نشریه دانش آب و خاک
سال بیست و ششم شماره 4 (زمستان 1395)

Crump weir is classified as a short-edged weir. The upstream slope of this weir is greater than its downstream slope, which allows easy discharging of the sediments. In this research, the performance of k-nearest neighborhood and support vector regression (SVR) methods were investigated for modelling crump weir discharge coefficient using experimental data. 174 data sets in 9 combinations of the input parameters including the upstream and downstream slopes (Sup, Sdo), Reynolds number (Re) and water head in upstream to weir height ratio (h1/P) were used for modelling the discharge coefficient. The training was done in four stages using 66, 70, 75 and 80 percent of experimental data and the rest of these data at each stage were applied for the test phase. According to the results, the highest accuracy for the both applied models was obtained using 80% of the data in the training and the rest 20% in the test phases. Also, this investigation showed that the nearest neighborhood method presented a more accurate result than SVR method. Furthermore, water head in upstream to weir head height ratio (h1/P) had a significant role in modeling crump weir discharge coefficient. This ratio was the only parameter which could be used for predicting the coefficient accurately. Finally, this work showed that input combination including h1/P, Sup, Sdo parameters gave the best outcome. Both the Nearest Neighborhood and Support Vector Regression methods with coefficient of determination values of0.987 and 0.969 respectively, provided accurate predictions.

In this research the wetting pattern of soil under subsurface drip irrigation was investigated through field experiments on two layered soil at the level and sloping lands, and the interaction and individual effects of the sloping and layered soil conditions on the wetting pattern were studied. Comparisons between observed soil moisture profiles in the level and sloping soils clarified that by increasing the application duration, the wetting patterns of the sloping soil showed more adaptation with that of the level soil. The results indicated that the effect of soil anisotropy was declined with increasing the water application duration. Due to high hydraulic conductivity value of the sublayer soil, the wetting front showed an inflection after reaching to the boundary of the two layers, so that the vertical expansion of pattern was increased and the wetting bulb transformed to an ellipse. The HYDRUS 2D software was applied to simulate the wetting patterns at the same conditions of filed experiments. The radial distance of the soil wetting fronts in the different angles from emitters were compared with corresponding simulations in order to evaluate the model accuracy. Results showed that HYDRUS simulations had a good agreement with observed data with Root Mean Squared Error (RMSE) value of 2.47 cm, correlation coefficient (r) value of 0.82 and model Coefficient of Efficiency (CE) value of 0.24 for the layered level soil. Also the values of these statistical criteria for sloping layered soil in the same order were 4.03 cm, 0.75 and 0.36 respectively. Generally, these results confirmed reliable ability of HYDRUS software for simulation of water movement in the studied conditions.

The compound arched circular-trapezoidal sharp-crested weirs are combinations of a circular arch notch at the bottom part and a trapezoidal notch at the top of the cross section. In this research, the discharge coefficient (Cd) of compound arched circular-trapezoidal sharp-crested was investigated. The experiments were conducted on weirs having the crest width of 15 cm, crest height of 15, 20, 25 cm and circular arch notch height of 5, 7.5 cm with different curve radii and the side walls slope of 0.5 (0.5H:1V) in a laboratory flume. The results indicated that the amount of discharge coefficient was in the range of 0.56 to 0.81. For a given hydraulic head, the amount of Cd is reduced approximately up to 5% by increasing the height of weir crest. In addition, for a given hydraulic head, by changing the height of circular arch notch, the amount of Cd for the compound arched circular-trapezoidal sharp-crested weirs increased about 25 to 30 percent with respect to the trapezoidal weirs. According to the root mean square error (RMSE) with value of 0.0563, the amount of Cd for the compound arched circular-trapezoidal weirs was estimated with acceptable accuracy, using a linear combination of the discharge relationships of circular and trapezoidal weirs. In this research, the discharge continuity over the compound weir for the various hydraulic heads was examined using the experimental data. The results showed that the least amount of discontinuity could be seen in the wide range of discharges.

