Characteristics of Clay Minerals in Saline Alkaline Soils in Alberta, Canada

Abstract

AbstractThe stability of clay minerals in extremely saline alkaline soils is not well understood, but may be expected to differ from those in other soils due to differences in the geochemical environment. A survey of the clay mineralogy of surface horizons of 39 salt‐affected soils in Alberta, Canada, showed that many samples had unusual x‐ray diffraction characteristics in that essentially no basal reflections for smectite minerals were recorded. Four sites were subsequently selected for detailed mineralogical characterization. Extremely diffuse smectite diffraction maxima were found to occur primarily in the coarse clay fraction of surface soils, and appear to be the result of interaction with organic matter. After traditional pretreatments to remove organic matter and carbonates, the clay mineralogy of salt‐affected soils was found to be similar to nonsaline soils. Slight changes were sometimes noted in the diffraction maxima of the smectite minerals, possibly indicating lower crystallinity and layer charge. Tetrahedrally substituted smectites were not identified, while variable amounts of high‐charge smectite or vermiculite were detected in most samples. Despite very high ionic strengths and pH values as high as 10, little or no degradation of clay minerals appears to be occurring in these soils. Analysis of immiscibly displaced pore water indicated that the soil solutions were supersaturated with respect to common phyllosilicates. Relatively low amounts of fine clay, however, indicate that neoformation of clay minerals is unlikely.