Measurement and Understanding of Emissions over London and Southern England by Airborne Eddy-Covariance

High anthropogenic emissions are a global problem with clear links existing between poor air quality and premature mortality, which is of great alarm to organisations such as the World Health Organisation (WHO). In Europe, high emissions of nitrogen oxides (NOx) are a concern with concentrations plateauing over the last 15 years. Emission assessment is a key part of the UK’s air quality strategy; this is done so by using tools such as the National Atmospheric Emissions Inventory (NAEI), to report annual emissions to the EU to meet strict air quality regulations. Due to the high importance placed on inventories such as the NAEI, their accuracy is vital.

This thesis details the development and implementation of an airborne eddy−covariance (AEC) strategy to measure anthropogenic fluxes over highly polluted areas, and compare these findings to UK emission inventories. The Ozone Precursor Fluxes in an Urban Environment (OPFUE) campaign was run over two consecutive years, aiming at evaluating emissions from London and Southern England. NOx emissions were evaluated over London showing high emissions coming from central areas. Comparison to the NAEI found NOx emissions were being underestimation by up to a factor of 2. Refinement using the NAEI + road transport estimates scaled via road side measurements showed good improvement, suggesting the need to refine road transport estimates used in the NAEI.

A variety of VOC emissions were also measured over London and Southern England. Measured VOCs over London showed good agreement to the NAEI, and highlighted the successful reduction of VOC emissions through air quality strategies. Measured biogenic emissions of isoprene were found to be higher than air quality model estimates, which could have implications towards regional air quality due to ground level ozone formation. Overall, the described methodology allows for real-time assessment of emission inventories which is key if the UK is to see improvements in its air quality.