Particle-size distribution of PAH in the air of a remote Norway spruce forest in northern Bavaria

The aim of the present study was to elucidate the distribution of particula te polycyclic aromatic hydrocarbons (PAH) in the air of a remote Norway spr uce (Picea abies (L.) karst.) stand. The study encompassed a total of twent y different congeners. Particles in ambient air were alternatively collecte d by two different Berner cascade impactors at the field site in Northern B avaria over a 14-weeks period from the end of April through to the end of J uly 1994 and subsequently analyzed for their PAH content. The concentration s of total suspended particulate matter (TSP) ranged from 9-31 mug m(-3), s uggesting that the field site is an area with a low level of airborne parti cles. There was a negative relationship of total particle concentrations wi th the amount of canopy precipitation due to particle wash out at precipita tion events. The distribution of the particle masses on the different size fractions with a maximum in the 1-mum range is typical for remote areas and indicates a medium-range transport. The aerosol-bound PAH load decreased f rom spring samples with 2-4 ng m(-3) to values <1 ng m(-3) in the summer sa mples. Concurrently, the proportion of low molecular weight congeners in th e total PAH load declined. Frequently, the highest PAH concentrations (refe rring to the air) were found in the 0.1-3 mum size separates (accumulation mode). The results suggest that apart from PAH input to the soil with litte r, dry and wet deposition of aerosol particles is an important pathway of P AH contamination of acid forest soils in the Fichtelgebirge mountain range.