JWSS - Journal of Water and Soil Science

Phytoremediation models are important to understand the processes governing phytoremediation and the management of contaminated soils. Little effort has been made for evaluating the potential of the phytoremediation of metals based on the mathematical models. Therefore, the purpose of this study was modeling the phytoremediation of the nickel-contaminated soils. For this purpose, a model was recommended for estimating the rate of the phytoremediation of nickel from the soil by means of relative transpiration reduction and concentration of nickel in the plant functions. To evaluate the model, soil was contaminated with different levels of nickel by nickel nitrate. Then, the pots were filled with contaminated soil and Basil (ocimum tenuiflirum L.) seeds were planted. To avoid the dry tension, the pots were weighed and irrigated to the point of field capacity (FC) at short time intervals (48 hours). The plants were harvested in four times. At each harvesting stage, the relative transpiration values and nickel concentration in the soil and plant samples were measured. The performance of the model was evaluated by statistical methods such as Maximum Error, Root Mean Square Error, Coefficient of Determination, Efficiency of Model and Coefficient of Residual Mass. Results demonstrated that in the case of nickel contamination in soil, changes in the relative transpiration of Basil can be measured by the two proposed models and the linear model (R2=0.94) has a better performance compared to the nonlinear one (R2=0.84). Also the model obtained from the combination of linear function and nickel's concentration in soil has a relatively good (R=0.7) fit with the measured values of the remediation rate of nickel in soil.

Modeling of flow and transport processes in variably saturated porous media requires detailed knowledge of the soil hydraulic properties. The hydraulic properties to be determined by the inverse problem solution are the unsaturated hydraulic conductivity K(h) and the water retention curve θ(h). The inverse modeling approach assumes that both θ(h) and K(h) as well as transport parameters can be determined simultaneously from transient flow data by numerical inversion of the governing flow and transport equations. In order to find answers to the questions of uniqueness, identifiability and stability of different experimental setups, a new numerical experiment of redistribution was carried out. To study the shape of the objective function near its minimum, response surfaces for the estimated parameters were generated. The sensitivity of model outputs with respect to changes in input parameters was also computed and analyzed. Results of the redistribution experiment suggest that the non-uniqueness increases when the model output variables are not sensitive enough to the optimized parameters. As expected, the estimated values of parameters were sensitive to the magnitude of error in the measured data. In this experiment, the parameter estimation based on the pressure head observations provides unique solution. Due to preferential flow in the sample, tensiometric observations may provide poor results for inverse problem solution. Taking into account information about saturated hydraulic conductivity, Ks improved the likelihood of uniqueness and reduced the errors in parameter estimation of the shape parameters (α, n). It was found that the sensitivity analysis could be a useful tool to design the optimal time and location distribution of experimental observations.

The effects of water quality, installation depth and space of subsurface drip irrigation (SDI) laterals on yield and visual quality of turfgrass were investigated. A field experiment was conducted at the experimental farm of Shahrekord University. The experimental design was a Split-Split Plot with experimental arrangement of completely randomized block design with 16 treatments and three replications. Treatments included two types of water quality: well water (W) and treated wastewater (WW), two installation spaces of SDI laterals (45 and 60 cm) and four depths of placement of SDI laterals (15, 20, 25 and 30 cm). Turfgrass indices recorded during the experiment included height, dry mass, color, visual density and growth uniformity. The ANOVA results showed that interaction of irrigation water quality × lateral spacing × installation depth of SDI laterals is significant on the height, dry mass and growth uniformity of turfgrass. Irrigation with wastewater as compared to well water produced grass with significantly higher height and more dry weight. Treatments irrigated with well water had a better growth uniformity than those treatments irrigated with wastewater. Results indicated that there was no significant effect of experimental factors on turfgrass color. The interactional effect of lateral spacing and installation depth on the turfgrass density was significant. Increasing installation depth and laterals spacing caused a decrease in turf’s yield and visual quality.

