Nitrate

The examination of water quality in terms of pollution is a crucial aspect in managing the quality of surface water, such as rivers. This study focused on analyzing the trend of nitrate (NO3) pollution in the 7.02 km long of the Abbas-Abad River in 2022. The HEC-RAS model was used to determine the river pooling, and then, the geometry was entered into the QUAL2Kw model. Calibration and validation were conducted using the data from May and July 2022, respectively, demonstrating the model's accuracy. The findings revealed an increasing trend in nitrate concentration of 7.6% during the non-agricultural season and an 8.0% increase during the agricultural season due to the use of fertilizers and chemical pesticides. To mitigate this, it is recommended to prevent pollutant entry into the riverbed.

Water resources face challenges such as climate change and human activities. Sustainable water management is extremely important to solve this problem. More and more people are using artificial intelligence, especially machine learning, to predict and manage water quality. These AI methods are excellent at identifying patterns in water data and improving water quality management. This study examines the water quality of the Maroon River using a combination of factor analysis and machine learning. Data on various water quality parameters were collected from three stations over a period of ten years and the water quality index was calculated. Then, different machine learning algorithms were used to predict the water quality index. In a further step, factor analysis was performed to extract the important features of the input for the optimal algorithm. The performance of the studied algorithms was determined at each step using evaluation criteria. The results showed that in the first step, the Random Forest algorithm (R2 (0.78), RMSE (2.65)) had the best performance in predicting water quality index. It was also found that among the three algorithms studied, nitrate is the most important input parameter, while acidity is the least important. By reducing the number of inputs to 3 important parameters, the performance of the Random Forest algorithm (R2 (0.74), RMSE (2.86)) almost reached the level of 8 input parameters. Combining insights from factor analysis and feature importance analysis can provide a more comprehensive understanding of the complex relationships among water quality parameters and help develop more effective water management.

The important issue regarding underground water resources is to know the extent of groundwater pollution, which leads to the management of areas prone to pollution. Groundwater vulnerability assessment can play a vital role in protecting, exploiting and prioritizing areas for controlling and using preventive plans. Due to the nature of the area, agricultural activities and nitrate increase, the DRASTIC method needs to be modified. The aim of the current research is to modify the weights of the DRASTIC model, which is considering the importance of modifying the ranking and the effect of weighting methods in the Yasouj aquifer.The frequency ratio framework was used to calibrate the DRASTIC index rates. Then, the weight correction of DRASTIC parameters was done in two stages of research, the first stage includes Shannon entropy and SPSA methods and the second stage includes BWM (Best Worst Method) and SWARA (Stepwise Weight Assessment Ratio Analysis) methods. Therefore, nine frames including FR_DRASTIC, DRASTIC_Entropy, DRASTIC_SPSA, DRASTIC_SWARA, DRASTIC_BWM, FR_Entropy, FR_SPSA, FR_BWM, FR_SWARA were obtained. The nitrate concentration of the well samples was used to validate the vulnerability indicators. Validation was done by ROC Curve method. FR_SWARA performed better than other methods with the area under the curve of 0.80.

In order to study the effect of plot-to-plot irrigation method on soil chemical characteristics and rice yield, a randomized block experiment was conducted in the research farm of the Faculty of Agricultural Sciences of University of Guilan. This research was done in three repetitions and each repetition included six plots which were named plot by plot in a vertical row from 1 to 6. The quality characteristics of the soil were evaluated at two depths of 0 to 15 and 15 to 30 cm, as well as grain yield. The results showed that the highest salinity (3.8 mmhos/cm), total soluble solids (2316.6 mg/l), nitrate (6.3 mg/l), sodium (407.5 mg/l), calcium (410.8 mg/L), and sodium absorption ratio (5.6 me/L) were observed at the depth of 0 to 15 cm in the sixth plot. But, the highest grain yield with 9035.54 kg/ha was related to the fourth plot. Despite the same agricultural operations in the plots, the amounts of nutrients, soil soluble salts and grain yield were different in them, which could be due to the difference in the amount of nutrients in the plots. Therefore, in order to prevent their amount from changing from one plot to another, the necessary opportunity for the absorption of water nutrients and soil solution by the plant in the plots should be created to affect the final yield. In general, due to the reduction of only 5.92 and 4.33 percent of paddy yield in the sixth plot compared to the fourth and first plots, respectively, it seems that due to the limited water resources in the north of the country, the use of plot-to-plot irrigation for planting Rice needs more and more detailed investigation in order to achieve the highest growth and yield in the region.

