title: Measuring and modeling ammonium adsorption by calcareous soils.
abstract: The aim of this study was assessment of ammonium (NH 4(+) ) adsorption isotherms in some agricultural calcareous soils and modeling of that by using the mechanistic exchange model. Ten surface soils (0-30 cm) were collected from areas covered with different land uses in Hamedan, western Iran. Isotherm experiments were carried out by concentrations of NH 4(+) prepared from NH4Cl salt (0, 10, 20, 30, 40, 50, 100, and 150 mg NH 4(+)  l(-1)) in presence of 0.01 M CaCl2 solution. The empirical models including simple adsorption isotherm and Freundlich equations were fitted well to the experimental data. The average amounts of adsorbed NH 4(+) in studied soils varied from 8.95 to 35.23 %. Adsorption percentage indicated positive correlation with pH, cation-exchange capacity (CEC), equivalent calcium carbonate, and clay content and had negative correlation with sand content. In order to predict and model NH 4(+) adsorption, cation-exchange model in PHREEQC program was used. The model could simulate the NH 4(+) adsorption very well in all studied soils. The values of CEC played the major role in modeling of NH 4(+) adsorption in this study indicating that cation-exchange process was the major mechanism controlling NH 4(+) adsorption in studied soils.
authors: Department of Soil Science, College of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
authors: F
authors: F
authors: Ranjbar
authors: M
authors: M
authors: Jalali
mesh_terms: D000327:Adsorption; D002119:Calcium Carbonate / Q000737:chemistry*; D004784:Environmental Monitoring; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D000644:Quaternary Ammonium Compounds / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry
chemical_list: D000644:Quaternary Ammonium Compounds; D012987:Soil; D012989:Soil Pollutants; D002119:Calcium Carbonate