Biomass burning aerosols observed in Eastern Finland during the Russian wildfires in summer 2010 – Part 1: In-situ aerosol characterization

Biomass burning smoke and associated aerosol particles from wildfires near Moscow, Russia during summer 2010 had a significant impact on air quality both in the close vicinity of the burning area and to a lesser extent in other parts of Eastern Europe. Smoke was also observed in Eastern Finland, about 1000 km northwest of the fire area, in city of Kuopio, at Puijo tower atmospheric measurement station and at the city of Kuopio air quality monitoring sites. The origin of air masses was confirmed by remote sensing observations and trajectory analyses. Despite the distance between Kuopio and the fire area and a travel time of 1–2 days, exceptional physical and optical properties of aerosol particles were evident. During smoke events, aerosol particles twice as large (geometric mean diameter 158 nm) as in background conditions (geometric mean diameter 76.3 nm) were observed and they contained record-breaking amounts of black carbon, up to 1.23 μg m−3, which exceeds typical values by a factor of 12. Thus, absorption coefficient was significantly different when compared to background summer conditions (8.12 Mm−1 vs. 0.651 Mm−1). Also scattering coefficients experienced a remarkable increase, on average from 12.0 Mm−1, 7.2 Mm−1 and 4.2 Mm−1 to 245 Mm−1, 169 Mm−1 and 111 Mm−1 for blue, green and red light, respectively. The amount of particulate mass also experienced a multifold increase. Depending on the measurement site, PM2.5 grew from 3 to 6 μg m−3 to 34–48 μg m−3 and PM10 from 4 to 17 μg m−3 to 40–76 μg m−3. Trace gas concentrations were also affected by the smoke presence, especially carbon monoxide, which is commonly used as a tracer for biomass burning smoke. The concentration of nitric oxide, nitrogen dioxide, ozone and sulfur dioxide was affected only moderately and partly masked by the emissions from local pollutant sources.