Insights into the characteristics of submicron particulate matter and their sources at the urban roadside in Hong Kong using aerosol mass spectrometry

Abstract

Hong Kong is one of the world’s most densely populated cities and has long suffered from air pollution. This work discusses the first high resolution aerosol mass spectrometer (HR-AMS) measurements of submicron particulate matter (PM₁) composition at a typical urban location in Hong Kong. Measurements were carried out in spring and summer 2013 at street level in a district with mainly commercial and residential activities. Primary goals of this study are the characterization and differentiation of important aerosol sources in the urban inner-city environment and their varying importance at different time scales including diurnal patterns, seasonal characteristics and changes with air mass origin. Total non-refractory PM₁ at the roadside was vastly dominated by organic constituents with primary organic aerosol from cooking and traffic found to be dominant. Findings were corroborated by additional measurements including wind rose analysis, traffic data, EC/OC data and gas phase species. The relationship of traffic-related organics and elemental carbon concentrations with traffic count data was studied in detail to evaluate the contributions of different broad engine types (gasoline, diesel, LPG) to roadside particulate matter concentrations. Cooking contributions in organic aerosol were assessed directly for the first time in Hong Kong and exceeded those related to vehicles although traffic was still the major PM₁ source when elemental carbon (EC) was included. Influences of traffic and cooking-related emissions on particle size distributions were examined. Secondary organic aerosol albeit at smaller contribution was consistently abundant. Episodic pollution events and their relation to various meteorological conditions, including land-sea-breeze conditions and typhoon-outflow circulations, and their effects on different inorganic and organic species were assessed. Regional transport, wet chemistry and photochemistry varyingly contributed to high particulate matter events. Elemental analysis of high-resolution mass spectra revealed that data alignment in the van Krevelen diagram was mostly related to different mixing of organic aerosol sources.

Date of Award	2016
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology