TEMPORAL TRENDS OF 137Cs AND 40K ACTIVITY FLUX FROM SOIL TO PLANT IN GRASSLAND ECOSYSTEMS

VELASCO, H.; JURI AYUB J.; BELLI M.; SANSONE U

JOURNAL OF ENVIRONMENTAL RADIOACTIVITY

Elsevier

Lugar: Oxford; Año: 2004 vol. 71 p. 225 - 241

0265-931X

A data set of 137Cs and 40K activity values in plant and soil samples, obtained under identical conditions during a four-year period, was analysed in order to determine the temporal trend of soil-to-plant transfer process. Aggregated transfer factor (Tag) was determined in each sampling site, showing the typical seasonal variations and the well-known uncertainties. The activity flux density (FD) and the activity flux density per soil activity superficial concentration (J), were used as more suitable variables to quantify the radionuclide soil-to-plant transfer process. A negative correlation between log J(137Cs) vs t was obtained (R= -0.99). In contrast, log J(40K) remains approximately constant with time (R= -0.67). The influence of the 40K content in soil on 137Cs soil-to-plant transfer is discussed. Temporal mean value of FD was 50-times larger for 40K than for 137Cs.  However, comparing temporal mean values, J(40K) was 26 times J(137Cs). The soil concentration level of 137Cs and 40K explains only 50% of the higher uptake of K than Cs in plant. The J(40K):J(137Cs) relationship was 5 for the first year and 32 for the last year, a behaviour that could be attributed to the radiocaesium fixation to soil components.