Using levoglucosan as a molecular marker for the long-range transport of biomass combustion aerosols

Samples of ambient particulate matter (PM10) collected during a regional haze episode are analyzed for the molecular marker levoglucosan (1,6-anhydro-β-D-glucopyranose) to track biomass-combustion generated aerosol. The particle samples were collected as part of an increased monitoring effort to measure the effect of emissions from biomass fires in Mexico and Central America on ambient particle concentrations in Texas. Atmospheric concentrations of levoglucosan quantified from PM10 samples collected at 9 sites in Texas vary from 0.2 to 1.2 μg m^-3. Levoglucosan concentrations are highest at border and coastal locations, where it represents between 1.1 and 1.3% of the total PM10 mass concentrations measured. To be used as a tracer for the long-range transport of biomass aerosol, levoglucosan must be conserved in transport from source to receptor and not be subject to atmospheric reactions that would selectively remove the marker. One possible reaction specific to levoglucosan, acid-catalyzed hydrolysis, is studied under conditions simulating the aqueous chemistry of atmospheric droplets. Results show no degradation of levoglucosan over a period of 10 days. This stability is incorporated into the long-range transport analysis of biomass combustion during the haze episode to determine the relative impact of long-range transport of combustion aerosol and local sources on PM1O levels on inland locations.