Accumulation of radioisotopes associated with the presence of wood-inhabiting fungi in scots pine (Pinus sylvestris L.) wood

Abstract

Growth of trees depends on the climatic conditions, environmental pollution and presence of wood-inhabiting fungi. Especial effect is caused by radioactive contamination. Radionuclides not only accumulate in plants, they also distinguish additional irradiation from ionising radiation. Plants lose their biological, environmental protection and material worth due to the action of this factor. In the present study, specific activities of 137Cs, 40K, 232Th and 226Ra in the wood of Scots pine (Pinus sylvestris L.) and transfer coefficients of those radioisotopes from the contaminated soil to the growing tree were determined. Fluctuations in values of 137Cs specific activity in the pine wood and transfer coefficients of 137Cs showed tight correlation with the fluctuations in general (atmospheric) radioactivity caused by nuclear weapons testings and the Chernobyl accident in 1986. A shift in the specific activity of 137Cs in the wood of the investigated pine tree was recorded as it became infected by a decay-causing fungus Heterobasidion annosum (Fr.) Bref. After 1988, a trend of decrease in the specific activity of this radioisotope was recorded. In a yearly perspective, the specific activity of 137Cs in the wood of pine showed positive correlation with an intensity of radioactive contamination of atmosphere and soil, as well as with the quality of growing (climatic) conditions and the presence of fungi within a zone of the respective growth ring. Radioisotope 226Ra showed a considerable decrease in the specific activity for the years of extremely bad growth (climatic) conditions, however, an impact of the optimal growth conditions or the presence of fungi was non-significant. The highest specific activity values of 40K in the pinewood were recorded for the periods of decreased increment (as compared to the mean value of annual radial increment).

137Cs savitojo aktyvumo pušies medienoje padidėjimas sutampa su oro ir dirvožemio radioaktyviosios užtaršos padidėjimu, geriausiomis augimo klimato sąlygomis ir grybų buvimu rievių mėginiuose. 226Ra savitojo aktyvumo pušies medienoje sumažėjimą lemia ypač blogos medžio augimo sąlygos, bet nenustatyta mikrobiotos ir itin gerų augimo sąlygų ryškios įtakos. 40K didžiausios savitojo aktyvumo vertės pušies medienoje nustatytos laikotarpiais, kai metinės rievės prieaugio indeksas (MRPI) yra mažesnis nei vidutinis arba artimas jam.