Abstract
Abstract. Biomass burning (BB) significantly influences the chemical composition of organic aerosols (OAs) in the East Asian outflow. The source apportionment of BB-derived OA is an influential factor for understanding their regional emissions, which is crucial for reducing uncertainties in their projected climate and health effects. We analyzed here three different classes of atmospheric sugar compounds (anhydrosugars, primary sugars, and sugar alcohols) and two types of biogenic secondary organic aerosol (BSOA) tracers (isoprene- and monoterpene-derived SOA products) from a year-long study that collected total suspended particulate matter (TSP) from an island-based receptor site in Gosan, South Korea. We investigate the seasonal variations in the source emissions of BB-derived OA using mass concentrations of anhydrosugars and radiocarbon (14C-) isotopic composition of organic carbon (OC) and elemental carbon (EC) in ambient aerosols. Levoglucosan (Lev) is the most abundant anhydrosugar, followed by galactosan (Gal), and mannosan (Man). Strong correlations of Lev with Gal and Man, along with their ratios (Lev/Gal is 6.65±2.26; Lev/Man is 15.1±6.76) indicate the contribution from hardwood burning emissions. The seasonal trends revealed that the BB impact is more pronounced in winter and fall, as evidenced by the high concentrations of anhydrosugars. Likewise, significant correlations among three primary sugars (i.e., glucose, fructose, and sucrose) emphasized the contribution of airborne pollen. The primary sugars showed higher concentrations in spring/summer than winter/fall. The fungal spore tracer compounds (i.e., arabitol, mannitol, and erythritol) correlated well with trehalose (i.e., a proxy for soil organic carbon), suggesting the origin from airborne fungal spores and soil microbes in the East Asian outflow. These sugar alcohols peaked in summer, followed by spring/fall and winter. Monoterpene-derived SOA tracers were most abundant compared to isoprene SOA tracers. Both BSOA tracers were dominant in summer, followed by fall, spring, and winter. The source apportionment based on multiple linear regressions and diagnostic mass ratios together revealed that BB emissions mostly contributed from hardwood and crop residue burning. We also found significant positive linear relationships of 14C-based nonfossil- and fossil-derived organic carbon fractions with Lev C, along with the comparable regression slopes, suggesting the importance of BB and coal combustion sources in the East Asian outflow.
Highlights
Organic aerosols (OAs), which account for a major fraction of up to 50 % of airborne total suspended particulate matter, have considerable effects on regional and global climate by absorbing or scattering sunlight (Kanakidou et al, 2005)
The 7 d isentropic backward air mass trajectories were computed using the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT, version 4; Stein et al, 2015) over the Korean Climate Observatory at Gosan (KCOG) for the sampling period using the meteorological datasets of the Global Data Assimilation System (GDAS) network
We investigated seasonal variations in primary organic components such as anhydrosugars, primary sugars, sugar alcohols, and biogenic secondary organic aerosol (BSOA) tracers in ambient aerosols from Gosan on Jeju Island
Summary
Organic aerosols (OAs), which account for a major fraction of up to 50 % of airborne total suspended particulate matter, have considerable effects on regional and global climate by absorbing or scattering sunlight (Kanakidou et al, 2005). Sugars are an important group of water soluble, primary organic compounds whose concentrations are significant in atmospheric aerosols over the continent (Jia and Fraser, 2011; Fu et al, 2008; Yttri et al, 2007; Graham et al, 2003). Anhydrosugars, such as levoglucosan, galactosan, and mannosan, are the key tracers of biomass burning (BB) emissions (Simoneit, 2002). Primary sugars and sugar alcohols are predominantly present in the coarse-mode aerosols, accounting for 0.5 %–10 % of atmospheric aerosol carbon matter (Yttri et al, 2007; Pio et al, 2008)
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