جستجوی مقالات مرتبط با کلیدواژه « nitrate » در نشریات گروه « محیط زیست »

The use of microalgae is an effective path in the process of advanced wastewater treatment in order to remove nutrients. In this study, living microalgae, Dunaliella salina was cultivated and then used in a series of batch experiments for the removal of nitrate and phosphate from wastewater.

The effect of changes in NO3- and PO43- concentrations (2.5-13 mg/l) on the removal efficiency using D. salina was evaluated during the 12-day growth period in the laboratory of Offshore Fisheries Research Center, Chabahar, 2017.

Results indicated that the maximum nitrate and phosphate removal efficiency using D. salina were 51.5% and 93.4%, respectively. The range of initial nitrate and phosphate concentrations were 0, 2.5, 5, 7.5, 10 and 12 mg/l and among them, the highest efficiency of nutrients removal after the control sample was obtained in 2.5 mg / l concentration of nitrate and phosphate. Phosphate removal efficiency was higher than nitrate at all concentrations and this shows that living microalgae D. salina has a good compatibility for growth in phosphate-contaminated wastewater. However, nitrate removal percentage is also significant and applicable to wastewater treatment systems. The Langmuir and Freundlich equilibrium models were also investigated in absorption process from solutions by living microalgae and the results of experiments were more consistent with Langmuir equilibrium model with R2 levels of 0.87 and 0.56 for nitrate and phosphate, respectively.

The results of this investigation suggested that D. salina is suitable as a biosorbent material for recovery and biosorption of nitrate and phosphate ions from aqueous solutions and wastewaters.

Groundwater is one of the sources used for drinking water.Nowdays, the amount of nitrate in most of the industrial effluents is outside the standard limit, and during the purification process, the efficiency of its removal should be carefully considered.Because, the infiltration of indaustrial wastewater into underground water, is unavoidable. In this study, it was conducted with the aim of investigating the health risk of nitrates present in the treatment of underground water extracted in the vicinity of one of the oil facilities located in the city of Tehran for reuse in a residential area. In order to assess the risk of purified water, the amount of nitrate output was sampled once every two weeks for a year and finally 25 samples were analyzed. The average measured nitrate concentration in the samples is equal to 3/63 mg/liter and the maximum measured concentration is equal to 7/134 mg/liter. Nitrate risk assessment method is selected based on EPA standard. The results showed that the level of non-cancerous risk in 84% of the samples for babies was above one (HQ ≥ 1) and consumption of this water can be dangerous for them. As a result, more sensitivity should be considered on the efficiency of nitrate removal in the treatment plant system.

Vegetables are the main food of the world's population, especially in developing countries. Currently, many vegetables, especially leafy vegetables, have a high percentage of nitrate due to the overuse of nitrogen fertilizers to accelerate vegetative growth. Many researches have been done on nitrate accumulation in crops worldwide, because of the harmful effects of excess nitrate in edible plants for humans and live stocks. Due to the necessity of such studies in country as well as the control of nitrate concentration in leafy vegetable and cucurbits, this study was done to investigate and monitor the nitrate concentration in some leafy vegetables and cucurbits (cucumber, tomato, potato, eggplant, pepper, onion, scallion and leafy vegetables) produced in some greenhouse and farms of Isfahan province.

In this study 142 different leafy vegetables (coriander, basil, chives, parsley, garden cress, dill, tarragon, mint, fenugreek) and cucurbits (fruit vegetables) including (cucumber, tomato, eggplant, pepper, onion, scallion and potato in coarse and fine sizes) collected from greenhouses and agricultural fields of Isfahan, Dorcheh, Falavarjan, Tiran, Dastgerd, Dehaghan and their surroundings. Nitrate content of plant samples was measured by spectrophotometer based on colorimetric method after reduction and production of aminoazo color complex. Then the nitrate concentration in the samples was compared with the maximum allowable nitrate concentration in agricultural products provided by the National Standard Organization of Iran.