Irrigation is necessary for the crop growth and determining crops water requirement is essential for supplying it. In arid and semi-arid regions, air temperature plays a fundamental role in evapotranspiration process. In this study, the temperature occurrence probabilities at the levels of 50%, 65% and 80% were applied for calculation of evapotranspiration. The Penman-Monteith FAO and Hargreaves equations were used to calculate the evapotranspiration in Tabriz area. The results showed that the Wakeby distribution function had the best adaptation with the temperature data set in the study area. Using different levels of probability for temperature in determining reference evapotranspiration in the Penman-Monteith FAO method, negligible effects were seen in the obtained results so the averaged temperature data was enough for calculations at the cases that there were no needs for precise values. It was concluded that the Penman-Monteith FAO equation was not sensitive to small changes in temperature values, on the contrary in Hargreaves model, using different levels of temperature probability had significant effects on the calculated reference evapotranspiration values. Finally, results of the both methods were compared with the exact evaporation data obtained from pan and the pan coefficient was obtained for each method and suitable pan coefficient values of 0.63 and 1.22 were determined for methods of Penman-Monteith FAO and Hargreaves models, respectively.

In this research vulnerability of Salmas-plain aquifer to pollution was evaluated using the DRASTIC model and Geographic Information System. In DRASTIC model seven effective hydrogeological parameters on groundwater contamination; namely depth of water table, aquifer net recharge, aquifer media, soil texture, topography, impact of vadose zone and hydraulic conductivity were combined. Vulnerability zoning map showed three main zones of low groundwater vulnerability zone (risk index: 64-100), moderate groundwater vulnerability zone (risk index: 100-140) and high groundwater vulnerability zone (risk index: 140-183). Areas with low, moderate and high risk zones comprise 13.55%, 72.09% and 14.36% of the studied area, respectively. Two sensitivity analyses tests including the map removal and the single-parameter sensitivity analyses were carried out. Both of sensitivity analyses tests showed that the depth of water table and vadose zone parameters had the most significant impacts on the vulnerability indexes at the studied region.

The purpose of this study was to determine the RDI, SPI and SDI indices for monitoring the meteorological and hydrological droughts in Bam plain, investigate their relationships with each other, and analyze the drought characteristics in different time scales and the probability of their occurrences. The results of paired t-test revealed significant differences in the results of severity, magnitude and frequency of the SPI and RDI and the most similar characteristics were obtained between RDI and SDI. Cross correlation coefficient test results indicated a high correlation in the 48-month time scale, simultaneously, and SPI-48-RDI-48, SDI-48-RDI-48 and SPI-48-SDI-48 had the coefficients values of 1, 1 and 0.53, respectively. The results of trend studies of climatic parameters using the Mann Kendall method showed decrease in the precipitation and flow rate trends and increase in the temperature trend which were not significant.

In order to investigate the effects of different levels of drought stress and arbuscular mycorrhizal fungion yield and morphological traits of eight landraces sesame (Sesamum indicum L.), an experiment was conducted using factorial split plot based on randomized complete block design with three replications in Research Station of Urmia Agricultural High School in 2014-2015 growing season. The main factor consisted of different levels of irrigation namely no drought stress irrigation (irrigation after 70 mm evapotranspiration), moderate drought stress (irrigation after 90 mm evapotranspiration) and severe drought stress (irrigation after 110 mm evapotranspiration) and mycorrhizal inoculation were considered as subplots including Glomus mosseae, Glomus intraradices and non-inoculated (control). Sub-sub plots consisted of eight landraces of sesame Jiroft13, Zanjan Tarom landrace, Moghan landrace, Naz of several branches, TC-25¡ TS-3, Darab 14 and Dashtestan 5. The results of variance analysis showed that the effects of different levels of irrigation, mycorrhizal fungi and sesamegenotypes on traits were significant. Means values comparison showed that with increasing severity of drought stress, grain yield, plant height, stem diameter, leaf, stem and capsule with grain dry weight, number of grains per square meter and number of branches per plant decreased significantly. Severe drought stress reduced grain yield and number of grains per square meter about 63 and 70 percent, respectively. Symbiosis mycorrhizal fungi improved all the above mentioned traits. Based on the results of this study, for increasing grain yield and morphological traits using mycorrhizal fungi especially, G.mosseae species was recommended. Also in three different irrigation conditions, Moghan landrace and Zanjan Tarom landrace were presented as superior landraces.

