Abstract
Abstract. Based on source-specific saccharide tracers, the characteristics of biomass burning (BB) and biogenic emissions of saccharides were investigated in three rural sites at Lincang, which is 65 % covered with forest in the southwest border of China. The total saccharides accounted for 8.4 ± 2.7 % of organic carbon (OC) and 1.6 ± 0.6 % of PM2.5. The measured anhydrosugars accounted for 48.5 % of total saccharides, among which levoglucosan was the most dominant species. The high level of levoglucosan was both attributed to the local BB activities and biomass combustion smoke transported from the neighboring regions of Southeast Asia (Myanmar) and the northern Indian subcontinent. The measured mono- or disaccharides and sugar alcohols accounted for 24.9 ± 8.3 % and 26.6 ± 9.9 % of the total saccharides, respectively, and both proved to be mostly emitted by direct biogenic volatilization from plant material or surface soils rather than byproducts of polysaccharide breakdown during BB processes. Five sources of saccharides were resolved by non-negative matrix factorization (NMF) analysis, including BB, soil microbiota, plant senescence, airborne pollen, and plant detritus with contributions of 34.0 %, 16.0 %, 21.0 %, 23.7 %, and 5.3 %, respectively. The results provide information on the magnitude of levoglucosan and contributions of BB, as well as the characteristic of biogenic saccharides, at the remote sites of southwest China, which can be further applied to regional source apportionment models and global climate models.
Highlights
Biomass burning (BB) and biogenic aerosols are thought to play important roles in air quality, human health, and climate through direct or indirect effects (Jacobson et al, 2000; Christner et al, 2008; Pöschl et al, 2010; Després et al, 2012; Chen et al, 2017; Tang et al, 2019)
The total saccharides quantified in PM2.5 accounted for 8.4 ± 2.7 % of the organic carbon (OC) and accounted for 1.6 ± 0.6 % of the PM2.5
This implied that the levoglucosan at the observation site was attributed to both the local biomass burning (BB) activities and BB smoke transported from the neighboring regions of Southeast Asia (Myanmar) and the northern Indian subcontinent
Summary
Biomass burning (BB) and biogenic aerosols are thought to play important roles in air quality, human health, and climate through direct or indirect effects (Jacobson et al, 2000; Christner et al, 2008; Pöschl et al, 2010; Després et al, 2012; Chen et al, 2017; Tang et al, 2019). Saccharide compounds including a variety of primary saccharides (monosaccharides and disaccharides) and sugar alcohols (reduced sugars) have been measured to estimate the contribution of biogenic aerosols, including fungi, viruses, bacteria, pollen, and plant and animal debris (Simoneit et al, 2004; Jaenicke et al, 2007). The proportion of houses that use wood burning for cooking is very high in villages in the vicinity as well as in a large area of Southeast Asia, and forest fires frequently occur in this area, especially in the dry season (March–April) These facts imply that there are abundant biogenic aerosols in Lincang, and BB pollution may be an essential potential source of air pollution. BB tracers, including anhydrosugars and K+, as well as biogenic aerosol tracers (primary saccharides and sugar alcohols), were measured to gain the information on source and contributions of BB and biogenic emissions to PM2.5 over the rural Lincang.
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