As there are some health and environmental concerns about wastewater, dewatered sludge, increase in green waste, and restricted legislation about burning them outdoors, environmental health engineers are investigating to find a simple, cost effective and efficient method. This is aimed to have healthy, safe and sustainable disposal of such materials. Co-composting of sludge and green waste is a newly developed process which can help us to achieve this goal. This study was to investigate the most suitable ratio of dewatered sludge to green waste from Chonibieh wastewater treatment plant in Ahvaz, Iran, and assess the feasibility of co-composting of this waste. So, dewatered sludge was composted with green waste as a bulking agent in three different ratios (1:1 ,2:1 ,3:1 : green waste: dewatered sludge W:W). Then composting proceeded in pilot vessels (M1, M2, M3) for 23 days. The C/N ratio, the percentage of total nitrogen, phosphorus, total organic carbon, humidity and pH were tested in certain periods and compared with the national standards. This study showed that in M1, M2, M3 pilots, all parameters (except for total phosphorus) including C/N ratio, percentage of total nitrogen and total organic carbon, humidity, pH could meet class 1 national standard in Iran. Moreover, this compost product could meet the EPA microbial standards, class A. So, the product of this compost process is completely stabilized and could be used in agricultural lands.

Determining the spatial distribution of different contaminants in soil is essential for the pollution assessment and risk control. Interpolation methods are widely used to estimate the concentrations of the heavy metals in the unstudied sites. In this study, the performances of interpolation methods (inverse distance weighting, local polynomials and ordinary Kriging and radial basis functions) were evaluated to estimate the topsoil contamination with copper and nickel in Golestan Province. 216 surface soil samples were collected from Golestan province, and their Cu and Ni concentrations were measured. Soil contamination was determined using different interpolation methods. Cross validation was applied to compare the methods and estimate their accuracy. The results showed that all the tested interpolation methods have an acceptable prediction accuracy of the mean content for soil heavy metals. RBF-IMQ and IDW1 methods had the lowest RMSE, whereas RBF-TPS method with the largest RMSE estimated a larger size for the polluted area. The greater the weighting power, the larger the polluted area estimated by IDW. Compared with the ‘‘sample ratio over the pollution limits” method, the polluted areas of Cu and Ni were reduced by 8.38% and 6.14%, respectively.

This study was conducted to determine some mineral content concentration in soil and plant of three elevation classes (1500, 2200 and 3000m) and two phenological stages of flowering and seedling start in north-facing slopes of Sabalan rangelands. Soil samples from the depth of 20cm and plant samples using 1×1m plots with 10 replications were collected. After sample preparation, the concentrations of minerals such as calcium, phosphorous, sodium, potassium, ion, copper, zinc and magnesium were determined using spectrophotometer and flame photometer. Data was analyzed by SAS9.1 software using Completely Randomized Design with a Generalized Linear Model procedure. Results showed that elevation had a significant effect on Ca, Fe, Cu, Zn and Mn of soil and P, Na, K, Mg and Mn of plants in the study areas (P&le0.05). Growing stages had a significant effect on all elements of plants except Ca (P&le0.05). Moreover, results showed that in three elevation classes the high demand minerals’ concentration was higher at the starting seedling stage in comparison with the flowering stage. In contrast, the low demand minerals’ concentration in three elevation sites was higher in the flowering stage in comparison with seedling stage. Interaction effect of elevation and growing stage was also significant in relation to all elements except Ca (P&le0.05).

A laboratory research program was arranged to study the effect of different factors influencing the stability of fine soils against wind action. For this purpose, a laboratory wind tunnel was stabilized and several soil samples were examined by putting the sample trays inside the wind tunnel for different rates of wind velocities. The tray for soil samples was 20´30 cm² with the depth of 5 cm, and the fine soil samples were chosen with different sizes of particle and porosity. Because the main aim of this research was to investigate the effect of some polymer additives to the soil, many samples were made of the soils improved by different additives in different percentages. Furthermore, the effect of infiltration of the liquid additives was also examined, which could show different infiltration heights as functions of soil type, additive type and the height of pouring. Some of the results were examined by using software. The lab results in this research were compared with some proposed theoretical ones. It was found that as the average diameter of particles increases, erodibility under the same wind velocity decreases, and the applied polymer emulsions decrease the erodibility up to 90% compared to the initial condition. Impacts of dust emission due to the suspended dispersion of fine particles and creeping movements of coarse particles are mitigated as a result of treatment with these emulsions. Variations in erosion of soils at various wind velocities depend on the value of threshold friction velocity with the result that the soil erosion values in case of coarser soils after the increase in velocity would be higher than those of threshold friction velocity. Finally, a relationship is proposed for estimation of soil erosion in terms of wind velocity. The results are consistent with the transport rate relationships proposed by different scholars.

