EVIDENCE OF LONG-DISTANCE TRANSPORT OF BETULA POLLEN

In April the eastern parts of Fennoscandia are frequently influenced by south to southeastern winds. These air-masses can bring with them large quantities of Betula pollen several weeks before the local flowering season begins. The pollen is transported with air-masses at a high level and then taken down by turbulent transport or washout. The number of pollen grains can be so high that sensitive persons exhibit allergic symptoms. Three localities from Sweden and six from Finland have been selected and numerical air-parcel trajectories have been calculated in order to determine the Betula pollen source. The results indicate that the distant pollen source areas can be identified, and that the travelling times for pollen grains transported in April 1989 were mostly in the range of 9 to 20 hours.