Abstract
ABSTRACTTo commemorate the 70th anniversary of the victory of the Chinese people's Anti-Japanese War and the World Anti-Fascist War, an international parade was held in Beijing in September 2015. In order to ensure satisfactory air quality during this event, a phased emission control measures were taken in Beijing and its surrounding provinces. The 24-h PM2.5 samples were collected in Beijing from August 1 to September 15, 2015 covering the period before, during and after this large-scale event. The observed PM2.5 data, meteorological data, emission reduction measures, and air mass trajectory simulation results were systematically analyzed to understand the pollution characteristics and chemical compositions of PM2.5 in Beijing. The results indicated that PM2.5 concentration during the two emission control phases was reduced by 61.7% comparing to the non-control period, but the regional transport of pollutants and meteorological conditions had a more prominent impact on PM2.5 than emission reduction during phase 2. The secondary water-soluble ions including SO42–, NO3–, and NH4+ were found as the main ions present in PM2.5. During the entire emission control period, organic carbon (OC) and elemental carbon (EC) mass concentrations were decreased by 53.1% and 57.9%. A PM2.5 mass balance was analyzed, and it was found that the organic matter accounted for 29.3, 37.6 and 28.5% of the PM2.5 mass before, during and after the emission control, while the contribution of mobile sources to PM2.5 was relatively outstanding after a series of emission control measures.
Highlights
Northern China has experienced significant economic growth over the past 30 years as a result of rapid industrialization and urbanization
The results indicated that PM2.5 concentration during the two emission control phases was reduced by 61.7% comparing to the non-control period, but the regional transport of pollutants and meteorological conditions had a more prominent impact on PM2.5 than emission reduction during phase 2
A phased emission control measures were taken in Beijing and its surrounding provinces in order to improve the air quality during the parade
Summary
Northern China has experienced significant economic growth over the past 30 years as a result of rapid industrialization and urbanization. Northern China experienced severe haze episodes with long duration which affected unusually sizeable areas in January 2013, October 2014 and December 2015, respectively It has more than 21.5 million residents and 5.6 million vehicles in 2014 (BMBS, 2015). Located in northern China, its main topography is plain, but it is surrounded by the Taihang and Yanshan mountains at approximately 1000–1500 m above sea level in the west, north, and northeast, respectively (Chen et al, 2015) This special terrain environment is beneficial to trap air pollutants. As the center of politics, culture, international exchange and technological innovation of China, Beijing hosted various large-scale international events, such as the 2008 Olympic Games and the 2014 Asia-Pacific
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