Abstract
Fine particulate matter (PM2.5) has been recognized as a serious hazard linked to deleterious health effects. In this study, all PM2.5 Pollution Episodes (PPEs) in Beijing during 2013 were investigated with hourly PM2.5 observations from the Olympic Sport Center site, and then their characteristics and evolution modes analysed. Results show that 80 PPEs, covering 209 days, occurred in Beijing during 2013. Average PM2.5 concentrations during PPEs were almost twice (1.86) the annual mean value, although the PPEs showed significant seasonal variations. The most hazardous PPEs tended to occur in winter, whereas PPEs with long duration occurred in autumn. The PPEs could be divided into six clusters based on their compositions of different pollution levels, which were strongly related to meteorological factors. We used series peaks of PM2.5 concentrations to analyse the evolution modes of PPEs and found that the more peaks there were within the evolution mode, the longer the duration, and the higher the average and maximum PM2.5 concentrations. Each peak within a PPE can be identified by “rise” and “fall” patterns. The “rise” patterns are widely related to relative humidity, whereas the “fall” patterns are affected principally by wind speed for one-peak PPEs and boundary layer height for multi-peak PPEs. The peak patterns cannot be explained fully by meteorological factors; however, they might also be closely related to complex and diversified human activities.
Highlights
The combination of urbanisation, industrialisation, and population growth in China has led to a remarkable increase in emissions, and the problem of air pollution has received increasing attention because of its influence on daily life via the climate, environment, visibility, and health.One of the most harmful air pollutants is particulate matter (PM)
115–150 μg/m3, and 31 hazardous Pollution Episodes (PPEs) with an average PM2.5 concentration > 150 μg/m3 observed during this period
Most of Double-peak PPEs in third category may be sensitive to meteorological factors, when the correlations tend to be higher and the variations are accorded with changes of PM2.5 concentrations (e.g., Supplementary Information Figure S9b)
Summary
The combination of urbanisation, industrialisation, and population growth in China has led to a remarkable increase in emissions, and the problem of air pollution has received increasing attention because of its influence on daily life via the climate, environment, visibility, and health. Few studies have focused on the evolution process of each specific PM2.5 Pollution Episode (PPE) These evolution processes, evolving through several different stages, such as emergence, stability, and dispersion, provide a comprehensive depiction of each PPE. These evolution modes can be used to retrieve historical PPE records and predict future PPEs. in this research, we use PM2.5 observations to further our understanding of PPEs. For this study, hourly PM2.5 observations were collected continuously at an urban site in Beijing for months (1 February 2013–28 February 2014).
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