Reload Index (ZRiChK UMCS)

 

 

INVESTIGATION OF ADSORPTION AND VERTICAL MIGRATION OF 137CS IN THREE KINDS OF SOIL
AT LUBLIN VICINITY

 

STANISŁAW CHIBOWSKI, JACEK ZYGMUNT

DEPARTMENT OF RADIOCHEMISTRY AND COLLOID CHEMISTRY

 

 

        Presented work encloses the results of field, column and laboratory studies carried out on three types of mineral soils soils - brown soil, lessive soil and podzol soil. Based on the field tests, average migration rates of 137Cs were calculated and the highest one was found for the brown soil. Caesium migrated with the lowest rate in the podzol soil and the column experiments confirmed the above observation. The average migration rates of 137Cs are presented in Table 1

Table 1. Average migration rate of 137Cs in the examined soil profiles.

 

Average migration rate [cm/year]

 

Brown soil

Lessive soil

Podzol soil

Global fallout

0,31

0,36

0,30

Chernobyl fallout

0,67

0,25

0,18

Column measurement

1,17

0,61

0,60

        In the laboratory tests, the adsorption and desorption isotherms of Cs were determined on samples taken from 0-2 cm layers of each soil profile. The isotherms show an exponential relationship and closely follow the Freundlich isotherm. Based on the adsorption-desorption isotherms, partition coefficients (Kd) were calculated. It was found, from the calculated partition coefficients, that Cs is always irreversibly bonded to some extent on all the soils tested but it appears to be completely and irreversibly immobilized on the podzol soil.

        The high retention of caesium in the podzol soil was also confirmed by microcalorimetric studies. The desorption energy was negligibly small and amounted to –0,21 mJ/g. In the brown soil, containing prevailing amounts of loamy minerals, the desorption energy was found to be 106,89 mJ/g. The investigations are supplemented by the sorption kinetics measurements. These indicate that the adsorption equilibrium is reached after a dozen, up to twenty or so minutes.

        Presented work confirms the view that further investigations are needed on the adsorption/desorption processes taking place in different types of soil. Such studies will certainly contribute to a better understanding of the mechanisms that govern the migration and transfer of radioisotopes in the environment.

 

References:

[1] J. Zygmunt, S. Chibowski, Z. Klimowicz, J. Radioanal. Nucl. Chem., Vol. 231, No 1-2 (1998) 57

Grant No. 3T09C 034 15