AMMONIUM ION ADSORPTION ON CLAYS AND SAND UNDER FRESHWATER AND SEAWATER CONDITIONS

摘要

Nitrogen enters rivers and coastal regions through runoff, atmospheric deposition and precipitation. This leads to increasing nitrogen input to the water body and subsequently to eutrophication problems. The ammonium ion is a major component of nitrogen loading to coastal areas and since nitrogen is the limiting nutrient in many coastal marine waters, sediments are a major site controlling the cycling and availability of nitrogen. Ammonium can diffuse to overlying water and be adsorbed onto the sediment. The purpose of this experimental study was to find the adsorption coefficient and the adsorption isotherm of the ammonium ion for clay (Kaolinite and Montmorillonite) and sand (coarse and fine grades) using distilled and artificial sea water. This study showed that the ammonium adsorption for all four sediment types investigated was almost linear and fitted to the Freundlich isotherm within different concentrations in both distilled and artificial sea water. The adsorption in Montmorillonite,Kaolinite and coarse and fine sand in distilled water was higher than the amount of ammonium ions adsorbed in artificial sea water. The adsorption coefficient was higher under distilled water and lower under artificial sea water.