Effects of the emergency control measures in Beijing on air quality improvement

Özet

Emergency air pollution control measures were successfully implemented in Beijing many times, such as duringthe Asia-Pacific Economic Cooperation (APEC) conference in 2014 and the Red Alert (RA) in 2015. Given that airquality was largely affected by wind speed, the efficiency of control measures and wind speed must be quantifiedto adjust the control measures under different wind speeds. During APEC and RA, source apportionment oforganic carbon (OC) was conducted using chemical mass balance receptor model (CMB) with organic tracers toreveal $PM_{2.5}$ source reductions caused by control measures. In the APEC control period, mobile sources contribution to organic carbon (OC) and dust contribution to $PM_{2.5}$ decreased from 3.7 μg/$m^3$ (63.7%) to 3.3 μg/$m^3$(38.8%) and from 5.1 μg/$m^3$ (16.6%) to 3.8 μg/$m^3$ (6.9%), respectively. For the RA day, coal combustion sourcecontribution to OC decreased from 11.3 μg/$m^3$(53.2%) to 2.3 μg/$m^3$ (6.2%), while mobile sources contributionchanged from 8.9 μg/$m^3$ (41.7%) to 14.7 μg/$m^3$ (40.3%). These data suggest that the vehicle restriction rule wasnot truly implemented. Control measures should be announced in advance to achieve the expected result. Inaddition, the effectiveness of control measures would decrease with the increase of wind speed, and the criticalwind speeds for sustaining an excellent $PM_{2.5}$ level (35 μg/$m^3$) and daily $PM_{2.5}$ concentration standard of China(75 μg/$m^3$) were determined by a power function as 11 km/h and 7 km/h, respectively. So wind speed should beconsidered before the selection of anthropogenic control measures.