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Mineral anions are among the most important toxic substances harmful to humans and animals even in low concentrations. Nitrate ions are considered important surface and groundwater pollutants for their high solubility in water. Nitrate is converted to nitrite and N-nitroso in the human body through certain reactions. N-nitroso combinations are considered carcinogenic and the primary cause of methemoglobinemia diseases. The existing nitrate in water resources is not easily separated for it is highly soluble and therefore the methods usually used for this purpose are very costly. Various methods can be used to remove or reduce the concentration of nitrate. Reverse osmosis, electrodialysis, electrocoagulation, ion exchange, and membrane processes are among the physicochemical methods of nitrate purification. Among the types of nitrate purification methods, biological processes with relatively high efficiency, the possibility of complete removal of the pollutant, and less harmful effects on the environment, are some of the most suitable options for the decomposition and removal of nitrate from water and groundwater. In a situation where the contaminated area is wide and it is not possible to pump water due to economic reasons or the large volume, treatment using in-situ methods will be a more suitable option. One of the types of in-situ biological treatment processes is the use of the permeable reactive bio-barrier (PRBB) method. PRBB is one of the novel and reliable methods used for in-situ groundwater remediation.  A PRBB is an emplacement of reactive media in the sub-surface designed to intercept a contaminated plume, provide a flow path through the reactive media, and transform the contaminant(s) into environmentally acceptable forms to attain remediation concentration goals down the gradient of the barrier. PRBB can degrade nitrate at a high rate under anaerobic conditions. In this research, different concentrations of four chemical substances including ZVI, nZVI, NaS2O3, and Na2S2O5 were used as Oxygen Capturing Compounds (OCC) in the removal of nitrate from polluted water in the PRBB process on a laboratory scale. Based on the obtained results, these substances affect the parameters of DO, pH, MLSS, turbidity, nitrate concentration, durability of DO, and ORP. After laboratory tests and taking into the opinion of experts, the qualitative effect of each parameter was calculated quantitatively and through the analytical hierarchy process (AHP), the best oxygen-capturing compound was selected. The results obtained from AHP (with an inconsistency ratio of 0.063), revealed that the priority of choosing OCC from three technical, economic, and environmental aspects is related to the concentrations of 750 mg/l ZVI, 240 mg/l Na2S2O3, 85 mg/l Na2S2O5 and 550 mg/l nZVI respectively. The concentration of 750 mg/l ZVI (the best OCC) during the experiments was able to reduce the DO from 7 to 0.05 mg/l in approximately 500 minutes and within the ideal range of the denitrification process (DO<0.05 mg/l). In addition, after the durability of DO tests, it was found that this substance has maintained its deoxygenation properties for longer than other used compounds. Also, based on the results, the concentration of 750 mg/l ZVI had a positive effect on the increase of MLSS and removal of nitrate. 

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Nowadays, investigating and researching on energetic polymers in order to increase mechanical, thermodynamic, and detonational properties of them have been highly regarded. One of these energetic polymers is GAP. In this paper, molecular dynamics simulation has been used to compare the properties of GAP and GTP energetic polymers. GTP, in principle is the modified form of GAP, in which functional group of triazolium methyl nitrate has been added instead of azide. The mechanical properties of GAP is a challenging topic in the field of energetic materials. Due to the attributes of the 3 azoliom methyl nitrate ring, the mechanical and thermodynamic properties of GTP are expected to be higher than GAP. The results obtained by molecular dynamics simulation showed that GTP is a stable material and its mechanical properties such as Young, and shear modulus compared to GTP have been decreased 27% and 32% respectively, and bulk modulus, Poisson coefficient, and K/G ratio compared to GTPhave been increased 17%, 42%, and 71% respectively. It was also found that the detonation speed, detonation pressure, and oxygen balance of energetic polymer compared to GAP, have been increased 5%, 14%, and 21% respectively. As a result, usage of GTP will increase as a modified GAP material in applications such as clean and chlorine-free propellants for the solid propellant rockets and also safety systems of automobiles.

