根釧地方の火山性土における塩化物イオンの拡散に及ぼす吸着と体積含水率の影響

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The effects of adsorption and water content on the diffusion of chloride ion(Cl^-)were examined in laboratory columns packed with a regosolic andosol(Thaptic Udivitrand), an ordinary andosol(Acrudoxic Vitric Melanudand), and a cumulic andosol(Pachic Melanudand)in the Konsen district, Hokkaido. The diffusion coefficient of Cl^- in soil, D, was determined from the measured Cl^- content profiles, employing a diffusion model in which D was assumed to be constant in each column. The value of D thus obtained increased with the molumetric water content of the soils. Although the soils were humic or coarse-textured, they had small but definite values of the anion exchange capacity(AEC) of 0.2-2.6 cmol_ckg^<-1> when measured by repeated equilibration with CaCl_2 solutions. The Cl^- adsorption, corresponding to the AEC of this size, was estimated to decrease the values of D in the soils to 0.20-0.70 times those expected in the absence of adsorption. The adsorption of Cl^- by the soils was found to be nonlinear. Hence, the effect of adsorption was most significant when Cl^- concentration was small, and greater values of D were obtained in the soil columns with larger Cl^- content. While AEC per unit mass of soil was in the order cumulic>ordinary>regosolic andosols, the soils with larger AEC had a smaller bulk density so that the resultant effect of adsorption on Cl^- diffusion did not differ much among the soils. Consequently, the relative magnitude of D among these andosols was most influenced by the volumetric water content and its function, the impedance factor. Thus, from the water retention curves detrmined on undisturbed cores, it was suggested that the easiness of Cl^- diffusion was in the order cumulic>ordinary>regosolic andosols under field conditions.
社団法人日本土壌肥料学会の論文
1996-02-05

根釧地方の火山性土における塩化物イオンの拡散に及ぼす吸着と体積含水率の影響

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