| heal.abstract |
The radioactive plume from the Chernobyl accident of April 26, 1986 reached Greece by May 1, substantially contaminating various regions and ecosystems of the country. Since then, the long-lived radionuclide 137Cs has been of particular concern. In the present study samples of the epiphytic lichens Anaptychia ciliaris, Lobaria pulmonaria, and Ramalina farinacea were collected from Quercus frainetto and Q. pubescens within a number of stands in the plain of Megalopolis-Peloponessos in 1988 and again in 1996, and the concentrations of the 137Cs were determined. The purpose of the study was to evaluate the level of contamination in deciduous oak forest at this southern region of Greece and to compare the ecological rate of 137Cs decline with time, the ecological half-life, and the ecological residence time in three lichen species. The mean concentrations of 137Cs in the 1988 samples were generally much lower than those reported by other workers in lichens from northern and central Greece in 1988, but significantly greater than the corresponding concentrations in the 1996 samples of this study. The concentrations of 137Cs in comparable (from the same stands) samples of 1988 and 1996 were used to estimate the ecological half-lives and the ecological residence times of 137Cs in the three species. Ramalina farinacea captures the smallest amount (952 Bq/Kg) and retains it the shortest time (ecological t( 1/4 ) = 2.87 yr.), while Anaptychia ciliaris captures the largest amount of 137Cs (1,220 Bq/Kg) and retains it the longest time (t( 1/4 ) = 4.78 yr.). The pH values of thallus is positively and significantly correlated to the 137Cs concentrations. Since A. ciliaris is also a common species in Greece and easy to collect, it is a good biomonitor of radionuclides. |
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