Emission characteristics of 99 NMVOCs in different seasonal days and the relationship with air quality parameters in Beijing, China.

In recent years, the haze incidents have occurred frequently in China. Therefore, more attention should be taken in comprehensively determination and analysis of the extended-ranges of volatile organic compounds (VOCs). Here, up to 99 non-methane VOCs (NMVOCs), including not frequently reported partial halocarbons and oxygenated VOC (OVOC) species, were monitored in atmosphere of Beijing. The mean concentration of total NMVOC (TNMVOC) decreased in the order of winter polluted days (216.05 μg m-3) > summer polluted days (127.01 μg m-3) > summer normal days (95.63 μg m-3) > winter normal days (50.25 μg m-3). The ethane to n-butane, ethylene to 1-butene, BTEX, acetaldehyde, acetone, n-hexanal, dichloromethane, chloroform and 1,2-dichloroethane, were determined to be the main composition in their respective alkane, alkene, aromatic, OVOC and halocarbon classes. The minor propylbenzene, diethylbenzene, ethyltoluene, and trimethylbenzene isomer ratios were within the narrow range of 1.3-3.21. Generally, the most abundant NMVOCs were alkanes in winter but OVOCs in summer. TNMVOC significantly positively correlated with PM10, PM2.5, CO, RH, SO2 (winter), NO2 (winter), but negatively with windspeed, SSD and PRS (winter). The opposite correlation was observed between TNMVOC and O3 in winter and summer. There was no meaningful correlation between TNMVOC and T, PRS (summer), SO2 (summer) and NO2 (summer). 3D surface graphs, built by MATLAB, were drawn to investigate the relationship between PM2.5 and NMVOC taking air quality parameters into account. The PM2.5 concentration increased non-linearly as TNMVOC concentration increased, with various surface graphs. Unlike other air quality parameters, O3 affected the relationship differently between winter and summer. The findings presented herein may provide a new train of thought for occurrence of haze.