Developing the Understanding of Air Pollutant Emissions in Urban Areas: Using New Analysis and Measurement Approaches

Volatile organic compounds (VOCs) and nitrogen oxides (NOx = NO + NO2) play an important role in the formation of ozone and particulate matter, which can both have detrimental effects on human health. Current understanding of urban air pollution largely relies on fixed monitoring sites, most of which do not include the measurement of VOCs and our understanding of the temporal and spatial variation of air pollutants is limited. Furthermore, there is limited understanding of the contribution made by vehicle exhaust emissions under real-world driving conditions. This thesis aims to develop the understanding of air pollutant emission sources through the development of a mobile laboratory using a selected-ion flow-tube mass spectrometer (SIFT-MS) and other trace gas instrumentation to provide on road, high spatial and temporal resolution measurements of VOCs, NOx and other trace gases. Two principal approaches are developed: point sampling, where fast response measurements are made of individual dispersing vehicle plumes, and mobile measurements that provide spatial information. New data analysis approaches are developed and tested to quantify vehicle emissions and other emission sources under a range of conditions. Emissions of NOx and VOCs are quantified for individual classes of vehicles using point sampling data from Milan and motorcycles and mopeds are identified as high emitters of NOx and VOCs, representing a source type that is currently less stringently regulated. Finally, emission patterns and sources in contrasting urban areas are quantified using mobile measurements collected in York, Manchester and Milan.