Subsurface Occurrence of Mirabilite in a Mollisol of Southern Alberta, Canada: A Case Study
- G. J. Beke * and
- C. J. Palmer
An efflorescent mineral, occurring at about 1 m depth in a moderately well-drained soil of southern Alberta, had a chemical composition which corresponded to that of mirabilite, a hydrated sodium sulfate mineral. The x-ray diffraction analysis of dehydrated crystals identified the anhydrous sodium sulfate mineral thenardite. The mirabilite crystals occurred in unsaturated soil beneath a melting frozen layer. Saturation extracts of bulk soil samples identified two zones of high ionic concentration, at the depth of mirabilite occurrence and below the water table. The dominant ions in these zones were sulfate and sodium and, to a lesser extent, magnesium. All saturation extracts and soil solutions from below the frozen layer and the groundwater were found to be saturated with respect to calcite, dolomite, and gypsum. Only the soil solutions from the 90 to 120 cm depth showed saturation with mirabilite. Mirabilite formation was attributed to the low soil temperatures, high soil water contents, and concentration of ions below the frozen layer.
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