Abstract
Abstract. Measurements of volatile organic compounds (VOCs) were performed at a suburban site and an urban site in Beijing during the winter of 2014–2015. The VOC concentrations and emission ratios (ERs) to CO were compared at these two sites. It is found that though the VOC concentrations at the urban site are 2.67±1.15 times of those at the suburban site, the ERs are similar (within a factor of 1.5). It is indicated that (1) the VOCs at suburban areas are mainly from the transportation from the urban areas and (2) the ERs measured at the urban areas are also valid for the surrounding suburban areas. By comparing the diurnal variations and the contribution of anthropogenic emissions at both sites, we find that the photochemical processes are very active at the urban site, and these processes play an important role in the daytime oxygenated VOC (OVOC) formation. The methanol at the urban site and the formic acid at the suburban site probably have additional sources, which are attributed to be solvent use and soil/agriculture, respectively. The festival effects from the Chinese New Year (CNY) were investigated. The VOC concentrations decreased ∼60 % during CNY holidays, probably due to the population migration during festival holidays. In addition, fireworks are found to be an important source of acetonitrile, aromatics, and some OVOCs during the CNY festival and should be controlled more strictly. This study provides key characteristics of wintertime VOCs in suburban and urban Beijing and has implications for better understanding the atmospheric chemistry of VOCs in and around this megacity.
Highlights
Volatile organic compounds (VOCs) play important roles in air quality as they can form secondary pollutants such as ozone and secondary organic aerosol (SOA) during their oxidation processes in the atmosphere (Atkinson and Arey, 2003; Seinfeld and Pandis, 2016)
A previous study found that ∼ 22 % of the signal at m/z 69 was isoprene in urban London during winter by comparing PTR-MS and gas chromatography (GC) data (Valach et al, 2014)
Wintertime volatile organic compounds (VOCs) were online measured by a PTR-MS at suburban and urban Beijing in December 2014 and February 2015, respectively
Summary
Volatile organic compounds (VOCs) play important roles in air quality as they can form secondary pollutants such as ozone and secondary organic aerosol (SOA) during their oxidation processes in the atmosphere (Atkinson and Arey, 2003; Seinfeld and Pandis, 2016). More strict control policy on fireworks should be conducted to reduce the concentrations of VOCs and other gas pollutants. The new policy conducted from 2018 is that fireworks are all prohibited in urban Beijing (within the 5th Ring Road), which may reduce the VOC emission from fireworks. The effectiveness of this new policy in cleaning the air during the CNY festival needs to be investigated in future studies
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