Retardation (hydrology)

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In the geosciences , the term retardation (from the Latin retardare to delay) is used primarily in hydrology in connection with the transport of substances. Here it describes the slowing down of a substance in relation to the moving medium in which it is transported.

Retardation occurs, for example, when a substance is transported through a medium with active surfaces on which it can adsorb . As a result of the processes of adsorption and desorption , the substance is slowed down compared to the transport medium. The so-called retardation factor R quantifies this process. Among other things, it is defined as the ratio between the distance speed, e.g. the transport speed of a non-sorbent substance, and the speed of the sorbent substance : ${\displaystyle v_{a}}$ ${\displaystyle v_{Stoff}}$

${\displaystyle R={\frac {v_{a}}{v_{Stoff}}}}$