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The adequacy of the SWAT model in the estimation of runoff, sediment yield and nitrate loss in the Gorganrood watershed was tested, using the existing spatial database as the primary data. The model was then executed for a 31-years’ time period. In combination with the SWAT model, the Sequential Uncertainty Fitting Program (SWAT-CUP and SUFI-2) was added used to calibrate and validate a hydrologic model of the watershed. The obtained values at 14 stations were between 0.48 to 0.83 for NS and 0.58 to 0.90 for R², respectively. The results showed that nitrate loss was higher in cultivated lands, and in the loess deposits. The maximum amounts of runoff and sediment yield were largely produced in steep areas of the watershed, where dry farming was practiced. In general, the results showed that SWAT could be a proper tool for simulating runoff, sediment yield and nitrate loss into the river.

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Research subject: In recent years, due to limited water resources and the extraordinary increase in nitrates in the environment, efforts to remove and control in order to benefit from the natural adsorbents have been made. Although according to the negatively charged surface of bentonite particles, absorbent needs improvement.
Research approach: In the current study, the adsorption of nitrate columns by the modified calcium montmorillonite adsorbent was investigated. Furthermore, In order to change the surface load and increase the adsorption efficiency, three-step acid leaching, oxidation layering, and loading of the cationic surfactant hexadecyltrimethylammonium bromide on the adsorbent were performed. Molecular interaction and crystallography of pure montmorillonite and synthetic nano-adsorbent (ACZ) were characterized by Fourier transform infrared spectroscopy and X-ray analysis. Moreover, the morphology of ACZ nano adsorbents was evaluated using Transmission electron microscopy and scanning electron microscopy.
Main results: Nanoparticle compaction and less access to pores and cavities in the fixed bed column reduced the adsorbent capacity inside the column compared to the discontinuous system.
The results showed that an increase in inlet concentration from 80 to 150 mg/L increased the adsorption capacity from 67.39 to 88.25 mg/g. Reducing the inlet flow rate increased the penetration time, interaction, and greater access to the binding sites for nitrate ions and finally improved the column performance and increased the inlet flow rate reduced the adsorption capacity and breakthrough time. Therefore, the adsorption of nitrate ions by the stage of internal mass transfer is controlled and depends on the duration of interaction and the possibility of penetration into the active sites. With increasing the bed height from 4.2 to 9 cm, there was a significant increase in adsorption capacity from 60.608 to 77.167 mg/g. The effect of detergents and recovery showed an absorption column; After 3 leaching steps, acid leaching played an important role in increasing column recovery. Experimental data with correlation coefficients of R²>0.95 corresponded to Thomas and Yoon-Nelson kinetic models.
In this study, the ACZ nano adsorbent column for rapid removal of nitrate ions from aqueous solutions was introduced and for use in reusable systems was proposed.
 

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  The current approaches applied for removing nitrate from drinking water, commonly uses many chemical additives that may have undesirable or unknown effects on human health and in some cases caused many by products more dangerous than nitrate in drinking water. In present there are few appropriate and economic processes in this field and because of water scarcity in many areas development a suitable technology for treatment of nitrate contaminated drinking water for application in actual scales is crucial. In this research we develop an economic process with high selectivity for nitrate removal and minimum disturbance in other drinking water quality parameters that utilizes only hydrogen and carbon dioxide, produced in a methanol based electrochemical gas generator by applying a very low DC voltage (5-10 volt). We evaluate the ability of hydrogenotrophic denitrification for removal of nitrate in a bioreactor packed by light expanded clay aggregates known as LEACA. The results showed by proper coupling of electrochemical gas generator and denitrification bioreactor only by injection of tow clean and harmless gases, hydrogen and carbon dioxide and without any other chemicals addition for common concentrations of nitrate in natural waters by hydraulic retention time of 2-5 hr, removal efficiencies greater than 95% can be achieved. Also in comparison with other conventional methods such as ion exchange, reverse osmosis, electrodialysis, and biological heterotrophic with organic carbon source this system has several advantages such as: high selectivity for nitrate ion, low biomass yields, low electrical energy consumptions, without any problems resulted from organic carbon source addition (for example: taste and odor problem, carcinogenic THM production in disinfection process and rapid clogging of biofilter), easy operation, and compatibility with health issues in drinking water treatment.