The results showed that the mean concentration of nitrate in cucumber samples was 1.48 times more than the Iranian National Standardization Organization (90 mg kg-1 of fresh weight); whereas the mean concentration of nitrate in potato, tomato and pepper samples was lower than the standard limits provided by National Iranian Standards Organization (170., 150 and 200 mg kg-1 of fresh weight respectively). The mean concentration of nitrate in fine sizes of potato, tomato and pepper was more than nitrate concentration in coarse sizes. Between the studied cucurbits, the highest and lowest average nitrate concentration were observed in cucumber and tomato respectively. Also the average nitrate concentration in cucumber skin was 16.7 times more than the mean nitrate concentration of its fruit. In general, the mean concentration of nitrate in leafy vegetables was more than the Iranian National Standardization Organization (1000 mg kg-1 of fresh weight). Between the studied leafy vegetables, the average concentration of nitrate in mint (457 mg kg-1 of fresh weight), fenugreek (262 mg kg-1 of fresh weight) and tarragon (695 mg kg-1 of fresh weight) was just lower than the Iranian National Standardization Organization. The others leafy vegetables probably have nitrate limitation for consumption.

According to the results, it seems that fruit size is not a suitable criterion for plant nitrate content and the management aspects of farms play a major role in plant nitrate content. On the other hand, the changes of nitrate content in the farms are very high, so it cannot be clearly stated that the consumption of vegetables is restricted in terms of nitrate content. However, it seems that the consumption of vegetables produced in the studied areas may be restricted for consumers’ health in some cases.

In this study, in order to identification and isolation of nitrogen-fixing bacteria in rainbow trout breeding ponds, sixty fish breeding ponds and four sampling stations in Firoozkooh city were selected. After taking a certain volume of pool water in the place of biofilters, their culture is optimized in Nutrition agar and LB-Broth medium and incubated at 25 to 30 degrees for 5 to 6 days. The final culture in Nitrosamines and culture medium Nitrobacteria was performed and the grown colonies were identified. The results showed that the highest number of isolated bacterial colonies (more than 300 colonies) were in the biofilter input and the lowest amount of nitrification bacterial colonies in the culture medium was related to the water well inlet culture (3 colonies).
The results of this study showed that the activity of fish farming can change the values of water parameters used during salmon farming and cause some undesirable physicochemical factors of the water used. The extent of this effect is largely due to environmental conditions to the process of fish farming and the intensity of nitrification bacteria in the pool water.

Nitrate contamination in groundwater resources and crops is increasing due to human activities and urban development. This study has aimed to investigate on nitrate contamination in groundwater, soil, and some crops of Fasa plain.

After sampling of groundwater, soil, and some crops, the nitrate content and the other quality parameters were measured. T-tests and a data correlation test were performed using SPSS and Excell software to investigate on nitrate contamination and its origin. Spatial zoning of nitrate also performed using ArcGIS.

The statistical test indicated the presence of nitrate contamination in the groundwater of the region; however, the soil did not show nitrate contamination in the area. Nitrate level in four types of crops, lettuce, beans, onions, and spinach, was within the allowable range, and in beans, it is close to the allowable limit. At the same time, among the leafy plants, the concentration of nitrate in lettuce was higher than in spinach, and it was lower in onions than in the others.

The lack of significant correlation between nitrate ions and the other ions of lithological origin suggests the anthropogenic origin of nitrate in the groundwater in the region. The high ratio of nitrate to chloride also indicates the significant impact of chemical fertilizers and the less important role of domestic wastewater, especially in the outlet of the plain. The amount of nitrate in some of the studied crops is close to the permissible level, shows the need to pay attention to their consumption and continuous monitoring of water, soil, and plants in terms of the pollution.

