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 a newly developed 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, will enable 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 be the first to use this new instrument and will be based around the following objectives:

- Assist in the development and characterisation of the new NO-LIF instrument for detection of NO and NO2.

- Investigate the unique ability of the NO-LIF instrument to distinguish between different NO isotopes to explore remote ocean NO sources. - Deploy the instrument at the Cape Verde Atmospheric Observatory

- Use the Cape Verde data 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.