Due to the toxicity of metals, their side effects may cause serious damage to soil organisms, plants and living organisms. Many conventional methods for cleaning pollution from soil have problems and limitations. The electro kinetic method is a relatively new method for remediating soils contaminated with heavy metals, which has a high efficiency in removing heavy metals from the soil compared to other existing methods.

In this research, the removal of chromium (VI) from nitrate-containing soil has been investigated. At first, the soil was artificially contaminated with potassium dichromate at a concentration of 250 mg/kg, and then in order to investigate the effect of nitrate on the removal of chromium. The soil was also impregnated with calcium nitrate.

By conducting electrokinetic experiments, it was found that with the increase of the electric current introduced into the soil, the electric gradient passing between the electrodes increased, as a result of which the transfer of ions also increased under the influence of the phenomenon of ion migration and electroosmosis. The percentage gives 98.28%. Also, the use of EDTA complexing agent compared to distilled water increases the efficiency of the method from 95.57% to 97.80%. As a result, the use of EDTA electrolyte and increasing the voltage increases the removal efficiency.

Results revealed experiments showed that the use of the electrokinetic method has a negligible effect on the removal of chromium (VI) from soil containing nitrate.

Due to the lack of highquality water resources, in many cases there is no other choice but to use lowquality or unconventional water. The filtration method is an efficient method for removing pollutants. For compare the amount of water purification in vertical and horizontal filters, two models of vertical and horizontal filters were made in Department of Irrigation and Development Engineering, University of Tehran.Three absorbent layers including sand, zeolite and rice husk were used. The purification rate was measured for three solutions contaminated with nitrate, salinity and TSS of each solution at two different concentrations. For each concentration of contamination, two purified samples were taken at two times of 5 and 10 minutes to determine the purification process over time. t-test was used in SPSS software to compare the filtration rate of vertical and horizontal filter and to observe the significance of the difference in filtration rates. The results showed that the amount of nitrate purification with concentrations of 36.72 and 59.08 mg/liter and at times of 5 and 10 minutes, respectively, in the vertical filter was 6.99, 9.25 and 7.72, 7.13% and in the horizontal filter was 3.18, 8.21 and 8.36, 5.70%. For EC, the filtration rate in two electrical conductivities is 31.6 and 11.02 dS/m and in two times for vertical filter 5.39, 2.54 and 5.26, 2.18% and horizontal filter 12. 4, 1.90 and 2.99, 1.54% were measured. The filtration rate of TSS for two solutions containing TSS with concentrations of 0.75 and 1.5 g/l and at two times were checked and the filtration rate of the vertical filter was 48.93, 43.87 and 73.20, 80.25% and the horizontal filter purification rate was 29.66, 38.40 and 61.31, 67.05%. Finally, the obtained results showed; There is no significant difference in nitrate, EC and TSS purification between vertical and horizontal filters.

