Cs-137 distribution among annual rings of different tree species contaminated after the Chernobyl accident

The distributions of Cs-137 among annual rings of Pinus sylvestris and Betula pendula at four experimental sites located in the most contaminated areas in the Russian territory after the Chernobyl accident in 1986 were studied. Trees of different ages were sampled from four forest sites with different tree compositions and soil properties. The data analysis shows that Cs-137 is very mobile in wood and the 1986 rings do not show the highest contamination. The difference between pine and birch in the pattern of radial Cs-137 distribution can be satisfactorily explained by the difference in radial ray composition. Cs-137 radial distribution in the wood can be described as the sum of two exponential functions for both species. The function parameters are height, age and species dependent. The distribution of Cs-137 in birch wood reveals much more pronounced dependence on site characteristics and/or the age of trees than pines. The data obtained can be used to assess Cs-137 content in wood. (C) 2002 Elsevier Science Ltd. All rights reserved.