AIR-POLLUTION EFFECT AND PALEOTEMPERATURE SCALE VERSUS δ~(13)C RECORDS IN TREE RINGS AND IN A PEAT CORE (SOUTHERN POLAND)

摘要

Carbon isotope analyses of peat profiles from the Karkonosze Mts. (SW Poland) and tree-ring cellulose from Wisla river valley in the Krakow region (S Poland) have been carried out. The samples analysed represent approximately the last 1100 years. The δ~(13)C profile in peat from the Szrenica peat bog ranges from -26.74 to -21.81 per thousand and the δ~(13)C value of tree rings range from -27.82 to -21.94 per thousand. The observed variations in the δ~(13)C values of the peat samples and tree rings from Poland in general correlated with each other (Figure 1). This suggests that the δ~(13)C value of organic matter in terrestrial conditions is generally controlled by the same environmental factors. On average, over the last millennium (X-XIX century), the δ~(13)C value of peat cellulose has been 1.8 per thousand isotopically heavier compared to the corresponding tree ring cellulose value. It is not possible to provide a precise calibration of isotope signatures in tree rings, as the assimilation isotope effect depends mostly on local microclimatic conditions and specific species demands. In the region under study, temperature was the dominant factor controlling the δ~(13)C value of tree ring cellulose and peat-bog Sphagnum before the XIX century. It is estimated that, in the temperate climate of Poland, the carbon isotope fractionation between living plants and atmospheric carbon dioxide (Δ~(13)C_(p-a)) for C3 plants is about -0.26 per thousand/1℃. This corresponds to 2.1 per thousand/1000 m of elevation. Since the mid-XIX, in the Wisfa valley when the river was regulated and water deficit in the neighbouring areas became common (Trafas, 1975), water availability plays a primary role in isotope fractionation of the vegetation. Since the 1955, just after the 'Lenin' steelworks started operation, pollution became the dominant factor controlling the carbon isotope signature of plants. Contamination of the atmosphere by fossil fuel burning from the 'Lenin' steelworks increased the δ~(13)C value of tree ring cellulose by about 1.3 per thousand. This was probably caused by an increased concentration of atmospheric pollution (SO_x and dust) limiting the ventilation rate of the stomata.