Nitrate pollution in groundwater and drinking water reservoirs has increased alarmingly in different parts of the world. The high concentration of nitrate in surface and groundwaters is due to the excessive use of chemical fertilizers and improper disposal of wastes caused by human activities and animal manure. Due to its high mobility, nitrate anion is easily washed from the soil and enters the surface and groundwaters. If the concentration of nitrate exceeds the limit (50 mg l-1), it causes the disease of children with methemoglobinemia, as well as the formation of carcinogenic nitrosamines. Various methods have been proposed to remove nitrate. These methods besides having side effects on water, are not economically viable. In recent years, the development of effective technologies for keeping nitrates in the soil has received much attention. Adding biochar to the soil is one of the effective ways to reduce nitrate leaching. Biochar is a carbon-rich and porous substance, that is produced by heating biomass such as organic waste, animal manure, plant residues, sewage sludge, wood, etc. in limited or oxygen-free conditions. Due to its high specific surface area, high porosity, and diverse functional groups, biochar increases the water retention capacity, cation exchange capacity, and surface absorption capacity after adding it to the soil. Therefore, this research aims to investigate the effect of biochar and biochar coated with trivalent iron on the amount of nitrate absorption from aqueous solution.

Biochar can be produced from materials with low economic value and is a suitable and inexpensive adsorbent for nitrate removal from water sources. According to the studies conducted for biochar production, the temperature and duration of storage in the furnace are the most important factors controlling the quality and strength of biochar in nitrate removal. In this research, four types of rice straw, rice husk, sugarcane bagasse, and dicer wood chips were used to produce biochars. First, the samples were passed through a 2 mm sieve and dried in an oven at 70°C for 24 h. Then they were converted to biochar for 3 h at 300 and 600°C in an electric furnace under oxygen-free conditions. To determine the best adsorbent with maximum nitrate absorption, 0.5 gr of each adsorbent was weighed and poured into a 50 ml centrifuge tube. Then, it was contacted at a constant time (60 min) at an initial concentration of 50 mg l-1 of nitrate solution. After determining the best adsorbent, kinetic experiments were done to determine the equilibrium time, optimum pH, and adsorbent dosage. The adsorption isotherms were conducted for soil, rice husk 300˚C (RSB 300), and Fe-coated RSB 300.

The results showed that among the eight types of biochar produced at two temperature conditions of 300 and 600 ˚C, RSB 300, with the initial concentration of nitrate solution of 50 mg l-1 and contact time of 60 min, had the most amount of nitrate absorption. The kinetic experiments were continued on this type of biochar. The kinetic experiment results showed adsorption nitrate with an initial concentration of 50 mg l-1 an equilibrium time of 90 min, pH 7, and an adsorbent dosage of 1.25 g l-1 was 23580 mg kg-1. The result of the adsorption isotherms study showed that the adsorption of nitrate on RSB and Fe-coated RSB were fitted to the Langmuir isotherm model. This result indicates the uniform or single-layer distribution of active sites on the absorbent surface. The maximum adsorption capacity of nitrate by RSB and Fe-coated RSB were 38.16 and 43.66 mg g-1, respectively.

The use of cheap absorbents can be a suitable solution for removing environmental pollution. In general, biochar can absorb pollutants and nutrients by its potential physicochemical properties, including high specific surface area, high porosity, high cation and anion exchange capacity, high surface charge density, low volume mass, and the presence of functional groups. The results showed that among the eight types of biochar tested, RSB with the initial concentration of nitrate solution of 50 mg l-1 and contact time of 60 min, had the highest absorption rate. The optimal conditions for nitrate absorption are estimated at 90 min of contact time, pH 7, and adsorbent dosage of 1.25 g l-1. The results showed that wastewater treatment by surface absorption process using biochar produced from vegetable waste is a very useful and effective method. Besides, the results of isotherm adsorption on the nitrate adsorption test data by biochar produced from RSB and Biochar Fe-coated RSB showed that nitrate adsorption on these adsorbents according to its correlation coefficient (R2=0.994) is consistent with the Langmuir isotherm model. The maximum absorption capacity RSB is 38.16 mg l-1, which is more absorbable than other studies. Now, when the above biochar was coated with Fe, the maximum nitrate absorption capacity increased by 43.66 mg g-1, which is a very high absorption. It can be concluded that RSB, especially when it has a Fe-coating, is a suitable adsorbent for removing nitrate from water. Therefore, it is suggested to investigate the effect of biochar covered with different cations on the mobility of other pollutants that are in anionic form.

