JWSS - Journal of Water and Soil Science

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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

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Transport of fluoride and consumption of groundwater with excess fluoride concentrations poses a health threat to millions of people around the world. The objective of this study was to simulate transport of fluoride (F) using HYDRUS-1D model. The study was conducted in lysimeters at Lavark research station site in Isfahan. The treatments consisted of two concentrations of F (157 and 315 mg kg-1). The duration of the study was 125 days. Some of soil physical and chemical properties, soluble F and total F concentration were determined during the study. The results showed the transport of F in calcareous soil profiles. This may be due to the high pH and desorption of F ion as a result of repulsion by the more negatively charged soil surfaces. The highest concentration of total F and water soluble F were observed in the 10 cm surface soil layer. The concentration of F decreased with increased soil depth. The correlation coefficient was significant between the water soluble fluoride and the total fluoride (1% level). Also, the difference between the observed t- value and a critical value on the t distribution is statistically insignificant. It showed that the model simulated successfully water soluble F concentration in the soil profile.

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In the present study Hydrus-1D software was used to simulate electrical conductivity, pH and sodium, potassium, calcium, magnesium, chloride and sulfate ions. Field experiments were performed at the Sugarcane Research Center located in south of Ahvaz on sugarcane varieties CP48-103 with four water treatments (one treatment was Karun river water and three treatments were diluted drainage water) and three replications. The samples were collected from 0-30, 30-60 and 60-90 cm soil depth before irrigation and electrical conductivity and anions and cations of soil were measured in the laboratory. Sensitivity analysis and calibration were first performed with the aim of verifying the Hydrus-1D software. The sensitivity analysis indicated that the software had maximum sensitivity to the saturated volumetric water content. Minimum sensitivity was for the inverse of the air-entry suction, tortuosity parameter, residual volumetric water contents and moderate sensitivity was for hydraulic conductivity at natural saturation. Also, the software did not show any sensitivity to empirical parameter related to the pore size distribution that is reflected in the slope of water retention curve. In calibration stage the amount of hydraulic conductivity at natural saturation, residual volumetric water contents, saturation volumetric water contents, the inverse of the air-entry suction, empirical parameter related to the pore size distribution and tortuosity were obtained as 18 (cm/day), 0.04 (cm³/cm³), 0.63(cm³/cm³), 0.012 (cm^-1), 1.2 and 0.6 respectively. The results showed that the coefficient of determination of all parameters was more than 0.85 which confirms the appropriate capabilities of the model in simulation of electrical conductivity, pH, anions and cations. In the modeling carried out the amount of NRMSE was between 11 and 18 percent which indicates good performance of the model. The Nash-Sutcliffe efficiency criterion was obtained 0.72 to 0.8 that indicates a good match of the model with reality. The coefficient of residual mass in this paper was positive for electrical conductivity, pH and sodium, potassium, calcium, magnesium and negative for chloride and sulfate. The positive and negative coefficient of the residual mass shows less and over estimation of the model.