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Multi-Method Observation and Numerical Simulation of a PM2.5 Pollution Episode in Beijing in October, 2014

Category: Urban Air Quality

Volume: 16 | Issue: 6 | Pages: 1403-1415
DOI: 10.4209/aaqr.2015.09.0532
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Zhanshan Wang1,3, Dawei Zhang1,4, Xuan Li5, Yunting Li 1, Tian Chen2, Baoxian Liu1, Lingjun Li1, Teng Nie5, Libo Pan3

  • 1 Beijing Municipal Environmental Monitoring Center, Beijing 100048, China
  • 2 Beijing Municipal Environmental Protection Bureau, Beijing 100044, China
  • 3 State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
  • 4 Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China
  • 5 National Engineering Research Center for Urban Environmental Pollution Control, Beijing Municipal Research Institute of Environmental Protection, Beijing 100037, China

Highlights

Meteorological conditions: calm wind, high relative humidity and low surface pressure.
Regional transport played a critical role in this PM2.5 pollution episode.
Reducing the concentration of O3 was a synergistic control of PM2.5.


Abstract

Multi-method observation and numerical simulation were applied to analyze a PM2.5 pollution episode in Beijing in October, 2014. The results of vertical observation showed that surface-level backscatter signal and extinction coefficient increased during the episode, suggesting that air pollutants accumulated near the ground. The main meteorological factors during this episode could be described as calm wind, high relative humidity and low surface pressure. The evolution of PM2.5 concentrations in this episode was divided into four stages, including two-steps type concentration climbing stages (P1 and P2), high concentration maintenance stage (P3) and rapid cleanup stage (P4). Analysis on ground-based observation, satellite remote sensing and atmospheric general circulation showed that regional transport, including crop residue burning, was the main incentive of this pollution episode. Subsequently, local pollutants emission and regional transport maintained and aggravated the episode under unfavorable meteorological conditions. Temporal variation of OX was in close agreement with that of PM2.5 and the concentration peaks of OX occurred few hours before those of PM2.5, which indicated that strong atmospheric oxidation could promote the formation of secondary PM2.5. The results of numerical simulation showed that during 8–10 October, the average contribution of regional transport to PM2.5 in the five sites exceeded 50%.

Keywords

Beijing PM2.5 Chemical compositions Numerical simulation Regional transport Crop residue burning


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