Chemical composition, impact from biomass burning, and mass closure for PM(2.5) and PM(10) aerosols at Hyytiala, Finland, in summer 2007

A comprehensive chemical aerosol characterisation was carried out at the forested site of Hyytiala, Finland, from 2 to 30 August 2007. PM(2.5) and PM(10) Nuclepore polycarbonate and quartz fibre filter samples were taken in parallel, typically for separate day-time and night-time periods. All samples were analysed for the particulate mass by weighing. The Nuclepore filters were analysed for over 20 elements by particle-induced X-ray emission (PIXE) spectrometry and for major anions and cations by ion chromatography. The quartz fibre filters were analysed for organic and elemental carbon by a thermal-optical transmission technique. A number of samples exhibited high K, Zn, and oxalate levels, indicating an impact from biomass burning. A noteworthy episode occurred on 12-13 August, when air masses were advected from the southern part of European Russia where extensive biomass burning had occurred. In the aerosol chemical mass closure calculations, eight aerosol types were considered. Organic matter (OM) contributed by far the most to the PM(2.5) and PM(10) mass; it accounted for about 70% of the average PM(2.5) and PM(10) mass and 48% of the coarse (PM(10-2.5)) aerosol. Crustal matter, deduced from the PIXE data, provided a rather small contribution; only 3% in PM(2.5), 13% in PM(10), and 32% in the coarse aerosol. The mean PM(2.5) and PM(10) mass concentrations and their attribution to the eight aerosol types for the 2007 campaign at Hyytiala were similar to those for the cold period of a 2006 summer campaign at the forested site of K-puszta, Hungary. OM was more important and nitrate was clearly less important at Hyytiala, though.