Archive > Volume 35 Issue 2 > 1998,35(2):202-209. DOI:10.11766/trxb199504050208 CSTR:[cstr] Prev Next
DIFFUSION OF PHOSPHATE IN SOILS Ⅲ. KINETICS AND ENERGY CHARACTERISTICS
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Abstract:
The diffusion amounts of phosphate in soils at varying time were determined by half-cell technique using 32P. Fve kinetic equation were used to fit the dynamic process of phosphate diffusion in the soils. It was found that parabolic found that parabolic. equations was the best model to describe the process diffusion. The temperature quotient (Q10) of phosphate diffusion in the soils at 20% water content was 1.2 or so, which was in agreement w ith that diffusion is a physical process. The activation energy EaD of phosphate diffusion in soils, calculated by Arrhenius equation, decreased with increasing soil moisture and varied from 12 to 34 kJ/mol with an average value of 25kJ/mol under low water tension range(<105 Pa), which was close to the activation energy of nutrient ion diffusion in solution. Therefore, it was suggested that the phosphate diffusion in soils at low water tension condition occurred mainly in the liquid phase. Moreover, the absolute reaction-rate theory was transplanted and used to investigate the diffusion process in soils. The parameters, net activation energy, activation entropy, activation enthalpy and activation free energy of phosphate diffusion in soils, were derived from the theory. The results showed that these parameters in the four soils at the same water content changed in the similar to EaD,which indicated that the parameters could be used to describe the energy characteristics of phosphate diffusion in soils.
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