Due to participation in the process of eutrophication, nitrate has caused a lot of damage to the environment. In this research, Clinoptilolite nanozeolite granules modified by hexadecyltrimethylammonium bromide surfactant named HD-Clinoptilolite were synthesized. The clinoptilolite zeolite of Sabzevar region was converted into nanozeolite by ball mill and then its granules were prepared. In this study, a continuous reactor with a fixed bed equipped with a peristaltic pump has been used to provide the necessary flow to remove nitrate from polluted water. For adsorption process, a continuous flow reactor with a diameter of 3 cm and a height of 54 cm, for investigation of pH parameters, flow intensity, initial concentration, and column height have been fabricated. A Uv-vis Array spectrophotometer was used to measure nitrate. Also, Thomas, Bohart-Adams, and Yoon-Nelson models have been used to predict column behavior. According to the results, with increasing nitrate concentration, the adsorption capacity increased from 3.16 to 95.21 due to the increased presence of nitrate ions. Also, with increasing pH and column height, the adsorption capacity increased, while with increasing flow intensity, the adsorption capacity decreased due to the reduction of contact time. The highest adsorption capacity occurred at a concentration of 200, pH equal to 8 and a column height of 54 cm. At a column height of 54 cm, the adsorption capacity is equal to 91.26 mg/g. The results indicate that the clinoptilolite nanozeolite granules modified with ammonium bromide ligand has the ability to remove nitrate from drinking water to a high extent.

This study was conducted to investigate the effect of soil salinity on nitrogen mineralization in the presence and absence of wheat straw in three soils with textural classes of clay, loam and loamy sand under laboratory conditions as a factorial arrangement based on a completely randomized design with 3 replications. The studied factors were salinity (1, 10, 20 and 30 dS/m), wheat straw (0 and 2% by weight with C/N=89.5) and time (2, 5, 12, 20, 28, 37, 46, 53, 64, 73, 85 and 90 days). After investigation of different Iranian agricultural soils, three soils with low salinity (0.84-1.1 dS/m) and low organic carbon (0.22-0.98%) were selected. Considering the results, in the three soils, the amount of ammonium and nitrate in the treatment without straw was higher than those in the treatment with straw. In straw treatment, there was an initial descending trend in the amount of ammonium and nitrate for the three soils, but after a period of time, ammonium and nitrate content of the soil showed an ascending trend and returned to the initial value. With increasing soil salinity, the amount of soil ammonium increased in clay and loamy sand soils but decreased in the loamy soil. Nitrate content showed a descending trend for the three soils with increasing salinity. In general it is concluded that the presence of wheat straw in the soil can mitigate the negative effects of high concentrations of salt on nitrogen mineralization and reduce nitrogen losses.

In the process of conducting this research, 110 studies on monitoring nitrate content in agricultural products produced in Iran were gathered. These studies were published until March 20, 2023. The collected studies underwent evaluation for methodology, quality control, and quality assurance of results and were then assessed based on standard research criteria. The evaluation of the study's methodology revealed that only 27.3% of the studies adhered to standard methods for sampling, storage, and sample transfer. In 15.5% of the studies, the method of preparation and extraction followed standard procedures. Additionally, in 30% of the studies, the nitrate measurement method was conducted according to established standard procedures. The evaluation of quality control in the studies showed that only 20.9% reported some indicators of quality control and assurance. The assessment of nitrate concentration in agricultural products revealed the weighted mean concentrations of nitrate (mg kg-1 fresh weight) as follows: potato 98.7, cucumber 120.9, tomato 40.7, onion 39.6, watermelon 19.9, melon 62.9, carrot 151.1, eggplant 235.2, peppers 329, other root and tuber vegetables 542.4, lettuce 907.7, spinach 995.4, celery 1093.4, fresh edible legumes 37.7, parsley 596.5, cabbages 414.7, other leafy vegetables 635.6, apple 32.4, and orange 37.2. The findings of the present research reveal that the mean nitrate concentrations in Iran’s agricultural products fall below the maximum permissible levels outlined by both the Iranian national standard and international standards. As a result, it can be generally concluded that there is no significant cause for concern regarding residual nitrate concentration in Iran’s agricultural products.

