Abstract
Ammonium nitrogen (NH4+-N) in sediments exists as two types; (1) Dissolved in interstitial water, (2) Adsorbed onto sediment particles.
In this paper, mechanism of NH4+ adsorption and it's effect on the release process were studied.
The conclusions were as follows;
(1) NH4+, together with other cations, is adsorbed onto the negative charge of sediment particles (Ion exchange adsorption).
(2) Adsorption equilibrium is expressed by the Freundlich equation.
(3) Adsorption equilibrium is changed mainly by two factors; (a) Cation Exchange Capacity (CEC) of sediment, (b) Coexisting cations in sediments (Ca2+, Mg2+, Na+, K+ etc.), especially relative concentration level of them and NH4-N in interstitial water.
(4) Mathematical model of release process was presented. As a result of calculation, it was found that correct evaluation of adsorption equilibrium was necessary to analyze or predict the release flux of NH4+-N from sediments.
