نشریه پژوهش های حفاظت آب و خاک
سال بیستم شماره 2 (خرداد و تیر 1392)

Metal contents in bulk soil samples are commonly used to evaluate pollution. However, many documents indicated that metal accumulations in soils are increased with decreasing particle size. We investigated the distribution of heavy metal (Zn, Pb and Cd) concentrations in various particle size fractions and assessed spatial variability of their concentrations in soil surface around Sepahan Shahr Town located 25 Km south of Isfahan metropolis. One hundred composite soil samples were taken randomly and after air-drying fractionated in five classes including 250-500, 125-250, 75-125, 50-75 and <50 μm. Results indicated that metal contents increased with decreasing particle size. The mean of Zn concentration increased from 224 mg kg-1 in 250-500 μm size fraction to 401 mg kg-1 for the finest fraction of <50 μm. The same trend was observed for the mean of Pb and Cd concentrations. Kriged maps indicated the same general pattern for all metal concentrations. The amount of metal pollution decreased with increasing distance from sources (mines). The results could provide important information that might be useful in assessing risks associated with urban soils and areas around Isfahan metropolis where under intensive development.

Broad-crested weirs are common engineering structures in irrigation systems and hydroelectric schemes. Varying the upstream and downstream face slopes are of the important factors affecting flow conditions and discharge efficiency of structure. In this paper, the Hydraulic Grade Line, free surface profile over the broad crested weir and separation zone at the upstream corner of it have been simulated by using Fluent software. The turbulence models considered are the standard and renormalization group (RNG). The simulation results are found in good agreement with measured data. The numerical simulations show that sloping the upstream face slope increases the discharge coefficient and decreases separation zone at the upstream corner and varying the downstream face slope does not affect the separation zone and discharge coefficient. Water depth before the critical depth in the weir with the steep upstream face slope however, is greater than the weir with the mild upstream face slope. The position of critical depth does not change by varying the downstream face slope. By using mild downstream face slope, negative pressure value decreases due to the decrease in curvature of streamlines, separation zone in downstream corner and the possibility of cavitations.

Actinomycetes are widely distributed in different habitats and involved in important processes. Therefore, evaluation of their distribution is important in understanding their ecological role. Many soil microorganisms (including actinomycetes) are able to transform different forms of insoluble organic and inorganic phosphorus into a soluble form suitable for plant uptake. The objective of this study was enumeration of common actinomycetes and determination of their phytate degradation by spectrophotometry and High Performance Liquid Chromatography (HPLC) methods. Ninty seven soil samples were collected from different soil ecosystems from the province of Golestan, Iran. The initial screening was made on modified glycerol arginin agar (MGAA) to isolate common actinomycetes and modified MGA-SE (MMGA-SE) for rare actinomycetes. The enumeration of common actinomycetes was achieved on GAA. Actinomycetes colony formed on GAA in different land use was significantly different (P<0.001) and climate variation affected some soil factors and actinomycetes number. Irrigated cultivated and pasture soils had maximum and minimum number of actinomycetes, respectively. The phosphate release was confirmed in liquid culture for 46.3% of the isolates. The selected isolates showed phytate-degrading activity and their capabilities was strongly dependent on media composition. A huge variation in the capacity to degrade phytate (1.65-95.2%) among different isolates was observed.

Change in climate is one of the common problems of the present human society and is considered a threat and a disaster for the world. Therefore to study and prediction of its elements, for the disaster management is extremely necessary. Due to importance of temperature prediction as one of the most important climatic parameters, its study is necessary to manage the crisis and prediction of the weather condition. Based on information gathered for the last twenty years, a time-series model has been proposed to forecast the minimum and maximum temperatures of Gorgan. Following the elimination of seasonal effects, trend and irregular variations, an ARIMA model was presented. To ascertain the properties of the proposed model, residuals and errors were examined and the model coefficients were estimated. Using the obtained model, the minimum and maximum temperatures from 1391 to 1393 were forecasted. Finally, it became clear that there will be an increase in the minimum and maximum temperatures in the coming years.