Transitions are commonly used structures in both natural and artificial open channels. With increasing the transition dimensions along the flow, the flow decelerates. Under subcritical steady state flow conditions, reducing the flow velocity increases the water pressure and reverses pressure gradient. This phenomenon creates separation zone and turbulent eddy flow, and causes the flow energy losses. Due to the complexity of flow pattern and scale effects, physical models can solely provide a clear understanding of the physical principles governing the flow field, so it is necessary to study flow pattern numerically along with the field and experimental studies. In this study, the flow pattern in a rectangular to rectangular expansive transition, has been simulated under subcritical flow with RSM turbulence model using Fluent software. Water surface and flow velocity profiles obtained by the two methods at different sections of transition were compared with experimental results. The results showed a good agreement between the simulated and experimental data. After validation of the numerical model, the effects of inflow Froude numbers on strength of secondary current, hydraulic efficiency of the transition, turbulent kinetic energy and bed shear stress at different cross sections were simulated. The results showed that with increasing the inflow Froude number, the strength of secondary current along the transition increased, while the hydraulic efficiency decreased. Maximum efficiency (60.83%) occurred in Fr1=0.40. Also, with increasing the Froude number, turbulent kinetic energy and bed shear stress increased, so that, from transition inlet to the outlet, turbulent kinetic energy for total Froude numbers decreased with a 30.71% reduction in turbulent power.

The major problem in surface irrigation methods is low irrigation efficiency which is mainly caused by the lack of suitable irrigation management. Noting the cost of pressurized irrigation systems and restrictions of applying them in some circumstances, it is necessary to improve surface irrigation methods. This study aimed to assess the current situation of furrow irrigation management, identifying weaknesses and ways to improve water consumption in four sugarcane agro-industries of Dehkhoda, Amirkabir, Hakim Farabi and Karun. In this study, the amount of water used, irrigation scheduling parameters, irrigation application efficiency and water distribution uniformity of the studied farms were evaluated. At total, 37 cases were evaluated at different stages of growth in the studied sugarcane agro-industries. In each of the studied farms, soil texture, bulk density, advance and recession times, inflow rate, soil moisture content (before and after the irrigation), two points of soil moisture characteristic curve, field slope, furrow cross section, and irrigation time were measured. Results showed that irrigation interval in the studied farms was short, irrigation time was long, and water consumption in most of the evaluated farms was more than the required water. Soil moisture before irrigation at depths of 33-66 cm and 66-100 cm and sometimes at depth of 0-33 cm in the most of the studied fields was close to field capacity (FC) or even it was more than it. Irrigation gross water depth ranged from 70 to 319 mm and application efficiency varied from 7 to 100 percent, average was 42.5%. Unlike application efficiency, water distribution uniformity was acceptable in the studied farms and its average was approximately 92%. Water losses in the studied farms were mainly due to deep percolation.

Pipelines passing through the seas and rivers as a means for transferring fluids (oil, gas, water, sewage) have a great importance since the pipelines change flow pattern, increase turbulence and intensify the bed shear stress around submerged pipes, which create scour holes under the pipes. Development of scour hole under pipelines leads to instability and failure of pipelines, which may cause severe environmental and economic damages. In this paper, the results of laboratory research on the effect of different attack angle of the approaching flow on the maximum scour depth under submerged pipes have been provided. Experiments were conducted in two modes: 1) scour under pipe with 90° angle of attack, 2) scour under pipe with less than 90° angle of attack. The pipe was also placed in 2 positions, i.e. on the bed and at a distance of D/4 from the bed. Three (45°, 60° and 90°) angles of attack were employed in the experiments. The results showed that the angle of attack is an effective parameter on the location of the maximum scour depth and performance of vortices. For angles smaller than 90 degrees, maximum scour depth occurred in the right hand side of the flume.

