Lessons from the Fukushima and Chernobyl accidents concerning the¹³⁷Cs contamination of orchard fresh fruits

Abstract

-The observations made in Japan in 2011 after the Fukushima-Daiichi accident and those made in France, Italy, Greece and Austria in 1986 after the Chernobyl fallout, show that the development stage of orchard trees at the time of atmospheric deposition is a major factor determining the level of caesium contamination in fruits at harvest. Both data sets are shown to be consistent and enable one to estimate, for mobile elements in plants such as caesium, an aggregated transfer factor (expressed in Bq.kg −1 of fresh fruit per Bq.m −2 deposited on the ground surface) whose value strongly depends on the time elapsed between fallout and harvest. The Fukushima data set also enables one to estimate effective half-lives (expressed in days), which are helpful for predicting the decrease in fruit contamination with time. We found an average value of 200 days for the one-year period after radioactive fallout, which is quite consistent with values estimated from post-Chernobyl surveys.

The Time-Dependent Transfer Factor of Radiocesium from Soil to Game Animals in Japan after the Fukushima Dai-ichi Nuclear Accident

“…After the publication of the handbook, many additional related publications on the fate of 137 Cs in forest ecosystems were published. − The data from Chernobyl fallout studies in forests showed that the [ 137 Cs] decreases with time in many different forest compartments such as tree leaves and understory plants. However, that in wild animals such as wild boar and roe deer, [ 137 Cs] remained high for a long time, with seasonal peaks depending on the animals diet. − After the Fukushima Dai-ichi accident, T ag values for different components of trees were reported − which decreased with time, as expected, due to processes such as the decreasing importance of direct interception of radiocesium and a reduction in the bioavailable fraction in soils. , For wild animals, no information has yet been reported in international literature on the time dependency of T ag for wild animals since the Fukushima Dai-ichi accident.…”

Reactor accident chemistry an update

“…This equation is normally used for fruit growing on the tree in the first year. The aggregated transfer factor is given by the following equation (Renaud & Gonze, 2014). Where IF is the interception factor (area of foliage for a given area of land), t is the current time, t a is the time of the accident, T fr (t − t a ) is the term containing the true translocation factor while λ is the physical decay constant (days −1 ) for the nuclide.…”

Radionuclides Behavior in Fruit Plants

“…Recent observations after the Fukushima accident provide evidence that translocation to fruit does occur from leaf and bark, the amount of translocation differs between plant types, and that translocation is very sensitive to plant growth stage at the time of deposition [9,[25][26][27]. Another process that can contribute to fruit activity, ascertained by various authors after the Fukushima accident, is the secondary contamination, resulting from weathering, by the action of wind and rain [10, 27-30 cited by 28].…”

“…They observed that T ag values of apricot samples were apparently higher when collected in low-elevation coastal areas (i.e., in Minamisoma-shi and Soma-shi municipalities, located to the North of the nuclear site, and Mito-shi to the South in Ibaraki Prefecture) than those collected from sites in mountainous areas. They suggested these differences were due to the stage of the vegetative cycle, as flowering would have occurred earlier in coastal regions than in inland elevated areas, resulting in greater transfer [9]. Similarly, the radiocesium activities of the foliar parts of woody species, 5 months after the Fukushima accident, were higher in evergreen species than in deciduous species, because the foliar parts of evergreen species (leaves from previous year) were present at the time of fallout but those of the deciduous species were not [10].…”

“…Renaud and Gonze [9], studying the 134 Cs contamination of orchard fruits in Japan in 2011, observed that some correlation exists between cesium concentration in fruits, at first harvest, and ground surface deposit. They calculated the aggregated transfer factors, T ag , expressed in Bq kg 1 of fresh fruit per Bq m 2 deposited on the ground surface.…”