نشریه آب و خاک
سال بیست و سوم شماره 1 (پیاپی 5، بهار 1388)

Uranium is a radioactive heavy metal. Development of nuclear industries and application of phosphate fertilizers contain uranium impurity resulted in soil contamination with uranium. A Pot experiment had been conducted under controlled condition. The experiment carried out in completely randomized design with two factors, including two plants (soybean and sunflower) and six levels of uranium (0, 50,100,250,500 and 1000 mg/kg). Plants harvested after 40 days of experiment and before the generative stages. Soil samples were extracted by DTPA and AAAcEDTA. Uranium concentration in plant tissue increased by increasing the uranium in soil. The ratio of uranium in root:shoot was between 20-100 in sunflower and soy bean. Extraction efficiency of DTPA and AAAcEDTA increased by increasing of uranium in soil. The results of the experiment showed that AAAcEDTA extracts more uranium in all applied uranium concentrations. Both extractants had a good correlation with uranium in plants; however, extraction efficiency of AAAcEDTA was well correlated by uranium concentration in plant tissues. The results of the experiment suggest that AAAcEDTA is suitable extractant for uranium as phytoavailability indicator.

In this research the thermal stratification of the water in the Torogh Dam Basin and the resulted changes in its quality with respect to temperature, salinity and dissolved oxygen was investigated using the Dynamic Reservoir Simulation Model. The results indicated that in wet years such as 1998, when the average annual precipitation and the resulted inflows to the basin is higher than its long-term average, the water level in the basin reaches above 50 m. Under such conditions, thermal stratification starts from mid-spring and lasts to the end of summer, and establishes through the total depth of the basin. Consequently, considerable changes in water quality occur through the depth. However in dry years such as year 2000, the water level in the basin diminishes considerably (16 to 20m in depth) and thermal stratification either does not establish or if establishes, it is incomplete, starts much earlier and persists for much shorter periods of time. On the basis of the model’s results, the differences observed in the average temperatures of the surface and deep layers of the basin during the spring and summer seasons of 1998 were 10◦C and 11◦C, respectively while in the spring of 2002, the observed difference was only 1.5◦C. The results of the study also showed concurrent occurrence of salinity stratification with thermal stratification which results in increase in salinity with increase in depth. The difference between salt concentration of the surface and deep water layers of the basin was observed to be 43 mg/lit in the spring of 1998 and 10 mg/lit for the summer of the same year. In regard to the dissolved oxygen concentration, the simulation results showed a difference in the range of 0 to 9 mg/lit between the surface and deep water layers. With the start of stratification, oxygen concentration decreases gradually with depth., such that in July the lowest 10m layer of the basin becomes completely anaerobic, providing conditions for production of undesired odors, tastes and color. During the period of 1998 to 2004 (period of data analysis and simulation run), the water quality of the basin was observed to be uniform in autumn and winter months indicating a complete mixing condition in the basin.

Natural disasters threatening and endangering human communities has resulted in the study and research of such disasters through the related sciences and present methods of forecasting their behavior with time and place and also from a qualification and quantity viewpoint. To this end, numerous methods for the determination of the maximum flood in various return period has been made available which can be refered to as flood frequency analysis methods. One of these methods is the regional flood frequency analysis in which instead of using the data from a single station, it considers the data and characteristics of a group of similar stations. In the case under the research this method uses L-Moments and Index Flood in North, Razavi and South Khorasan water basins and MATLAB software. Maximum annual flood statistics were used from 68 Hydrometric stations with minimum and maximum statistical periods of 6 and 39 years. Using Cluster analysis the region under study was divided to 7 partitions. Discordance test has conducted and only one station in region C was found as discordance station. Because of knowing the homogeneity of the regions, the parameter of Kappa distribution were estimated and with using the simulation method of Monte Carlo with 500 times, the homogeneity measure was tested in 7 regions. Using homogeneity test all regions was found homogen. Using goodness-of-fit measure z and Kolmogrove-Smirnov the Log normal 3 parameters distribution were selected for two regions of A and B, GEV for C, Generalized Pareto for D and E, Generalized logistic for F and Pearson III for G. Besides, GEV distribution was found appropriate for all of the regions, only their parameters are different in any regions. For estimating of index flood a logarithmic model has found for each region with 4 variables of area, height, average slop and form factor. Using of these models, the index flood can be estimated in each region and it can be used for standardize the statistics of maximum flood values.

