Sources and formation of non-refractory submicron aerosols in the Pearl River Delta, China

Abstract

Atmospheric aerosols have been widely recognized as one of the environmental threats in millions in China. Depending upon locations and seasons, the physical and chemical characteristics of aerosols can vary greatly because of the differences in emission sources, transportations and atmospheric processes. It is important to characterize submicron aerosols under different locations and atmospheric conditions in real-time manner. High-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) has been employed in intensive campaigns at two different sites in the Pearl River Delta (PRD) region to provide insights into sources and formation of submicron aerosols. In Guangzhou, PM₁ (particles with diameter <1 μm) concentration, dominated by organics, was relatively high (average~55 μg/m³). Hydrocarbon-like organic aerosol (HOA), which is traffic related primary organic aerosol, was an important contributor (40%) to the high concentration of organics at night. We also observed efficient secondary organic aerosol (SOA) photochemical production even in late autumn and winter, possibly caused by the large amount of traffic emissions of VOC at night. The contribution from nitrate increased as PM₁ concentration increased. Photochemical oxidation and nighttime chemistry of NO_x were possible formation routes of nitrate. In Hong Kong, the sources and formation of aerosols were then investigated with high-PM episodes across the four seasons. Both regional transport and secondary formation contributed to high PM levels. Sulfate and organics dominated in all episodes. In a particular local photochemical episode under an established land-sea breeze pattern, the production of sulfate and SOA were efficient during the course of six hours. Semi-volatile organic aerosol (SVOOA) was formed at a rate initially higher than low-volatity organic aerosol (LVOOA) but subsequently transformed to LVOOA at later stage of photochemical aging. In this study, spatial and temporal heterogeneity of aerosol components within PRD region were revealed. Such sources and formation of aerosols are also relevant to other megacities, and facilitate the development of chemical transport models and regional PM pollutants controlled strategies.

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