The rainfall-runoff process and flooding are hydrologic phenomena that are difficult to study due to the influence of different parameters. So far, different methods and models are provided to analyze these phenomena. Therefore, the purpose of this study is evaluation of artificial neural networks (ANNs) for storm runoff coefficient forecasting using two transfer functions, hyperbolic tangent and sigmoid, in hidden layer and linear in output layer. For this reason, Barariyeh watershed was chosen in Neishabour and the data of 33 events were collected during 1952 to 2006. The factor analysis (FA) were used for determination of independent variables in storm runoff coefficient forecasting in which four variables were selected as independent variables, including average rainfall amount, third, first and fourth quartiles rainfall intensity and also five variables including index and first to fourth quartiles rainfall intensity. ANN was performed using sigmoid and hyperbolic tangent functions. The result of variables through factor analysis was acceptable for ANN using sigmoid transfer function but wasnt acceptable for ANN using hyperbolic tangent transfer function due to different performance of this activation function. So, other variables combined based on their hydrological role, were considered as ANN inputs. The results revealed that ANN using first to fourth quartile rainfall intensity, rainfall duration, average rainfall amount and total rainfall of five days ago inputs and hyperbolic tangent transfer function can predict storm runoff coefficient with R2=0.98 and RMSE=0.0337 and MAE=0.0275.

To study the effects of different levels (0, 2.5 and 5%) of alfalfa residue with and without gypsum or aluminum sulfate on chemical properties of a sodic soil, a greenhouse experiment with 9 treatments was conducted using a completely randomized design and three replications. After addition of treatments to soil samples, they were incubated for four months at moisture content of field capacity. The results showed that 2 and 4 months after incubation, treatments with 5% alfalfa residue + aluminum sulfate and 5% alfalfa residue + gypsum increased the electrical conductivity of soil samples significantly. Treatment with 5% alfalfa residue + aluminum sulfate decreased the pH values of soil samples to 1.36 and 1.55 units compared to control 2 and 4 months after incubation respectively. Treatments with gypsum and aluminum sulfate decreased water dispersible clay to 89.43 and 93.03% compared to control after 4 months of incubation respectively. Treatment with 5% alfalfa residue increased water dispersible clay by 4.8 and 2.2% 2 and 4 months after incubation respectively. Similarly, these treatments decreased sodium adsorption ratio respectively by 54.19 and 43.85% compared to control 4 months after incubation but treatments with 2.5 and 5% alfalfa residue increased sodium adsorption ratio respectively by 0.7 and 3.83% compared to control after 2 months of incubation.

Occurring fire in rangelands is one of the main degradation factors of soil and ecosystem. The objective of this study was to investigate the impact of fire on some crucial factors of soil quality in semi-steppe rangeland of Karsanak region in Chaharmahal and Bakhtiari Province. Therefore, several sites which were affected by fire at three, two and one years before this study (i.e. 2008, 2009 and 2010, respectively) were chosen. Soil water infiltration was measured using tension infiltrometer in 54 points of the study sites. Since the soil samples were taken from depths (0-10 and 15-25 cm) of each site, the numbers of soil samples for laboratory analysis were 108. Independent t-test (P=5%) was used to assess the difference between the measured properties at the burnt and control sites. The results showed that in the burnt areas compared with control areas, saturation hydraulic conductivity and basic water infiltration decreased significantly in 1, 2 and 3 years after fire. Also, the soil organic matter and mean weight diameter of aggregates (MWD) in surface layer reduced significantly in 1 and 2 years after fire. Particulate organic matter (POM) significantly decreased in surface layer of the burnt areas compared with the control areas, while their differences were not significant in sub-surface layer. Furthermore, soil water dispersible clay (WDC) and bulk density increased significantly in surface layer of all burnt areas compared with control areas. The study results showed that fire had immediate and direct impact on soil physical properties and organic matter and therefore reduced the soil quality of rangelands.

