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Characterization of Chemical Composition in PM2.5 in Beijing before, during, and after a Large-Scale International Event
Xiaowen Yang1, Shuiyuan Cheng1,2, Jianbing Li3, Jianlei Lang1, Gang Wang1
1 Key Laboratory of Beijing on Regional Air Pollution Control, Beijing University of Technology, Beijing 100124, China
2 Collaborative Innovation Center of Beijing City Traffic, Beijing University of Technology, Beijing 100124, China
3 Environmental Engineering Program, University of Northern British Columbia, Prince George, British Columbia V2N 4Z9, Canada
- The PM2.5 concentrations decreased by 61.7% during the emission control phases.
- SO42–, NO3–, and NH4+ were found as the main ions in PM2.5 in Beijing.
- SO42– concentrations decreased largest during the emission control phases.
- The ratios of NO3–/SO42– and Cu/Pb were higher during the emission control phases.
To 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.
Air mass trajectory; Chemical composition; Emission control; Water-soluble ion; PM2.5.