kationivahetusvaigu

kationivahetusvaigu (cited as kationivahetusvaikutus in Finnish literature) refers to the capacity of a soil or sediment to adsorb and exchange positively charged ions, also known as cation exchange capacity (CEC). This property is primarily determined by the quantity, distribution, and charge of exchange sites on mineral surfaces, organic matter, and clay particles within the material. Cation exchange sites are typically negatively charged, enabling them to attract and hold cations such as calcium, magnesium, potassium, and sodium. The total amount of cations that can be retained per unit mass is expressed in milliequivalents per kilogram (meq kg⁻¹) or centimoles of charge per kilogram (cmolc kg⁻¹).

CEC influences several key aspects of soil fertility and behavior. It regulates the availability of essential nutrient cations to plants, buffers soil pH by exchanging base cations for acidic ones, and affects soil structure and water retention through the formation of stable aggregates. In agrochemical management, knowledge of CEC guides the choice and dosage of fertilizers, lime, and organic amendments to optimize nutrient use efficiency and minimize leaching losses.

Measurement of CEC is typically performed using ion-exchange techniques such as the ammonium acetate method, sodium acetate method, or the use of radioactive tracer isotopes. The measured value is usually obtained after a controlled desorption step that replaces naturally occurring exchangeable cations with a known ion, allowing calculation of the total exchangeable capacity of the sample.