نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال هجدهم شماره 2 (پیاپی 68، تابستان 1393)

Soil surface roughness (SSR) is one of the important factors in wind and water erosion studies and control. Several parameters such as surface rock fragments influence SSR. Main objectives of this paper are to study and compare (Allmarass) random roughness (RR) and tortuosity (Tb) indices in coarse، medium and fine grain plains of Yazd-Ardakan and investigate the relationship between indices and desert pavement coverage. Roughness data were obtained by pin roghness-meter and roller chain in the three mentioned plains. RR and Tb were measured in 90cm transect length with systematic sampling pattern after determining the boundary of three kinds of plains. In each plain، 30 transects were randomly sampled and the height of soil surface roughness fractions was recorded. Distance of pins in the applied roughness meter is about 2cm. Therefore، in each 90 cm transect the height of 46 points was measured. Desert pavement coverage was measured in 20×20cm2 plots. The result showed that desert pavement coverage in coarse، medium and fine grain plains were in the range of 55-100، 40-85 and less than 5%، respectively. The relationship between RR and desert pavement was significant. The result of ANOVA (Duncan) showed، RR and Tb were significantly different in coarse، medium and fine grain plains (p-value<0. 01). In addition، by increasing desert pavement percentage RR and Tb increased exponentially in base of Neper number. The relation between RR and desert pavement coverage is stronger than Tb and desert pavement coverage. Correlation between the two measured indices was calculated and compared in different plains. The result revealed that about 54، 33 and 14% of the arability in Tb could be explained by RR in coarse and medium grain plains، respectively. The correlations of two indices were significant in coarse and medium plain and insignificant in fine grain plain. The trend of RR and Tb decreased from mountain to plain center. Although RR increased slightly in fine grain plain، the difference was not significant.

Many studies have been carried out on pure minerals to study the effect of plant roots on minerals weathering، but information on mineral weathering that normally occurs in different soil fractions is limited. To investigate the effect of German Chamomile (Matricaria chamomilla L.) cultivation on mineral weathering of clay and silt fractions in five different soil series amended or not amended (control) with cattle manure، a factorial experiment was performed in a randomized complete block design (RCBD) with three replications. At harvest time، rhizosphere soil was separated and mineralogical studies were performed through X-ray diffraction (XRD) and compared to before cultivation Results showed that in clay sized particles، trioctahedral chlorite transformed to di-octahedral chlorite while kaolinite disappeared. In silt sized particles، feldspar transformed to amphibole and vice versa The pots amended with manure showed the same changes for clay and silt sized particles as the pots without manure.

Zeolite is widely used for removing heavy metals from aqueous solutions. The objective of this study was to assess three sizes of zeolite in removing lead، nickel and cadmium from wastewater. A splite-plot experimental design was employed with 45 treatments and three replications at Shiraz University Lab in 2011. The treatments were five different concentrations of the pollutant and three sizes of zeolite (0. 075، 0. 2 and 0. 425mm). The concentrations for lead were: 40، 250، 500، 1000 and 1250 mg/l and 4، 6، 15، 20 and 40 mg/l for nickel and cadmium. The results showed that the effect of concentrations of pollutant was significant، and by increasing the concentration of pollutant، absorption of heavy metals by zeolite increases linearly. Maximum lead absorption occurred at 1250 mg/l with 59. 97 mg and minimum absorption of lead was related to the concentration of40 mg/l with 1. 82 mg for 1 grams of zeolite. Maximum and minimum nickel absorptions were related to the concentration of 40 and 4 mg/l with 1. 92 and 0. 16 mg for 1 grams of zeolite، respectively. The values were 1. 87 and 0. 18 mg for 40 and 4 mg/l for cadmium، respectively. The effect of size of zeolite on the pollutant adsorption was not significant.

