Black carbon aerosol at the background site in the coastal zone of the Baltic Sea

Abstract

Carbon particulate matter constitutes an important portion of the atmospheric aerosol and directly participates in the formation of the Earth’s radiation balance by influencing the global and regional climate. Continuous data (March, April, 2002) of 20-minute concentrations of airborne black carbon (BC) particles at the Preila Environmental Pollution Research Station (55^◦20′ N, 21^◦00′ E) have been used for the investigation of diurnal and weekday variation as well as the different air mass influence on BC transport. The measurement of BC mass concentration with the Aethalometer™, Model AE40 Spectrum, manufactured by Optotek, Slovenia was carried out. The origin of an air mass was detected by using air mass backward trajectories calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectories (HYSPLIT) model. Approximately 73% of BC measured concentrations were found in the range of a low value mode centered at ~0–1000 ng m^–3. The remaining concentrations were in a high-concentration mode at ~1000–3000 ng m^–3, probably indicating a direct impact of emissions from combustion activities. BC concentration in various air masses over that period varied from the average value of approximately 140 ng m^–3 to the maximum value of 2410 ng m^–3. The highest BC concentrations were associated with the prevailing southern transport air masses. Simultaneously, the daily concentration variation of black carbon and SO₂, NO₂, O₃ was measured and analysed. Total aerosol concentrations and size distributions were measured as well. The aerosol size distribution was plotted as contour plots for each day (as a function of time). Most studies were focused on the BC aerosol particle size distribution and modal aerosol concentration. For each event, the growth rate was calculated graphically from the contour plots (“banana–plots”) and was analysed for the possible nucleation events. Some aerosol measurements were carried out at an urban site in order to evaluate the BC concentration of the freshly emitted traffic aerosols.
Keywords: black carbon aerosol, mass concentration, size distribution, variations, air mass backward trajectories
PACS: 92.60.Mt, 92.10.Lq, 92.20.Bk