., Kalberer, M., King, A.C.F., Thomas, E.R., Wolff, E.W., & Zennaro, P. 2018. Prospects for reconstructing paleoenvironmental conditions from organic compounds in polar snow and ice. Quaternary Science Review, vol. 183, pp. 1–22., DOI: 10.1016/j.quascirev.2018.01.007
Applying
You can find out about applying for this project on the Department of Chemistry page.