Local scour around piers is the major cause of their foundation failure in the river bends that endangers the stability of the structure and its efficiency. Riprap is commonly placed around the bridges piers for local scour protection. The aim of this study was to present an equation for estimating stable riprap diameter around a cylindrical bridge pier in river bends. In this study، using an experimental model with a 180 degree bend stability، four different riprap diameters under different flow conditions and clear water flow were studied. Empirical relationships based on dimensional analysis for stable riprap design around the bridge foundation was presented. The experimental results were compared with equations provided by other researchers، including Lauchlan (1999)، Parola (1995) and Chiew (1995). Results showed that the presented equation in this paper has a good precision. The simple equation presented in this study included all factors important to the instability of the riprap، and recommends designing ripraps around the bridge pier in river bends.

Usually، dry soil readily absorbs water. However، not all soils display such characteristics. Some soils (hydrophobic soils) show resistance to wetting. Because of the importance of this subject and lack of research، we evaluated the effect of heating on water repellency and some of soil physical and chemical characteristics. So soil was combined with compost and heated at deferent temperatures، 100، 200، 300، 400 and 500 °C for 30 minutes in an oven or muffle furnace. The results showed that control treatment and heated soil at 300 °C had WDPT and MED 45 (s)، 17% and 80 (s)، 23% respectively. So، little water repellency was present prior to heating the soil. When soil was heated up to 300°C، intense water repellency resulted، but it was abruptly eliminated by increasing the heating. The soil texture was changed from loam to sandy loam at high temperatures (400 & 500 °C) and the sand percentage was increased. Organic matter decreased by increasing the temperature. Amount of pH decreased up to 200 °C and then increased at 500°C because of increasing ash in soils. Diminution of mineral and organic matter caused EC to decline in all the heated soils.

Organic carbon pools and carbon lability directly affect soil biological، physical and chemical characteristics. Besides، capacity of self-organization of soil is related to the organic carbon pools. Sand size fraction (> 50 µm) organic matter is more labile than silt+clay size fraction organic matter. Assessment of this organic carbon variation can be a suitable index to determine soil quality. The aim of present study was to evaluate the impact of land use change on particle size fractions of organic carbon and carbon pool index. In September 2010، soil samples were collected from the three major land use types including wetlands around the lake، wetlands converted to wheat، and alfalfa cultivations. Soil samples were collected from the 0-30، 30-60 and 60-90-cm depths in each of land use. According to the results of particle size fractionation of organic carbon in 0-30-cm layer، the highest and lowest amounts of sand size fraction organic carbon were obtained in wetland (67. 01 g. C. kg-1soil) and wheat land use (24. 57 g. C. kg-1soil)، respectively. Land use change from wetland to alfalfa and wheat caused a decrease of silt+clay size fraction organic carbon in 0-30-cm by 48. 39 and 45. 14 t. C. h-1، respectively. In the 30-60-cm layer of cultivated land، soil organic carbon storage in silt+clay size particle was more than sand size fraction organic carbon. Results showed that carbon pool index in alfalfa، and wheat land was decreased by 50 and 60% compared to wetland، respectively. And carbon management index in alfalfa and wheat was declined by 44. 90% and 66. 70%، respectively.

Biocalcite infilling and bridging in a sandy soil was studied in the present research. Effects of 2 bacterial species (Sporosarcina pasteurii and Sporosarcina ureae)، 3 reactant concentrations (0. 5، 1. 0، and 1. 5 M of urea and CaCl2 mixture)، and 6 reaction times (12، 24، 48، 96، 192، and 288 hr) on saturated hydraulic conductivity and mechanical strength of a sandy soil were studied as a factorial experiment. Soil samples were selected from sand dunes of Joopar area، Kerman Province. Bacterial inoculums and reactant solutions were daily added to soil columns. Results of the study showed that S. pasteuriihad had a higher effect on decreasing hydraulic conductivity of the treated samples (11. 57 cm/h) compared to the blank (41. 61 cm/h) than S. ureae. Increasing reaction times (from 12 to 288 hrs) and reactant concentrations (from 0. 5 to 1. 5 M) decreased hydraulic conductivity by 49 and 16 %، respectively. S. pasteurii increased strength of treated samples up to 2. 6 Mpa pressure compared to S. ureae. Reactant concentrations and reaction times increased soil strength significantly (2. 13 and 4. 1 Mpa، respectively). Micromorphological observation showed calcite crystals bridging soil particles and filling pore spaces.