Access to safe water is one of the main components of sustainable development, and monitoring of water resources used by humans is necessary and essential. In order to better understand the water quality of human societies, the analysis of physical and chemical parameters of water resources is done with the help of indicators and statistical methods. In this research, the quality of urban water resources of Nahavand was investigated and zoned with the help of nitrate parameter interpolation methods. For this purpose, 48 samples of drinking water from 16 districts of Nahavand city were taken randomly and pH, EC and No3 parameters were measured in them. Wilcox, WQI and NPI indices were used to determine the quality of water sources. The comparison of the values of the studied parameters with the WHO standard and the national standard of Iran was done by a one-sample t-test. Nitrate zoning map and WQI index in Nahavand urban water sources were also prepared by using Kriging method. Based on the obtained results, there was a statistically significant difference between the values of the investigated parameters with the national standards of Iran and WHO (p<0.05). So that the average pH and No3 were lower than the standard limits and the average EC was higher than the standard limit and according to the Wilcox classification, 44% of Nahavand city water samples were in medium salinity condition and 56% of the remaining samples were in medium salinity condition.

Due to the necessity of regular and rapid evaluation of nitrate, the development of methods with the ability to detect this compound accuratly and simple is important. Nowadays, colorimetric methods have received much attention due to their ability to detect simple and visual. In this study, which was carried out in 2022 with cooperation of Tehran university and the Agricultural Biotechnology Research Institute, a colorimetric method based on etching of gold nanorods for qualitative and quantitative detection of nitrate was presented. the measurement of nitrate ions (after reduction of nitrate to nitrite by zinc powder) at room temperature is possible by changing the size of the plasmonic nanoparticles and subsequently generating measurable signals, including spectral and color changes. Under optimal conditions, a good linear relationship between nitrate concentration and colorimetric response in the range of 0.5 to 3.0 mM (R2=0.995) with a detection limit of 173.3 μM was found. Also, considering that vegetables, especially leafy vegetables, have a high potential in nitrate absorption, in this research cress plant was used as an indicator plant to investigate the efficiency of the sensor in determining the nitrate of leafy plants. Recovery values for nutrient solution and cress tissue samples was in the range of  94.4 to 101.9 and 93.4 to 98.5%, respectively, and relative standard deviation (RSD) for all samples was calculated below 2.1%. As a result, the presented method in this study provides the possibility of monitoring the actual level of nitrate in cress plant samples.

 Iranian shallot, scientifically known as Allium hirtifolium Boiss. is a perennial plant of the Allium genus and native to Iran. The Allium genus has many antioxidant properties due to its being rich in organic compounds of sulfur and phenol. The shallot is used to treat rheumatic and inflammatory pains, soothe superficial wounds, treat some stomach diseases, be antispasmodic, and also as a spice and flavoring in some foods. Considering the health benefits of shallot and its application in the food industry, shallot corms are harvested from the natural resources in different stages of growth. Therefore, it is necessary to preserve the natural habitats of shallot and also supply the market demand for this plant. It appears that the cultivation of shallots within agricultural systems could serve as a significant strategy for meeting the demands of the expanding global market. Furthermore, shallots are known for their low water requirements, making their cultivation a focal point in Isfahan province in recent years. Additionally, this crop stands out as a high-income generator in the region. Despite its economic potential, there has been limited research into optimizing the growth conditions for this valuable plant. Hence, this study aimed to explore the impact of urea and cow compost on the yield of Iranian shallots in the Fereydun Shahr region, focusing on the uptake of nitrogen, phosphorus, potassium, and nitrates.
 
