Characterization of submicron particles during autumn in Beijing, China

Peng Xu , Junke Zhang , Dongsheng Ji , Zirui Liu , Guiqian Tang , Changsheng Jiang , Yuesi Wang


Received October 29, 2016,Revised March 22, 2017, Accepted March 28, 2017, Available online April 08, 2017

Volume 30,2018,Pages 16-27

In this study, we performed a highly time-resolved chemical characterization of non-refractory submicron particles (NR-PM1) in Beijing by using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR–ToF–AMS). The results showed the average NR-PM1 mass concentration to be 56.4 ± 58.0 μg/m3, with a peak at 307.4 μg/m3. Due to the high frequency of biomass burning in autumn, submicron particles significantly increased in organic content, which accounted for 51% of NR-PM1 on average. Secondary inorganic aerosols (sulfate + nitrate + ammonium) accounted for 46% of NR-PM1, of which sulfate, nitrate, and ammonium contributed 15%, 20%, and 11%, respectively. To determine the intrinsic relationships between the organic and inorganic species, we used the positive matrix factorization (PMF) model to merge the high-resolution mass spectra of the organic species and NO+ and NO+2 ions. The PMF analysis separated the mixed organic and nitrate (NO+ and NO+2) spectra into four organic factors, including hydrocarbon-like organic aerosol (HOA), oxygenated organic aerosol (OOA), cooking organic aerosol (COA), and biomass burning organic aerosol (BBOA), as well as one nitrate inorganic aerosol (NIA) factor. COA (33%) and OOA (30%) contributed the most to the total organic aerosol (OA) mass, followed by BBOA (20%) and HOA (17%). We successfully quantified the mass concentrations of the organic and inorganic nitrates by the NO+ and NO+2 ions signal in the organic and NIA factors. The organic nitrate mass varied from 0.01–6.8 μg/m3, with an average of 1.0 ± 1.1 μg/m3, and organic nitrate components accounted for 10% of the total nitrate mass in this observation.

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