Abstract
Abstract. As part of Campaigns of Air Quality Research in Beijing and Surrounding Region-2008 (CAREBeijing-2008), an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed in urban Beijing to characterize submicron aerosol particles during the time of 2008 Beijing Olympic Games and Paralympic Games (24 July to 20 September 2008). The campaign mean PM1 mass concentration was 63.1 ± 39.8 μg m−3; the mean composition consisted of organics (37.9%), sulfate (26.7%), ammonium (15.9%), nitrate (15.8%), black carbon (3.1%), and chloride (0.87%). The average size distributions of the species (except BC) were all dominated by an accumulation mode peaking at about 600 nm in vacuum aerodynamic diameter, and organics was characterized by an additional smaller mode extending below 100 nm. Positive Matrix Factorization (PMF) analysis of the high resolution organic mass spectral dataset differentiated the organic aerosol into four components, i.e., hydrocarbon-like (HOA), cooking-related (COA), and two oxygenated organic aerosols (OOA-1 and OOA-2), which on average accounted for 18.1, 24.4, 33.7 and 23.7% of the total organic mass, respectively. The HOA was identified to be closely associated with primary combustion sources, while the COA mass spectrum and diurnal pattern showed similar characteristics to that measured for cooking emissions. The OOA components correspond to aged secondary organic aerosol. Although the two OOA components have similar elemental (O/C, H/C) compositions, they display differences in mass spectra and time series which appear to correlate with the different source regions sampled during the campaign. Back trajectory clustering analysis indicated that the southerly air flows were associated with the highest PM1 pollution during the campaign. Aerosol particles in southern airmasses were especially rich in inorganic and oxidized organic species. Aerosol particles in northern airmasses contained a large fraction of primary HOA and COA species, probably due to stronger influences from local emissions. The lowest concentration levels for all major species were obtained during the Olympic game days (8 to 24 August 2008), possibly due to the effects of both strict emission controls and favorable meteorological conditions.
Highlights
Due to China’s severe levels of air pollution, the air quality during the 2008 Beijing Olympic Games was of global concern
As part of the CAREBeijing-2008 campaign, a high resolution (HR)-ToFAMS was deployed in urban Beijing to characterize submicron particles during the 2008 Beijing Olympic Games (24 July to 20 September 2008)
Organic species were the most abundant PM1 components accounting for 37.9% of the total mass
Summary
Due to China’s severe levels of air pollution, the air quality during the 2008 Beijing Olympic Games was of global concern. A series of special temporary measures during which around half of the vehicles (∼1.5 million) were removed off roads by an odd-even license car ban and some other traffic restriction measures were executed in Beijing from 20 July to 20 September 2008. It is necessary and important for both scientific understanding and future policy making to evaluate the effectiveness of these drastic control measures on the air quality of Beijing. Several satellite-based studies have recently indicated significant reduction of air pollutants during the 2008 Beijing Olympic Games (Cermak and Knutti, 2009; Mijling et al, 2009; Witte et al, 2009). Especially analysis of ground-level measurement results with high time resolution, are necessary to interpret in depth variation of surface air quality during the Olympic period
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