In recent years, automatic weather stations have been widely used for recording meteorological data in different time scales. Therefore the accurate estimation of ETo by combination equations can be evaluated using these set of short time scales data. Daily ETo can also be calculated by summation of hourly ETo values. The purpose of this study is to compare the ETo values estimated by hourly and daily data. Totally, 7270 hourly meteorological data obtained from the automated weather reference station where placed in Shahid Bahonar university of Kerman, Iran during April to December 2005 and January to March 2006. The Penman-Monteith equations proposed by the Food and Agriculture Organization (FAO-56) and American Society of Civil Engineers (ASCE) were used for hourly and daily (24 hours) ETo estimation. The paired t- student test was used for comparison of estimated ETo values by two methods (daily and hourly summation) in each month. The results of this study showed significant differences between ETo values estimated by daily and hourly summation data in both equations at 5 percent level. The hourly summation method overestimated ETo values from 5.8 to 44.6 percent in different months using FAO-56 Penman-Monteith equation and from 7.4 to 47.6 percent using ASCE Penman-Monteith equation. The regression coefficients of correlation equations between the daily and hourly summation method in both combination models were strongly significant.

Obtaining reliable precipitation observations is important for hydrological simulations and weather forecasting. Radar data can provide insight in the spatial variation of precipitation and can also detect large areas of rain and estimate rainfall rates. Weather radar systems nearly always operate in S-, C- or X-band. Since X-band systems require smaller antennas than those at C- or S- band, they are particularly suitable for monitoring small hydrological working. However, radar rainfall estimation can be prone to errors because of attenuation and ground clutter. In this study, the potential of X-band radar systems for rainfall estimation over an urban area in the Netherlands was discussed. A methodology was presented for removing ground clutter and attenuation from X-band radar measurements and finally measurements of rainfall from radar were compared against measurements from 4 tipping bucket rain gauges for a rainfall event. In general, the analysis demonstrated that the radar follows the general trend of the rain gauge measurements but the radar measurements need to be calibrated and corrected for errors.

Irrigation planning and management requires continious monitoring and measurements of soil moisture content. Application of Gypsum blockes (GB) are common in soil moisture measurements. GB readings are subjected to its geometry and soil solution concentration. This study was carried on 90 GB in research greenhouse of Faculty Agricultural, Ferdowsi University of Mashhad. At the begining, all GB were calibrated in distilled water. Further, readings were collected in four solutions of 2, 6, 10 and 18 dS/m salinity. Then, three soil media with different textures (sandy loam, loam, clay loam) at 5 levels of salinity rate (trace, 2, 6, 10 and 18 dS/m of saturated extract) were studied, as 15 treatments. GB readings, at different soil moisture contant, were made by ELE-5910A. For each treatment, readings vs. soil moistures were plotted. These curves were compared with that of standard (same soil texture with trace salinity). Finally, some corrector functions were developed to eliminate the salinity effects from GB readings.

Plants growth and development and physiological activities occur in a certain air temperature range. Spit of this fact that zero temperature named as a freezing temperature, in agriculture meteorology, freezing happen in lower temperature which is different for plants that lead to their tissues damage. Early autumn freezing cause damage to harvesting of cotton and sugar beet and affect on time of wheat and barley planting in Khrasan Razavi. There are also many damages on agricultural products due to late spring freezing each year. This problem leads to loss the flowers during the trees flowering. In order to investing this phenomenon in Khorasan Razavi, the autumn, spring and winter freezing were considered based on suitable temperature threshold and the occurrence probability obtained and mapped. Results show that early freezing in autumn begins from the north and then spread toward the southern regions. The late freezing in spring ends in the south sooner than other areas. Results also show that the winter freezing more occurs in the north.

