Publication Date:
2017-09-12
Description:
An intensive measurement campaign was conducted in Beijing during the Asia-Pacific Economic Cooperation (APEC) Summit 2014 to investigate the effectiveness of stringent emission controls on aerosol optical properties and direct radiative forcing (DRF). Average values of PM 2.5 , light scattering ( b scat ), and light absorption ( b abs ) coefficients decreased by 40, 64, and 56%, respectively, during the APEC-control period compared with non-control periods. For the APEC-control period, the PM 2.5 mass scattering and absorption efficiencies were both smaller than the non-control period by a factor of ~2. Calculations based on a revised IMPROVE method and linear regression showed that sulfate, nitrate, organic matter, elemental carbon, and fine soil contributed comparably to the light extinction coefficient ( b ext ) in both periods, but the b ext values were 27–64% lower during the APEC period. A positive matrix factorization receptor model showed that b ext from two secondary aerosol sources, biomass burning, traffic-related emissions, and coal burning decreased by 26–87% during the APEC-control period. The average DRF calculated from the Tropospheric Ultraviolet and Visible radiation model was -11.9 and -4.6 W m -2 at the surface during the non- and APEC-control periods, respectively, suggesting an overall cooling effect. The reduction of DRF from each emission source ranged from~30–80% during the APEC-control period. The results suggest that the pollution control measures implemented for APEC substantially reduced air pollution and could help mitigate the cooling effects of aerosols at the surface in Beijing.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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