Needle and lichen sulphur analyses on two industrial gradients

Total S concentrations in Scots pine (Pine sylvestris L.) needles and the lichen Hypogymnia physodes collected from the vicinity of an oil refinery in southern Finland and a steel works in northern Finland were used as a bioindicator for SO₂ deposition. The mean total S concentration in the youngest pine needles decreased by 22% (p <0.001) and that of the second youngest needles by 28% (p < 0.001) as emissions from the oil refinery were reduced by nearly 50% from 1980 to 1985. Total S concentration in both needles and lichens were higher in the vicinity of the oil refinery due to the greater influence of long-range transport S deposition in southern Finland. The two industrial plants had approximately equal SO₂ emissions in 1985. The results suggest that the total S concentration in pine needles is a better indicator of SO₂ changes in the ambient air, while that in Hypogymnia physodes seems to be a better bioindicator of total S deposition, past and present.