Relationship between surface charge and water characteristic curve of clays

在基质电位-1.4JKg^<-1> ~ -800JKg^<-1>范围内，从风干土壤中分离出的Allophane胶体含水量比新鲜土壤低23-29%。由于制备的两种样品的Stokes直径都小于50 nm，因此这种不可逆性归因于亚微观的不可逆聚集。在-100JKg^<-1>以下不同ph值下，从新鲜土壤中分离出的allophane胶体的水特征曲线基本一致，在-100JKg^<-1>以上，从平均颗粒分离3.1 nm开始，水特征曲线逐渐偏离。磷素电荷绝对值越低，水含量越高，高于-100JKg^<-1>。除在-100JKg^<-1>以上的高电荷外，磷烷的水特征曲线是不可逆的。在任何基质电位下，铁长石的含水率均高于蒙脱石，且在-10JKg^<-1>以下的含水率是allophane的两倍以上。在-400JKg^<-1>以上，铁矾石的含水率高于蒙脱石。当蒙脱石与同种粘土混合时，由于插层作用，其含水率在-100JKg^<-1> ~ -800JKg^<-1>范围内均高于两种粘土。伊莫长石的高保水性不仅与它的高比表面积有关，还与纤维颗粒相互交织形成的亚微观孔隙有关。

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.