One of the losses decrease's ways in fields, is the proper irrigation management, which its base is the accurate estimation of crop water requirement. Equations which are used to calculate the reference evapotranspiration (ETo), do not use the same climatic parameters and due to their empirical base, are not match to all climatic situations. So it is needed to clarify proper methods for each region. In this investigation, lysimeteric data, which are taken from the climatologic station of Mashhad University in a 6-month period tests, ware compared with the F.A.O-Penman-Montieth (F.P.M), evaporation pan, monthly and yearly adjusting coefficient. Also the F.P.M's calculated ETo for all the synoptic stations of Razavi Khorasan province were regression with the air temperature, radiation and psychrometeric coefficient to suggest a simple equation. The best results were obtained from the F.P.M equation with the monthly (R2=0.99) and yearly (R2=0.92) adjusting coefficient, respectively. So it is advised to assess the reference situation of the station and use adjusting coefficients for the non-reference ones.

Methods of tillage and organic matter affect root growth and distribution and therefore nutrient uptake by plant and its growth. This study was performed consecutive two years. Tillage treatments included disk harrowing + two disk harrowings as reduced tillage (15 cm plowing depth) and moldboard plowing + two disk harrowings as conventional tillage system (30 cm plowing depth). Also, three levels of 0, 30 and 60 tons per hectare farmyard manure were used as organic manure treatments. The above mentioned treatments were done in a split block design with 3 replications and under corn cultivation for two years. To determination of root morphological properties of plant, sampling was done by a cylinder with a cap from top of the row and root length and density were measured. The results showed, tillage systems had a significant effect (p=0.05) on root length and density of corn in 0-20 cm soil depth. In the reduced tillage treatment, root length and density in the stages of 9 and 11 leaves increased significantly in comparison conventional tillage, but root depth was higher at conventional tillage than reduced tillage. This is due to presence of soft soil (disturbed soil) in lower soil depth from top of the row under conventional tillage. The results indicated that manure had no significant effect on morphological root characteristics, but increased biological yield of corn.

Deficit irrigation technique can be used for produce more yield for every unit of irrigation water, and cause to increase crop economical benefit. Main purpose of deficit irrigation is high water use efficiency with decreasing in irrigation sufficiency. In this research potential of CROPWAT model in deficit irrigation management for two crops, wheat and barley in Karaj climate was studied. The results of reliability index such as RMSE and CRM with about are 9.8-17.2 percent and 0.32-0.51 value respectively, showed that the model in both crops underestimated the yield reduction compared with actual data. Negative values of EF index achieved for both crops with 14 days irrigation interval show inefficiency of model in yield reduction predicting in this irrigation interval. This difference was more obvious in deficit irrigation treatments. Considering only drought stress and neglecting other stresses -such as salinity- is the most important limitation of CROPWAT model. Model crop coefficients could also caused differences between actual data and model results. This study shows that application of CROPWAT model without calibration of crop coefficients and soil characteristics would be result in significant errors and this is should be considered. In this study water use efficiency for studied crops were achieved in the range of 1.3-2.3 Kg/m3 and maximum values of that was in 20% deficit irrigation. Applying optimum deficit irrigation management could have considerable role in increasing water use efficiency.

Saffron (Crocus sativus, L.) is one of the most important economical crops for Khorasan farmers. Almost all saffron yield in Iran comes from Khorasan provinces. First irrigation times is the crucial factors which affect the amount and quality of yield based upon an on farm investigation it was found that when air temperature reaches to 12 c The most amount of flower is yielded. Also it was found that 2 to 3 weeks after irrigation flowering starts. The one irrigation should be applied in such a way that after this period of time saffron could be harvested. In this study the most appropriate date for the time of irrigation with 50, 75 and 95% probability was derived for different points of Khorasan provinces. Also Khorasan provinces were zoning for this purpose. Based on results, flowering date and first irrigation time for saffron are very different and depended on climate and temperature of studied zone. In the locations with higher elevation above the sea level and lower daily air mean temperature, usually flowering date and first irrigation time are very soon in the autumn early while decreasing of elevation above the sea level and increasing of daily air mean temperature, flowering date and first irrigation time are in the mid autumn or even autumn late.

