Characterization of Urban Atmospheric Aerosols and Development of Single Particle Mass Spectrometer to Understand Chemical Mixing of Individual Particles in Real Time

Abstract

Atmospheric aerosols are having a concern due to its impacts on global climate change and adverse health effects. The impacts are strongly dependent on the physical and chemical properties such as particle size, chemical composition and mixing state. Once emitted from the source, atmospheric particles experience chemical and physical transformation (atmospheric aging) in a very short time scale. On-line instrumentation for size-resolved chemical information of ambient aerosols is needed. The objective of this thesis was to understand the chemical and physical characteristics of atmospheric aerosols and its sources. The chemical composition of non-refractory PM1 and black carbon were measured by commercially available Quadrupole Aerosol Mass Spectrometer and Aethalometer, respectively (Chapter 3) during the Megacity Air Pollution Studies-Seoul (MAPS-Seoul) campaign (5/18/2015-6/13/2015) and the KORea-US Air Quality (KORUS-AQ) study campaign (4/21/2016-6/14/2016). The data were compared with those from satellite, backward trajectory, and meteorology to identify the source of them. To complement the limitation of QAMS employing thermal desorption followed by electron impact ionization, the new Single Particle Mass Spectrometer (SPMS) which based on the laser desorption/ionization was developed and applied to build the source profile of various combustion-related particles (Chapter 4). Finally, the detection efficiency of SPMS was improved by coupling light scattering module in the system (Chapter 5). The use of light scattering module increased the hit rate in triggering mode 10 times compare to the free-firing mode. To the best of our knowledge, this study is the first to build an SPMS in Korea, and this will provide chemical mixing of a single particle as a complementary to the bulk analysis.