Influence of pollution control on air pollutants and the mixing state of aerosol particles during the 2nd World Internet Conference in Jiaxing, China

摘要

Strict pollution-control measures were implemented in Jiaxing and surrounding regions in China during the 2015 2nd World Internet Conference (WIC) to ensure good air quality. To investigate the variations of air pollutants and the sources and mixing state of size-resolved aerosols in response to the emission controls, trace gases (O-3, SO2, NO2, and CO), particulate matter (PM2.5 and PM10), and single particle aerosols were measured in Jiaxing, China during December 11-25, 2015. During the WIC (from 00: 00 on Dec. 16 to 16: 00 on Dec. 18, 2015), the average concentrations of PM2.5, PM10, NO2, and CO in Jiaxing were 38.7, 75.0, and 43.5 mu g m(-3) and 0.7 mg m(-3) and were decreased by 62.1%, 47.1%, 31.2%, and 41.7% and 60.0%, 45.7%, 34.7%, and 41.7% compared to before and after the WIC, respectively. These changes were caused mainly by strict measurement of traffic restrictions and industrial emission reductions. By using the single particle aerosol mass spectrometer (SPAMS), 8,350,772 particles with aerodynamic diameters ranging from 0.2 to 2.0 mm were identified. Of these particles, 877,397 were successfully ionized. The aerosol particles collected for SPAMS data analysis employed 96.0% of the hit particles to recognize 5 major particle classes: K-rich particles (K-CN, K-Secondary, and K-mixed Elemental Carbon (K-EC)), sodium particles, carbon-rich particles (EC-Nitrate, EC-Secondary, and Organics and Elemental Carbon (OCEC)), ammonium particles, and heavy-metal particles (Fe-Secondary, Pb, and Cu-V). Signals from 23 [Na] (+) were uniformly observed among these 11 types of particles, which may have been affected by sea salt particles in the coastal city of Jiaxing. During the WIC, the proportions of K-EC (4.5%), EC-Secondary (2.0%), Fe-Secondary (1.9%), EC-Nitrate (0.5%), and Ammonium (0.7%) decreased, the proportions of K-CN (15.2%), OCEC (27.5%), and Cu-V (16.8%) increased significantly, and the proportions of K-Secondary (17.2%), sodium (11.6%), and Pb (2.0%) changed slightly. During the WIC, the peaks representing different particle classes shifted to fine particle segments at 0.5-0.6 mu m, and the peak width was relatively narrowed compared to before and after the WIC. The reduction of air pollutant emissions significantly influenced the K-CN, OCEC, Cu-V, EC-Secondary, Fe-Secondary, and K-EC particles with sizes of 0.4-1.4 mu m. The information obtained on variations of air pollutants, the mixing state, and the temporal variation of particle types is essential for developing an understanding of air quality assurance control for subsequent WICs and of the origin and evolution processes of atmospheric aerosols. (C) 2017 Elsevier Ltd. All rights reserved.