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

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