Biomass burning emissions contaminate winter snowfalls in urban Beijing: A case study in 2012

Three monosaccharide anhydrides levoglucosan, mannosan and galactosan were detected in winter snowfall samples of 2012 in urban Beijing. Concentrations of three isomers vary from 0.15 to 54.43 ng mL−1, with an average value of 10.49 ng mL−1. Levoglucosan is the most abundant component. Winter snowfalls are contaminated by biomass burning emissions seriously in urban Beijing. The main sources are softwood and crop residue burnings around Beijing from late autumn to early winter, while long-range transport of biomass burning emissions contribute more during the late winter. Concentrations of monosaccharide anhydrides in snowfall samples may be affected by both topography and the meteorological conditions around urban Beijing.