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

CEN-SCK, Radiation Protection Research Department, Boeretang 200, 2400 Mol, Belgium

Abstract

We used a chronosequence approach to compare the distribution of ¹³⁷Cs 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 ¹³⁷Cs immobilisation in wood. ¹³⁷Cs and K redistribute rather similarly between tree components, by circulating through the same pathways. ¹³⁷Cs immobilization in wood is, however, more important than for K, especially in old stands. Although the old stand accumulated more ¹³⁷Cs from the Chernobyl event than the young stand, a much less limited pool of ¹³⁷Cs characterises its current annual cycling when compared to K. Differences in the current ¹³⁷Cs content between young and old stands most likely reflect divergences occurred during the early redistribution rates after the fallout connected with differences in ¹³⁷Cs interception rate. The WIP approach (combining ¹³⁷Cs radial pattern and biomass increment) was then preferred to the TF coefficient concept to quantify the actual ¹³⁷Cs immobilization in wood of each stand due to root uptake. Independently of the stand age, higher WIP values were related with the higher bio-availability of the ¹³⁷Cs located in organic layers.