Gully erosion is a kind of water erosion that has high priority in Fars Province due to sediment production and enormous damages to land, roads and infrastructures. In this study, 15 gullies were selected and their morphometric characteristics, such as catchment area, soil, cover vegetation and climate were measured. In order to determine influential factors on the sediment production and gully development, relationship between gully volume as dependent variable and gully characteristics such as, length, width, depth and watershed characteristics such as area, slope, form factor, particle size, vegetation cover and maximum raining during 24 hour as independent variables were analyzed by using step wise method in SPSS (recipe 13) software. The results revealed that sediment production due to gully development was related to five variables of clay, sand, silt, slope and cover vegetation of the watershed above the gully heads. This result implied on the impact of the characteristics of soil, geology and watershed on the sediment production of gullies. Impact of soil and geologic factors indicated were more important than watershed characteristics. Investigation on the topographic threshold indicated that positive environmental than exponent implied that sub surface runoff is dominant on gully development. These results also indicate the impact of field observations proved the dominance of subsurface acting due to tunneling the geological formation on the gullies sediment yield.

Recharge of aquifers by using wastewater, is one of the important and applicable ways for reusing this valuable water resource, especially in arid and semi-arid regions. As the necessity of local practices for finding the proper management strategies and optimum use of recharge systems (conforming to climate, soil, etc.), a preliminary study was carried out. Three physical models were designed and made with a height of 2 m and diameter of 0.6 m. The models were filled with a soil of silty clay sand texture. Treated domestic wastewater of Ekbatan housing complex was used. Transfer of important pollutants indexed by BOD5, COD, nitrogen and phosphorous to shallow grounwaters were studied. Three management practices of wet-dry periods have been used: 1-permanent or long ponding (PP), 2- short period ponding and drying (SP) as 12 hours wetting and 12 hours free drainage, and 3- Moderate ponding (MP) and drying by means of wetting for one week and then drying for another week. The results showed that optimum BOD5, COD and nitrogen reduction occurred in the application of short period ponding management system (mean reduction percentage of 93.5%, 79.5% and 40.4%, respectively). The phosphorous reduction in all strategies was 65% - 75%. The efficiency of microbial indices removal (coliform and fecal coli.) from treated wastewater was high in all management systems. The amount of reduction in this case was between 97% to 99%.

In order to study the effects of cultivation method and water quantities in drip irrigation on yield of potato, an experiment was carried out using a split plot based on randomized complete block design with 4 replications in Torogh Agricultural Research Station (Mashhad, Iran) for tow years (2001 and 2002). The main-plots were divided into 3 levels of irrigation: I1= 100, I2= 80 and I3= 60 percent of evapotranspiration. Sub-plots were 3 cultivation B1= distance between rows were 75 cm with one drip irrigation lateral, B2= two cultivation rows with distance of 35 cm and a lateral between them and distance between laterals was 135 cm and B3 = two cultivation rows with the distance of 45 cm and a lateral between them and distance between laterals was 150 cm. The results showed that Total yield in maximum irrigation (I1) was higher than I2 and I3. the B2 cultivation pattern had the highest total (19.7 t/h) and economic (18.5 t/h) yield. The B2 cultivation had the highest tubers yield (35-55 mm). Water use efficiency (WUE) of B2 cultivation with 3.54 kg/m3 was more than B1 and B3, but it was not significant. Water stress lead to reduction of total tubers yield, economic yield and WUE. maximum irrigation level (I1), had the most tubers yield (35-55 and bigger than 55 mm) and had significant difference with I2 and I3 irrigation treatment. WUE in maximum irrigation (3.53 kg/m3) was better than lower irrigation level in drip irrigation of potato and had significant difference.

The quality of soil maps depends upon their ability to show the soils variability. Thus, the accuracy of the maps used for crop recommendations is due to the accuracy of soil maps. This study was performed to investigate the amount of soil properties and crop yield spatial variability in S¬2 and S3 units of a semi-detailed quantitative suitability map (1:50000 scale) for irrigated wheat in Shahr-e-Kian area, Chaharmahal-Va-Bakhtiari province. Eighty soil samples were collected in each land unit at 0-30 cm depth using multi-scale sampling method to determine available P, K, total N, %O.M., %CaCO3 equivalent, soil texture and particle size distribution, EC and pH. A 0.5×0.5 m plot of wheat was harvested at each of 160 sites previously sampled to determine crop biomass, 1000 seeds weight and harvest index. The highest CV was related to available potassium (47.43 for S2 and 46.46 for S3 units, respectively) and the lowest one was related to pH (1.07 for S2 and 0.925 for S3 units, respectively). Variography showed a good spatial structure for all variables in both land units. Ranges for variograms were from 17.75 for N to 61.06 m for EC in S2 unit and from 17.47 for P to 62.93 m for 1000 seeds weight in S3 unit. Kriging maps showed high spatial variability of soil properties as well as biomass, wheat yield and harvest index within two land units. This indicates that suitability maps have not enough credibility for precision agriculture. Using information of all pedons as well as representative pedons in land units and combining the information of suitability maps with geostatistical data can be a choice way to improve the accuracy and quality of land suitability maps.