Improvement of soils is among the major concerns in civil engineering, therefore a variety of approaches have been employed for different soil types. The annual budget of implementing the projects of this kind in countries clearly implies the importance of the subject. The loose granular soils and sediments have always imposed challenges due to their low strength and bearing capacity. Bio-mediated soil improvement has recently been introduced as a novel link of biotechnology (biotech) and civil engineering for improving the problematic soils, i.e. utilizing some bacteria to precipitate calcite on the soil particles. Bio-grouting is a branch of Bio-mediated soil improvement which is a method based on microbial calcium carbonate precipitation. In this regard, the soil samples were stabilized by injecting the bacterium Sporosarcina pasteurii in the first phase of the process and Urea and Calcium Chloride in the second phase of the process (two-phase injection) as the nutrients into the sandy soil columns and subjected to unconfined compressive strength test. In this research, Taguchi method was utilized for design of experience (DOE). Based on results obtained, the activity of the bacteria caused the precipitation of calcium carbonate in soil samples so that after 21 days, the unconfined compressive strength of the soil increased from 85 kPa in the control sample to 930 kPa at optimum condition.

Accurate estimation of ET₀ in any region is very important. The aim of this study is to compare and calibrate the 20 empirical methods of estimating evapotranspiration (ET₀) based on three categories in monthly timescale at the Urmia Lake watershed. These categories are: 1) temperature-based models (Hargreaves (HG), Thornthwaite (TW), Blaney-Criddle (BC), Linacre (Lin)), 2) radiation-based model (the Doorenbos-Pruitt (DP), Priestly-Taylor (PT), Makkink (Mak), Jensen-Haise (JH), Turc (T), Abtew (A), McGuinness-Bordne (MB)) and 3) mass transfer-based model (Meyer (M), Dalton (D), Rohwer (R), Penman (P), Brockamp-Wenner (BW), Mahringer (Ma), Trabert (Tr), WMO and Albrecht (AL)). For this purpose, the information of 10 synoptic meteorological stations during the period of 1986-2010 was used. Results from the above mentioned methods were compared with the output of the FAO Penman-Monteith (PMF-56) method. Performance of the methods evaluated using the R², RMSE, MBE and MAE statistics. The best and worst methods of each category were determined for the study area. The best methods of each category were calibrated for the area under study. Results indicated that there is a significant difference between the results of selected methods of each category and the PMF-56 method. Performance of the selected methods remarkably increased after calibration. Among the temperature-based group, the HG method having the median R² value of 0.9597 was recognized as the best method. After calibration the medians of RMSE, MBE, and MAE were 72.09, 3.14 and 10.70 mm/ month, respectively. After HG, the Lin and BC found to be the best second and third methods in the study area. The TW showed Large error, therefore, it was not a suitable method for ET₀ estimation in study area. Among the radiation-based group, the DP model was selected as the best method in the study area. Furthermore, the median of R² values was 0.982. In this method, the medians of RMSE, MBE and MAE after calibration were 7.89. -0.62 and 6.03 mm/month, respectively. Following DP, the PT method was recognized as the 2^nd best one. The methods namely M, JH, T, A and MB were put in the 3^rd to seventh rank of the radiation category. Finally, among the mass transfer-based group, having R²=0.8945, the Meyer method was selected as the best method of this group for the study area. In the mentioned method (after calibration) the medians of RMSE, MBE, and MAE were 21.8, -8.7 and 17.3 mm per month, respectively. From mass transfer based group, the D method was found as the second best method in the study area. The methods namely R, P, BW, Ma, Tr, WMO and A were ranked 3^rd to 7^th, respectively. In general, the performance of radiation based methods was superior than others in Urmia Lake basin. Temperature based methods and mass transfer based methods were ranked second and third, respectively. Further examination of the performance resulted in the following rank of accuracy as compared with the PMF-56: DP (Radiation based), HG (Temperature based) and Meyer (Mass transfer). In general, it can be concluded that after calibration the DP method is suitable to estimate reference crop evapotranspiration among 20 selected methods in the Urmia Lake basin.

