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International audience; Preferential water flow in soil macropores such as underground channels formed by worm activity and plant root growth, can move a large volume of water and contaminants to groundwater resources in a short time. To describe these types of water flow in soil, Di Pietro et al. (2003) developed and proposed kinematic-dispersive wave (KDW) model. They suggested this model by adding a dispersive term to the kinematic wave (KW) model that was severely convective and was presented by Germann in 1985. The fundamental assumption of this model is that the water flux (u) is exclusively a function of the mobile water content, but in the KDW model, considering its additional dispersive term, it is assumed that the water flux is a non-linear function of the mobile water content and its first-time derivative. The first term of this assumption is a power function where the water flux depends on the mobile water content. This equation is just a mathematical equation and has no significant physical meaning. In this research, this power function is substituted by the shape of van Genuchten model that has an acceptable physical meaning, and thus the kinematic-dispersive wave van Genuchten (KDW-VG) model is introduced for the first time as the innovation of this research. The models were calibrated and validated with observations of four different rainfall intensities that were applied on the surface of a soil column with artificial preferential pathways. The output water fluxes from the bottom of the soil column versus the soil mobile volumetric water content in the column were recorded at set times. First, both the KDW and KDW-VG models were calibrated and their indefinite coefficients were determined by minimizing the error function between the observed and modelled water fluxes versus mobile volumetric water content using particle swarm optimization (PSO) algorithm. Next, both models, which are second-degree non-linear partial differential equations, were solved using numerical finite difference method with the MAMAS programming language, and were validated by experimental observations of rainfall hydrograph that was passed through the preferential routes of a physical model and was recorded from the bottom of the soil column. Root-mean-square error (RMSE) comparison of the models predictions and observations indicated that the proposed model (KDW-VG) could predict the observations more accurately compared with the KDW model, and also had better performance in the calibration stage.

In the present study, the adsorption of zinc (Zn2 +) and lead (Pb2 +) from aqueous solutions by nanostructured cedar leaf ash as biosorbent was investigated in batch tests under different experimental conditions. The chemical and morphological structures of biosorbent were investigated by scanning electron microscopy (SEM), elemental analyzer (CHNSO), particle size analyzer (PSA), X-ray Fluorescence spectroscopy (XRF) and Fourier-transform infrared spectroscopy (FTIR). The effect of different parameters such as solution pH, contact time and adsorbent dosage were investigated on the biosorption of two studied metals by nanostructured cedar leaf ash. The biosorption process was found to be relatively fast and equilibrium was achieved within 30 min for Zn2 + and Pb2 +. The adsorption data were analyzed using different isotherm models (Langmuir, Freundlich, Redlich–Peterson and Sips (Langmuir–Freundlich)) and kinetic models (pseudo-first-order, pseudo-second-order and intraparticle diffusion). Results revealed that pseudo-second-order kinetic model could well describe the adsorption kinetics of Zn2 + and Pb2 + biosorption, and Sips (Langmuir–Freundlich) model was found to fit well for Zn2 + and Pb2 + adsorption. The maximum adsorption capacity from Langmuir model was calculated as 7.23 and 4.79 mg g− 1 for Pb2 + and Zn2 +, respectively.

Heavy metals in water resources are one of the important environmental problems. These metals have hazardous effects on human health. This study was conducted to investigate the comparison between adsorption of cadmium from aqueous solution using nano/milli-sized adsorbents of cedar leaf ash by batch experiments and with variation of impressive parameters such as pH, contact time, and adsorbent amount. The results showed, the optimum pH of adsorption was 5. Adsorption equilibrium times for nano/milli-sized adsorbents were obtained in 30 and 45 min, respectively. With increasing the amount of milli-sized adsorbent, adsorption efficiency increased but increasing of nanosized adsorbent at first, caused the increase in adsorption efficiency and then adsorption efficiency decreased because of clogging phenomenon of adsorbent in aqueous solution. The experimental data were analyzed using two isotherm models (Langmuir and Freundlich) and two kinetic models (pseudo-first-order and pseudo-second-order). Ba...

The increased use of nitrogen fertilizers in agriculture would cause migration of nitrogen to surface and groundwater; accordingly, would lead to water resources contamination. The objective of this study is to investigate the effect of potassium zeolite on nitrate and ammonium ions sorption and retention in a saturated sandy loam soil in a laboratory condition. The study was conducted as a completely randomized block design with four treatments of 0, 2, 4 and 8 g zeolite per kilogram soil and three replications. Ammonium nitrate fertilizer with concentration of 10 g l−1 was added to soil columns and then leaching was performed. The results show that increasing potassium zeolite to soil causes reduction to the mobility of both nitrate and ammonium and enhancement of the retention of ions in soil. Ions leaching were simulated with convection–dispersion-equation (CDE) and mobile–immobile model (MIM) using HYDRUS-1D code. The results indicate that ammonium ion sorption by soil followed the Freundlich isotherm model. Absorption isotherms and dispersion (De) coefficient were determined through the inverse modeling for both ions. Based on the results, optimized values of Freundlich isotherm were much less than the observed amounts. This shows that the HYDRUS-1D model underestimated the adsorption parameters to predict the ammonium ion mobility in soil macropores. Since soil has been disturbed, the prediction of CDE model was equal to MIM model approximately. Both models showed that as the amount of applied zeolite increases, the dispersion (De) coefficient of nitrate and ammonium ions in the soil increases.

The study of rainfall characteristics changes is critical for agricultural, environmental and water resources projects. Generally, trend test performs for evaluation of direction and magnitude of changes, but the test is not able to demonstrate abrupt change in time series if it occurs. In this research work, recent changes of rainfall characteristics of the Karun and Dez watershed, located in southwest of Iran, were evaluated. For determination of change points and trends of rainfall characteristics of varrious time series, Pettitt and Man-Kendall tests were applied to analyse these time series. A forty-eight (48)-time series from 12 meteorological stations in the aforementioned watershed were investigated. Results of the study showed that the change points in 5-time series were statistically significant at 95% confidence level. Change points produced considerable errors in evaluation of magnitude and direction of trends of the time series. Therefore, for prevention of false conclusion, it is suggested that change points of the time series must be known before analysis.