Relationship between surface charge and water characteristic curve of clays

在-1.4JKg~(-1)~-800JKg~(-1)的范围内，风干土壤中分离出的尿磷脂胶体比新鲜土壤中的水分低23~29%。由于这两个样品的斯托克斯直径都小于50 nm，这种不可逆性被归因于亚微观不可逆聚集。从新鲜土壤中分离出的尿磷脂胶体的水分特征曲线与表面电荷在-100JKg^-1&gt；以下的不同pH值一致，而在-100JKg^-1&gt；-100JKg^-1&gt；以上逐渐偏离平均颗粒分离的3.1 nm。尿囊素的sb溶质值越低，水分含量越高，达到-100JKg^~(-1)~(-1)。除-100JKg~(-1)~(-1)以上的高电荷态水特征曲线不可逆外，其它水分特征曲线均不可逆。在-10JKg~(-1)~(-1)~(-1)以下，蒙脱石的含水率均高于蒙脱石，是尿磷矿的两倍多。在-400JKg^~(-1)~(-1)以上，尿囊石的水分含量高于蒙脱石。蒙脱石与变光粘土混合后，由于插层作用，蒙脱石的含水率在-100JKg^-1~-800JKg^-1&gt；范围内高于两种粘土。这种高保水性能不仅与其高比表面积有关，还与纤维颗粒相互交织形成的亚微孔有关。

Allophane colloid, separated from air-dried soil, showed lower water content than that from fresh soil by 23-29% over the range from -1.4JKg^<-1> to -800JKg^<-1> of matric potential. Since both samples were prepared to be less than 50 nm in Stokes'diameter, this irreversibility was ascribed to submicroscopic irreversible aggregation. Water characteristic curves of allophane colloid separated from fresh soil were coincident regardless of different pHs, i.e.different surface charges below -100JKg^<-1>, and diverged gradually above -100JKg^<-1>, from 3.1 nm in average particle separation. The lower the sbsolute value of allophane charge was, the higher the water content was above -100JKg^<-1>. Water characteristic curves of allophane were irreversible except for highly charged one above -100JKg^<-1>. The water content of imogolite was higher that of montmorillionite at any matric potential, and showed more than twice as much as that of allophane below -10JKg^<-1>. The water content of allophane was higher than that of montmorillonite above -400JKg^<-1>. When montmorillonite was mixed with allophanic clay, the water content became higher than either of clays in the range from -100JKg^<-1> to -800JKg^<-1> due to intercalation. The high water retentivity of imogolite can be explained not only in terms of it's high specific surface area but also submicroscopic pores made up by intertwined fibrous particles.