Non-Optimal use of irrigation water, limited water resources and growing need for more food require the application of modern management techniques to save water and increase water use efficiency. This is possible only with accurate estimation of crop water requirement and timely irrigation. In this study, the differences between water use efficiency, value and yield specifications in two irrigation treatments was compared. Irrigation treatments were: irrigation based on evapotranspiration calculated by real time climatic data of the field and irrigation based upon evapotranspiration calculated by mean meteorological data of the non-reference station (Saveh city). The results showed that in the control, field 5383 m3/h water were used and the yield was 38.58 Ton/ha. Therefore, water application efficiency was 7.16 kg/m3. In the other field, these amounts were 6310.2 m3/h, 30.2 ton/ha and 4.78 kg/m3 respectively. The results of the variance showed a significant difference between the diameter of the corn and number of grains, at 5%. There were also no significant difference between the other yield properties in the field. Therefore with automated irrigation management in the field and estimation of the actual water plant requirement, in additional to reducing water use and increasing water use efficiency, not only there were no significant change in yield properties but also in some cases there was increase in quality.

The sufficient amounts of essential nutrients should be supplied for plants normal growth if the soil cannot provide them. For this purpose, it is necessary to find appropriate measurement method for determining the rate of nutrient deficiency. DRIS is an efficient method due to problems of nutrients concentration critical level and sufficiency limit methods, variations of these limits in different plant cultivars and climatic conditions, and dependence of results to sampling time. Thus, an experiment has been conducted in 61 peach orchards of Golestan province for two years (1388-1390). The orchards were divided into high and low yielding populations according to DRIS method (on the yield basis of 30 kg/tree); then, all expression forms, their variances in the two populations and variance ratios of the low (SB) to high (SA) yielding populations were determined. DRIS-derived sufficiency ranges originated from high yielding populations and taking into account variance ratios (SB/SA), which were 2.46, 0.24, 2.29, 2.03 and 0.56% for N, P, K, Ca and Mg and 132.7, 32.5, 14.5 and 42.9 mg/kg for Fe, Mn, Cu and Zn, respectively. The DRIS indices for the 9 nutrients were calculated in the low yielding populations using DRIS calibration formulas and Nutrient Balance Index (NBI) was determined for each of these orchards. Results indicated that the average order of nutrients requirement in the low yielding orchards is as following: Ca>P>Mg=Mn>K>Fe>Cu=Zn>N.

Hydrological models are one of the currently used techniques for simulating runoff produced from rainfall. These models by simulatation of rainfall-runoff process, are able to estimate runoff values in ungauged cachments without spending high cost and long time. AWBM rainfall-runoff model developed by Boughton in 1993, can calculate runoff based on hourly and daily rainfall. Daily and hourly results obtained from the modelling are used in flood mangement and planning, respectivly. This model includes set of surface storage parameters (C1, C2, C3), partial area parameters (A1, A2, A3), and using daily rainfalls and discharges, monthly runoffs and evaporations. In this study, in order to evaluate the model performance, six sub-catchments located in the south of Sistan and Balochestan province were chosen under a case study. The analysis was carried out by the available data from these sub-catchment including Bah in Sistan and Balochstan Province. Daily rainfall data by using TPSS method were converted to regional data and daily diacharge to specific discharge in mm. Finally, accurancy and efficiency of the AWBM model in simulating runoff evaluated by efficiency was and determination cofficients. The results show the model can simulate runoff reasonably in all sub-catchments under study and other ungauged catchments, and also can be used as a useful tool for research and modelling hydrological process of rainfall-runoff in catchments located in arid and semi-arid regions.

