Variations in δ13C values of levoglucosan from low-temperature burning of lignite and biomass

Abstract

Levoglucosan, an anhydrosaccharide, is commonly used as an organic tracer for biomass burning, but has also been identified from coal smoke particulate matter (PM) including lignites. Here we showed that stable carbon isotope analysis specifically of levoglucosan may be one possible way to determine the relative contributions from coal combustion versus biomass burning sources. PM sampleswere collected from low-temperature burning/ smoldering of Miocene lignites from Poland and basket willow (Salix viminalis L.) representative of biomass. The calculated levoglucosan δ13C values of xylites varied from −23.6 to−21.6‰, while for detritic coal samples they ranged from −24.2 to −23.1‰, with means of −22.7 and −23.7‰, respectively. The calculated levoglucosan δ13C value of basketwillow woodwas−27.1‰. Values ofwillowwoodmixtureswith xylite varied from−25.8 to−23.4‰(with an increasing proportion of xylite), while values of mixtures of willow and detritic coal ranged from−26.9 to−24.6‰(with an increasing proportion of detritic coal). The δ13C values for themixtures changed proportionally to the contents of individual components with R2=0.88 and 0.89 for willow with xylite and detritic coal, respectively. The hopanoid distributions characteristic for low-temperature lignite/peat burning, with a predominance of 22R-α,β-homohopane, ββ-hopanes and hopenes, as well as low or very low values of the homohopane index,were observed in smokePMfrommost lignite samples and absent in the basket willow sample. Thus, the relatively high content of hopanes (with the occurrence of 22R-α,β-homohopane, ββ- hopanes and hopenes) in atmospheric PM samples can be treated as additional tracers of lignite combustion.