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 mu g/m(3) at the oceanic background site AZO ( Azores) to 0.52 mu 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 mu g/m(3) at AZO to 4.3 mu g m(3) at AVE. Winter ( DJF) averages at the low- level sites AVE and KPZ were 10.8 and 6.7 mu 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.