Estimation of Vermiculite Content Using Rubidium-Fixation Procedures in Four California Soils

摘要: Quantification of phyllosilicates in soils often depends on a combination methods, including x-ray diffraction (XRD), cation exchange and fixation capacities, microscopy. We examined Rb method to quantify vermiculite content California derived from granitic nongranitic alluvium. Whole soil (<2-mm) samples were saturated with heated 110°C followed by displacement NH 4 (Rb ). Fixed was determined directly instrumental neutron activation analysis. The amount (g kg -1 ) calculated as fixed (cmol c )/0.154 (based capacity for 154 cmol For comparison, also estimated after 1-h incubation 1hr 2 mmol L RbCl 30-min extraction Cl. more rigorous heating treatment almost 35 times than the method. positively significantly correlated clay content. XRD data showed, however, that fractions dominated smectite, mica, chlorite, while vermiculite, major K- Rb-fixing mineral, dominant mineral most silt fractions. Greene-Kelly test showed that, smectitic clays, some charge originated tetrahedral sheet. Silt but not fixation. Our suggest overestimates when tetrahedrally substituted smectites are fractions, includes minerals fraction.