Sugars and plyol compounds in ambient aerosols and cooking fume aerosols
Sugars and polyols are broadly distributed in a wide range of living organisms. They can become airborne through biomass burning, cooking, soil re-suspension, wind abrasion of vegetables, and bubble-bursting of sea water. Their abundance and sources in the ambient environments are little known because of a lack of suitable and simple analytical methods. In this thesis work, I have explored and established analytical methods for the determination of total water-soluble monomeric carbohydrates (WSMC) and individual sugar and polyol compounds in aerosol samples. Ambient fine aerosols collected in Hong Kong, Nanjing, and Jeju Island (Korea) were determined for WSMC concentrations and similar WSMC levels in the range of 228-640 ng/m3 were found at different locations. The average water-soluble carbon mass percentage contribution by WSMC at different locations varied from 2.5% in the Nanjing samples to 7.6% in the Hong Kong samples. These results indicate that WSMCs are ubiquitous in the ambient environment and their contributions to water-soluble organic aerosol mass were not negligible. The application of a gas chromatography-based method for individual sugars and polyols to cooking aerosols has allowed the assessment whether cooking is an important source for glycerol and levoglucosan in the ambient environments. It was found that cooking processes produce glycerol and levoglucosan, but comparison with ambient aerosol measurements indicated that cooking was not a major source for these two carbohydrate-like compounds in the ambient environment. Two analytical methods using liquid chromatography-mass spectrometry (LC-MS) were successfully developed in this thesis work and were found to be simple and most suitable for the determination of various sugars and polyols in ambient aerosols. The application of the LC-MS methods to a set of thirty ambient aerosol samples collected in Hong Kong, in conjunction with the measurements of the major aerosol constituents, has identified biomass burning and soil/soil microbiota to be the major sources for ambient sugars and polyols. Such a finding is also consistent with the total WSMC measurement results made for bulk aerosols and size-segregated aerosols. Future work is suggested to focus on the application of the LC-MS methods on both the source aerosols (e.g., suspended soil dust, vegetative detritus, and sea salt aerosols) and the ambient aerosols. The analysis of these compounds in the source aerosols will help to quantify the contributions of theses sources to ambient aerosol loadings. Their measurement in ambient aerosols will help to understand the role of sugars and polyols in enabling their host particles to serve as cloud condensation nuclei.