Modelling of Cs-137 cycling in forests: recent developments and research needed

Abstract. As the chemical behavior of radiocesium is expected to be almost identical to that of stable Cs, analyses of stable Cs and related stable elements should be useful to understand the long-term behavior of radiocesium and its equilibrium distribution in forest ecosystems. In this study, the concentrations of stable Cs and related alkali and alkaline earth elements in mushrooms, plants and soils were determined by inductively coupled plasma-mass spectrometry (ICP-MS) or inductively coupled plasma-atomic emission spectrometry (ICP-AES). Samples were collected in forests with different contamination levels in Japan. Germany, Finland, Italy, Ireland and Belarus. Vertical distributions in soils, and concentrations in mushrooms and plants were summarized for radiocesium and related stable elements. Relationship between radiocesium and stable Cs in mushrooms and plants, and transfer from soil to vegetation were also discussed. The results indicated that the ratio between radiocesium and stable Cs is useful for judging the equilibrium of deposited radiocesium in different parts of a forest ecosystem. The stable Cs analyses might be also useful to predict the long-term radiocesium contamination of mushrooms and plants.

Section: Transfer From Soil To Vegetationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stable elements - as a key to predict radionuclide transport in forest ecosystems

Yoshida¹,

Muramatsu²,

Steiner

et al. 2002

“…This feature was well illustrated by the post-Chernobyl radioactive fallout which affected large forested area with long-lived radionuclides such as 137 Cs and ^Sr, especially in CIS and to a lesser extent in Western Europe. Several in situ studies made after the Chernobyl accident revealed a much higher recycling of radiocaesium in contaminated forest compared with agricultural area [1]. The persistence of an important bio-available pool of radioceasium in humus layers is mostly responsible of its long-lasting transfer to forest vegetation [2].…”

Section: Introductionmentioning

confidence: 99%

General process, dynamics and modelling of radiocaesium cycling in contaminated forest: A whole-ecosystem approach

Goor

Thiry

2002

Self Cite

We used a chronosequence approach to compare the distribution of l37 Cs and potassium (K) in the different compartments of three Scots pine stands. The cycling dynamic of both element was assessed as a function of stand development with emphasis on 137 Cs immobilisation in wood. lî7 Cs and K redistribute rather similarly between tree components, by circulating through the same pathways. U7 Cs immobilization in wood is, however, more important than for K, especially in old stands. Although the old stand accumulated more " 7 Cs from the Chernobyl event than the young stand, a much less limited pool of ll7 Cs characterises its current annual cycling when compared to EC. Differences in the current ll7 Cs content between young and old stands most likely reflect divergences occurred during the early redistribution rates after the fallout connected with differences in " 7 Cs interception rate. The WIP approach (combining n7 Cs radial pattern and biomass increment) was then preferred to the TF coefficient concept to quantify the actual IJ7 Cs immobilization in wood of each stand due to root uptake. Independently of the stand age, higher WIP values were related with the higher bioavailability of the '3?Cs located in organic layers.

“…137 Cs migration in soils depends on the type of soil, chemical features and granulometry, sorption and desorption processes, moisture, mineral composition, etc. In situ measurements after the Chernobyl accident showed that nutrient cycling and storage led to a much longer persistence of radiocesium in forest ecosystems in comparison with cropping systems [11,12,13]. Consequently, it is very important to document the forest ecosystem clearance and describe the potential transfer of radiocesium and its mechanisms in forest ecosystems in order to improve risk assessment.…”

Section: Introductionmentioning

confidence: 99%

Soil-plant transfer of radiocaesium in weakly contaminated forest ecosystems

Lamarque¹,

Lucot²,

Badot³

2005

Abstract. During the Chernobyl accident, large areas in Europe, particularly forests, were contaminated by radiocaesium. Soil-plant transfer is often the first step by which 137 Cs enters to food chains by incorporating the forest biogeochemical cycle. The present work is devoted to assess the soil-plant transfer of radiocaesium in weakly contaminated forest area, in the Franche-Comté region (16 202 km 2 ) in North Eastern France. This region has been markely contaminated after the Chernobyl accident. Twelve sites, with various functional features and high diversity of ecological contexts were selected to sample forests trees. Two species (Picea abies and Fagus sylvatica) and two organs, (leaves or needles and young branches) were sampled for radioactivity measurements. Radiocaesium activities in soils varied between 61 to 280 Bq.kg -1 DW at 0-5 cm depth and between 14 to 224 Bq.kg -1 DW at 10-15 cm. Radiocaesium activities in leaves, needles and branches displayed high variability. We reported a large variability of Aggregated Transfer Factors (T ag ) values with respect to vegetation type, organ type and soil features. The activity concentration in the leaves and needles were generally higher than those measured in the branches. The T ag values could be explained by the radiocaesium bioavailability variability in relation to soil type, soil features and environmental parameters.