Determination of the Effect of pH On Exchangeable and Soluble Na+, K+, Mg2+, and Ca2+ for Seven Horizons In a Dry Pond Soil, Kamloops, British Columbia, Canada.

Keywords:  Saline ponds, cations, flame atomic absorption spectrometry

Kamloops is located in a semi-arid climate in the interior of British Columbia.  Drought conditions have persisted over the last number of years and pond water levels have dropped. Many ponds are completely dry.  This has provided a unique opportunity to study the physical and chemical properties of soils which otherwise would be under water.  Batchelor Lake, in 1999, covered 5.5 hectares and was two metres deep.  It dried out in 2007 and has not re-hydrated.  Two soil pits were established in the fall of 2008, Batchelor 1 and Batchelor 2.  Electrical conductivity, pH, total carbon and organic carbon values were determined in 2009 for both sites. Seven horizons, from each profile were described and sampled for physical and chemical properties.  In this project soluble Na⁺, K⁺, Mg²⁺, and Ca²⁺, and cations that are extractable with ammonium acetate were determined with flame atomic absorption spectroscopy for the Batchelor 2 profile. The pH values of the ammonium acetate extractions were adjusted to match the pH of the saturated soil paste in order to determine if variations in pH affect the concentration of cations extracted from the soil. Controlling the pH of the ammonium acetate extraction to match the pH of the saturated soluble paste does not cause a significant effect on the extraction efficiency of cations. This trend is observed in all horizons except for the Mg²⁺ in the Ahk horizon, Ca²⁺ in Cskg3 and Cskg4, and K⁺ in Cskg4 where there is a significant difference in cations extracted at pH 7.5 and 8.5. The source of this difference is unknown. The extractable and soluble cations Na⁺, K⁺, Mg²⁺, and Ca²⁺, were used to calculate CEC, ESP and SAR. This project has developed a reproducible and efficient method to determine extractable cations accounting for the pH of the extract.