Abstract
Abstract. We explore the impacts of short-term emission controls on haze events in Beijing in October–November 2014 using high-resolution Weather Research and Forecasting model with Chemistry (WRF-Chem) simulations. The model reproduces surface temperature and relative humidity profiles over the period well and captures the observed variations in key atmospheric pollutants. We highlight the sensitivity of simulated pollutant levels to meteorological variables and model resolution and in particular to treatment of turbulent mixing in the planetary boundary layer. We note that simulating particle composition in the region remains a challenge, and we overpredict NH4 and NO3 at the expense of SO4. We find that the emission controls implemented for the Asia-Pacific Economic Cooperation (APEC) summit period made a relatively small contribution to improved air quality (20 %–26 %), highlighting the important role played by favourable meteorological conditions over this period. We demonstrate that the same controls applied under less favourable meteorological conditions would have been insufficient in reducing pollutant levels to meet the required standards. Continued application of these controls over the 6-week period considered would only have reduced the number of haze days when daily mean fine particulate matter exceeds 75 µg m−3 from 15 to 13 d (days). Our study highlights the limitations of current emission controls and the need for more stringent measures over a wider region during meteorologically stagnant weather.
Highlights
Air pollution poses serious health risks to urban residents and is one of the most important environmental problems facing cities around the world (Liang et al, 2017)
In this study we investigate the effectiveness of shortterm emission controls and how meteorological processes influence this, using the Asia-Pacific Economic Cooperation (APEC) period as an example
These include measurements of NH4, NO3, SO4, and organic carbon (OC) from an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) instrument at 260 m altitude (Sun et al, 2016b) and from a high-resolution aerosol mass spectrometer (HR-AMS) instrument at the surface (Xu et al, 2015), and black carbon (BC) at the surface was measured with an aethalometer
Summary
Air pollution poses serious health risks to urban residents and is one of the most important environmental problems facing cities around the world (Liang et al, 2017). Li et al, 2017; Zhou et al, 2017) and atmospheric chemical transport models (Zhang et al, 2016; Guo et al, 2016; Wang et al, 2017; Gao et al, 2017) and found that PM2.5 concentrations were much lower than during the preceding weeks. Many of these studies attributed this improved air quality largely to the emission controls that were applied without thoroughly evaluating the role of meteorological variations.
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