Using the Rietveld Method for the Estimation and Characterization of Chrystalline and Amorphous Material in the Clay Fraction of Ten Hawaiian Soils

Abstract

The ability to measure the amount and composition of amorphous material in the clay fraction of soils offers opportunities for discovering the roles that these materials play in influencing soil behavior and performance. An objective of this research was to develop a methodology for the determination of the crystalline phase concentrations and the total amorphous material by the Rietveld method for ten agriculturally important Hawaiian soils. The oxide composition of the amorphous material was estimated by difference after the assignment of oxides found by X-ray fluorescence were allocated to the crystalline phases. A large disparity was found between the total amorphous material determined by the Rietveld method and the amorphous material determined by oxalate extraction, possibly because the two methods are reporting different portions of the clay fraction. For the first time correct crystalline phase concentrations can be determined because reliable estimates of the total amorphous material can be made.