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Nitrate concentration of the soil, at the start of growing season, is high due to minerali-zation of soil organic N during the Fall and the addition of N fertilizers. It may be useful to exploit this N form as much as possible. Therefore, the nitrate uptake, assimilation and dry matter production of several wheat cultivars were examined in a series of experiments using a hydroponic culture system. Seedlings were grown at two rates of nitrates (0 and 1.0 mM) and the experiments lasted for 26 days. Significant genetic variation in the growth and nitrate uptake were observed. The Atila and Yavarous cultivars consistently produced large seedlings absorbing higher quantities of nitrate from the nutrient solution, compared to the Falat, Star and Seri 11 cultivars which produced smaller seedling and took up lower amounts of nitrate. However, apart from seedling vigor, there was evidence that some cultivars were more efficient physiologically in assimilating nitrate. For compa-rable amounts of nitrate taken up from solution, total dry matter production in this group of cultivars was considerably greater than others. Results of this work revealed that ge-netic differences among wheat cultivars affect nitrate uptake, which in turn indicated the influence of plant status and in particular root system on the potential of nitrate uptake.

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Today, the continuous release of environmental pollutants into aquatic ecosystems has made these environments extremely vulnerable and turned them into a storage sites for these toxic substances, so it is necessary to investigate the effects of these pollutants on aquatic life. The present study was conducted with the aim of determining the toxicity of silver nitrate and observing the behavioral changes of Litopenaeus vannamei during its exposure. To determine the toxicity, the standard method of OECD was used. At first, the viability and survival of Litopenaeus vannamei were checked after two weeks of acclimatization to laboratory conditions, then by conducting preliminary tests, the actual lethality values ​​of silver nitrate were obtained. In order to determine the median lethal concentration, shrimps were exposed to concentrations of  0.025, 0.05, 0.1, 0.2, 0.4 and 0.8 mg/L of silver nitrate for 96 h and their mortality were recorded daily every 24 h. The LC₅₀, LOEC, NOEC and MATC were calculated based on shrimp mortality. During the viability and survival test, no mortality were observed up to 96 hours, and the survival rate of shrimps was 100%. The value of LC₅₀, NOEC, LOEC and MATC were determined as 0.084, 0.02, 0.025 and 0.0084 mg/liter, respectively. In different concentrations of silver nitrate, shrimps showed behaviors such as abnormal swimming, fast movements of swimming legs, coming to the surface of the water, twisting the body around itself and eventually losing balance.

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DRASTIC model has been used to map groundwater vulnerability to pollution in many areas. Since this method is used in different places without any changes, it cannot consider the effects of pollution type and characteristics. Therefore, the method needs to be calibrated and corrected for a specific aquifer and pollution. In the present research, the rates of DRASTIC parameters have been corrected so that the vulnerability potential to pollution can be assessed more accurately. The new rates were computed using the relationships between each parameter and the nitrate concentration in the groundwater. The proposed methodology was applied to Astaneh aquifer located in north of Iran. Samples from groundwater wells were analyzed for nitrate content in thirteen locations. The measured nitrate concentration values were used to correlate the pollution potential in the aquifer to DRASTIC index. Pearson correlation was used to find the relationship between the index and the measured pollution in each point and, therefore, to modify the rates. The results showed that the modified DRASTIC is better than the original method for nonpoint source pollutions in agricultural areas. For the modified model, the correlation coefficient between vulnerability index and nitrate concentration was 68 percent that was substantially higher than 23 percent obtained for the original model

