Fine particulate matter (PM_2.5) emitted from on-road vehicles, primarily comprises organic and elemental carbon (OC and EC), represents a major source of urban air pollution, which needs an accurate quantification in its contribution. The central goal of this thesis is to explore the optimal use of receptor models for estimating vehicular PM_2.5 (PM_vehicle) contributions, using field measurement data collected in Hong Kong. This thesis consists of three major parts. First, PM_vehicle contributions at a suburban roadside site in Lok Ma Chau are estimated through hourly OC/EC monitoring coupled with the EC-tracer method, and through positive matrix factorization (PMF) and chemical mass balance (CMB) analyses of filter-based chemical speciation data. Comparison of the three approaches shows...[ Read more ]

Fine particulate matter (PM_2.5) emitted from on-road vehicles, primarily comprises organic and elemental carbon (OC and EC), represents a major source of urban air pollution, which needs an accurate quantification in its contribution. The central goal of this thesis is to explore the optimal use of receptor models for estimating vehicular PM_2.5 (PM_vehicle) contributions, using field measurement data collected in Hong Kong. This thesis consists of three major parts. First, PM_vehicle contributions at a suburban roadside site in Lok Ma Chau are estimated through hourly OC/EC monitoring coupled with the EC-tracer method, and through positive matrix factorization (PMF) and chemical mass balance (CMB) analyses of filter-based chemical speciation data. Comparison of the three approaches shows that the EC-tracer method could yield robust estimate for PM_vehicle at roadside locations. Second, hourly monitoring data of OC/EC, nitrogen oxides and volatile organic compounds are used in tandem in PMF analysis to give separate PM_vehicle estimates for diesel and gasoline vehicles, at an urban roadside site in Mong Kok. With this approach, the long-term trends (2011–2017) in diesel and gasoline PM_vehicle contributions are reported for the first time, which provide important implications to the effectiveness of control measures targeting diesel vehicle emissions. Third, a scheme to account for gas-particle partitioning of organic aerosol and oxidation degradation of hopanes (the organic tracers for PM_vehicle) in CMB model is developed, with the aim to improve PM_vehicle estimation, using PM_2.5 speciation data from a general urban site in Yuen Long for illustration. A key finding is that accounting for these ubiquitous effects would shift the diesel-gasoline split in PM_vehicle contributions from being diesel-dominant to gasoline-dominant at the site, with support from PMF analysis. Potential areas for future research that could improve PM_vehicle estimation are also discussed.