 This research was carried out in the crop year of 1400-1401 in a field with an area of 300 square meters (32° 55' 53" N, 49° 56' 43" E) located in Fereydunshahr city of Isfahan province. The experiment was conducted according to a completely randomized design. Factorial arrangement of experimental treatments including two fertilization factors (urea and cow compost) was used. Plots with dimensions of 2 × 3 meters were created with a distance of 50 cm between the rows. The treatments were considered as urea fertilization at four levels (0, 120, 240 and, 360 kg ha-1) and cow compost treatment at three levels (0, 40 and, 60 tons ha-1). After plotting and applying cow compost treatments, shallot corms were planted at a depth of 10 to 15 cm in November 1400. Urea fertilizer treatment was applied in two stages, the first stage when the plant germinated (mid-April) and the second stage before flowering (second half of May). All treatments were applied in 3 replications. It should be noted that the treatments in this research are shown as 0-0 (control), 0-40, 0-60, 120-0, 120-40, 120-60, 240-0, 240-40, 240-60, 360-0, 360-40 and 360-60. The corms were harvested in June 1401 and the fresh and dry yield of the shallots was determined. The amount of nitrogen, phosphorus and, potassium in shallots was measured. Nitrate concentration was also measured in the harvested corms based on the Iranian national standard No. 4106. The nitrogen, phosphorus and, potassium uptake by shallots was obtained from the product of yield and the concentration of these elements. Results were analyzed using analysis of variance (ANOVA) procedure and the means were compared using the protected least significant difference (LSD) test at р < 0.05 probability level using SAS 9.3 software.
 
 The results showed that the combined use of chemical fertilizer (urea) and cow compost has a significant effect on the shallot yield increment, as the highest yield was obtained in the combined treatment of urea fertilizer 240 (kg ha-1) and cow compost 40 (ton ha-1) application. Although the highest nitrogen concentration and uptake were observed in the treatment of 360 (kg ha-1) of urea along with 60 (ton ha-1) of cow compost, it was not significantly different from the treatment of 240-40 (the treatment with the highest yield). In general, the concentration of shallots nitrate was much lower than the permissible limit according to the national standard of Iran No. 16596. The highest nitrate concentration (24.63 mg kg-1 of fresh weight) was observed in the combined treatment of 120 (kg ha-1) of urea and 60 (ton ha-1) of cow compost application (120-60), which was significantly higher than other treatments. On the other hand, the concentration of shallots nitrate in the 240-40 treatment was significantly lower than the treatments of 360 kg of urea per hectare along with 40 or 60 (ton ha-1) of cow compost.
 
 According to the results, to achieve the best yield, the most suitable level of urea application was 240 kg ha-1 and the best level of cow compost was 40 ton ha-1. It seems, utilization more amounts of urea or cow compost will only cause additional costs to the farmer and a waste of capital. Moreover, it can increase environmental pollution and nitrate concentration of product, which cause to quality decrement.

As a new product, nanoabsorbents play an important role in controlling and removing environmental pollution. Fe3O4 nanoparticles, due to their high absorption level, have a great ability to increase the efficiency of zeolite adsorbents in removing pollutants. Naeej et al. (2013) explained Zeolite modified with zero iron nanoparticles, due to having many absorption sites as a reducing agent, can have a great ability to remove nitrate from drinking water. Yaghmaian et al. (2015) investigated the removal of nitrate from aqueous solutions with zero-valent iron nanoparticles and stated that at a pH of 5.8 and a contact time of 55 minutes, more than 80% absorption is obtained. Qarlaqi et al. (2015) investigated the efficiency of iron oxide nanoparticles for urban sewage treatment. They stated that at pH equal to 3 and contact time of 15 minutes, the maximum amount of absorption is obtained. Therefore, in this study, clinoptilolite zeolite adsorbent and nano composite prepared from A Zeolite Fe3O4 nanoparticles were prepared in order to remove nitrate ions from real wastewater in industrial system. Also, zeolite treatment and zeolite- clay treatment were tested for comparison.

