CATION-EXCHANGE CAPACITY VARIATIONS IN ACIDIC FOREST SOILS FROM SUTTON, QUEBEC, CANADA

Single values of the cation exchange capacity (CEC) are widely used in modeling soil solution chemistry in soil and water ecosystems. Our ai m was to determine the CEC as a function of pH and ionic strength in a n acidic forest soil. We examined the cation exchange of two Humo-Ferr ic Podzols (Haplorthods) equilibrated with artificial soil solutions o f different concentrations. Aliquots of acid (HCl) or base (NaOH) were added to generate a pH range of 3 to 6. The CEC, determined by displa cement with BaCl2 showed little or no increase with increasing pH and a definite increase with lower pH. This anomalous behavior was attribu ted to the precipitation of aluminum (Al) at high pH and to its dissol ution at low pH.