Cation-exchange capacity

The cation exchange capacity (abbr.: CEC, T value ) is a measure for the exchangeable cations, and thus the number of binding sites of negative cation in the soil. It depends on the chemical composition of the soil and of the mechanical, as the effective active surface area is related to the size of the colloids. This is an important characteristic of the soil represents the sum of the exchangeable cations - both the basic effective as Na , K , Mg2 , Ca2 and the acidic as Al3 , Fe3 in addition to H - which bound to the negative binding sites of organic and inorganic exchanger in the ground are experimentally determined by the exchange with a neutral salt solution (e.g., barium, ammonium, or calcium chloride).

The cation exchange capacity is measured in cmol / kg or mmolc / kg. No longer in use is the statement in meq / 100 g

Here are the individual symbols for the following sizes:

• K - total number of sorbed cation species
• Ni - number of moles of cation i
• Zi - valence of the cation i (example: Al3 has the value 3)

The potential cation exchange capacity KAKpot specifies the maximum number of free cation binding sites and refers to ISO 13536 on the cation exchange capacity at a slightly basic pH ( pH = 8.1 ) of the soil. International classifications (FAO - UNESCO, U.S. Soil Taxonomy ) determine the potential CEC at pH = 7 (neutral ).

The effective cation exchange capacity ECEC are the actual number of free cation binding sites again at the information currently present pH value of the soil.

Importance

Exchangeable cations can be moved within the soil, are in adjacent ecosystems (eg water ) displaced or absorbed by plant roots. So you directly affect the supply of nutrients and metabolism of landscapes. In addition, the exchangeable cations influence important soil properties such as the structure, the air and water budget, soil reaction, and not least the biological activity. The cation exchange capacity of the soil can therefore be regarded as a Bodenbewertungsmaß (for example, agricultural land estimating maps).