Water is one of the most essential parameters for crop production. There is a direct relation between crop yield and water use in plants. Agriculture in arid regions has special aspects. In these areas, agriculture is limited by water and irrigation. Therefore, agricultural practices are organized for optimum water use and maximum yield per unit volume of water which is used. Sprinkler irrigation is one of the methods which has important role in suitable use of water and increasing water use efficiency (WUE). In this research, water use efficiency and yield (quantity and quality) of sugar beet in sprinkler and furrow irrigation was studied in Mashhad, Karaj and Esfahan. In the first year, experiments were done in three locations based on T student test without replications. In the second year, experiments were done in three replicates with randomized block arrangement in Mashhad and Karaj. Irrigation treatments were sprinkler, conventional and cut back furrow irrigation. Water requirement in sprinkler irrigation treatment was calculated based on Penman-Monteith method. Ordinary furrow irrigation treatment applied according farmer's conventional methods. Also, cut back irrigation treatment was applied based on reducing irrigation discharge to 0.6-0.7 after delivering of water to the end of furrows. Results showed that there were significant different in root yield, net and gross sugar yield, water use efficiency and sugar content between experimental regions. However, there was significant difference in root yield and water use efficiency between irrigation treatments. The sprinkler irrigation treatment produced the highest root yield (56.5 ton/ha). The cut back and conventional furrow irrigation treatments produced root yield of 48 and 43.6 ton/ha, respectively and were place in the same statistical level. Root and gross sugar water use efficiency in sprinkler irrigation treatment were 5.55 and 0.86 kg/mЗ, respectively. This treatment was better and has significance difference with two other irrigation treatments. Although, cut beck irrigation had better performance compared to conventional furrow irrigation but in overall, sprinkler irrigation treatment had better performance in used water, irrigation efficiency, root yield, sugar yield and WUE with respect to furrow irrigations. According to obtained results, it is recommended that in regions with limited water resources, sprinkler irrigation has been applied for increasing yield and WUE. However, in region with limitation in application of sprinkler irrigation methods (such as high ¬speed winds, heavy soils, etc.), it is recommended that modified furrow irrigation method such as cut back method has been applied for increasing irrigation efficiency and WUE.

Infiltration is a significant process which controls the fate of water in the hydrologic cycle. The direct measurement of infiltration is time consuming, expensive and often impractical because of the large spatial and temporal variability. Artificial Neural Networks (ANNs) are used as an indirect method to predict the hydrological processes. The objective of this study was to develop and verify some ANNs to predict the infiltration process. For this purpose, 123 double ring infiltration data were collected from different sites of Iran. The parameters of some infiltration models were then obtained; using sum squares error optimization method. Basic soil properties of the two upper pedogenic layers such as initial water content, bulk density, particle-size distributions, organic carbon, gravel content, CaCO3 percent and soil water contents at field capacity and permanent wilting point were obtained for each sampling point. The feedforward multilayer perceptron was used for predicting the infiltration parameters. Two ANNs types were developed to estimate infiltration parameters. The developed ANNs were categorized into two groups; type 1 and type 2 ANNs. For developing type 1 ANNs, the basic soil properties of the first upper soil horizon were used as inputs, hierarchically. While for developing type 2 ANNs the basic soil properties of the two upper soil horizons were used as inputs, using principal component analysis technique. Evaluation results of these two types ANNs showed the better performance of type 1 ANNs in predicting the infiltration parameters. Therefore, this type of ANNs was used for predicting the cumulative infiltration. The reliability test indicated that the developed ANNs for Philip model have the best performance to predict cumulative infiltration with a mean RMSE of 6.644 cm. The developed ANNs for Horton, Kostiakov-Lewis and Kostiakov have the next best ranks, respectively.