In this research, the effects of pile cap thickness and its top level of installation, arrangement and diameter of piles on variation of local scour around the inclined bridge piers group were investigated experimentally. A Physical model of piers group having two inclined rectangular piers with 28 degrees inclination angle was constructed on a pile cap. Experiments were performed on piles group with relative diameters ( ) of 0.6 and 0.9, piles arrangement of 2×2 and 2×3, relative pile cap thicknesses ( ) of 0.9 and 1.4 and the pile cap relative installation levels ( ) of 1.5, 1, 0.5, 0 and also its buried condition at the level of -0.7 and -1.2. Comparison of the maximum scour depth indicated that the change of pile arrangement from 2×2 to 2×3 caused 50 and 60 percent increases in the scour depth related to the ratio of with the amount of 0.6 ad 0.9, respectively. However, changes of the pile diameter and arrangement did not have any effect on the maximum scour depth as pile cap installed in the same level of bed or lower than it i.e. in buried condition. Comparison of the results showed that changes of the pile cap thickness from 0.9 to 1.4 times the pier width, caused the maximum scour depth for all pile geometry and top level installation of the pile cap to be increased 20 percent approximately. Furthermore, as pile diameter increased from 0.6 to 0.9 bridge pier width, the maximum scour depth for installation of the pile cap above the bed increased 5 and 10 percent approximately for pile arrangement of 2×2 and 2×3, respectively.

Amino cyclopropane carboxylate (ACC) deaminase enzyme can increase plant growth by reducing the ethylene production in plants. In this study the effect of genetically modified strain of Pseudomonas mendocina with enhanced enzyme production property was evaluated on the seed germination of monocots and dicot plants in petries and also on the stimulation of plant growth in pots. Petries containing tomato and wheat seeds were divided into 3 groups of 5. All petries were irrigated with 10 ml of any distilled water, water containing wild and transgenic strains for 5 days, gradually. In stimulating growth study by the bacterium on the growth of tomato and wheat plants, the same-sized plants were selected and divided into three pots groups consisting of control, wild and transgenic. After 5 weeks of growth, stem length, root length and biomass content were assessed. Results of the tests showed that, stem lengths of tomato seedlings inoculated with genetically modified bacteria (test) were 50±2% more than stem lengths of control and 31.2±3% more than the samples inoculated with wild bacteria. Root lengths of the test samples were 28.6±1% more than those of the control and biomass quantities of the test were 34.1±3% more than those of the control (p

In this study, the WetSpa model was utilized to simulate the snow accumulation and melting processes in the Bar Arye mountainous watershed with an average altitude of 2225 meters above the mean sea level. The input data used in this study included daily records of precipitation, air temperature and potential evapotranspiration, covering the period of 2003 to 2008, as well as three types of maps, namely; land use, soil texture and topography maps. According to Nash-Sutcliffe assessment index values (0.67, 0.69) for the calibration and validation periods, the model could simulate the Bar Arye river flow with high accuracy. The results indicated that the temperature threshold for snow formation in this catchment was 0.11°C. According to the water balance components, it was indicated that the maximum amounts of equivalent snow water belonged to the months of December (29.25 mm) and January (37.94 mm), while the maximum snow melt values were observed during March and April , as 38.89 mm and 37.14 mm, respectively.