Community acceptance prediction of management actions is an important component of watershed assessment to achieve integrated watershed management. The focus of this research has been the prediction of the community attitude towards vegetation-based management scenarios targeting flooding and soil erosion issues in the Chel-chai watershed. The Chel-chai watershed with an approximate area of 25680 ha and with rural population of 14048 inhabitants is located in Golestan Province and is a tributary of the Gorgan-Rud River basin. Four vegetation-based actions and 16 possible management scenarios have been developed. A social survey by completing a constructed questionnaire was conducted to predict the community acceptance of the management scenarios in the watershed. In the social survey, on the basis of the Cochran equation, 139 stakeholders inhibited in different parts of the watershed were consulted as a proportional sample of the watershed community to predict the acceptance level of the management scenarios among the community. To this end, the Binomial probability distribution was used. Social survey participants were enquired about their intention to implement the vegetation-based scenarios in the 5 years ahead (starting from 2009). In this research four levels of acceptance (no acceptance, low, moderate, and high acceptance) were considered. The analysis revealed that from farmers point of view, Scenario 2 (terracing), Scenario 4 (orchard development), Scenario 5 (agro-forestry), Scenario 9 (tree plantation and orchard development) and Scenario 15 (tree plantation, orchard development, and agro-forestry) have a better performance from social acceptance perspective among the 16 scenarios. In contrast, Scenario one (the current situation) is characterized with the lowest acceptance level. This approach is useful in choosing management scenarios and exploring the probable outcomes arising from implementing the scenarios necessary for decision making.

The accurate estimation of sediments transported by rivers is very important in many water resource management projects. Due to nonlinear behavior of hydrologic variables, application of classic methods e.g. sediment rating curve (SRC) does not have adequate precision. Therefore, intelligent methods can be applied as an efficient tool in hydrologic parameters modeling. In this study, artificial neural networks (ANNs) such as multilayer perceptron (MLP) and radial basis function (RBF) and different SRC methods including annually, hydrologic similar, high and low flows, clusters average limit, classification of discharges, hydrograph condition and seasonal classification were carried out for daily suspended sediment load estimation in Ghazaghli station, located in Gorganroud watershed. For this reason, the measured daily suspended sediment load data during the period of 1982 to 1985 were used. Three years of data were used for training sets and 1 year for testing sets. The results show that, the classic discharge method and MLP which is used current streamflow, antecedent streamflow and two days of antecedent streamflow as input parameters are the best models among the various selected models. The results also show that the accuracy of neural networks methods is more than the SRC methods.

Local scour around bridge pier is one of the most important destruction factors of bridges. Many researchers have investigated scour around bridge pier; however, there is still not available single solution for this issue due to complexity of the problem and multiplicity of the effective factors. Different methods have been proposed to prevent or reduce scouring around bridge piers such as Riprap, collar, slot, submerge sheet and so on. According to researches, installing a collar around the base to delay the onset of scour in some cases significantly reduced the depth of scour around the base. In this study, by using the rectangular collar around the cylindrical pier, the effect of the collar thickness on scour reduction around bridge pier was investigated. The results of the experiments showed with installation of the collar not only velocity of scour is reduced but the depth of scour hole around the pier especially in downstream of the pier is also decreased. Also, with increasing collar thickness, the performance of the collar is reduced. Based on the results, the collar thickness was equal to 5 percent of the pier diameter and less than that had negligible reduction in the performance of the collar. However, the performance of the collar decreased when the collar thickness was more than 5 percent. Therefore, the appropriate thickness of the collar is proposed 5 percent of the pier diameter.

Flooding phenomena accounts as a serious problem that affects most of watersheds so that the control of this catastrophic phenomena requires reduction of runoff and increasing soil infiltration. Nanotechnology is one of the newest technologies that because of its high potential and unique characteristics, it has extensive applications in all of aspects of science such as natural resources and soil conservation. This study has been done in order to assess the effects of different percentages of Nanozeolite (0.2, 0.4, and 0.6 gram per square meter) on marl soils in several slope degrees (7, 9 and 14 degree) using FEL3 rainfall simulator. The plot was used in this study had 0.5 meter in width, 1 meter in length and 0.4 meter in height. In each of plots 0.3 meter of height was dedicated for draining and the plots were filled with 0.1 meter of marl soil. After adding Nanozeolite to the soil surface, the samples were influenced by 90 millimeters per hour rainfall intensity during 30 minutes. Results showed that all of the Nanozeolite levels (0, 0.2, 0.4 and 0.6) in the three slope angle (7, 9 and 14 degrees) had not significant differences in decreasing runoff in comparison with control treatment.