Plant- growth promoting rhizobacteria enhance plant growth and yield directly and or indirectly. A factorial experiment was conducted in greenhouse to determine the efficacy of four strains of Fluorescent Pseudomonas on wheat yield and yield component under saline conditions. the experiment was carried out with the following treatments (non –inoculation control and inoculation with P.fluorescens strain153 P.fluorescens strain169 P.putida strain108 and P.putida strain 4) and four salinity levels (1,4,8 and 12 dS/m) in a completelyrandomized design. A combinationof (NaCl+ CaCl2 +MgCl2 with equal equivalent) dissolved in distilled water and added to soils to meet the desiredsalinity treatments. wheat seeds were inoculated whit strains before planting. During growing period, the pots were irrigated with distilled water to maintain soil moisture around 0.8 FC. before harvest, growth indices including: plantheight, number of tillers and heads and after harvest,dry weight of shoots and grain yield were determined. Results showedthat with increasing salinity level, grain yield,1000 weight, number of grain per spick, plant height and biologic yield decreased significantly (P)

Prediction of input flow into water resources is regarded as one of the most important issues in optimum planning and management in producing electro-water energy and optimum allocation of water into different consumption sources. Different parameters affect on input discharge into dams. Climate variables including temperature and rainfall have the most effect on input runoff rate to water resource in dry and semi-dry regions like Iran. A suitable monthly runoff-rainfall model is a strong tool to consider the climate changes effect on accessibility of water to produce electro-water energy. The investigations have shown that the relation between runoff rate and effective variables is non-linear and complicated. Artificial Neural Networks due to their unique properties have a tremendous capability in non-linear relations simulation. Artificial Neural Networks establish a great change in analyzing dynamic systems behavior in different water-science engineering. In this paper it has been attempted to design static network to recover the non-linear relations between dependant and independent variables, so that the intelligent discharge estimation of average monthly input to Vahdat dam can be done by its help. In addition, by designing and extension of dynamic neural network model based on times series performance, the amount of the monthly input discharge to the dam was predicted. Considering the capability of Artificial Neural Networks, these networks were used for modeling the rivers monthly discharge non-linear time series. Analysis of time series having two major goals; random mechanism understanding or modeling and future series value prediction was done base on previous ones. Also, the performance of the designed models was evaluated by comparing results of the static and dynamic neural network. The results of the investigation showed that there is a good conformity between the predicted values given by combined neural network and observed data. Furthermore, the results showed that the time series dynamic neural network model predict the monthly discharge more accurate than static model.

Suspended sediment resulted from distributed soil erosions facilitates soil nutrients transportation and influences soil depletion. Soil erosion plays a key role in loss of organic matter and therefore study of the relationship between organic matter and soil erosion processes and soil nutrient loss is very important. The present case study was conducted in Kojour Educational Forest Watershed with an area of 13263 ha to determine the relationship between eroded suspended sediment and organic matter through daily sediment sampling and measurement of suspended sediment. The water and suspended sediment sampling was made via depth-integration. The determination of suspended sediment and organic matter contents was made by decantation and loss on ignition methods, respectively. Then the relationship between variables was assessed by bivariate regression method and descriptive statistics. The results of this study showed that there were high variations of organic matter and suspended sediment with respective coefficient of variation of 150 and 107. Similar trend in variation for both variables in different time periods was also proved by developing regression models with correlation coefficients from 0.48 (P)

Solar radiation, nowadays has a lot of application in different fields of agriculture, irrigation, and hydrology engineering and due to these various applications, different models has been proposed for it’s estimation. Angstrom-Prescott equation is one of the most important well known models for solar radiation estimation. This equation has empirically coefficient that various for each location. In this paper, the data gathered in Mashhad Synoptic station during 1378 and 1380, Angstrom-Prescott coefficient has been identified according to the ratio of actual sunshine hours (n) to the maximum sunshine hours (N). Also a Regression local equation has been proposed considering several meteorology parameters including daily gathered data of saturation vapor pressure deficit, precipitation, air temperature mean, relative humidity percentage and n/N. Finally the proposed model has been evaluated according to the independent measured data during 1381 to 1382. The statistical analysis of the results not show a significant difference between multi coefficients-local equation with Angstrom-Prescott equation, and therefore without more accuracy and more additional meteorology data and only with the data including sunshine hours and calculating extraterrestrial solar radiation, global solar radiation can be used with a high precision. For instance our model for Mashhad can be used with a=0.23 and b=0.44 which are the coefficient of the Angstrom-Prescott equation. This coefficient should be calibrated and validated for each zone individually.

