Abstract
Abstract. In this study, 121 daily PM2.5 (aerosol particle with aerodynamic diameter less than 2.5 μm) samples were collected from an urban site in Beijing in four months between April 2009 and January 2010 representing the four seasons. The samples were determined for various compositions, including elements, ions, and organic/elemental carbon. Various approaches, such as chemical mass balance, positive matrix factorization (PMF), trajectory clustering, and potential source contribution function (PSCF), were employed for characterizing aerosol speciation, identifying likely sources, and apportioning contributions from each likely source. Our results have shown distinctive seasonality for various aerosol speciations associated with PM2.5 in Beijing. Soil dust waxes in the spring and wanes in the summer. Regarding the secondary aerosol components, inorganic and organic species may behave in different manners. The former preferentially forms in the hot and humid summer via photochemical reactions, although their precursor gases, such as SO2 and NOx, are emitted much more in winter. The latter seems to favorably form in the cold and dry winter. Synoptic meteorological and climate conditions can overwhelm the emission pattern in the formation of secondary aerosols. The PMF model identified six main sources: soil dust, coal combustion, biomass burning, traffic and waste incineration emission, industrial pollution, and secondary inorganic aerosol. Each of these sources has an annual mean contribution of 16, 14, 13, 3, 28, and 26%, respectively, to PM2.5. However, the relative contributions of these identified sources significantly vary with changing seasons. The results of trajectory clustering and the PSCF method demonstrated that regional sources could be crucial contributors to PM pollution in Beijing. In conclusion, we have unraveled some complex aspects of the pollution sources and formation processes of PM2.5 in Beijing. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterizations and source apportionments of PM2.5 aerosol speciation in Beijing by applying multiple approaches based on a completely seasonal perspective.
Highlights
Particulate matter (PM) is composed of various chemical components (Seinfeld, 1989).SPMolipdrofEouanrdtlyhaffects our living environments in terms of air quality, visibility, direct and indirect radiative forcing, Published by Copernicus Publications on behalf of the European Geosciences Union
We identified and apportioned the main sources to PM2.5 by employing chemical mass closure construction and the positive matrix factorization (PMF) model in conjunction with trajectory cluster and potential source contribution function analyses according to the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model
By utilizing the PMF model with the obtained full data set as input data, we identified six main sources: mineral dust, biomass burning, coal combustion, traffic emissions plus waste incineration, industrial pollution, and secondary inorganic aerosol
Summary
Particulate matter (PM) is composed of various chemical components (Seinfeld, 1989).SPMolipdrofEouanrdtlyhaffects our living environments in terms of air quality (in close relation to public health), visibility, direct and indirect radiative forcing, Published by Copernicus Publications on behalf of the European Geosciences Union. R. Zhang et al.: Chemical characterization and source apportionment of PM2.5 in Beijing climate effects and ecosystems (Watson, 2003; Streets et al, 2006; Andreae and Rosenfeld, 2008; Mahowald, 2011). The diverse effects of PM2.5 could be a function of its complex chemical components and composition (He et al, 2009; Niwa et al, 2007; Malm et al, 2005; Eatough et al, 2006)
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