• plant debris;
  • vegetative detritus;
  • bioaerosol

[1] Atmospheric “free cellulose” has been determined as a proxy for “plant debris” 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 cellulose (biannual averages) range from 16.3 ng/m3 at the oceanic background site AZO (Azores) to 181 ng/m3 at KPZ (Hungary). Concentrations decrease with elevation, winter levels at the midtropospheric Sonnblick site (SBO, 3106 m) are comparable to clean Atlantic conditions. The atmospheric concentration of plant debris (biannual averages) was derived from the cellulose data and ranges from 33.4 ng/m3 at AZO to 363 ng/m3 at KPZ. Relative contributions of plant debris to organic matter (OM) range from around 2% at the semirural coastal site Aveiro (AVE) to 10% at SBO. Surprisingly high relative concentrations of plant debris in OM were observed for wintry conditions at the elevated sites. The relative fraction of plant debris in OM ranged as averages from 6.1% at Schauinsland, Germany (1205 m) to 10.1% at Puy de Dome, France (1405 m) and 22.4% at Sonnblick, Austria (3106 m). Thus plant debris is a very important constituent of the organic material at elevated background sites with summer concentrations of around 5% and winter levels from around 6–22% depending on elevation. Since cellulose is considered rather long-lived with respect to atmospheric oxidation processes, it may become enriched on the way to background regions, which may explain the elevated relative levels at elevated sites.