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Measurements of urban emissions of NOx

Project Description

This project will be supported by a CASE award from Syft Technologies (

Air pollution is currently the largest environmental health stressor on the UK population. At present the main pollutants of concern in urban centres are nitrogen dioxide (NO2) and particles less than 2.5µm in diameter (PM2.5), alongside ozone in suburban and rural environments. It is estimated that air pollution has an effect equivalent to 40,000 premature deaths/year in England, and costs the UK economy between £10 billion and £20 billion/year. However, since our transport systems, the way we heat our homes, our energy supply, our use of solvents and our agricultural systems are all changing, we know that profound changes in pollutant emissions are likely in the coming years.

Use of models to forecast the effects of changes in emissions relies on accurate and complete inventories and a complete description of physical and chemical atmospheric processes. Emissions inventories have frequently been found lacking, most recently exemplified by the under-representation of NO2 emissions from passenger diesel vehicles. Estimates of emissions in the National Atmospheric Emissions Inventory (NAEI) are derived annually based on a paper exercise, with only occasional quantification using observations - largely as the latter are not available. It is known that this method can contain large uncertainties, with errors propagating through into errors in models.

Currently, it is a critical time with respect to expected reductions in emissions due to new vehicle emission technologies introduced from 2016 onwards (Euro 6/VI standards) (Carslaw et al, 2019). Previous standards have failed to deliver the expected reductions in emissions under ‘real world’ driving conditions and the unique combination of direct emission measurements from both individual vehicle exhaust and the total emitted from a wider area will help assess the effectiveness of the new technologies and provide better estimates of the NOx traffic source in the inventories. As a result, there is a critical research need for improved direct assessments of urban NOx emissions to test whether these are responding as predicted to vehicle fleet changes and implementation of new policies in the UK.

This project will link total measured emissions with direct vehicle exhaust emission measurements made within the flux footprint, thus allowing a detailed assessment of the performance of emission inventories and improved inventories to be developed. Emissions are measured via eddy covariance which utilises high time resolution measurements of NO, NO2 and micrometeorological data from a tall tower site. Eddy covariance has been widely used to assess greenhouse gas budgets in rural/agricultural areas for many years but is more recently being used for air quality pollutants and in urban environments. NOx emissions measurements in London will be made over the period of the PhD at the BT tower in London, calculated via classical and continuous wavelet transform eddy covariance techniques, the latter giving improved temporal information about the emissions. Footprint modelling links these local fluxes to the surface allowing them to be compared with emission inventories. in addition direct vehicle exhaust emission measurements of five gaseous pollutant concentrations (CO, HC, NO, NO2 and PM) and their ratio to CO2 will be made. These are combined with vehicle speed, acceleration and other information retrieved from the DVLA (make, model, fuel type, Euro standard, model year, etc.) to give vehicle specific emissions data. Comparisons can then be made between the real-world emissions and those set by the Euro standard of the car in question.

Policy makers rely on modelling studies and the emissions inventories that inform them to look at how changing vehicle fleets will affect concentrations. They are also interested in how future policies, like the introductions of Clean Air Zones in cities will impact measured concentrations and therefore achievement of the legal objectives for air quality in different areas of the UK. More accurate information on real world emissions, and how they affect emissions and concentrations at the roadside, at the street scale and at the city scale is key to understanding the drivers of changing pollutant concentrations in our cities. The work carried out in this PhD will be of direct relevance to current considerations of the Joint Air Quality Unit that sits between the Government Department for Environment, Food and Rural Affairs and Department for Transport around the effective reduction in nitrogen dioxide concentrations in urban areas.

You will be based in the Department of Chemistry at the University of York. This PhD starts on 1 October 2020. Project details can be found on the NERC PANORAMA DTP web page (

Funding Notes

Value: The studentships are fully funded by the NERC Panorama DTP for 3.5 years and cover: (i) a tax-free annual stipend at the standard Research Council rate (£15,009 for 2019-2020, to be confirmed for 2020-2021 but typically increases annually in line with inflation), (ii) research costs, and (iii) tuition fees at the UK/EU rate.
Eligibility: Unless stated otherwise, fully funded studentships (stipend + fees) are offered to both UK and EU applicants.
This PhD project is available to study full-time or part-time (50%).


Candidate selection process:
• Applicants should submit a PhD application to the university of Leeds by Monday 6 January 2020
• Supervisors may contact candidates either by email, telephone, web-chat or in person
• Supervisors rank the candidates for the assessment panel
• The assessment panel will shortlist candidates for interview from all those nominated
• Shortlisted candidates will be invited to a panel interview at the University of Leeds on the week commencing 24 February 2020
• The Leeds PANORAMA DTP awarding committee will award studentships following the panel interviews
• Candidates will be notified of the outcome of the panel’s decision by email
• Successful candidates will then need to submit a formal PhD application to the University of York

Related Subjects

How good is research at University of York in Chemistry?

FTE Category A staff submitted: 47.06

Research output data provided by the Research Excellence Framework (REF)

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