Abstract
PM2.5, PM2.5-10, and PM10 samples were collected in Zhengzhou in 2014 to examine the chemical characteristics and sources of aerosols in this area. The PM concentrations, nine water soluble inorganic ions, organic carbon, elemental carbon, and twenty-two elements were determined, and positive matrix factorization (PMF) and chemical mass balance (CMB) were used for source apportionments. The meteorological impact was also evaluated by back-trajectory cluster analysis. Severe PM pollution was present in the study area, and the aerosol concentrations of PM2.5 samples (92%) and PM10 samples (85%) significantly exceeded the recommended levels of the Chinese National Ambient Air Quality Standard (NAAQS), with the average annual mass concentrations of PM2.5 and PM10 reaching 187 and 281 µg m–3, respectively. Secondary inorganic aerosols were the major ions in PM and accounted for 36%, 10%, and 27% of PM2.5, PM2.5-10, and PM10, respectively. The annual concentration of As (0.029 µg m–3) and Cd (0.010 µg m–3) in PM10 also exceeded the Chinese NAAQS levels, indicating a high health risk. Results from source apportionment by PMF modelling indicated that dust, vehicular traffic, coal combustion, secondary aerosols, and industry were the main pollution sources, accounting for 13.1%, 14.1%, 16.1%, 35.8%, and 14.6% of PM2.5; 25.1%, 20.8%, 21.8%, 10.5%, and 11.6% of PM2.5-10; and 19.8%, 15.8%, 18.5%, 22.5%, and 13.5% of PM10, respectively. Dust sources played an important role in PM pollution, especially coarse particles; however, secondary aerosol sources contributed the most to PM2.5. Both of these observations were consistent with the results of mass reconstruction of the size-segregated aerosols. The CMB results coincided with the PMF results for PM2.5. Cluster analysis showed that air quality in the study area across the four seasons was mainly affected by air masses from the northeast and the east.
Highlights
Through transport and dispersion, air pollution influences climate and weather patterns at relatively large spatial scales (100–1000 km) (Hadley, 2017)
NO2 and SO2 concentrations varied from 29 μg m–3 to 108 μg m–3 and from 17 μg m–3 to 244 μg m–3, with approximately 29% and 8% of sampling days exceeding the Chinese National Ambient Air Quality Standard (NAAQS)
This study investigated the major precursors, mass levels, chemical compositions, and source apportionments of sizesegregated aerosols, i.e., PM2.5, PM2.5-10, and PM10, in Zhengzhou, an emerging megacity of east-central China
Summary
Air pollution influences climate and weather patterns at relatively large spatial scales (100–1000 km) (Hadley, 2017). PM pollution has become a common environmental problem in megacities worldwide and is attracting considerable attention in different research fields (Chen et al, 2003; Kang et al, 2004; Sun et al, 2006; Zhang et al, 2013a) This pollution type is closely related to particle constituents and meteorological conditions, and holds important implications for human health, visibility, economy, weather, and the global climate (Charlson et al, 1992; Chameides et al, 1999; Ramanathan et al, 2001). Studying the chemical compositions of PM is important in assessing the effects of PM on air quality and human health and for conducting source apportionment (Tao et al, 2013). Positive matrix factorization (PMF) and chemical mass balance (CMB), are advanced source apportionment methods for successfully assessing particle source contributions and have been applied in numerous locations worldwide
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