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Wastewater treatment with microalgae and its reuse is an effective step toward reducing water consumption and preserving water resources. The possibility of growing spirulina microalga on cattle effluents and the possibility of purifying effluents using microalga were investigated. Different concentrations of standard culture medium (Zaruk)-wastewater were used to measure the optimal algal growth on wastewater and to determine the concentration of effluent-Zaruk for optimal algal growth. The treatments were T1 including 100% Zaruk and no wastewater, T2 including 75% Zaruk and 25% wastewater, T3 including 50% Zaruk and 50% wastewater, T4 including 25% Zaruk and 75% effluent and T5 including 100% effluent without Zaruk. Treatments that had more Zaruk, showed more optimal growth, and those that had a higher concentration of effluent often showed a relatively lower growth of algae biomass. The results showed the high growth of algae on the concentrated effluent. T1 with 0.35 and T2 with 0.3 g/liter of dry biomass had the highest biomass of microalgae. T1, T2, T4, T3, and T5 had the highest to the lowest amount of phycocyanin pigment production in microalgae, respectively. The highest removal of nitrate belonged to T5 and T4 with 82.57% and 78.21% removal respectively, and the lowest nitrate removal belonged to T1 and T2 with 57.17% and 70.94%, respectively. The highest removal of phosphate belonged to T1 and T2 with 94% and 92.11% removal, respectively. The lowest removal of phosphate belonged to T4 with 84% removal. Findings indicated the high potential of microalga for treating cattle wastewater.
 

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Due to extensive usage of nitrogenous fertilizers and discharge of industrial and domestic wastewater, nitrate contamination of water is becoming a main environmental concern. High levels of nitrate in drinking water causes serious health problems such as methemoglobinemia in infants and gastric cancer. Because of such health problems, nitrate removal from water is urgent and has been a hot topic over the recent years. Various technologies such as the ion exchange, reverse osmosis, electrocatalytic, adsorption, electrodialysis and biological process, have been used to eliminate nitrate ion from water and wastewater. Nevertheless, these methods have several drawbacks such as high installation and maintenance costs, difficult operation, brine production, membrane fouling, further treatment, slow process and carbon source requirement. A large number of investigators thus have focused on the reduction of nitrate by the electrochemical process usually because of its efficiency, very low sludge production, small area occupation and facile operation. Integration of electrochemical and biological processes as bioelectrochemical systems has been recommended to overcome the potential problems. In bioelectrochemical denitrification, denitrifying microorganisms make use of hydrogen generated at the cathode by the electrolysis of water as an electron donor to reduce nitrate into nitrogen gas. Autohyrogenotrophic denitrifying bacteria commonly adhere to the cathode surface and make a biocathode. Therefore, Cathode electrode material is one of the major factors that affecting in the bioelectrochemistry efficiency. Cathode material can directly affect to denitrifying bacteria attachment, hydrogen production, electron transfer and electrical conductivity. Bioelectrochemical process can be used to eliminate nitrate through a catholic reduction process. Carbon material has high mechanical strength and a rough surface which is ideal for the formation of biofilm as compared with metal materials. However, carbon materials are difficult to apply in large scale processes due to high electrical resistivity that tend to increase electrode ohmic losses. Hence, carbon electrodes are supported by a conductive material current collector such as carbon nanotubes and metallic materials. Carbon nanotubes have a good biocompatibility with bacteria and have not shown negative effect on biofilm formation. It had been reported that carbon nanotubes can facilitate transfer of electrons between bacteria and electrode in bioelectrochemistry. The aim of this study is bio-electrochemical removal of nitrate from wastewater using carbon nanotubes immobilized in cathode. This study has been done in a bathe scale bioelectrochemical rector with a two chambers. Considering that nitrate reduction done in biocathode, carbon nanotube used in cathode for increasing nitrate removal. The effects of pH, current density and retention time were evaluated for nitrate removal in a bio-electrochemical reactor.The highest nitrate reduction rates were occurs in neutral pH and current density of 15 mA/cm2. Furthermore, at current density of 15 mA/cm2 and retention time of 8 hours, the bioelecterochmical system can reduce the nitrate levels to below the environmental standard.The results showed that multi-wall carbon nanotube as cathode modifier increase the nitrate reduction efficiency about 14 persent. The use of multi-wall carbon nanotube can increased biofilm formation and therfor the reduction time for achieving to nitrate standard was reduced.

