Answer:
Relationship between Kd, Koc and soil organic matter
Soil adsorption coefficient (Kd) measures the amount of chemical substance adsorbed onto soil per amount of water. It is also called Freundlich solid-water distribution coefficients (Kf).
Kd = Concentration of chemical in soil/Concentration of chemical substance in water
Values for Kd vary greatly because the organic content of soil is not considered in the equation. Since adsorption occurs predominantly by partition into the soil organic matter, it is more useful to normalize the Kd to the organic carbon content of a soil and express the distribution coefficient in Koc.
Koc is known as organic carbon-water partition coefficient.
Koc = [tex] (Kd * 100)/ % Organic carbon [/tex]
Koc is also frequently estimated based on octanol-water partition coefficient Kow and water solubility.
The relationship between adsorption coefficient (kd) and organic carbon content in unit mass of soils (Coc) can be expressed as
d = [tex] Koc * Coc + α [/tex]
Koc is defined as an average of the contribution of organic matter to kd and intercept α expresses a fraction of adsorption by soil constituents other than organic carbons.
Why Kow can be used as a predictor of adsorption
Since accurate prediction of the adsorption properties of fluid mixtures in equilibrium with surfaces and/or nanoporous structures is of considerable scientific and practical importance, partition coefficients (Kow) as defined as the concentration ratio of a chemical between two media at equilibrium is used as a predictor of adsorption for optimum accuracy. Partition coefficients are also important to describe the redistribution of a chemical in the body.
Explanation:
