The Science of the total environment
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Sci. Total Environ. · Dec 1994
Comparative StudyVertical radionuclide transfer by infiltration water in forest soils in the 30-km Chernobyl accident zone.
Vertical intrasoil flow within the 30-km zone of the Chernobyl nuclear power plant (ChNPP) was investigated by a lysimetric method in 1989-1990. The regularity of radionuclide migration within the flow has been found to be dependent on the contamination density, the type of radionuclide, and the type of ecosystem and depth.
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Sci. Total Environ. · Dec 1994
Comparative StudyMain investigation results on the forest radioecology in the Kyshtym and Chernobyl accident zones.
As a result of the long-term studies of radionuclide migration in forest ecosystems in zones of radioactive contamination after the Kyshtym and Chernobyl accidents, the following trends were revealed: (1) High retention capacity of stand canopy with respect to radioactive fallout. This leads to high doses absorbed by apical and leaf meristems, beta-radiation giving the main part of the dose; (2) Fast self-decontamination of crowns during the growth period and relatively slow decontamination in the phase of physiological rest, regardless of amount of atmospheric precipitation. The rate of crown decontamination determines the value and duration of radiation stress on woody plants; (3) Accumulation not less than 95% of the total radionuclide amount in the forest litter 1-2 years after the cessation of radioactive fallout; (4) Relatively slow migration of strontium and cesium radionuclides along the forest soil profile; (5) High capacity of the forest when serving as a biogeochemical barrier to the routes of horizontal and vertical radionuclide migration and export out of the zone of initial contamination, including migration into the river water; (6) Considerable difference between strontium and cesium when migrating in forest soils and in the soil-plant system; (7) Broad variations in transfer factors for uptake of cesium-137 from soil into forest plants depending on the plant species and soil type. The primary radiobiological effects connected with irradiation of organisms are considered and secondary disturbances due to changes of ecological bonds between the components of irradiated forest ecosystem are discussed.
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Sci. Total Environ. · Dec 1994
Comparative StudyRadionuclides in the liquid phase of the forest soils at the Chernobyl accident zone.
The relative content (alpha) of 137Cs (1987-1991), 106Ru, 134Cs, 144Ce (1987) and the chemical speciation of radionuclides in the liquid phase of forest soils at different plots in the 30-km Chernobyl zone were studied. One year after the accident, substantial variations in the alpha-value between the different plots and a variation in alpha along the soil profile were observed due to unequal physico-chemical properties of nuclear fallout and soils. The alpha-value calculated for the total contaminated layer (alpha av) at different plots varied within relatively narrow limits. ⋯ The alpha-value for 137Cs for all plots in the Chernobyl 30-km zone and the differences in alpha value between plots had a tendency to decrease with time. These data indicate that the process of 137Cs fixation by the soil solid phase was prevalent. Now, the 'soil-soil solution' system is approaching equilibrium for the radionuclide distribution between solid and liquid phases.
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Sci. Total Environ. · Dec 1994
Comparative StudyBiological pathways of radionuclides originating from the Chernobyl fallout in a boreal forest ecosystem.
In an attempt to understand the mechanisms governing the transfer and retention of radiocaesium in the understorey vegetation, 39 macromycetes species and 33 plant species, together with humus samples, were systematically collected from the undercover vegetation in a boreal coniferous forest. The results indicate that the main factors determining interspecific differences in contamination level are the rooting depth in plants, the depth of mycelium in fungi, and the ecophysiological behaviour of fungi, mycotrophism or plant parasitism. A comparison between the investigated species and the same species growing in similar ecosystems, albeit under different climatic conditions, resulted in an almost identical ranking in terms of radiocaesium contamination levels; the contamination ratios between species were also relatively constant. From an experiment involving humus samples, it was shown that up to 40% of the radiocaesium could be retained by the microflora, particularly by mycelia.