2] partial pressure used in the previous approaches were used in this one, with the exception of the selectivity coefficients for cation exchange.
Visconti F, de Paz JM, Rubio JL (2012) Choice of selectivity coefficients for cation exchange using principal components analysis and bootstrap ANOVA of coefficients of variation.
Cation selectivity coefficients based on mass action law, such as the Vaneslow (1932) and Gapon (1933) equations, are frequently used to describe cation equilibria between exchangeable and solution phases based on knowledge of the SAR or PAR.
Soil-solution equilibration procedure for measurement of selectivity coefficients
Calculation of selectivity coefficients in binary and ternary systems
were worked out using Rothmund-Kornfeld approximation.
Gaines-Thomas selectivity coefficients
were used to investigate changes in cation preferences for exchange sites as depth increased.
V,i] is the individual Vanselow selectivity coefficient of sites i, and KAR (potassium adsorption ratio) is the activity ratio ([K.
A functional relationship between the Gaine--Thomas selectivity coefficient and the equivalent fraction of potassium on the exchanger can be derived from Eqns 3 and 8 in terms of Rotbmund Kornfeld empirical parameters.
2, the decrease in the potassium selectivity coefficient with an increase in the potassium saturation on the exchanger was adequately described by Eqn 16 for both soils with an excellent agreement between the [K.
Suarez and Wood (1993) developed a mixing model which is able to approximate the nonconstant values of the soil selectivity coefficient by taking into account the organic matter content of the soil and using the published constant selectivity values for clay and organic matter.
These simulations have been performed using generalised cation selectivity coefficients and without consideration of the effects of soil levelling after leaching.