In this research, Fe3O4 nanoparticles were used to increase the efficiency of zeolite in removing nitrate from aqueous solutions and real wastewater. Laboratory columns made of PVC material with a height of one meter and a 100 mm diameter were used. The investigated columns were filled up to a height of 60 cm with the investigated materials and 20 cm of wastewater was continuously placed on the columns. The investigated treatments include three adsorbent materials: a) six kilograms of zeolite (clinoptilolite), b) three kilograms of zeolite and three kilograms of clay, and c) six kilograms of nanocomposite prepared from zeolite and nanomagnetic with an optimal ratio (Ratio of Zeolite: 0.5 Fe3O4) was laboratory. Synthetic wastewater with a concentration of 40 ppm was prepared and used. The temperature of the wastewater used was 20 degrees Celsius and the pH of the treated wastewater was measured as 7.2. The experiment was carried out factorially and in the form of a completely random basic design in three replications.

The results showed that the nano composite based on zeolite and Fe3O4 can absorb 70% of nitrate in a small laboratory scale and non-continuous flow. In continuous flow and on a large-scale laboratory that has industrial application, the absorption rate of nanocomposite will reach 27% after 8 hours of continuous flow. This absorption rate is 17% for zeolite-clay and 13.4% for zeolite. Decreasing the contact time and increasing the amount of wastewater in continuous flow will reduce the effect of absorbents. The results of the average comparison of the nitrate concentration in the wastewater from the columns with different absorbers show that the difference between the nitrate concentration in all measurement times between the nanocomposite absorber and the other two absorbers is statistically significant at the 1% level. Also, the results of one-way analysis of variance to compare the effect of wastewater removal on an industrial scale between the adsorbents used showed that the nanocomposite adsorbent used has more efficiency than zeolite and zeolite-clay adsorbents. Due to the fact that the composition of nanocomposite (zeolite modified with nano Fe3O4) has more surface area than zeolite and clay adsorbent due to having nano compounds, so the reactivity of this adsorbent is increased and nitrate absorption in this adsorbent is more than other adsorbents. In general, the results of this research show that the nanocomposite used in this study has a relative ability to remove nitrate from the water environment, and if the contact time is increased, it can be used on an industrial scale with a suitable absorption percentage. The current research was done with continuous flow and short contact time. This is despite the fact that in most of the investigated studies, the contact time was more than 50 minutes. Therefore, the amount of absorption is less than the laboratory scale and non-continuous flow. To solve this problem, the continuous flow system should be designed in such a way that the contact time reaches at least more than 50 minutes. In addition, with proper design, passing through the filter can be done in two stages so that maximum absorption takes place.

Nitrate is one of the pollutants that affects groundwater in most aquifers of the country. In order to investigate the behavior of hydrogeochemical parameters of groundwater in the Ardabil plain aquifer, the results of qualitative data of 139 wells that were measured in both wet and dry seasons during the water year 2012-2011 were used. Using XLSTAT software, contamination was identified and samples were classified using principal factor analysis (PCA) and hierarchical clustering (HCA). Factor analysis method led to the extraction of five factors affecting groundwater quality with a total variance of 68.09 percent. Also, the results of factor analysis showed that the first, fourth and fifth factors are due to geogenic processes and the second and third factors are due to anthropogenic processes. The results of the hierarchical clustering method divided the samples into three groups, each group having two subsets. The set related to cluster one is spread in the northern, eastern, southern and parts of the center, west by mix(agriculture-garden), medium pasture and dry farming as well as urban areas. The set of the second cluster is often spread in the central, western and urban areas of the aquifer, with mix(agriculture-garden) and residential areas. The set of third cluster has been expanded to southwestern and urban areas. Generally, the existence of dissolution and ion exchange processes on the one hand, as well as leaching of fertilizers and incomplete development of the sewage system in the aquifer on the other hand has provided the groundwater pollution.

