PLSC204 Lecture 21: CEC and AEC processes
28 Jan 2019
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Simplified silicate clay crystal, complement of adsorbed cations, and ions in surrounding soil solutions charged surfaces. Comprises sheetlike layers with both external and internal negatively. Cations and anions in bulk solution can be leached out of soil in particular the anions since not held by soil colloids / not attracted to soil colloids. Cerxns occur on a per change basis. All else being equal, cation frequencies on colloids reflect their relative contributions to the total cation pool (in solution + adsorbed) This principle is called the ratio law or mass action effect . Monovalent cations are more likely to be replaced. Divalent are less likely to be replaced. Charge is more important (monovalent or divalent) than radius size. Hydrated radius is important since the bigger radius means a greater distance between the positive charge of cation is from the negative charge on the colloids - installation .
