Nitrogen oxides in remote tropical ocean environments and their impact on air pollution and climate

Nitrogen oxides (NOx = NO+NO2) play a central role in the chemistry of the atmosphere, controlling both the production and loss of key air pollutants and climate gases such as methane, ozone, and particulate matter. Primarily emitted by human activity over land, NOx levels are typically very low in remote ocean environments, and yet still regulate key atmospheric processes in these environments.

Due to the size of the Earth's oceans, small changes in NOx levels can have large impacts on the atmospheres response to changing emissions. Recent work has highlighted significant apparent knowledge gaps in our understanding of NOx in remote ocean environments, which need to be addressed if we are to inform effective policies to tackle air pollution, climate and ecosystem health.

This PhD project will use the custom built York NO-LIF instrument to make highly sensitive measurements of NOx in a remote tropical Atlantic environment, and use these data to advance our knowledge of this keystone of atmospheric chemistry.

A major challenge in the study of NOx in remote ocean environments is that levels are so low that they are close to or below the limits of detection of current technologies. The Wolfson Atmospheric Chemistry Laboratories at the University of York have recently built a new instrument, based on laser-induced fluorescence (NO-LIF), for the highly sensitive and selective detection of NO.

This instrument, the second of its kind in the world, enables measurements of NOx with previously unprecedented levels of accuracy and precision, and through comparison with data from state-of-the-science computation models will allow our understanding of this important chemistry to be challenged and improved.

This PhD project will involve the use of the York NO-LIF instrument as part of the NERC funded ConstrAining the Role of sulfur in the Earth System (CARES) project, which will make detailed atmospheric composition measurements in the North Atlantic region from both ship and aircraft platforms in 2025. The PhD project will be primarily based around the following objectives:

- Deploy highly sensitive instruments for the detection of Nitrogen oxides as part of the CARES field experiment aboard the UK FAAM 146 research aircraft and/or a NERC research vessel - Use the data collected to investigate the sources and chemistry of NOx in the remote North Atlantic.

- Working with project collaborators, use the new data and understanding gained to challenge and improve our understanding of remote ocean atmospheric chemistry, through comparison with model predictions, and its impact on regional air pollution and climate.

This work will address an important knowledge gap in our understanding of atmospheric chemistry and thus directly improve our ability to design effective environmental policies.