Diffusion of 137Cs and 65Zn in different soils

The self-diffusion coefficients of Zn and Cs in six different soils collected from different agroecological zones of the country were determined. The apparent self-diffusion coefficient of Zn (Da Zn) varied from 0.75x10-9 to 40.02x10-9 cm2 sec-1 and higher value of Da Zn were observed in acid soils than in neutral to alkaline soils. DaZn was negatively correlated with soil pH (r=-0.953). The DaCs values ranged from 0.41x10-10 to 40.17x10-10 cm2 sec-1 and were also higher in acid soils. The volumetric moisture content showed a significant positive correlation (r=0.549) while soil pH showed a highly significant negative relationship (r=-0.928) with DaCs. The distribution coefficient (KD values) and the retardation factors of 65Zn and 137Cs were higher in neutral to alkaline soils. The lower KD values and retardation factors signify that the rate of movement or the leaching of the radionuclides is more in acidic soils than in neutral to alkaline soils. (author)