Influence of Meteorological Factors and VOCs on PM2.5during Severe Air Pollution Period in Shijiazhuang in Winter

The object of this study was to investigate the chemical compositions of PM2.5 and its correlations with the concentration of volatile organic compounds(VOCs) and meteorological parameters during severe air pollution period in Shijiazhuang, a northern city, China in winter. PM2.5 samples were collected from November 26, 2015 to December 3, 2015. The results showed that the hourly average concentration of PM2.5was from 239.9μg/m 3 to 1062.8μg/m 3 .The correlation analysisshowed that PM2.5 had higher correlations with wind speed (r=−0.78) and relative humidity(r=0.79), and therewas an apparent correlation between PM2.5 and the concentrations of VOCs(r=0.88). Moreover, the major compositions of PM2.5comprises carbonaceous fractions, namely organic carbon(OC) and elementalcarbon(EC). During this period, (OC/EC) min was 2.12, by which calculating that the average concentration of secondaryorganic carbon (SOC)was 20 ug/m 3 , accounting for 50.5% of OC, indicating serious SOC pollution in Shijiazhuang. Since VOCsare the origin of SOC, it is further confirmed that VOCs are one of the main sources of PM2.5.