MINERALOGICAL, PHYSICAL, AND CHEMICAL CHARACTERISTICS OF AMORPHOUS CONSTITUENTS IN SOME PODZOLIC SOILS FROM BRITISH COLUMBIA

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Abstract
The inorganic clay constituents of the B horizons of three Podzolic soils from British Columbia were analyzed by X-ray diffraction, infrared, electron-optical and chemical methods. The amorphous inorganic constituents comprised from 51 to 82% of the clay in these Podzol B horizons. Quartz, feldspar, chlorite, and vermiculite were the dominant minerals in the crystalline portion of the clay. Infrared spectra suggested the presence of appreciable amounts of imogolite in the fine clays of the three soils. Electron optical evidence confirmed its presence in small amounts (< 3%) in the fine clays of the Haney and Marble Hill soils. The majority of the fine clay particles appeared gel-like and did not show the 50 Å spherical "unit particle" characteristic of allophane. The amorphous clay constituents had SiO2/Al2O3 ratios of 0.2–0.4 and consisted therefore mainly of sesquioxides. A portion of the sesquioxides was probably derived from organic-complexed Al and Fe that was precipitated as hydrous oxides during peroxide treatment prior to clay separation. Although the chemical composition and micromorphology of the Podzol B amorphous clay constituents were different from those of allophane, their effect on some soil properties was the same as that of allophane. For example, the soil-surface charge was strongly dependent on pH and the high soil plasticity was lost during drying. This behavior was probably significantly enhanced by the relatively high organic matter contents of the samples studied. There was no evidence, however, for any specificity in cation exchange, such as retention of Rb against exchange with Na.

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