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In order to assess the effect of salinity constraint on some agro-physiological and biochemical traits in Medicago sativa L., four Alfalfa populations (Tafilalet 1, Tafilalet 2, Demnate and Tata), originated from mountains and oasis of Morocco, were tested. The plants were grown under greenhouse conditions in pots filled with sand and peat under three salt treatments (0, 100 and 200 mM NaCl). Thereafter, plants were harvested 45 days after salt treatment and some agro-physiological and biochemical parameters related to salt tolerance, such as plant biomass, water content, membrane permeability, nutrients contents, nitrate reductase and acid phosphatase activities, were measured. Results showed that increase in NaCl concentration gradually reduced plant biomass, which displayed significant differences among the tested populations. Thus, Tata population appeared to be the most tolerant population to salinity, Tafilalet 1 population was the least tolerant one, while Tafilalet 2 and Demnate displayed moderate salinity tolerance. Variations in plant growth were associated with changes in physiological and biochemical parameters. Indeed, salinity caused a decrease in relative water content, perturbation of membrane permeability, and nutrients concentrations. Results also showed that salinity inhibited nitrate reductase activity in leaves of all tested populations, but acid phosphatase activity was increased in both leaves and roots of stressed plants. Salt tolerance of alfalfa populations was associated with high inorganic ion accumulation and the maintenance of membrane integrity and an adequate level in terms of nitrate reductase and acid phosphatase activities.

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High efficiency and uniformity of water and fertilizer application are usually, considered as the ultimate goals of an appropriate design and management of irrigation and fertigation systems. The objective followed in this paper was to present a simulation-optimization model for alternate vs. conventional furrow fertigation. Two simulation models (surface fertigation and SWMS-2D models) along with an optimization approach (genetic algorithm) were employed. Inflow discharge, irrigation cutoff and start times as well as duration of fertilizer injection were chosen as decision variables to be optimized for maximizing two objective (fitness) functions based on water and nitrate application efficiency plus uniformity. Experiments were conducted to collect field data (soil water content, soil nitrate concentration, discharge and nitrate concentration in runoff, as well as advance and recession times) in order to calibrate the simulation models. The simulation-optimization model indicated that variable and fixed alternate furrow fertigations benefited from higher water and nitrate efficiencies than the conventional furrow fertigation. However, minor differences were observed between these types of furrow irrigation regarding water and nitrate uniformity. This approach substantially improved water and nitrate application efficiency as well as uniformity, taking into account the field experimental conditions. Water and nitrate application efficiencies ranged from 72 to 88% and from 70 to 89%, respectively. Christiansen uniformity coefficients for water and nitrate varied between 80 and 90% and from 86 to 96%, respectively. A higher improvement was observed in conventional furrow fertigation than those in both alternate furrow fertigation treatments. The potential of the simulation-optimization model to improve design and management of furrow fertigation is highlighted.

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It is extremely challenging to measure first-order rate coefficients for soil nitrate transformation processes directly, either in the laboratory or in the field. In this study, an improved inverse method was proposed to optimize the first-order rate coefficients by considering the intermediate changing processes of the integrated functions. A numerical experiment was designed to test the accuracy of the method in optimizing the coefficients. Comparisons between the optimized and theoretical results indicated that all the relative errors were within 10%. Data collected from a field experiment were used to validate the optimization procedure and to demonstrate its applications in practice. Using the established model and the estimated values by the inverse method, the simulated source-sink term (SST) distributions of September 2-12, 2007, were in good agreement, with the root mean squared error (RMSE) between them being as low as 0.00021 mg cm^-3 d^-1. Based on the established nitrate transformation model, the distributions of soil water content and nitrate concentration during September 2-12, 2007, were simulated, and compared well with the measured profiles, with the RMSE of 0.023 cm³ cm^-3 and 0.017 mg cm^-3, respectively. The improved inverse method should be useful for optimizing the first-order rate coefficients for nitrate transformation, establishing the nitrate transformation model, and simulating the nitrate transport in the soil-plant system.

