Abstract
Analysis of chemical composition characteristics of PM2.5 under different pollution degrees can reveal the changes of pollution sources. In order to make clear the evolution process of PM2.5 compositions in autumn and winter, PM2.5 samples were continuously collected and analyzed at Liaocheng city, China. The collected samples were classified as clean days (CLD), mild-moderate pollution days (MMD) and severe-serious pollution days (SSD). It was concluded that with the increase of pollution degrees, the concentrations of water-soluble ions and carbon components increased significantly, while elements only increased slightly. In addition, as the pollution degrees increased, the percentage of NO3−, SO42− and NH4+ increased significantly, from 23.0% in CLD to 49.0% in SSD, while the percentage of other components decreased, especially crust material. The PMF analyzed results showed that secondary transformation (36.7%), combustion sources (20.4%), secondary organic aerosols (SOA) (11.7%), vehicle sources (11%), dust (10.5%) and industrial processes (9.7%) were the main sources of PM2.5 during autumn and winter in Liaocheng. The contribution of secondary transformation reached 57% at the SSD level, which indicated that it was the main reason for the increase of PM2.5 concentrations. The air mass mainly came from five paths to Liaocheng. The secondary transformation contribution of the air mass with short transmission distance was higher, while the contribution of the dust was higher from the long distance.
Highlights
In recent years, China has experienced rapid economic developments along with serious air pollution problems, especially extreme haze episodes
∑ Xij = gik × fkj+eij j=1 where Xij is matrix X of i by j dimensions, i is the number of samples and j is the number of chemical species, p is the number of factors, f is the species profile of each source, g is the amount of mass contributed by each factor to each individual sample, and eij is the residual for each sample/species
The 24 h backward trajectories of air mass during the pollution processes were investigated by the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model developed by the National Oceanic and Atmosphere Administration (NOAA), and the ARL archives of the NOAA were used as the meteorological input data in this study
Summary
China has experienced rapid economic developments along with serious air pollution problems, especially extreme haze episodes. The PMF model was selected in this paper to analyze the sources of PM2.5 in Liaocheng. Liaocheng is located at the northwest inland area of Shandong Province, and it is one of the important transport channels of air pollution in the “2 + 26” cities area. The air pollution problem of Liaocheng has been widely concerned because of its low ranking in the Shandong province. The research of PM2.5 in Liaocheng mainly focuses on the analysis of the characteristics of chemical components and sources [17,18,19], but there was no report on the characteristics and source apportionment of PM2.5 under different pollution degrees, as well as research in the whole autumn and winter period. This study analyzed the characteristics and sources of PM2.5 under different pollution degrees in the autumn and winter of Liaocheng in order to provide data support and scientific support for air pollution control in Liaocheng
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