Prediction of sediment load transported by rivers is a crucial step in the management of rivers، reservoirs and hydraulic projects. In the present study، in order to predict the suspended sediment of Taleghan river by using artificial neural network، and recognize the best ANN with the highest accuracy، 500 daily data series of flow discharge on the present day، flow discharge on the past day، flow depth and hydrograph condition (respectively with the average of 13. 83 (m3/s)، 15. 42 (m3/s)، 89. 83 (cm) and -0. 036) as input variables، and 500 daily data series of suspended sediment، as the output of the model were used. The data was related to the period of 1984-2005. 80 different neural networks were developed using different combinations of variables and also changing the number of hidden-layer neurons and threshold functions. The accuracy of the models was then compared by R2 and RMSE. Results showed that the neural network with 3-9-1 structure and input parameters of flow discharge on the present day، flow discharge on the past day and flow depth was superior (R2= 0. 97 and RMSE= 0. 068) compared to the other structures. The average of the observed data of sediment and that predicted by the optimal model (related to test step) were 1122. 802 and 1184. 924 (tons per day)، respectively.

Due to adhesion properties of fine sediments، chemical physics factors of fluid can cause changes in the behavior of sediments. In this study، the characteristics of sediment deposition with three levels of waste water، different shear stresses and initial sediment concentrations were investigated in the annular flume located at Hydraulic Laboratory of Shahrekord University. Sediments for experiments were taken from the Pirbalut dam reservoir. The velocity and the shear stress profiles were measured using an Acoustic Doppler Velocimeter (ADV). The results showed that the concentration of cohesive sediment was decreased with time and finally it reached an equilibrium concentration of sediment. The equilibrium concentrations to initial concentration (Ceq/C0) in special shear stress، for different initial sediment concentrations and different levels of waste water were almost the same. Equilibrium concentration was dependent on the initial concentration sediment. Threshold and full deposition shear stresses were increased in waste water. Shear stresses of full deposition for 0، 30 and 60 % wastewater were 0. 053، 0. 075 and 0. 070 N/m2، respectively. Also، for specified levels of waste water، the values were obtained 10، 15 and 17، in which the suspended sediments would remain.

Rate of nonexchangeable K release can significantly influence K availability. Kinetics of K+ release was studied by extraction using 0. 01 M CaCl2 in 12 surface calcareous soils of Kohgilouye Province. Results showed that cumulative K release ranged from 89. 9 to 460. 9 mg kg-1 (Average 195. 4 mg kg-1). Calcium carbonate، nonexchangeable K، cation exchange capacity and mica showed a significant correlation with K release. Maximum of potassium release was observed in Alfisols، probably because of high amount of clay content and the clay mineral of mica. The amount of K release was in the following order: Alfisols> Entisols> Inceptisols. Elovich، parabulic diffusion and power function equations could reasonably describe the K release kinetics. Fitting the data to these equations indicated that release of K is controlled by diffusion process.

In this study، the effect of soil structure under saturated and unsaturated flow conditions on nonreactive bromide (BR) transport was investigated. The soil structure treatments consisted of undisturbed columns (prismatic and granular structures)، and disturbed columns (single- grain structure). A constant concentration (C0= 0. 005 M) of bromide was supplied on the surface of the columns in a steady-state flow condition. For the saturated flow condition، a flux equal to the highest saturated hydraulic conductivity (Ks) of the columns was applied on all of the columns. To create the unsaturated flow condition، a flux equal to the half of the lowest Ks of the columns was imposed on all of the columns. The leaching of the columns was followed for five pore volumes (5PV) and the bromide concentration of the effluent was measured at 0. 2PV intervals using bromide selective electrode. The breakthrough curve (BTC) of single- grain structure was sigmoidal (S-shaped) and similar to piston-capillry flow form. In contrast، BTCs of the granular and prismatic structures had a steep initial part and later gradual tailed part. The preferential pathways caused the early appearance of bromide in the leachate of columns of these two structures. Tailing of the BTCs might be due to dispersion and diffusion between mobile and immobile water fractions. In saturated condition، the bromide plume appeared earlier than that in the unsaturated condition because of domination of mass flow and rapid macroporous stream. The results demonstrated the importance of soil structure، preferential pathways، and flow conditions in solute and pollutant transport.

