Abstract
Abstract. As a part of the CAREBeijing-2008 campaign, observations of O3, oxides of nitrogen (NOx and NOy), CO, and hydrocarbons (NMHCs) were carried out at the air quality observatory of the Peking University in Beijing, China during August 2008, including the period of the 29th Summer Olympic Games. The measurements were compared with those of the CAREBeijing-2006 campaign to evaluate the effectiveness of the air pollution control measures, which were conducted for improving the air quality in Beijing during the Olympics. The results indicate that significant reduction in the emissions of primary air pollutants had been achieved; the monthly averaged mixing ratios of NOx, NOy, CO, and NMHCs decreased by 42.2, 56.5, 27.8, and 49.7 %, respectively. In contrast to the primary pollutants, the averaged mixing ratio of O3 increased by 42.2 %. Nevertheless, it was revealed that the ambient levels of total oxidant (Ox = O3+NO2+1.5 NOz) and NOz were reduced by 21.3 and 77.4 %, respectively. The contradictions between O3 and Ox were further examined in two case studies. Ozone production rates of 30–70 ppbv h−1 and OPEx of ~8 mole mole−1 were observed on a clear-sky day in spite of the reduced levels of precursors. In that case, it was found that the mixing ratio of O3 increased with the increasing NO2/NO ratio, whereas the NOz mixing ratio leveled off when NO2/NO>8. Consequently, the ratio of O3 to NOz increased to above 10, indicating the shift from VOC-sensitive regime to NOx-sensitive regime. However, in the other case, it was found that the O3 production was inhibited significantly due to substantial reduction in the NMHCs. According to the observations, it was suggested that the O3 and/or Ox production rates in Beijing should have been reduced as a result of the reduction in the emissions of precursors during the Olympic period. However, the nighttime O3 levels increased due to a decline in the NO-O3 titration, and the midday O3 peak levels were elevated because of the shift in the photochemical regime and the inhibition of NOz formation.
Highlights
Urbanization is undergoing worldwide, in the developing countries
During August 2008, including the period of the 29th Summer Olympic Games, an intensive atmospheric chemistry experiment was conducted at the air quality observatory of the Peking University in Beijing, China
The measurements were compared with the results of the CAREBeijing-2006, which was carried out in the summer of 2006, to infer the emission reduction in the Olympic month
Summary
The intensive human activities unavoidably result in substantial emissions of air pollutants in urban areas. With a total population over 10 million, Beijing is one of the megacities in the world. The economic development has brought up the number of vehicles, factories, as well as power plants in the Beijing metropolitan area during the last two decades. As a result, Beijing has suffered from serious air pollution (Wang et al, 2006; An et al, 2007). Being the host city of the 29th Summer Olympic Games, the Beijing government setup rather aggressive action plans to reduce the emissions of air pollutants in Beijing and its surrounding areas during the Olympic period. The traffics were restricted temporarily to reduce the vehicular exhausts within the Beijing City (Wang et al, 2009a). Emission inventory studies indicated that the traffic emissions of volatile organic compounds (VOCs), carbon monoxide (CO), Published by Copernicus Publications on behalf of the European Geosciences Union
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