One of the most critical and controversial issues regarding the pollution of water resources and agricultural products is the challenging relationship between nitrate intake and the risk of gastrointestinal cancers. During the last two centuries, human activities have fundamentally changed the global nitrogen cycle and increased the amount of nitrate in the soil. Nitrate and nitrite move quickly in the environment due to the high solubility. Nitrate in wastewater or fertilizers used to increase crop production can be accessed to surface and groundwater by rainfall or irrigation. Nitrate in the diet is absorbed into the bloodstream and enters the oral fluid through the salivary glands. Approximately 25% of nitrate in the human body enters the salivary glands after absorption in the upper gastrointestinal tract, and it is actively concentrated up to 20 times in saliva. Nitrite disrupts young vertebrates by destroying hemoglobin in the blood and forming the toxic compound methemoglobin. Nitrite also causes hypotension (reduction of arterial pressure), a precursor to the formation of carcinogenic nitrosamines. However, there is no conclusive evidence that nitrate can cause cancer without amines containing nitrosamines.Since accurate information about the amount of nitrate in drinking water sources and vegetables used in Mazandaran province is not available, this study aimed to obtain accurate and up-to-date data on nitrate concentration in drinking water and vegetables. Also, the relationship between nitrate concentration in drinking water and vegetables in areas of Mazandaran province with a high and low prevalence of gastrointestinal cancers was investigated.

In this study, two areas with high incidence and low incidence of gastrointestinal cancers (Savadkuh and Simorgh counties, respectively) were identified. Information on patients with gastrointestinal cancer was prepared between 2014-2016. Then the patients living in the studied counties were separated and coded. Nitrate concentration in 30 samples of vegetables (60 samples in total) and water was analyzed by spectrophotometry and compared with international standards.The selection of vegetable samples was made according to the prevailing consumption pattern of the people. Selected vegetables included tomatoes, lettuce, potatoes, onions, cucumbers, garlic, cress, and spinach. According to the available instructions, plant samples from each region were quickly transferred to the laboratory. Nitrate concentration was measured by the semi-micro distillation method. The relationship between nitrate concentration and the incidence of gastrointestinal cancer and the ASR index of gastrointestinal cancer were determined using SPSS (26) software for Mazandaran province.Discussion of

Statistical analysis of the data showed that nitrate concentration of all studied crops in the Savadkooh region showed a significant difference compared to the Simorgh region, except potato. In the Simorgh region, nitrate concentration in lettuce, cress, potato, and spinach was lower than the maximum limit, while other vegetables were significantly higher than the standard. The data showed that in Savadkuh and Simorgh regions, the highest nitrate concentration was observed in garlic and the lowest in onion. According to the data, except for potatoes, all other vegetables in the Savadkooh region were significantly higher than the Simorgh region (p <0.01). The average concentration of nitrate in the drinking water of Savadkooh and Simorgh counties was significantly lower than the standards presented in the literature.The effect of nitrate concentration variables (in the regression model presented) in tomatoes, potato and cucumber, and drinking water was more than the allowable error (0.05). Therefore, changes in the nitrate concentration of these products and the amount of nitrate in drinking water will not significantly affect changing the dependent variable (the incidence of cancer). On the other hand, the significance level of the t-test for the effect of nitrate concentration variables in spinach, garlic, cress, and onion was less than the allowable error (0.01). Therefore, changes in the amount of nitrate in these variables significantly affect changes in the dependent variable. Based on the coefficients related to β, the most effect on the changes of the dependent variable will be the change in the amount of nitrate in spinach and garlic with a coefficient of β of 0.372 and 0.367, respectively. The amount of nitrate in the variables of cress and onion are of the following ranks. Comparison of residual nitrate levels in vegetables in Savadkuh and Simorgh showed that nitrate levels in Simorgh city were lower than Savadkuh, and nitrate concentration in four vegetables i.e. lettuce, cress, onion, and spinach, was less than the maximum limit. However, other products far exceeded the maximum limit. According to the researchers of the Razi University of Kermanshah, the concentration of nitrate in all cases under investigation in Kermanshah was exceeded by the National Standard Institute of Iran. The highest and lowest nitrate concentrations were observed in the Savadkuh region with an average of 3398 and 71 mg/kg in garlic and onion crops, respectively, and in the Simorgh region with an average of 2259 and 38 mg/kg in garlic and potato as well. The common denominator between the two regions is the lowest nitrate concentration observed in the onion crop. Significant differences between the two counties in terms of nitrate concentration in the studied products, except potato, can be examined from various aspects. It seems that the management of fertilizer consumption, especially nitrogen fertilizers in the Simorgh region, has been done better. The result has been shown by reducing nitrate accumulation in agricultural products of the region. Nitrogen in chemical and organic fertilizers is converted to nitrate after use in soil by soil bacteria such as Nitrosomonas and Nitrobacter. Nitrate absorbed in the root is reduced and converted to ammonium compounds and transferred through the vascular system to different parts of the plant, and used in physiological processes of the plant. Suppose the amount of soil nitrate increases for any reason, including excessive consumption of nitrogen fertilizers, and the plant does not have the necessary ability to reduce it. This compound enters the plant organs through the mass transfer mechanism and the vascular system and accumulates there.It has been found that there is a direct relationship between the concentration of nitrate in the environment and the amount of nitrate accumulation in agricultural and horticultural products, so that the most important environmental factor affecting the accumulation of nitrate in the product is the amount of available nitrate ions. In addition, harvest time (morning or evening) is also an essential factor in the amount of nitrate output through the harvested product. Receiving light energy during the day increases the plant's photosynthesis, and the production of more assimilates and increases the activity of the enzyme nitrate reductase in the plant. The average nitrate concentration in drinking water was 10.4 mg/L in Savadkuh and 15.8 mg/L in Simorgh. Fortunately, this concentration is lower than the standard defined for drinking water (50 mg/L) in both areas.