In many water resource projects such as dams، flood control، navigability، river aesthetics، environmental issues and the estimation of suspended load have great importance. The complexity of sediment behavior and mathematical and physical model inability in simulation of sedimentation processes have led to the development of new technologies such as fuzzy logic which has the ability to identify nonlinear relationship between input and output variables. In this study، the application of fuzzy clustering algorithm in estimating the annual amount of sediment was studied. So، the corresponding data of flow and sediment discharge of Valykben station in kasilian basin during 1349-1350 till 1353-1354 period was daily determined. The data was divided in two groups i. e. 75% as training data and 25% for test data. Then، the efficiency of model was obtained by using statistical parameters such as correlation coefficient، nash-satklyf coefficient، mean square error root and variance ratio. The result showed that the classification of data on the annual time scale and use of fuzzy clustering algorithm can estimate 0. 49 values of the measured annually suspended sediment transport. Furthermore، on the same scale of classification، i. e. annual scale، this value was obtained 0. 19. Thus، using fuzzy clustering algorithm can lead to higher accuracy and reliability than rating curve method، which is suggested for estimating suspended sediment transport.

Effects of five various tillage systems on soil porosity، volumetric water content، diurnal and nocturnal soil temperatures، plant water uptake and dry matter yield was investigated using a completely randomized design with five treatments and four replications in Gorgan University of Agricultural Sciences and Natural Resources research farm located in Seyed-Miran during 2009-2010 growing season. Tillage systems were: moldboard plough followed by one discing (20-25 cm); rototiller (12-17 cm); double disc (8-10 cm); Chisel plow (25-30 cm); No-tillage. Results show that during all stages of wheat growth، the highest and the lowest soil porosities at 0-8 cm depth were obtained by moldboard plough and No-tillage treatments respectively. For all stages except before tillering and harvest، the highest soil porosity obtained by moldboard treatment at 8-16 cm depth. Increasing tillage intensity increased those porosity that keep water in potentials greater than -5 and those in potentials less than -15 bar. No-tillage and moldboard induced the highest and the lowest soil temperatures respectively before earring stage. Tillage intensification، increased soil porosity and root density. More roots reduced soil water content in response to increased water uptake by wheat، resulting greater dry matter accumulation.

The combined system of gate and weir is used for flow measurement in open channels. But in case the passing water has floating material and sediment it damages their performance and hence error of measurement will increase. In order to solve this problem، weir and gate can be combined and a concentrated hydraulic system known as weir-gate can be developed، thus allowing sediments transportation from under the gate and floating particles on weir. The principal goal of this study was to investigate the passing flow characteristics by trapezoidal weir and sharp-edge rectangular sluice gate in rectangular channel، and also suggest a discharge coefficient for combinational flow in different flow conditions. The experiments were carried out in laboratory channel on models with different geometric dimensions under various hydraulic conditions. Discharge coefficient was presented for various condition of passing flow of trapezoidal sharp-edge weir and below rectangular sluice gate using statistical analysis conducted on dimensionless geometric parameters affecting the flow. Resulting discharge coefficients were in agreement with laboratory results.

In order to investigate the effect of pest and water stresses on different growing stages of cowpea (Vigna sinensis) and pest occurrence، an experiment was conducted in Khazaneh Research station of Isfahan University of Technology. The experiment was carried out in a factorial complete randomized block design، in two different farms، with and without insecticide application. The treatments included severe water stress (50% water requirement)، moderate water stress (75% water requirement) in four stages of cowpea growth، the first stage (from seed germination until flower in، second stage (from flowering until pod-filling)، third stage (from pod-filling until harvesting) and the whole period of cowpea growth، in three replications. There was a control treatment in each farm with no stress in the whole period of cowpea growth، in three replications. The results showed that water stress had no significant effect on percentage of protein and mineral material. Result also showed that water stress had a significant effect (P≤ 0. 01) on population of insects. Water stress significantly (P≤ 0. 01) reduced the population of nymphs and adults of Empoasca decipiens Paoli and leaf minor damages، but water stress increased population of Thrips tabaci Lind. Considering the duration of first stage of growth (63 days)، it is concluded that this stage had less sensitivity to water stress than the other stages. In regions، where farmers encounter water shortage for cowpea planting، the best performance can be obtained when moderate water stress (75% water requirement) is applied at the first stage of growth.

