Atmospheric chemistry at the ocean surface: Using novel detectors to probe air-sea exchange

Co-supervised by Professor Dwayne Heard at the University of Leeds.

The exchange of chemical species across the ocean-air interface exerts a profound influence on the chemistry of the atmosphere with impacts on climate, regional air quality and marine biological productivity. The sea surface microlayer (SML, the uppermost few microns of the water in contact with the air) represents a particularly reactive region that can lead to the production of chemicals and particles at the ocean surface and/or modify air-sea exchange rates.
It has been hypothesized that reactive dicarbonyls (notably glyoxal and methylglyoxal) can be produced from processes at the air–sea interface. Such compounds are attracting considerable attention as key precursors of secondary organic aerosol in the marine atmosphere. However the precise mechanisms and the environmental relevance for processes occurring in the SML are highly uncertain. A major barrier is that it remains exceptionally challenging to study chemical processes in this microscopic interfacial region. Furthermore, in most cases appropriate model and experimental frameworks for extrapolating laboratory results to the atmosphere do not exist.
We have made very recent progress in both these areas and in this project aim to combine novel lab-on-a-chip technology and fast in-situ laser-based techniques to measure chemical processes in a simulated air-sea interface in both liquid and air phases, with process modelling to understand the importance of such mechanisms in the environment.

Specific objectives:
You will work with leading experimental scientists at York and Leeds at the forefront of applications of microfluidics and ultrasensitive laser-based detection methods in atmospheric science. Microfluidics or lab-on-chip technologies are used increasing widely in analytical chemistry because of their potential for automation, parallel sample processing and high-throughput analysis. Miniaturized systems have the ability to handle small amounts of sample, which is a significant advantage for the study of systems with limited sample availability such as interfacial regions. Laser spectroscopy offers an in situ, non-intrusive, highly selective and sensitive method to probe small radicals and oxygenated VOCs that are either directly emitted by processes at the water-air interface or generated subsequently by reactions in the gas phase.
We envisage that the following specific objectives will be important to reach the overall goals of this project:
1. Development of an integrated microfluidic system capable of rapid and comprehensive determination of soluble VOCs specific for capturing processes occurring at the gas-liquid interfaces.
2. Experiments to probe the chemical mechanisms occurring in the SML driven by ozonolysis and by photooxidation, under a range of conditions.
3. Laboratory determination of ozone deposition rates to water characteristic of different types of seawater (e.g. containing different types and abundance of dissolved organic matter).
4. Development of theoretical and experimental frameworks to extrapolate the laboratory results to the real environment.
5. Determine the abundance of small carbonyls in the ocean surface and overlying atmosphere
Training
You will work under the supervision of Prof Lucy Carpenter and Prof Alastair Lewis in the Wolfson labs as part of a vibrant group of around 40 students, postdocs, researchers, experimental officers and academic staff. You will also work with Prof Dwayne Heard from Leeds whose group has extensive experience of field measurements of atmospheric composition using laser-based methods. We appreciate that this PhD project encompasses several different science and technology areas, and we don’t expect applicants to have experience in many of these fields. The project is very well supported with experienced scientists in the Wolfson Labs and training in these new techniques and disciplines is all part of the PhD.
This project will provide a high level of specialist scientific training in: (i) State-of-the-science measurements of carbonyl compounds in air and water including lab development and field deployment; (ii) novel and cutting edge microfluidics technology and microfabrication methods; (iii) high power tunable laser technology, vacuum and optical systems, (iv) environmental metrology, measurement traceability and uncertainty, and (iv) data handling and interpretation including some chemical modelling. The successful PhD student will have access to a broad spectrum of training workshops offered by the DTP in measurement techniques, atmospheric science, data manipulation, programming, through to managing your degree, to preparing for your viva.

Interviews will take place at Leeds between 23 and 27 February 2015.

The Department of Chemistry at York is 7th in the REF 2014 Research Power table and holds an Athena SWAN Gold Award recognising its committment to supporting equality and diversity for all staff and students