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Discharging wastewater effluent to surface water or groundwater is so dangerous for environment, while it includes nutrient. As the phosphorus and nitrogen combinations in the aquatic environments have harmful impacts (mainly the poisonousness of ammonia, overgrowth of aquatic plants, groundwater pollute to nitrate and diseases caused by drinking the polluted water, and also eutrophication, resulting in frequent outbreaks of algal blooms and threatening the reliable supply of drinking water resources), some limitations were imposed on the consistency of these combinations in the entry waste. So nowadays removal of these combinations must be considered in designing of the treatment plants and also systems designed for treating the municipal wastewater must be able to remove nitrogen and phosphorus combinations to reach the standard limit. Therefore, in order to good performance of the aerobic-anaerobic A2/O method, it is proposed in this research and a study in advanced treatment of municipal wastewater using the A2/O method to remove nitrogen and phosphorus in the pilot scale in Ekbatan WWTP has been done.
In this research, firstly the principals of biological removal of nitrogen and phosphorus, and secondly the basis of designing biological treatment plants have been investigated. Then for laboratorial studies, an A2/O pilot has been made. This pilot consists of anaerobic, anoxic and aeration tanks and also sedimentation tank. The volume of these 4 tanks are 40, 60, 170 and 120 L, respectively. In order to simulate the real condition, this pilot has been set up in Ekbatan plant and the experiments were done to observe the effect of hydraulic residence time on nitrate, ammonia and phosphorus removal and also the effect of oxic mixed liquor recycling ratio on nitrate removal has been conducted. In order to observe the nitrate, ammonia and phosphorus removal process efficiency, the experiments were done in a period of three months and in 5 aeration hydraulic residence times, 4, 6, 8, 10 and 12 hours. In these experiments, the returned sludge was 25% and the oxic mixed liquor recycling ratio was 75%. After determining the best hydraulic residence time, experiments continued in 5 different oxic mixed liquor recycling ratios, 75%,150%, 225%, 300% and 375%.
It was concluded that at aeration hydraulic residence time of 8 hours, 96% COD , 95% ammonia and 79% phosphorus (effluent: 9 mg/L COD, 0.87 mg/L ammonia, 2.1 mg/L phosphorus, 18.7 mg/L nitrate) removal were achieved and that was the best HRT. Furthermore, according to the mixed liquor recycling ratio experiments, when the oxic mixed liquor recycling ratio was about 180 - 200%, optimum removing nitrate has been occurred. Although the mixed liquor recycling ratio of 225 - 275% resulted better efficiency for nitrate removal, it is not proposed, because effluent limitations in Iran for the nitrate is up to 10 mg/l which it is resulted in the mixed liquor recycling ratio of 180 -200%, and the other reason is that, with increasing the oxic mixed liquor recycling ratio, energy costs will increase, too.

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A three-year field experiment was conducted under conditions of Luvic Chernozem soil. Diversified nitrogen fertilization with 0, 60, 120, and 180 kg N ha^-1, and microbial preparations improving soil properties were applied to potatoes, cv. ‘Satina’, cultivation. N–NO₃ concentration in the soil profile (0–0.9 m) in autumn after potato harvesting fluctuated from 28 kg N ha^{-1 in the N}₀ treatment to 70 kg N ha^{-1 in the N}₁₈₀ treatment, whereas N–NH₄ content varied from 22 to 48 kg N ha^-1, respectively. The level of nitrogen fertilization also had a significant effect on the change in soil N–NO₃ content during the autumn-winter period. The decrease in N–NO₃ content in the N₀ treatments was 7% compared to 24% in the N₁₈₀ treatments. Application of microbial preparations to potato cultivation caused an increase in N_min content in soil after crop harvesting. However, after the autumn-winter period, a lower amount of N–NO₃, compared to the control treatment, was found in the treatments where microbial preparations had been used. 