In order to investigate the cumulative effect of three-year application of municipal solid waste compost (C) and the compost accompanied with chemical fertilizer (CF) on the concentrations of some heavy metals in various organs of rice plant، a field experiment with completely randomized design in three replications was performed in 2009. Treatments were as follows: Control (without C and CF)، CF (100 kg urea، 100 kg super phosphate and 100 kg potassium sulphate per ha)، 15، 30 and 45 tons of C without CF، 15، 30 and 45 tons of C with 25%، 50% and 75% CF. Results showed that application of compost in three years would increase the amounts of Ni، Pb، Cd and Cr in different organs of rice plant. Also، application of C accompanied with CF increased the amount of Ni، Pb، Cd and Cr in various organs of rice compared to C. The highest concentration of nickel and lead (9. 1 and 7. 8 mg. kg-1 respectively) were obtained in grains in 45 ton C + 50% CF per ha treatment. Meanwhile، the maximum content of cadmium in grain (1. 6 mg. kg-1) in 30 ton C + 75% CF ha-1treatment، and the highest amount of chromium in grain (1. 8 mg. kg-1) resulted from 30 ton + 25% CF ha-1treatment.

Continuous decline of groundwater quality for agricultural purposes has become a major concern in extensive arid and semi-arid regions. Therefore، mapping the quality of groundwater on a broad scale is an essential step in land management. This study aimed to map spatial distribution of two important groundwater quality indices including EC and SAR in Isfahan province، Iran، using geostatistical techniques. Different techniques such as Kriging، IDW and RBF were applied to water quality data of 540 groundwater wells to map continuous variations of the EC and SAR indices in Arc GIS 9. 3 environment. Among the interpolation methods، the Kriging by circular variogram model performed best and had the lowest RMSe error. Therefore، the produced maps from this technique were classified based on Wilcox method. Results showed that EC varies across the province from 392. 2 in the west to about 17917. 6 µmmhos/ cm in the northwest and eastern parts of the study area. The highest and lowest SAR values were estimated in the towns of Khour va Biabanak and Semirom، ranging from 38. 9 to 0. 13، respectively. According to the map of irrigation water quality based on Wilcox method، about 12. 13 % of the region was classified as good، 16% as moderate، 17. 5% as unsuitable and 54. 35% as unusable category. In general، the quality of groundwater in Isfahan province decreases from west to east and also from south to north، especially in playas (non-agricultural lands) where the unusable class is dominant.

In this study، the effect of clinoptilolite zeolite، as a soil amendment، on the parameters related to water and nitrogen movement in soil was investigated. Parameter and uncertainty estimation in the unamended (control) and amended soil (Z)، was performed using the sequential uncertainty fitting algorithm (SUFI-2) which is linked to LEACHN (in the LEACHN-CUP software). The goodness of prediction uncertainty was judged on the basis of P-factor and R-factor. P factor، R-factor، and Nash-Sutcliffe coefficient (NS) was obtained 0. 71، 0. 76، and 0. 92، respectively، in the prediction of the accumulated drainage from control. The results in prediction of the accumulated drainage from Z treatment using hydraulic parameters obtained in control were satisfactory (P-factor = 0. 87، R-factor = 0. 78، and NS = 0. 87). P-factor، R factor، and NS were 0. 87، 1. 36، and 0. 91، respectively، in the prediction of NO3-N leaching at control. According to the P-factor and R-factor values (P-factor = 1، R-factor = 2. 46)، application of the control parameter ranges in the prediction of NO3-N leaching at Z treatment produced a large uncertainty. By adjusting the parameters in control for zeolite amended soil، the estimated values for denitrification rate، distribution coefficient، and soil/solution NO3-N nitrification rate were greater in zeolite-amended soil compared to control.

