Non-refractory submicron aerosol (NR-PM₁) was characterized using an Aerosol Chemical Speciation Monitor (ACSM) in one year from September 2013 to August 2014 at the roadside in an Asian megacity environment in Hong Kong. Organic aerosol (OA), characterized by application of Positive Matrix Factorization (PMF), and sulfate were found dominant for each season. The detailed analysis of organic aerosol (OA) during fall and winter showed that traffic-related organic aerosol correlated well with other vehicle-related species, and cooking aerosol displayed clear meal-time concentration maxima and association with surface winds from restaurant areas. Semi-volatile oxygenated OA (SV-OOA) mass concentration was variably correlated with hydrocarbon-hydrocarbon-like OA (HOA), cooking OA (CO...[ Read more ]

Non-refractory submicron aerosol (NR-PM₁) was characterized using an Aerosol Chemical Speciation Monitor (ACSM) in one year from September 2013 to August 2014 at the roadside in an Asian megacity environment in Hong Kong. Organic aerosol (OA), characterized by application of Positive Matrix Factorization (PMF), and sulfate were found dominant for each season. The detailed analysis of organic aerosol (OA) during fall and winter showed that traffic-related organic aerosol correlated well with other vehicle-related species, and cooking aerosol displayed clear meal-time concentration maxima and association with surface winds from restaurant areas. Semi-volatile oxygenated OA (SV-OOA) mass concentration was variably correlated with hydrocarbon-hydrocarbon-like OA (HOA), cooking OA (COA) and low-volatile oxygenated OA (LV-OOA) under different conditions and period of a day. Secondary aerosols are responsible for high day-to-day episodic haze events. The episodes frequently occurred though out the one year covering 137 days, with the dominance of continental transport episodes (CTs; ~45%) concentrated on fall and winter, to a lesser extent land-sea-breeze episodes (LSBs) and typhoon-related episodes accounting for 16% and 13% respectively. Significant increase of the contribution from secondary aerosol (SA) was observed in CTs relative to their adjacent non-haze periods, from about 70% to 80% of total NR-PM₁ concentration. The NR-PM₁ during LSBs also increased significantly and this increase came from nearly all components due to effective accumulation under a land-sea-breeze circulatory conditions. In addition, both CTs and LSBs showed increasing fractions from SV-OOA and nitrate, while these fractional increases were associated with transported input from outside of Hong Kong in CTs but local formation and their circulatory accumulation in LSBs. The mass increase in typhoon-related episode was mainly driven by the increase in SA, especially LV-OOA and sulfate. This obvious increase in SA was caused by the intensive local formation, accumulation and the air subsidence.