The radial increment and stemwood element concentrations of Scots pine in the area influenced by the Narva power plants in Northeast Estonia.

In the northeastern part of Estonia, near the town of Narva, there are two large oil shale fueled power plants, Baltic PP and Estonian PP. On burning oil shale the main atmospheric pollutants are fly ash, sulphur oxides and nitrogen oxides. The radial increment was measured and concentrations of Ca and Cu were estimated in the stemwood of Scots pine (Pinus sylvestris L.) from four sites in the influence area of the Narva power plants. Increment cores were taken also from two sites in an unpolluted area located 112 and 120 km northwest from the Estonian PP. The stands selected for investigation were similar as to their edaphic conditions and forest survey indicators (75- to 80-year-old (Oxalis-) Myrtillus-type pine stands of 0.7-0.8 density and of quality class II). The strongest effect of air pollution on radial increment was observed on the sampling site in the direction of dominating winds at a distance of 22 km to northeast from the Estonian PP. Using the annual rings, the core samples were divided into five-year sections (1945-1949; 1950-1954 etc.). The concentration of Ca increased and that of Cu decreased from the youngest, outermost annual rings towards the centre of the stem. High concentrations of Ca and Cu in stemwood in 1970-1974 may be due to the launching of the Estonian PP in 1969 in addition to the Baltic PP, which has operated since 1959.