TY - JOUR T1 - Dynamic Sorption of Ammonium by a Sandy Loam Soil Treated with Zeolite and Evaluation of Convection-Dispersion and Mobile-Immobile Models TT - جذب دینامیک آمونیوم به‌وسیله یک خاک لوم شنی تیمارشده با زئولیت و ارزیابی معادلات جابه‌جایی - انتشار و رطوبت متحرک- غیرمتحرک JF - JSTNAR JO - JSTNAR VL - 16 IS - 62 UR - http://jstnar.iut.ac.ir/article-1-2502-en.html Y1 - 2013 SP - 163 EP - 173 KW - Ammonium KW - Zeolite KW - BTC curves KW - Modeling KW - Hydrus-1D. N2 - The objective of this study was to investigate the effect of potassium zeolite on ammonium ion sorption and retention in a saturated sandy loam soil in laboratory conditions with four treatments of 0, 2, 4 and 8 g zeolite per kg soil. The study was conducted as a completely randomized block design. Simulation of ammonium ion leaching was performed using Hydrus-1D model in the soil columns. Ammonium nitrate fertilizer with a concentration of 10g per liter was added to soil columns and then leaching was performed. Results of the study showed that adding potassium zeolite to soil causes reduction in the mobility of ammonium ion and increase in the retention of ammonium in soil. Also, the results of the Convection- Dispersion (CDE) and Mobile- Immobile (MIM) models investigation indicated that the ammonium ion sorption by soil followed the Freundlich isotherm model. Absorption isotherms and diffusion and dispersion coefficients were determined using the inverse modeling technique. Based on the results obtained, optimized values of Freundlich isotherm of model were much less than the observed amounts. This shows that the Hydrus-1D model is not able to predict the ammonium ion mobility in soil macropores, and as a result, reduces greatly the amount of absorption parameters. Because the soil was disturbed, CDE model estimation was closer to the observed values in all four treatments M3 ER -