The aim of this study was estimation of some hydrological and hydrogeological parameters for Balukhlu-chay basin, Ardabil province, using SWAT model. Required data for this study including soil properties, soil, land use and topography maps, daily rainfall, temperature, air humidity and surface water discharge were collected from Natural Resources Office and Regional Water Company of Ardabil province. Curve number, coefficient of evaporation from soil surface, soil water availability, precipitation, snowmelt temperature, and delay time for aquifer recharge were identified as the most important and sensitive parameters. The hydroclimatologic data of the years 2000 to 2004 were used in calibration stage and the data of the years 2005 to 2007 were used in validation stage of the model evaluation. The R2, RMSE and RE indices were used to evaluate the goodness of simulation. Hydrological and geohydrological parameters including curve number, delay time for aquifer recharge and saturated hydraulic conductivity were estimated. The values ​​of these parameters, respectively 70 to 80, 30 days, and 12 to 24 mm per hour were estimated for Balukhlu-chay basin. During calibration process, the values of 0.81, 0.98 and 0.07 were obtained for R2, RMSE and RE, respectively. Similarly, these values were calculated as 0.63, 0.89 and 0.08 for R2, RMSE and RE, respectively, during the validation. The results showed that river flow was well simulated by the SWAT model, compared with the measured data. The amount of error in the validation stage showed that hydrological and hydrogeological parameters were estimated with good accuracy.

The six-leg elements with trade name of A-jack frequently have been used in coastal structures and recently have been recommended as an effective tool for controlling river bank erosion. The purpose of this study was to investigate the applicability of such elements in reduction of scour depth at bridge piers. Therefore, two series of tests without and with the mentioned elements in three different quantities of rows were carried out. Five different flow conditions, with Froude number in the range of 0.16 to 0.24 around the cubic bridge pier, were performed and bed topography was measured in all experiments.The results of this study show that for Froude number of 0.16, the six-leg elements can reduce the maximum scour depth by as much as 44%, 83% and 100% when the elements are placed in single row, in two rows and in three rows, respectively. The increase of Froude number causes reduction of the effect of six-leg elements on scour depth. So, for Froude number equal to 0.24, the above-mentioned percentages of maximum scour depth reductions were found to be 44%, 63% and 81%.

Flood is one of the natural catastrophes which has been occurring since ancient times. The main purpose of this study is assessing the statistical index methods used for flood mapping. Consequently, elevation, slope, land topography, the land wetness index, stream power, rainfall average, distance from the river, geology and landuse parameters of the Haraz watershed located in Mazandaran province were used. In order to prepare the landuse map of 2013, the images of Landsat Satellite, ENVI 5.1 and neural networks algorithm were utilized. The digital maps of all parameters were provided using ArcGIS software 10.1 and SAGA GIS 2 with Raster format. Then, the geographical positions of the 211 floodpoints of the region were prepared. These floodpoints were randomly divided into two groups, with 151 points (71%) and 61 points (30%) for calibration and validation, respectively. The set of calibration group points and effective parameters on the flood were introduced as the dependent and independent variables respevtively using the frequency ratio method. Then, the probability of the flood occurring for each class of parameters was calculated. At the end, the obtained weights for each class in the Geographical Information System (GIS) were applied to the corresponding layer and flood risk map of the studied region was prepared. The prediction accuracy of this method in order to prepare map within the region of Haraz is equal to 90 percent. The findings imply that the present technique for predicting the potential of flood risk is useful and reliable, especially for regions with no statistical data.