Although the concentration of nitrate in the drinking water of Savadkuh county is significantly higher than Simorgh one, the concentration of nitrate in the drinking water of both counties is below the standard limit. Therefore, there is probably no significant relationship between the prevalence of gastrointestinal cancers and nitrate concentration in drinking water sources in these areas.Nitrate concentration in vegetables consumed by patients with gastrointestinal cancers in the Savadkuh region was significantly higher than the Simorgh region and, to some extent, maximum contaminant level. The results showed that the consumption of spinach, garlic, cress, and onion had played an influential role in increasing the incidence of gastrointestinal cancers. Therefore, management practices in agriculture, especially changes in the consumption pattern of nitrogen fertilizers, are inevitable to reduce the accumulation of nitrate in vegetables. It is strongly recommended that the vegetables be harvested in the afternoon to reduce nitrate accumulation in the plant tissues. It is suggested that new strategies to reduce nitrate accumulation in food, especially vegetables, be studied to reduce the incidence of gastrointestinal cancers in this province.

Rivers and water resources polloution caused by uncontrolled industrial wastewater discharge. Precence of high concentration of phosphate ' sulfate and nitrate anions in sugarcane indusrial wastewater ' required treatment of the waste water for nutrients and corrosive substances deletion. This study is an attempt to investigate the effect of electrical current' initial wastewater PH and retention time on phosphate ' sulfate and nitrate pollutants removal of sugarcane industrial wastewater. In this study ' the electro coagulation method with aluminum electodes were applied for wastewater treatment in sugar cane of Hakim Farabi. 6 electrodes – aluminium in vertical position were connected to power supply by monopolar method. Septic tank was selected for sampling. Initial wastewater concentration and PH were measured for phosphate' sulfate and nitrate. Then the effect of three operation parameters: PH(5' 7' 9' 11) electrical potential (10 and 30 volts) and retention time (15' 30' 45' 60 minutes) for phosphate ' sulfate and nitrate removal efficiency have been investigated. The results showed that in equal retention time and different initial PH the removal of phosphate' sulfate and nitrate could be promoted by increasing the electrical potential from 10 volt to 30 volt.. The results indicated that the highest removal efficiency of phosphate was observed in neutral condition and increasing PH decreases phosphate removal. whereas the highest removal efficiency for sulfate and nitrate was observed in alkaline PH .also the results proved that in all condition of PH and voltage' increasing retention time cause increasing in removal percent for phosphate' sulfate and nitrate.

