Interception and retention of Chernobyl-derived 134Cs, 137Cs and 106Ru in a spruce stand.
The time dependence of the specific activity of Chernobyl-derived 134Cs, 137Cs and 106Ru was determined in vegetation and soil samples from an old spruce stand within a period of 600 days after the beginning of the radioactive fallout. The results show that 70% of the total activity of radiocesium and 60% of radioruthenium deposited in the spruce stand were retained initially in the canopy. They were removed from the needles and twigs as a result of weathering (rain, wind, litter fall) and transferred to the forest floor, but only rather slowly (half-lives in the canopy: radiocesium, 90 days for the period 0-130 days, 230 days for the period 130-600 days; radioruthenium, 95 days for the period 0-200 days). The transfer of radiocesium and ruthenium to the forest floor by litter-fall was small when compared with that of weathering by rain or wind (radiocesium 7%, radioruthenium 8%, with respect to the total activity deposited in the canopy). The total deposition of radiocesium and ruthenium in the spruce stand was higher by 20 and 24%, respectively, than that observed in nearby grassland. The deposition velocity of radiocesium in the spruce stand was estimated at 5.5 mm s-1, higher by a factor of 10 than the figure for grassland. Similar values were found for radioruthenium.
Bunzl
K
K
Institut für Strahlenschutz, Gesellschaft für Strahlen-und Umweltforschung, Neuherberg, Federal Republic of Germany.
Schimmack
W
W
Kreutzer
K
K
Schierl
R
R
D000059:Accidents; D002588:Cesium Radioisotopes / Q000032:analysis*; D005859:Germany, East; D006801:Humans; D009688:Nuclear Reactors; D010944:Plants / Q000032:analysis*; D012429:Ruthenium Radioisotopes / Q000032:analysis*; D014197:Trees; D014455:Ukraine; D014887:Weather
D002588:Cesium Radioisotopes; D012429:Ruthenium Radioisotopes