Response of fine particulate matter to reductions in anthropogenic emissions in Beijing during the 2014 Asia-Pacific Economic Cooperation summit

The nested-grid capability of the global chemical transport model GEOS-Chem, with a horizontal resolution of 1/ 4 degrees x 5/ 16 degrees (latitude x longitude), was used to identify the chemical species whose reductions made the largest contributions to decreases in PM2.5 concentrations (fine particulate matter; diameter <= 2.5 mu m; defined in this study as the sum of sulfate, nitrate, ammonium, black carbon, and organic carbon aerosols) in Beijing during the 2014 Asia-Pacific Economic Cooperation (APEC) summit. A number of numerical experiments were carried out for the period 15 October-29 November 2014. The model reproduced the observed daily variations of concentrations of PM2.5 and gas-phase species (carbon monoxide, nitrogen dioxide, and sulfur dioxide). Simulated PM2.5 concentrations decreased by 55.9%-58.5% during the APEC period, compared to other periods in October and November 2014, which agreed closely with measurements. Sensitivity results showed that emissions control measures regarding nitrogen oxides and organic carbon over North China led to the largest reductions in PM2.5 concentrations in Beijing during the APEC summit, which led to overall reductions in the PM2.5 concentration of Beijing by 5.7% and 4.6%, respectively. The control of ammonia emissions was found to be able to greatly reduce PM2.5 concentrations in the whole of North China during the APEC meeting.