Seasonal features and origins of carbonaceous aerosols at Syowa Station, Antarctica

Abstract. We measured equivalent black carbon (EBC) concentrations at Syowa Station, Antarctica from February 2005 to characterize seasonal features of EBC concentrations and their origins, and to monitor long-range transport of aerosols from mid-latitudes to the Antarctic coast. Results show that EBC concentrations were below the detection limit (0.2 ng m −3 ) to 63.8 ng m −3 at Syowa Station (median, 1.8 ng m −3 ; mean, 2.7 ng m −3 during the measurement period). Although seasonal features and year-to-year variations of EBC concentrations were observed, no long-term trend of EBC concentrations was clear during our measurement period. Seasonal features of EBC concentrations showed a spring maximum during September–October at Syowa Station. The absorption Angstrom exponent (AAE) was 0.5–1.0 during April–October; it reached its maximum values (1.0–1.5) during summer. The AAE features imply that EBC was mixed internally in the Antarctic troposphere and that organic aerosols engendered high AAE in the summer. To elucidate EBC transport processes, origins, and the potential source area (PSA), we compared EBC data to backward trajectory analysis and model simulation. Results show that EBC might be transported directly to Syowa Station from mid-latitudes mainly via the boundary layer and the lower free troposphere. Some BC was transported to Antarctic regions via the upper free troposphere. Biomass burning in South America and southern Africa is the most dominant PSA for BC transported to Syowa Station. Fossil fuel combustion in South America and southern Africa also have important contributions.