In this study, the influence of Irrigation with raw (RWI) and treated (TWI) wastewater on the quantitative and microbial properties of wheat in comparison with using safe water for Irrigation (SWI) was investigated under a completely randomized block design. Irrigation water quality was analyzed every two weeks during the growing season. At the end of the growing season, the yield and yield components were determined. Also, the Escherichia coli and Parasitic Nematode were determined in soil samples, taken from 0-30 cm depth, and plant samples. Results showed that despite favorable water quality of SWI, the values of EC, pH, BOD5, COD, total coliform and fecal coliform in raw and treated wastewater exceeded the available standard values. Using raw wastewater caused significant increase in the number of grain per spike, spike length, fertile spike number, total grain number, grain yield, biological yield and harvest index, in the ranges of 0.86-30 and 4.4-88.1 percentages compared with those for SWI and TWI treatments, respectively. However, insufficiency of nutrients in TWI as well as the degradation of soil physicochemical properties under unmanaged usage of treated wastewater led to a significant reduction of 827.3 Kg ha-1 in grain yield. Nevertheless, the soil and plant microbial conditions were favorable under TWI treatment. The existence of E. coli and Parasitic Nematode beyond the standard values in soil and plant under RWI treatment indicated the necessity for stopping irrigation with this water resource in the study area. The favorable conditions of soil and plant regarding the microbial contaminants, showed the possibility of substituting the fresh water with the treated wastewater through suitable application management.

Alluvial rivers often have wide floodplains which play an important role in flood passage, enhancement of environmental habitat, soil fertility and extending recreational and agricultural activities. For calculation of flood discharges in main channel and floodplains and recognition of erodible sections of the river, simulation of lateral velocity and bed shear stress distribution are important. In the flooding situation, however, advanced and expensive pieces of equipment are required to measure lateral profile of velocity and specially bed shear stress. Therefore, application of quasi 2-D mathematical models based on solutions of continuity and momentum equations is important in river engineering projects. In this paper, at first, by application of Shiono and Knight model numerical solution and use of finite element method, lateral distribution of flow velocity in Minab river (at Berentin station) was calibrated based on field data. The maximum error was around 13 percent for flood discharge computation. Then, lateral distribution of bed shear stress for a flood event in the year 1374 (Iranian calendar) was simulated, based on which lateral variations of river cross section were analyzed. Results of this research showed that erosion and sedimentation situation in river width computed by mathematical model based on bed shear stress presented good agreement with the actual data.

Least limiting water range (LLWR) is one of the important characteristics of the soil and is a soil structure identifier with difficult, costly and time-consuming measurement. Resistance to soil compaction is an index of soil organic matter, texture, structure and other properties which controls, the compression and its components and LLWR. So there is a correlation between the LLWR and compression curve, which has not been investigated so far. Since, the measurement of the confined compression curve is relatively quick and simple, therefore it can be used to estimate the LLWR. In this study, 24 disturbed and undisturbed soil samples were taken from West Azarbayjan and their soil water retention curves, soil penetration resistance curves and confined compression curves were determined. The ratio of silt to sand, the clay content, organic carbon, cation exchange capacity, calcium carbonate, aggregates mean weight diameter and confined compression parameters were used to estimate LLWR. The ability of each of the input variables, including confined compression characteristics, in improving the estimation of LLWR using regression models was evaluated. Using the confined compression parameters improved the estimation of the LLWR, significantly. Because, many characteristics affecting the confined compression are the same ones determining the LLWR. Relative improvement (RI) values were calculated for pedotransfer functions (PTFs) in suction 60 cm were 11.5, 19.7 and 28.53 % for PTF2, PTF5 and PTF7, respectively which showed considerable improvements in the estimation of LLWR by using confined compression and other properties as predictors. So, LLWR can be estimated with acceptable accuracy (R2=0.54) using confined compression parameters as estimators.

The combined effects of biochemical composition and amount of plant residues returned to soils affect stability of aggregation and the rate of aggregate turnover. To investigate the influence of vegetation type on aggregate size distribution, five vegetation types including rainfed wheat (RW), grasses (G), Astragallus–Bromus (A-B), Astragallus–Lactuca (A-L) and Astragallus–Artemisia (A-A) were studied under similar environmental conditions in terms of parent material and slope aspect in Gonbad watershed, Hamadan. Total organic carbon (TOC), soil carbohydrates (Ch), mean weighted diameter (MWD), size distribution of water-stable aggregates (AS) and aggregate carbon (AC) were measured in surface (0-15 cm) soils. The amounts of TOC, Ch, MWD and AC (present in all aggregate size fractions) were significantly greater in soils under A-B and A-A than the soils of other vegetation covers, while the lowest values were observed in soils under RW and G. The highest AS>2 mm and lowest AS 2 mm were lower in soils under A-L, G and RW compared to other aggregate sizes. A-B and A-A vegetation types had greater canopy, annual production, plant diversity and litter content compared to other vegetation types.Frequent soil ploughing in RW site andlow plant diversity and canopy cover in A-L and G sites contributed to reduced soil aggregation and lower content of coarse aggregates;AS in 0.5-0.053 (mm) fraction in soils of aforementioned vegetation types was greater than other aggregate sizes. It was concluded that Ch and 0.5-0.053 (mm) aggregate size fraction might be reliable soil quality indicators that reflected land use and vegetation type changes.

