Background concentrations and source apportionment of polycyclic aromatic hydrocarbons in south-eastern Finland

Polycyclic aromatic hydrocarbons (PAH compounds) were measured in the PM10 fraction [from ambient air] at Virolahti, Finland. The sampling site is located in a rural area in the south-eastern corner of Finland, near the Russian border. Altogether, 51 daily and 85 weekly filter samples were collected in 2007–2008. The yearly average concentration of benzo(a)pyrene at Virolahti in 2007 was 0.21 ng m−3, which is well below the annual target value of 1 ng m−3 set by the European Union. The positive matrix factorization (PMF) method was applied in source apportionment for daily PAH data combined with other pollutant data. A three-factor solution of the PMF analysis with 28 components was chosen. These three factors were identified as long-range transported secondary particles (F1), combustion (F2) and a sea-salt factor (F3). The conditional probability function (CPF) was used to combine wind direction sectors with the PMF factors. In cases F1 and F2, pollutants mainly originated from the south-east, whereas pollutants in F3 came from the south-western sector. ntered into the combustion factor 2 together with SO2, NOx, black carbon and potassium. This suggests that the PAHs at Virolahti originated from traffic and industrial pollution, as well as biomass burning. Elevated concentrations occurred throughout the winter period and most frequently originated from the south-eastern sector between 90°–135°. This sector includes, among other transboundary areas, the metropolis of St. Petersburg at a distance of 160 km.