Particulate carbon in precipitation at European background sites

The particulate carbon content of precipitation was investigated in samples collected at five background sites located over a west-east European transect, from the Azores, in the mid-Atlantic Ocean, to the Hungarian plain, in central Europe. Sampling was performed on an event basis and the particulate carbon (elemental carbon, EC, and water insoluble organic carbon, WIOC) content was concentrated on quartz filters for the subsequent analysis by a thermal optical method in order to separate the EC and WIOC fractions. The average EC concentrations range from low values at the Azores (2.8±4.3 μg C L−1) and at the high mountain site of Sonnblick (5.2±3.7 μg C L−1) to high values at the more inland sites of Schauinsland (28±38 μg C L−1) and K-Puszta (24±24 μg C L−1). The average WIOC concentrations range from 98±56 μg C L−1 at the coastal site of Aveiro and 113±78 μg C L−1 at the Azores to 358±194 μg C L−1 at the continental site of K-Puszta. These results are discussed in terms of factors affecting the spatial distribution of particulate carbon, such as emissions from surrounding areas and prevalent meteorological conditions. EC is found to be a minor contributor to total particulate carbon present in rain and snow samples (from 2.5% to 15%). This is particularly true at the remotes sites, where the EC contribution to total particulate carbon is