137Cs and 90Sr contamination of spruce needles in the northern region of Austria

Abstract

37Cs and 90Sr concentrations in spruce needles have been determined in samples gathered from Norway spruce trees at various locations the northern part of Austria. In needles from 1985 137Cs concentrations ranged between ⩽5 and 160 Bq/kg. After the Chernobyl accident a maximum of 1466 Bq/kg can be seen in needles of age group (I), harvested in September 1986 and up to 3800 Bq/kg for those of the age group (II), which are one year older, when collected also in September 1986. Right after the Chernobyl contamination of 1986, 90Sr concentrations in spruce needles of the age group (II) reached 25–50 Bq/kg, which was about twice as high as the values before, in 1985. A maximum value of 66 Bq/kg was measured. Radionuclide ratios of 90Sr/ 137Cs amounted to approximately 0.10 in less contaminated areas according to a lower 137Cs deposition. In the higher contaminated areas, these ratios remained ⩽0.05 or even ⩽0.02, if corrected for the background levels of 90Sr from 1985. These values corresponded with the ratios of 0.012 and 0.014 determined in air filter samplings from Vienna and Linz, respectively.