Abstract
Abstract. Non-refractory submicron aerosol is characterized using an Aerosol Chemical Speciation Monitor (ACSM) in the fall and winter seasons of 2013 on the roadside in an Asian megacity environment in Hong Kong. Organic aerosol (OA), characterized by application of Positive Matrix Factorization (PMF), and sulfate are found to be dominant. Traffic-related organic aerosol shows good correlation with other vehicle-related species, and cooking aerosol displays clear mealtime concentration maxima and association with surface winds from restaurant areas. Contributions of individual species and OA factors to high NR-PM1 are analyzed for hourly data and daily data; while cooking emissions in OA contribute to high hourly concentrations, particularly during mealtimes, secondary organic aerosol components are responsible for episodic events and high day-to-day PM concentrations. Clean periods are either associated with precipitation, which reduces secondary OA with a lesser impact on primary organics, or clean oceanic air masses with reduced long-range transport and better dilution of local pollution. Haze events are connected with increases in contribution of secondary organic aerosol, from 30 to 50 % among total non-refractory organics, and the influence of continental air masses.
Highlights
The Special Administrative Region of Hong Kong is a global logistics and finance center located at the southeastern edge of the Pearl River Delta (PRD) region, China’s largest manufacturing area and one of the world’s most densely populated regions
Aerosol Chemical Speciation Monitor (ACSM) Non-refractory PM1 (NR-PM1) concentrations co-vary with that of PM2.5 measured by TEOM (R2 = 0.64, slope = 0.59; Fig. S1); the low slope value may be caused by the different size cuts of ACSM and TEOM and the presence of refractory materials such as elemental carbon which the ACSM cannot detect
A marked difference is observed in the distribution of primary Organic aerosol (OA) (POA) and secondary OA (SOA); whereas in spring and summer (AMS) POA makes up 65 % of total organics, the reverse is observed for fall and winter (ACSM) when POA only amounts to 42 % overall
Summary
The Special Administrative Region of Hong Kong is a global logistics and finance center located at the southeastern edge of the Pearl River Delta (PRD) region, China’s largest manufacturing area and one of the world’s most densely populated regions. A high-resolution aerosol mass spectrometer (HR-ToF-AMS) was applied at an urban site in the Shenzhen metropolitan area and a rural site in PRD region during October and November (He et al, 2011; Huang et al, 2011). They found that organic concentration dominates followed by sulfate, which is similar to this study, but the fraction of sulfate at the rural site is larger than that of the urban site. While HOA showed a stronger relationship to SV-OOA overall, COA can be an important contributor to SV-OOA during mealtimes
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