This funded PhD project is part of a £2M European Research Council (ERC) Advanced grant to study how gaseous ozone (O3) interacts with the ocean surface or “sea surface microlayer” (SML). The highly interdisciplinary study involves aspects of physical chemistry, atmospheric chemistry, ocean chemistry, biology and physics, and engineering. The overall theme is to unify observations of the ocean surface from above, within and below, offering insight into this complex yet sparsely studied interface and applying this knowledge to the atmosphere.
Tropospheric ozone is a significant climate gas, in addition to having a major influence on air quality, public health, and on food security and ecosystem viability. Dry deposition of O3 to the Earth’s surface is estimated to account for about a quarter of overall tropospheric O3 removal. However, losses to the ocean surface, believed to be the largest single deposition sink, are highly uncertain with very poor knowledge of the mechanistic details.
The deposition velocity of O3 is significantly enhanced by chemical reactions in seawater, an effect called ‘chemical enhancement.’ The dominant chemical reaction is widely acknowledged to be with iodide (I-), and this also represents a rich source of reactive gaseous iodine to the marine atmosphere, which in turn causes further chemical loss of tropospheric O3. We have previously demonstrated that the major volatile iodine products of this reaction are HOI and I2. We calculated oceanic emission fluxes for these species which are now used in global atmospheric chemistry models. However, the experiments underpinning these calculations were performed at much higher than ambient levels of HOI and I2, because of poor detection limits. Further, there are no direct measurements of HOI in the atmosphere to evaluate the calculated emissions. Since ambient HOI fluxes are expected to be an order of magnitude higher than those of I2, it is vital that better quantification is obtained, at much lower concentrations than previously achieved.
This project will focus on developing a technique for HOI detection at part per trillion (ppt) levels and using it to better constrain oceanic iodine emission fluxes. A promising method is based on the so-called LOPAP (long path absorption photometer) technique which is widely used to measure gaseous HONO using wet chemical sampling and photometric detection. You will investigate different methods of selectively converting and trapping gaseous HOI to condensed products which have sufficiently strong and characteristic absorption features. We envisage using microfluidics to ensure efficient chemical conversion to such products. An alternative method is to use Chemical Ionisation Mass Spectrometry (CIMS). We envision testing CIMS using I- and Br- as chemical ionisation agents. To evaluate the developed technique/s we will work with Dr Steve Ball from the University of Leicester who is developing sensitive broadband cavity enhanced absorption spectroscopy (BBCEAS) to quantify HOI.
You will be based in the Wolfson Atmospheric Chemistry Laboratories in the Department of Chemistry and be supervised by Prof Lucy Carpenter and Dr Marvin Shaw. Applications from candidates with a strong background in chemistry, physics or environmental science are encouraged. Willingness to develop and build instrumentation, and to handle diverse experimental techniques, will be indispensable.
All research students follow our innovative Doctoral Training in Chemistry (iDTC): cohort-based training to support the development of scientific, transferable and employability skills. All research students take the core training package which provides both a grounding in the skills required for their research, and transferable skills to enhance employability opportunities following graduation. Core training is progressive and takes place at appropriate points throughout a student’s higher degree programme, with the majority of training taking place in Year 1. In conjunction with the Core training, students, in consultation with their supervisor(s), select training related to the area of their research.
Training specific to the project will include in gas handling, kinetic and surface studies, and in analytical techniques including mass spectrometry, microfluidics, and absorption spectrometry. WACL has significant technical support including an Experimental Officer and two technicians, and you will also be supported in your project by postdoctoral research associates working on related studies.
The Department of Chemistry holds an Athena SWAN Gold Award and is committed to supporting equality and diversity for all staff and students. The Department strives to provide a working environment which allows all staff and students to contribute fully, to flourish, and to excel: https://www.york.ac.uk/chemistry/ed/
This PhD will formally start on 1 October 2020. Induction activities will start on 28 September.