In order to study the chemical behavior of nickel and cadmium in the presence of organic matter, an experiment with two different soils (4 and 30 percent CaCO3), two different texture (8 and 40 percent clay), two levels of nickel (0 and 100 mg.kg-1), two levels of cadmium (0 and 25 mg.kg-1) and organic matter in the form of sewage sludge in two levels (0 and 100 t. ha-1), at three times (0, 30, 60 days) in a completely randomized design with three replications was carried out. Concentration of cations, anions, dissolved organic carbon and pH were measured in soil extracts. Soil solutions were speciated for chemical forms of nickel and cadmium by MINTEQA2 model. The results of this study showed that nickel, cadmium and dissolved organic carbon in sewage sludge treated soils increased significantly. The amount of available nickel and cadmium decreased significantly with time. Nickel and cadmium in sandy loam soil was significantly higher than clay soil. Sewage sludge application decreased the amount of free hydrated cadmium significantly. In solution phase the proportion of free hydrated cadmium and nickel was higher in soil with 4 percent lime. In contrast, in soil with high lime, the percentage of nickel and cadmium in the form of carbonate was higher. In general, it seems that in the study soils calcium carbonate plays a key role in chemical behavior of nickel and cadmium in solution phase. Therefore, it can be expected that the recommended threshold by environmental protection agencies should be higher in calcareous soils.

In order to investigate the removal of copper, nickel, zinc and chromium from industrial waste water by a sand–soil–organic matter filter column, this experiment was conducted at a completely randomized design with sixteen treatments and four replications. P.V.C tubes (columns) with 66.5 cm height and 10 cm diameter were chosen and filled from down to top by coarse gravel (15 cm), sand (15 cm), soil (2.5 or 5 cm), organic matter (15 cm) and fine gravel (5 cm), respectively. Then, 1100 ml of electroplating industry waste water was added to the filter and 30 ml of leachate was collected and transferred to the laboratory for measurement of pH and heavy metals concentrations by atomic absorption spectroscopy technique. The action was repeated at nine pore volumes for each filter. The results showed that application of this filter led to increased pH to neutral and low alkaline range and often meaningful decreased heavy metals concentrations in the leachates during nine pore volumes. The probable mechanisms (such as adsorbtion, precipitation, ion exchange and chelation) by which the filter led to changes in the chemical properties of leachate were also discussed. Generally, it seems that the application of sand–soil–organic matter filter column was effective and therefore, could be advisable for the removal of studied heavy metals from industrial waste water.

Low molecular weight carboxylic acids (LMW) play an important role in improving the bioavailability of soil nutrients. Nonexchangeable soil K, trapped between the interlayers of clay minerals, is an important source of K for plants in many soils. The objectives of this study were to determine the effect of selected LMW organic acids on the release of K from micaceous minerals and to investigate the resulting mineralogical changes. A laboratory dissolution study was carried out using a completely randomized design with three replicates. Muscovite and phlogopite (< 60 μm size) were reacted with 0, 500, 2000 and 4000 μM solutions of oxalic, citric and malic acids for a period of 5 hours to 120 days. The amount of K released to the solution was determined with flame photometer. The rate of K release varied with the type of organic acids and also the kind of mica. Citric acid solution with a concentration of 4000 μM was able to release more K from minerals. The higher the concentration of organic acid, the higher the amount of K released. The amount of K released from minerals was in the order of phlogopite>muscovite. The kinetics of non-exchangeable K release from minerals consisted of two phases, the first phase was relatively rapid and then it had a constant rate untile the end of experiment. Strongly coordinating LMW carboxylic acids enhance the mineral dissolution and weathering reactions through the detachment of surface complexes into solution. There was not any XRD detectable changes in minerals reacted with organic acids up to 4 months.