Surface-chemical study on effects of wet and dry conditions to soil colloids.

在一些中粗质土轮作稻田中，表层土在压浆后异常硬化是一个较为严重的问题。应用表面化学的方法，对itsuki现象进行了研究。结果表明：连作水田风干土壤经过强还原处理后，再湿润土壤中氧化铁总含量降低，而与土壤胶体ph依赖电荷密切相关的无定形氧化铁含量相对增加；这些土壤中的有机物质也因还原过程而减少，认为这些有机物质的损失与到达的氧化铁结合在一起。应用几种粘土矿物对土壤胶体的电荷特性进行了估计。蒙脱土在较宽的pH值范围内具有较高的负电荷，高岭土的负电荷与pH值无关，但较低。另一方面，磷素的正电荷和负电荷都是非常依赖于pH的，在pH 5.5时观察到净电荷为零的现象。本研究提出的铯离子吸附方法对土壤胶体中阳离子交换容量和零净电荷点特性的研究是非常有效的。与以前使用钠离子或钾离子的方法相比，这种新方法能够在测量过程中防止污染。将激光散射法测定土壤的粒度分布与传统沉降法测定土壤的粒度分布进行了比较，发现两者具有较高的相关性。该方法特别适用于观察同一粘土或土样中粒径的连续分布。电声振幅法在较宽的pH值范围内可快速测量黏土矿物和土壤胶体的ζ电位，是一种有效的估算黏土矿物和土壤胶体ζ电位的方法。少

The abnormal hardening of topsoil after puddlig so called "itsuki" has been serious problem in some rotational paddy fields of middle- to coarse-textured soils. This study was carried out for the purpose of clarifying the itsuki phenomenon by application of surface chemistry. The results is summarized as follows :Total contents of iron oxides decreased, but amorphous iron oxides which affect closely to pH-dependent charge of soil colloides increased relatively, in the re-wetted soils after a strongly reductive procedure of the air-dried ones which were collected from continuous cropping paddy fields. Organic materials in these soils were also decreased by the reductive procedure, and it was suggested that this losted organic materials combined with reached iron oxides.Charge characteristics of soil colloids were estimated by applying several species of clay minerals. Montmorillonite had high negative charge constantly in the wide range of pH values, and negative charge of kaolin minera … More ls were pH-independent but it was low. On the other hand, positive and negative charge of allophane were both extremely pH-dependent, pont of zero net charge was observed at pH 5.5.A casium ion adsorption methods which had been presented in this study was very effective for the investigations on characteristics of cation exchange capacity and point of zero net charge in soil colloids. This new method was able to prevent contaminations during the measurement procedures compared with the previous methods by using sodium or potassium ions.Determination of particle-size distribution of soils by a laser scattering method was compared with the customary sedimentation method, the high correlation was established between them. This method was useful especially for the observation of continuous distribution of particle size in same clay or soil sample.An electrokinetic sonic amplitude method should be effective for the estimation of ζ potential of clay minerals and soil colloids because of probability to measure rapidly it in wide rage of pH value. Less