Particulate carbon in precipitation at European background sites

Abstract

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 midAtlanticOcean,totheHungarianplain,incentralEurope.Samplingwasperformedonanevent basis and the particulate carbon (elemental carbon, EC, and water insoluble organic carbon, WIOC)contentwasconcentratedonquartzfiltersforthesubsequentanalysisbyathermalopticalmethodinordertoseparatetheECandWIOCfractions.TheaverageECconcentrationsrange from low values at the Azores (2.8±4.3 gCL−1) and at the high mountain site of Sonnblick (5.2±3.7 gCL−1) to high values at the more inland sites of Schauinsland (28±38 gCL−1) andK-Puszta(24±24 gCL−1).TheaverageWIOCconcentrationsrangefrom98±56 gCL−1 at the coastal site of Aveiro and 113±78 gCL−1 at the Azores to 358±194 gCL−1 at the continentalsiteofK-Puszta.Theseresultsarediscussedintermsoffactorsaffectingthespatial 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,wheretheECcontributiontototalparticulatecarbonis < 6.5%,consistentwithanegligible impact of anthropogenic combustions locally. The EC and WIOC scavenging ratios were estimated and compared with those of sulfate, also evaluated at the same sampling sites. The results indicated that EC is removed from the atmosphere by wet deposition less efficiently than WIOC, and in turn this species is removed less efficiently than sulfate.