Artificial and natural radionuclides in spruce needles in Upper Austria from 1983 to 2008 - an application for radioecological monitoring

For more than 25 years, spruce needles have successfully been used as bioindicator for identifying nutrient imbalances and the spatial and temporal distribution of atmospheric pollutants in Austria. The radioecological interest in spruce needle analyses grew instantly after the Chernobyl accident in 1986, because of the possibility to study the mechanisms of deposition as well as the long-term behaviour of radionuclides in forest ecosystems. For this thesis 782 spruce needle samples from the Austrian Bioindicator Grid of the last 22 years were analysed by gammaspectrometry for the following artificial and natural radionuclides: 137Cs, 40K, 210Pb, 226Ra, 228Ra and 238U focusing on the radioactive contamination before and after the Chernobyl fallout of 1986.

The spatial and temporal distribution of activity concentrations in spruce needles were comprehensively analysed and illustrated. Further on, the relation between natural and artificial radionuclides in spruce needles was determined. To estimate the long-term behaviour of 137Cs, ecological half-lives were calculated for the compartment spruce needles. Additionally, soil samples were taken at selected sites and analysed radiometrically to determine the radionuclide inventory in soil and to study the soil-to-plant transfer. Based on these results, detection limits for additional deposits were calculated to pursue the question, whether it is possible to use the bioindicator spruce needle for environmental radioactivity monitoring.

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