Nitrate contamination in drinking and agricultural water is increasing in the Kabudrahng plain. Farmer's Tendency to use a variety of animal and chemical fertilizers has increased the amount of nitrate in groundwater in this region. This study aims to determine the most appropriate geostatistical methods to analyze the spatial variation of nitrate and electrical conductivity of the Kabudrahng groundwater plain.

The trend of nitrate changes and groundwater electrical conductivity in 41 and 152 wells were investigated using MNITAB16.2 software and the most suitable geostatistical method was determined with ARCGIS9.3 software. To determine the most appropriate geostatistical methods for zoning nitrate and groundwater electrical conductivity used the ordinary kriging (OK), simple kriging (SK) and the specific methods include the inverse distance, weights (ID(, radial basis functions (RBF), global polynomial interpolator (GPI) and local polynomial interpolator (LPI) with ARCGIS9.3.

The results showed that the best method for zoning the electrical conductivity was the RBF method with RMSE=837.07, MAE= 548.01 and R=0.841 and simple kriging (SK) with RMSE=900.68, MAE=581.8 and R=0.699 and the best way to zoning the nitrate was the RBF method with RMSE=3.76, MAE=2.42 and R=0.351 and ordinary kriging (OK) with RMSE=3.86, MAE=2.51 and R=0.372.

According to the standard of California, 8 percent of the plain area had an electrical conductivity less than 700 μmho/cm, 77 percent between 700 to 3000 μmho/cm, and 15 percent above 3000 μmho/cm. The distribution of nitrate concentrations showed that about 85.57% of the area was lower than 5 mg/liter, 14.43% between 5-30 mg/l,  and there was no severe pollution in the plain. The spatial distribution pattern indicated that high levels of electrical conductivity were observed in the western and southwestern parts of the plain. The amount of nitrate in groundwater was in the good range, but in southern and southwestern plains was higher than the standard.

Springs as one of the groundwater sources and suppliers of high volume of river basin discharge have been less analyzed and studied.  The origin of these resources, due to the passage of natural heights and filtration, has a good quality and only some formations or human activities cause a change in the quality of these resources. This study evaluated the quality of springs in Ajabshir study area in the east of Urmia Lake in 2018. According to the type of geological formations, discharge and location of springs in the region, 13 springs were analyzed for qualitative analysis and evaluation of qualitative changes. Studies have shown that 100% these springs are very good quality in terms of drinking, and the GQI quality index is 33.23-95.32, indicating good to excellent condition for these resources. In terms of exploitation in the agricultural sector, the only issue was the high level of electrical conductivity (157-6490 µs/Cm) in some springs, and the alkalinity of all springs was in class S1 in Wilcox diagram. The quality situation from the industry point of view also indicated a low range of changes, and 77% of the springs in the region were corrosive. Evaluation of water source in this area showed a high ratio of sodium to chlorine and differences in calcium and sodium origin, so that the initial sections of the study area and the east of the area had magnesium source and the rest had calcium source. Finally, the study of geological formations showed their low impact on quality and the high concentration of nitrate in the part leading to the plain and aquifer due to human activities and sewage leakage was evident and reached 27 mg/l.

Excessive use of nitrogen pollutes water, soil and plant resources. One of the appropriate solutions in determining the correct and timely amount of nitrogen fertilizer is the use of chlorophyll meter. The purpose of this study is to reduce the use of nitrogen fertilizers and prevent nitrate leaching and its entry into groundwater sources.

Using chlorophyll assay in leaves, an experiment using 6 treatments of nitrogen fertilizer including: 50, 150, 100, 200, 250 and 300 kg per hectare of urea source in a randomized complete block design with three replications, two locations and It ran for a year. At the stem stage, the chlorophyll in the leaves of the wheat flag was read using a chlorophyll meter. Considering the number 45 as a reference, the amounts of nitrogen road fertilizer at the stem stage were calculated and, if necessary, provided to experimental plots.