Salt cedar is widely spread out in most part of the country but there is lack of information about its symbiosis with arbuscular mycorrhizal fungi. Then, the main objective of this study was to evaluate the symbiosis of AMF with salt cedar and its affectability by distance from river and soil physiochemical properties. For this purpose, riparian Maroon forest width was divided to three locations including riverside area, intermediate area and the area far from river with 200-hundred-meter interval. In each site 10 salt cedars were randomly selected and soil plus hair root samples were gathered from the salt cedar rhizosphere. Our result indicated that root colonization and spore density in the intermediate distance had the lowest and highest values, respectively. These values were significantly different compared to the other two sites. The average root colonization percent in the riverside area, intermediate area and the area far from river sites were 82.37, 73.77 and 80.17, respectively. While the average spore density in the riverside area, intermediate area and the area far from river were 189, 245.5 and 188.8 in five gram soils, respectively. Root colonization had significant positive correlation with soil potassium while spore density had significant correlation with studied soil physiochemical properties. Also, soil nitrogen, organic carbon, potassium and clay showed 52.6, 51.19, 50 and 23.4% decreasing trend from the riverside area to the area far from river. Regarding this research results, salt cedar showed high level of symbiosis with arbuscular mycorrhizal fungi but this symbiosis could be affected by distance from river in riparian forest.

Traditionally, most corn field in Hamedan Province is prepared for planting by moldboard plowing followed by a number of secondary tillage operations. In recent years conservation tillage systems have become more popular. This research was conducted in the form of a split plot experimental design with six tillage treatments and three replications. Main tillage methods including: (T1) conventional tillage (moldboard plow + cyclotiller equipped with roller), (T2) combination tiller (chisel plow equipped with roller) (T3) bandary tillage with chisel blades were considered as main plots and two P fertilizer application including: (F1) fertilize broadcasting and (F2) fertilizer bandary placement were considered as sub plots. During growing seasons, soil mechanical resistance (cone index), soil bulk density and water infiltration in soil were measured. At the end of the growing season (harvesting time), corn yield and its components were measured. Results indicated that tillage methods and soil depth had a significant effect on the soil bulk density and cone index. The effect of tillage on water infiltration in soil was significant. The effect of P fertilizer application on corn yield was significant (P≤0/01) and P fertilizer bandary placement with mean corn yield of 10862 kg/ha had higher yield value than the fertilizer broadcasting with mean corn yield of 9965 kg/ha. Although the difference between tillage methods for corn yield was not statistically different, T2 treatment with mean corn yield of 10913 kg/ha had higher yield value than the other two tillage treatments (T1 with mean corn yield of 10106 kg/ha and T3 with mean corn yield of 10222 kg/ha).

To evaluate the effect of supplemental irrigation and seed priming on yield and some quantity and quality characteristics of vetch (Vicia dasycarpa) rainfed maragheh cultivar, an experiment was carried out at the Research Farm of Faculty of Agriculture, University of Urmia, West Azarbaijan province, Iran, during 2011. The experiment was laid out using split-plot, based on Randomized Complete Block design in three replicates. The factors studied were: Supplemental irrigation at four levels: without supplemental irrigation (I₁), 1 time of supplemental irrigation (I₂), 2 times of supplemental irrigation (I₃) and 3 times of supplemental irrigation (I₃). The subplot included four levels of seed priming: Control (C), Water (W), Phosphate (P) and Nitroxin (N). Plant height, pod number in stems, 1000-grain weight, wet and dry forage yield in the second and third harvest and fiber percentage in the second and third harvest, protein yield in the second and third harvest, biological yield and harvest index were influenced by the supplemental irrigation. Wet and dry forage yield in the second harvest and wet forage yield in the third harvest were highest in I₄ with respectively 14.5, 16.72 and 3.56 (tons/hectare) yield and lowest with respectively 7.73, 7.47 and 2.06 (tons/hectare) yield. As a result, applying 2 times of supplemental irrigation and seed treatment with phosphate and nitroxin had positive effects on quality and quantity yield of vetch and they could improve the quantity and quality of Vetch forage.