Levoglucosan levels at background sites in Europe for assessing the impact of biomass combustion on the European aerosol background

Atmospheric levoglucosan has been determined as a proxy for “biomass smoke” in samples from six background stations on a west–east transect extending from the Atlantic (Azores) to the mid‐European background site KPZ (K‐Puszta, Hungary). Concentration levels of levoglucosan (biannual averages) in the west–east transect range from 0.005 μ g/m 3 at the oceanic background site AZO (Azores) to 0.52 μ g/m 3 at AVE (Aveiro, Portugal). The atmospheric concentration of “biomass smoke” (biannual averages) was derived from the levoglucosan data with wood‐type‐specific conversion factors. Annual averages of wood smoke levels ranged from 0.05 μ g/m 3 at AZO to 4.3 μ g/m 3 at AVE. Winter (DJF) averages at the low‐level sites AVE and KPZ were 10.8 and 6.7 μ g/m 3 , respectively. Relative contributions of biomass smoke to organic matter (OM) range from around 9–11% at the elevated sites SIL, PDD and SBO, as well as for AZO, to 36% at the low‐level site AVE and 28% at KPZ. Surprisingly high relative concentrations of biomass smoke in OM (68 and 47%) were observed for wintry conditions at the continental low‐level CARBOSOL sites AVE and KPZ. Thus biomass smoke is a very important constituent of the organic material in the mid and west European background with summer contributions to organic matter of around 1–6% and winter levels of around 20% at the elevated mountain sites and 47–68% at rural flat terrain sites, not including secondary organic aerosol from biomass combustion sources.