Abstract
The characteristics of biogenic aerosols in an urban area were explored by determining the composition and temporal distribution of saccharides in PM2.5 in Shanghai. The total saccharides showed a wide range of 9.4 ng/m3 to 1652.9 ng/m3, with the averaged concentrations of 133.1 ng/m3, 267.5 ng/m3, 265.1 ng/m3, and 674.4 ng/m3 in spring, summer, autumn, and winter, respectively. The saccharides include anhydrosaccharides (levoglucosan and mannosan), which were higher in cold seasons due to the increased biomass burning; saccharide alcohols (mannitol, arabitol, sorbitol); and monosaccharides (fructose, glucose), which were more abundant in warm seasons and attributed to the biological emissions. Through positive matrix factorization (PMF) analysis, four emission sources of saccharides were resolved, including biomass burning, fungal spores, plant decomposition, and pollen. Moreover, the process analysis of high concentrations of leveglucosan was conducted by backward trajectory and fire points. We found that concentrations of anhydrosaccharides were relatively stable under different pollution levels, while saccharide alcohols exhibited an obvious decrease with the concentration of PM2.5, indicating that biomass burning was not the core reason for heavy haze pollution. However, high level PM2.5 pollution might inhibit the effects of biological activities.
Highlights
Organic aerosols are important parts of fine atmospheric particulate matter, which account for about 20–60% of the PM2.5 mass in urban sites, 30–50% in remote areas, and even up to 90% in the low troposphere [1]
Seven saccharides were detected during the sampling period, including two species of anhydrosaccharides, two species of monosaccharides, and three species of saccharide alcohols
Four factors of biomass burning, fungal spores, plant decomposition, and airborne pollens were obtained through positive matrix factorization (PMF) analysis, with contributions of 46%, 22%, 22%, and 10% of the atmospheric saccharides in Shanghai
Summary
Organic aerosols are important parts of fine atmospheric particulate matter, which account for about 20–60% of the PM2.5 mass in urban sites, 30–50% in remote areas, and even up to 90% in the low troposphere [1]. Saccharides are important substances of WSOC in aerosols, which account for 13–26% of the mass of continental aerosols, and 63% of the mass of marine aerosols [6]. Atmospheric saccharides mainly contain three species: Anhydrosaccharides, primary saccharides (monosaccharides and disaccharides), and saccharide alcohols. Anhydrosaccharides mainly include levoglucosan, mannosan, and galactosan, which originate from primary emissions during the process of biomass burning, and levoglucosan has been widely used as an effective tracer for biomass burning emissions [7]
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