Impact of Environmental Change on the Radioecology of Spruce Trees in Upper Austria : Poster presented at IRPA 12 - 12th International Congress of the International Radiation Protection Association - Buenos Aires - Argentina - 19 / 24 October 2008
In a two years project spruce needle samples of the Austrian Bioindicator Grid were analysed by gamma spectrometry to detect the geographical and temporal distribution of radionuclides in spruce needles of the last 25 years with the main focus on the radioactive contamination before and after the Chernobyl fallout in 1986. This radioecological evaluation is an important part of an existing environmental surveillance programme in Upper Austria in order to gain basic information on the impact of environmental changes on the radioecological behaviour of spruce trees. Moreover, the results of the current studies can be an important input for the discussion of using whole trees for biomass energy. Every year spruce needle samples of the two youngest needle sprouts are taken from two spruce trees at each location of the Bioindicator Grid. For this study samples of selected locations — evenly spaced out among the area of Upper Austria — were analysed for different natural and anthropogenic radionuclides: 137Cs, 40K, 210Pb, 226Ra, 228Ra, 238U. Additionally, soil samples were taken at selected sites to study the relationship between 137Cs- and 40K-activity concentrations in soils and spruce needles and to estimate transfer factors. Another important question of the study is the correlation between anthropogenic pollutants and radionuclides. To date more than 500 spruce needle samples were analysed. 137Cs- activity concentrations reach D.L. (2 Bq/kg)–5150 Bq/kg, whereas the maximum was measured after the Chernobyl fallout in 1986. In time series of 137Cs-activity concentrations Caesium cycling was observed. The activity concentrations of 40K reached D.L. (15 Bq/kg)–294 Bq/kg and 210Pb reach D.L. (5 Bq/kg)–45 Bq/kg. The measured 226Ra, 228Ra and 238U concentrations were mostly below detection limits. Most samples of younger sprouts revealed higher 137Cs-activity concentrations than older sprouts. 40K-activity concentrations showed nearly the same level in different aged samples, whereas 210Pb-activity concentrations were much higher in older sprouts. Furthermore, spruce needle samples with high 137Cs-activity concentrations showed low 40K-activity concentrations and vice versa in samples with high 40K-activity concentrations low 137Cs-activity concentrations were measured.