With the recommendation of nitrogen fertilizer road using chlorophyll meter, nitrate concentration in soil and plants was reduced. In this study, the nitrogen fertilizer road recommendation was saved so that in the application treatments of 250 and 300 kg / ha nitrogen fertilizer was 25 and 21%, respectively.

By using chlorophyll meter in recommending nitrogen fertilizer road in wheat, significant savings can be achieved in consumption. This will produce a healthy crop with less nitrate and prevent nitrate from entering groundwater.

Due to the potential of sewage to contaminate food and water resources, it is emphasized on the treatment of sewage. One of the most effective biological methods in the treatment of sewage is the use of plants. A group of these plants, which have recently been considered by researchers to treat sewage, are microalgae. Microalgae use sunlight to absorb nutrients from the sewage and make them more useful to biosphere. In this study, the possibility of removal of some pollutant parameters of wastewater was investigated using microalgae Chlorella vulgaris. For this purpose, microalgae was cultured in TMRL medium and the wastewater was prepared from the fish farming pool in Khuzestan province. The growth of microalgae in control and wastewater  treatment was measured every 48 hours, under constant conditions (temperature 27-23 ° C, 20ppt salinity, 2500 lux light intensity) in the period of 15 days. COD, BOD, nitrate, nitrite and phosphate were measured and calculated every 48 hours. The results of statistical analysis showed a significant change in the number of microalgae in the control treatment, so that the highest number of algae was observed on the 11th day but it decreased relative to the 14th day. Also, the results showed a significant difference in the amount of BOD and COD removal was micro-algae culture, with the lowest amount of these two factors observed on the tenth day. The remaining nitrate also received the highest and lowest values on the third and tenth day, respectively. Nitrite was also the highest on the third day and on the 15th day it was the lowest.Phosphate levels also decreased significantly on days 3, 5, 10 and 15 compared to the first day (P <0.05). These results showed the ability of microalgae to reduce wastewater nitrogen and phosphorus and its potential for wastewater treatment. It seems that this microalgae is capable of removing nitrates and phosphates as well as the production of algal biomass in refining systems the effluent of the fish ponds is to be used before entering the natural environment, and the pool effluent can be used as a suitable fertile environment for mass production of this algae.

Large amounts of nitrate and nitrite in water cause different diseases in human and jeopardize plants and animals growth cycles. In this study in order to remove nitrate and nitrite ions from input of sample water, including high concentrations of nitrate by combining biological and physical methods a pilot was designed and tested. It should be noted that industrialization, cheap and availability of used materials in this pilot are benefits of this pilot.

The pilot was designed in the form of a cube with four drawers and a glass chamber at one end. The pilot drawers were filled with sawdust, wastewater (wastewater treatment plant in Islamic Azad University, Tehran) of treatment plant, including the best strain, handmade nitrate solution, the bentonite and twice washed sand. The experiments showed that the designed pilot in addition to the elimination of nitrate also removes the nitrite of the medium. The concentration of nitrate and nitrite was analysed by HACH/DR5000 spectophotometer.

In the case of the pilot performance of the continuous system and using the strains taken from the wastewater of the treatment plant after the aeration phase, the nitrate and nitrite removal efficiency of the input of sample water in 20 minutes retention time were measured 74.84% and 99.8% respectively. Additionally, in the case of the pilot performance in the continuous system and using the strains taken from the sludge of the treatment plant wastewater before the aeration phase and the yeast, the nitrate and nitrite removal efficiency in 20 minutes retention time were measured 72.63% and 56.33% respectively. 

Discussion and Conclusion:

During the experiments, the designed pilot had a promising role in the nitrate and nitrite removal. In the case of the pilot performance of the continuous system and using the strains taken from the wastewater of the treatment plant after the aeration phase, the maximum amount of nitrite and nitrate ions were removed. It should be noted that through the pilot performance in all cases, pH and temperature had an increasing and decreasing trend respectively.

