Examples of Ion Exchange in Soils

We shall not dig further into the formal and thermodynamics aspects of ion exchange the interested reader is referred to the abundant accounts in the literature (see, e.g., McBride 1994 Sposito 1999 Sparks 2002 Evangelou and Phillips 2005). Instead, we will present now a few examples of ion exchange studies in soils to discuss its main features. Most of them address the K+-Ca + exchange, one of the most important cases, which has been extensively studied because it affects the plant s available K+ (Beckett 1964 Beckett 1972 Evangelou, Wang, and Phillips 1994). 

With just the few examples given here one should realize that a simple view of purely electrostatic intaaction between point charges is not adequate to understand the phenomena of ion exchange. The first question here is what types of sorbed ions 

FIGU RE 5.11 Ca-K exchange isotherms in horizon B of a Rhodic Acrudox (Soil Survey Staff 1998) soil from the northern part of Sao Paulo state, Brazil. (From Alves, M. E., A. Lavorenti, Aust. J. Soil Res. 41,1423-1438, 2003. With kind permission of CSIRO Publishing, Australia.) 

If A+ is strongly bound to the exchanger phase, the activity (concentration) of A+ in solution will be small but still can be washed away by if a sufficiently 

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