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ŠUMARSKI LIST 7-8/2021 str. 21     <-- 21 -->        PDF

Distribution of 137Cs and 40K in the tissue of silver fir trees (Abies alba Mill.) from Lika (Croatia)
Distribucija 137Cs I 40K u tkivima stabala obične jele (Abies alba Mill.) iz Like (Hrvatska)
Marina Popijač
The research on activities of 137Cs and 40K, which was conducted on the silver fir (Abies alba Mill.) from Lika has included sampling of the trees in the field (rings of the bole from three different heights separated into bark, growth rings, roots, needles, shoots, and the soil surrounding the cut down trees), laboratory analysis of samples using the gamma-ray spectrometry and the statistical analysis of the collected data. The radial and vertical distribution of cesium (137Cs) in trees was investigated. 137Cs has contaminated forest ecosystems by remote atmospheric transport and radioactive precipitation as a result of nuclear test including the nuclear accident in Chernobyl. On a longer time scale, the variability of the 137Cs distribution determined in the organisms of the silver fir depended on the half-life, while the seasonal dynamics were influenced by the degree of physiological activity and the characteristics and functions of plant tissues. The highest activity of 137Cs was determined in the bark and the physiologically most active parts of the silver fir (shoots and needles). The highest activity concentration of the 137Cs in the growth rings was measured in the lowest parts of the silver fir trees. This research contributed to understanding the behavior of 137Cs, which entered the organisms of dominant tree species in the forest ecosystem, as well as its distribution in time and space.
Key words: forest ecosystem, radionuclides, distribution, bioindicators, silver fir
Forest ecosystems provide the basic requirements for maintenance of all life on Earth. Forests directly involved in the purification of groundwater and surface water, protect reservoirs of drinking water from pollution, play an important role in flood protection, protect the soil from erosion and sliding, and prevent the occurrence of avalanches and sliding snow weight (Prpić et al. 2005). The larger forest areas affecting the climate mitigation of major changes in temperature, increase humidity during summer, prevent changes in the microclimate of a particular area, protect against contaminated air, strong wind and noise, hold large amounts of dust, and provide shelter and food for numerous animal and plant species (EEA 2016). Anthropogenic pollution of forests, forest ecosystems and the overall environment is one of the largest problems of our time, which in many areas takes on catastrophic proportions. Many pollutions in forest ecosystems are monitored systematically, their appearance, performance, duration and disappearance are recorded. The radioactive cesium isotope l37Cs appeared in the environment in significant quantities after atmospheric nuclear testing during the 1950’s and 1960’s. (UNSCEAR 1993, FAS 2002), and a large amount of l37Cs