Comparative analysis of organic and elemental carbon concentrations in carbonaceous aerosols in three European cities

Sampling and analysis of carbonaceous compounds in particulate matter presents a number of difficulties related to artefacts during sampling and to the distinction between organic (OC) and elemental carbon (EC) during analysis. Our study reports on a comparative analysis of OC, EC and WSOC (water-soluble organic carbon) concentrations, as well as sampling artefacts, for PM2.5 aerosol in three European cities (Amsterdam, Barcelona and Ghent) representing Southern and Western European urban environments. Comparability of results was ensured by using a single system for sample analysis from the different sites. OC and EC concentrations were higher in the vicinity of roads, thus having higher levels in Amsterdam (3.9–6.7 and 1.7–1.9 μg m−3, respectively) and Barcelona (3.6–6.9 and 1.5–2.6 μg m−3) than in Ghent (2.7–5.4 and 0.8–1.2 μg m−3). A relatively larger influence of secondary organic aerosols (SOA), as deduced from a larger OC/EC ratio, was observed in Ghent. In absolute sense, WSOC concentrations were similar at the three sites (1.0–2.3 μg m−3). Positive artefacts were higher in Southern (11–16% of the OC concentration in Barcelona) than in Western Europe (5–12% in Amsterdam, 5–7% in Ghent). During special episodes, the contribution of carbonaceous aerosols from non-local sources accounted for 67–69% of the OC concentration in Western Europe, and for 44% in Southern Europe.