OBSERVATIONS ON LEAD CONTENT OF LICHEN AND BARK ADJACENT TO A HIGHWAY IN SOUTHERN FINLAND

The Pb contents of lichen (Hypogymnia physodes) and its substrate (bark of Pinus sylvestris) were studied along a busy 4-lane highway on the coast of S Finland. The Pb determinations of the samples were performed by an isotope-excited X-ray fluorescence analysis. The decrease in the Pb content of the lichens was statistically significant between 20-100 m from the road, but not between 100-200 m. There appeared to be no correlation between the Pb content of lichens and traffic density. The Pb content of bark changed significantly between the distances of 20-100 m and 100-200 m, and correlated significantly with the traffic density. Pine bark was a better indicator than lichens of Pb emission from motor vehicles. This could be caused by effective Pb accumulation in lichens even where there was moderate traffic flow.