Three types of soil, differing in their dominant clay mineral (smectite, illite and allophone) and a kaolin samples were compared for retention of dissolved organic carbon (DOC) extracted from vermicompost. The samples were equilibrated with DOC solution (carbon content 200 mg.l-1). The amount of retained DOC was calculated from the difference between the initial and final OC contents. The retention capacity was significantly different among the samples (p

In this study the unsteady flow in AMC canal of irrigation network of Tabriz plain was simulated using CanalMan model. The aim was to evaluate different settings of canal control structures and turnout in passing from months with low to high water requirements and choose the most appropriate operational program among the considered options. For this purpose 10 operational options for an increasing discharge rate were considered and compared with each other for a 10-hour water delivery duration. The criteria for comparing different options included shortage of water delivery, absolute rate error of discharges and the average root-mean-square of error. The results showed that the tenth option with the least values in all three criteria, was the best option. The temporal changes of discharges for control structures and turnouts in the tenth option were presented. According to the results the disturbance travel time from canal inlet to the control structure and its damping time periods were the least in the chosen option.

Phosphorus is one of the most important limiting elements for plant growth. Using phosphate solubilizing microorganisms (PSM) is one of the main strategies to meet plant P demand. In Vitro screening of phosphate solubilization potential in order to use as biofertilizers, is influenced by nutrient composition of media. The purpose of this study was modeling the effects of different carbon and nitrogen sources and tricalcium phosphate on phosphorous solubilization using Placket-Burman design and response surface methodology with a central composite design. At the first step, 12 experiments based on Placket-Burman design were carried out to screen and identify the effective carbon and nitrogen sources in phosphorous dissolution by Pseudomonas fluorescens. Results indicated that yeast extract was more effective source of nitrogen in comparison with other nitrogen sources. According to the results of the first step, response surface methodology with central composite design was employed to evaluate and to model the effects of sucrose, yeast extract and tricalcium phosphate concentrations on phosphate dissolution. The analysis of variance (ANOVA) depicted the high performance of the central composite predictive model of phosphorus dissolution (R2= 0.896 and RMSE=0.0372 g L-1). The yeast extract and tricalcium phosphate were the most significant parameters for phosphate solubilization. Increasing of the yeast extract concentration at the range of 0-4 g L-1 and the tricalcium phosphate at the range of 0-20 g L1 significantly increased the soluble phosphate concentration. According to central composite design, maximum phosphate dissolution was obtained at the yeast extract, sucrose and tricalcium phosphate concentrations of 4, 18.58, 17.97 g L1 respectively.

In recent years, quantity and quality of groundwater resources have been faced with the vulnerability risk due to increasing population and industrial and agricultural activities. In this paper, variations of the groundwater quality in Sangan-Khaf plain have been evaluated. With considering the spatial variability of various pollutants, the groundwater quality index (GQI) was used to describe the quality of the groundwater. Main parameters such as TDS, SO4, Ca, Cl, Mg, and Na were used in GQI index calculation. GQI values were obtained between 66.01 to 81.39% which showed that the water quality in the region was in the moderate to good class. The groundwater quality index decreased in the direction of groundwater flow which indicated the effect of lithological changes, carbonate beds and clay zones in the region.