Drought is a one of the most important natural disasters that have high socio-economic and environmental impacts. However، drought is more than a physical phenomenon or natural event. Its impact results from the relation between a natural event and demands on the water supply، and it is often exacerbated by human activities. The traditional approach to drought management has been reactive، relying on crisis management. Due to the drawbacks of crisis management، employing proper risk management techniques has been suggested. In order to move from crisis management to risk management، in this study، risk of drought in Isfahan province was evaluated. Drought hazard index and vulnerability index are components of the drought risk management. Standardized Precipitation Index (SPI) was used as the index of drought hazard. For the calculation of SPI، the monthly rainfall data in 47 meteorological stations during the period of 1975-2007 were collected. The time series of rainfall data were prepared and for calculation of the standardized precipitation index in a 12 month timescale they were imported to SPI program. Percentage of drought occurrence in each severity was calculated and then the drought index map was obtained. Vulnerability index was calculated through socio-economic indicators (population density and percentage of people involved in agriculture)، and physical indicators (available water capacity of soil and land use). Weighted Linear Combination (WLC) technique was applied for combination of vulnerability indicators. To assign weights to the criteria، an Analytical Hierarchy Process (AHP) was used. After providing the maps، fuzzy membership functions for every criterion were used for their standardization. For the weighting of the criteria، a questionnaire was prepared and criteria comparison was done using the participatory approach by a group of experts. Finally، the drought risk index was calculated by multiplying the drought hazard index and vulnerability index. The results showed that hazard of very severe drought is mainly concentrated in the central part of province. The North and North East of Isfahan province could experience condition of severe drought. South West of Isfahan province is under moderate drought condition compared to the other parts of the province. Map of drought vulnerability index showed that the most vulnerability is in the West، South and North-East of province. Map of drought risk index showed that the Northern Province demonstrated high risk. To reduce the drought risk in Isfahan province، improving monitoring، early warning، increasing environmental awareness، and promoting water resource management practices should be considered.

In a pot experiment، the effect of soybeans، mung beans and beans on the corn and sunflowers in a cadmium contaminated soil was studied in a completely randomized design with three replications. The treatments consisted of intercropping of corn and mung bean corn and beans، corn and soybean، sunflower and mung bean، sunflower and beans، sunflower and soybean monoculture of corn، and monoculture of sunflower. There were significant effects of cocropping of companion crops on shoot dry weigh، the concentration of cadmium and zinc and the chlorophyll content of corn and sunflower. In this study the shoot weight of corn grown with bean and soybean and that of sunflower grown with bean plants was decreased as compared to the related monocultures. The concentration of cadmium was increased in the corn grown with soybean or mungbean and in sunflower grown with soybean. Co- cropping with bean plants had no significant effects on the concentration of cadmium in corn or sunflower. Among companion crops، the concentration of cadmium was higher in bean plants compared to those of soybean and mungbean plants. The chlorophyll content in the leaves of corn plants grown with mungbean was increased with an increase in cadmium concentration. However، this trend was not observed in other treatments. The results of this study show that co- cropping with either soybean or mungbean may increase cadmium uptake by corn and sunflower which in turn may increase the risk of inflowing of toxin cadmium into the food chain. However، further study needs to re-evaluate the effect of these companion crops on the distribution of cadmium in the edible parts of corn and sunflower.

In recent years، due to the increased population، urbanization and changes in human consumption patterns، urban، industrial and agricultural soils have been exposed to various pollutants such as heavy metals. The objective of this research was to identify hotspots of Pb by using global and local Moran Indices in urban and suburban soils of Kashafrood catchment. A total of 261 surface soil samples (0-15 cm deep) were taken using irregular girding network method and their total Pb concentrations were measured. The positive Moran index at confidence level of more than 99 percent showed the spatial clusters between observations. On the basis of local Moran index results، 15 samples were introduced as hotspots (high-high value) located southeast of Mashhad plain. Exclusion of extreme values resulted in the addition of high-high cluster (hotspots) leading to the extension of these areas to the West of the Mashhad city. These areas are introduced as hotspots due to the urban land use، the direction of prevailing wind، and the area being close to Mashhad airport.