Drinking water supply is an important environmental challenge throughout the world. Water pollution with nitrate is a serious human health hazard in Iran. The main purpose of this study is to evaluate the applicability of synthesized zero-valent iron (ZVI) nanoparticles in removal of nitrate from water emphasizing on the influence of pH variation on performance of nanoparticles.

ZVI nanoparticles were synthesized in the laboratory and measured for dimension with Transition Electron Microscopy (TEM) before using in the experiment. Impact of ZVI nanoparticles dosage on the removal of nitrate from water was also examined in this study.

Results indicated that performance of ZVI nanoparticles in the removal of nitrate is greater in acidic environment compared to neutral and basic state. In addition, pH increased over the course of the experiment at initial acidic and neutral states.

 Discussion and Conclusion

Application of small amount of ZVI nanoparticles can reduce nitrate content in water significantly. The principal fraction of removal reaction was achieved at initial stages due to acidic condition. Results of the present study showed application of small amounts of ZVI nanoparticles can reduce nitrate concentration in waster scales significantly.

Today, development of irrigated lands is faced with limited resources. With the increased water scarcity, the importance of using municipal, industrial and agricultural wastewater is increasing. This study was conducted on laboratory scale to investigate the efficiency of some bioadsorbents (rice husks, wheat straw, woodchips and cotton stalks) in removing nitrate from aqueous solutions and their application as bio filters in agricultural wastewater treatment.

First, absorbents were well-washed with distilled water, dried and crushed by the mill, and percolated through a standard sieve mesh 30 to obtain uniform powder from the absorbent samples. In order to prepare the required concentrations, nitrate solution was added to the distilled water with certain amount of potassium nitrate. For each bioadsorber, a spectrophotometer was used to measure the extent of nitrate removal at contact periods in order to determine the periods required to reach equilibrium, the optimum pH values of adsorbents, and the suitable concentrations of adsorbents.

Results indicated the significant differences at the confidence level of 99% among the adsorbents in removing nitrate and these adsobents significantly reduced the nitrate in aquous soloutions. In the four adsorbents, the nitrate removal rates at the studied contact periods (5, 10, 20, 30, 60 and 90 minute) were statistically significant at the confidence level of 99%. Results from determining the suitable concentrations of the four studied adsorbents to reach the maximum efficiency showed that 1 g in 40 ml solution was the most suitable concentration. Moreover, reduction in the adsorbents amounts reduced their efficiencies. Study of isotherm models indicated that for all the studied adsorbents correlation coefficients in Langmuir’s isotherm model were higher compared to Friedrich isotherm model. Therefore, Langmuir isotherm model was more suitable for predicting nitrate removal from aqueous solutions by bioadsorbents. Discussion and

Plant absorbers significantly reduce the amount of nitrate in aqueous solution. In this study, Langmuir model can be used as an adsorption isotherm.for adsorption of the bioadsorbents.

In this study, to investigate the effects of silver on juvenile common carp (Cyprinus carpio), the fish were exposed to sub-lethal concentrations of silver-nanoparticles and silver nitrate. For this purpose, at first, Lethal Concentration (LC50-96 h) for two silver forms was obtained and then fish were exposed to sub-lethal concentrations (0.04 and 0.08 mg/L for silver NPs and 0.025 and 0.025 mg/L for silver nitrate) for 21 days and desired indicators were measured. After exposure to silver, various lesions have been observed in the tissues, that most important of these are the following: epithelial lifting, shorting and collapse of secondary lamellae in gills, nucleus degradation and necrosis and hypertrophy of hepatocytes in the liver and also destruction of the structure of intestinal villi. Results of this study showed that long exposure with silver NPs, caused significantly increase Hsp70 gene expression and after exposure of common carp with silver nitrate, Hsp70 greatly increased however, in term of gene expression, there was no difference between two genes. Also, the most effects observed among the tissues studied in this study were observed in the liver of fish exposed to two forms of silver and at the highest concentration and there was no difference between the two forms of silver in term of toxicology.