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In this study, we try to evaluate the effect of ionic strength, pH and temperature of washing solutions on nitrate percentage in many leafy and root vegetable. For this purpose three edible solutions including NaCl as high ionic strength solution, baking soda (NaHCO₃) as basic solution and vinegar as acidic solution selected as nitrate losing agents for leafy vegetables (mint, basil, savory, tarragon, parsley, coriander, cress, radish and chives) and the effect of temperature evaluated using warm water (70 -100 ˚C) on nitrate percentage in root vegetables (potato and onion). Nitrate percentage in vegetables changed with different patterns. High ionic strength increased leafy vegetable nitrate percentage in wide rang (20.25 - 85 %(w/w)), pH increasing by baking soda solution increased nitrate percentage of group 1(Mint & Basil) leafy vegetables (33 %(w/w)) and decreased it in other groups partially (0.22 - 6.2 %(w/w)). However, pH decreasing by vinegar solution decreased nitrate percentage in all cases (14.6 - 41 %(w/w)). Optimum concentration of vinegar solution and treatment time in this solution, for maximum nitrate losing were 20 % (w/w) and 10 minutes, respectively. In the second part of this study, effect of solution temperature on nitrate percentage of root vegetables (potato and onion) was evaluated. Results show by this pretreatment nitrate percentage decreased 68.6 %(w/w) about potato and 26.6% (w/w) about onion. The important advantage of this study is vegetables nitrate percentage decrease, while the freshness and safety of these products preserved.  

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A greenhouse study was carried out to determine the effect of nitrogen forms and different O₂ levels on growth and mineral nutrient concentrations of eggplant. The experimental design was a completely randomized factorial experiment with two factors, namely: (i) Two nitrogen forms (Ca(NO₃)₂ and (NH₄)₂SO₄) and (ii) Three O₂ levels of the nutrient solutions (1±0.3, 2±0.3, 3±0.3, and 4±0.3 mg L^-1 O₂). The results showed that ammonium application reduced all measured parameters of vegetative growth, whereas high oxygen levels increased the vegetative growth. Comparing with nitrate-N, ammonium application increased the concentrations of NPK and Zn in leaves and Zn and Cu in roots, while it decreased the concentration of Mg, Ca, Cu, Mn, and Na in leaves and Ca, Mg, Mn, and Na in roots. High levels of O₂ increased N, Mg, Ca, Cu, and Mn content of leaves, as well as Mn and Na content in roots, while it decreased the concentration of K in leaves and P and Zn in roots. According to the results, the increase in O₂ amount of the nutrient solutions partly alleviated ammonium toxicity in eggplant. Therefore, in floating hydroponic cultures, O₂ level and its distribution should be controlled and must not be lower than 4 mg L^-1.

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The toxic effects of chromium in plants, animals and human beings in the environment have been widely studied. In the present study, pot experiment was conducted to determine the effects of chromium on photosynthetic pigments, Nitrate Reductase (NR) activity and total amino acid, proline, total protein and leghaemoglobin content of Sesbania grandiflora (L.) Pers. The seedlings were treated with Chromium Cr (VI), concentrations ranging from 0.38-1.92 mM Kg^-1 of soil with 0.35 mM Ethylene Diamine Tetra Acetic acid (EDTA) and without EDTA. The efficacy of EDTA in its presence and absence was compared for periods of 30, 60 and 90 days. Our results in comparison with our control indicate the inhibitory effect of chromium to S.grandiflora. From the results it has been observed that, increasing concentrations of chromium in the presence of EDTA showed a significant increase in proline and total amino acid contents, while the total chlorophyll, leghaemoglobin content and total protein content decreased and the NR activity of the plant was also affected greatly.

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Fertilization of plants in greenhouse soilless cultivation is used in a closed system with recirculating nutrient solution or in an open system where the excess of nutrient solution is discharged into the soil or sewage. In Poland, most of basic greenhouse vegetables are grown in the open soilless system. The excess of highly concentrated nutrient solution leaking from growing slabs causes contamination of soil and shallow groundwater. The aim of the study was to monitor component changes in nutrient solution and nitrate nitrogen in the plant root zone, drainage water, as well as in shallow groundwater present in arable lands in the immediate vicinity of the soilless tomato culture. The study was conducted in 2013 - 2015 and compared tomato cultivated in Rockwool versus biodegradable organic substrate. Changes of nutrient content including N-NO₃ in the root zone and drainage water depended on the type of the substrate in which tomato plant was cultivated as well as on the plant growth stage. Higher content of nitrate nitrogen in the root zone and drainage water was found in tomatoes grown in Rockwool compared to the organic substrate. The peak content of N–NO₃ (117 mgdm^-3)was detected in the groundwater present directly under the soilless tomato culture and it decreased proportionally to the distance from the greenhouse.