Water is a renewable resource that naturally follows a hydrologic cycle. Huge groundwater tables are essential resources that are utilized as underground water. Irregular population increase in the last three decades, limited surface waters, and too much utilization of groundwater tables damaged the Iranian aquifers irreparably, both quantitatively and qualitatively. Today, with the introduction of extensive industrial activities and chemical fertilizers in agriculture, the most important source of human life is at risk. Groundwater pollution is often caused by toxic wastewater from industries, agriculture, or sewage storage sources. The effects of different pollutants in the environment are different. One of these pollutants is nitrate. The contamination of underground water with nitrate ions is an important global problem, the most important source of which is arbitrary agricultural activities and the excessive use of nitrogenous chemical fertilizers. Numerical simulation of groundwater flow and contamination transport is a vital aquifer resource management tool that estimates the hydraulic and hydrologic parameters of the aquifer. In previous studies conducted by researchers, only flow modeling or only pollution transfer has been discussed, which we have studied both cases in the present study. Therefore, in this research, the flow and transfer of pollution has been investigated separately and completely.

In this research, the flow and transfer of pollution were investigated separately and completely. In this paper, the general aquifer software simulation algorithm is first discussed. The Damaneh aquifer is then introduced. Damaneh is located in Isfahan Province in the catchment basin of the Falat Markazi. The region’s specifications are given, and its hydrologic and hydrogeological features are stated. The process of creating the conceptual and numeral model is discussed, and the aquifer modeling process is examined in detail. The last section discusses the modeling of contaminant transport. According to the climatic conditions of the region, the Damaneh plain faces alternating wet and dry periods. For this reason, for the model to better match the nature of the aquifer, a wet and dry period has been applied to the model. According to the monthly rainfall statistics, from 2005 to 2008 was a dry season and from 2009 to 2013 there was a large relative drop in rainfall, which was applied to the model as a drought period. This study presents the results of mathematical modeling of the groundwaters’ flow and contaminant transport and their simulation in the Damaneh aquifer. Groundwater modeling system (GMS) software was used. The necessary information, such as geological, hydrological, hydrogeological information, and topographic maps are gathered. The aquifer flow model in stable and unstable states was run next. The model is optimally calibrated for hydraulic conductivity and specific yield up to a particular standard error. It was verified using an unsteady period to ensure the simulation results’ accuracy. To predict the water level fluctuations and the response of the two optimized coefficients, the Damaneh aquifer was simulated for a specific time interval using two distinct scenarios.

Statistical analysis of flow model errors in a stable state gived maximum observed and calculated water levels of 0.87 m and RMSE and correlation coefficients of 0.99 m and 99.9 % and 1.113 m and 99.7 % for calibration and verification periods, respectively. The correlation coefficient between the observed and calculated data for transport modeling was 89.1 %. The error values indicate that the designed flow and contamination transport mathematical models match the aquifer’s natural conditions well. They give a good simulation of the hydrological system. In the aquifer, the presented results of these discoveries have high uncertainty, because, in some wells of the adjacent logs, drastic differences between the type and profile of these logs can be seen. To calculate the path length and movement time of pollution particles on the surface of the aquifer, points were determined and the MODPATH model was run in Forward mode. The results showed that the transit time was between 2 and 7 years, and the shortest and longest paths traveled by the particles in this period of time were 312 m and 6200 m, respectively. As the modeling results showed, the concentration of nitrate in most areas of the Damaneh aquifer exceeded 80 mg/l during the past years 2007 to 2008 and according to drinking water consumption standards, it is necessary to reduce the nitrate concentration or clean the Damaneh aquifer. A sensitivity analysis shows that the flow model is more sensitive to hydraulic conductivity and specific yield. The transport model is most susceptible to the surface recharge, porosity, and longitudinal coefficient of variation parameters, respectively. It is not sensitive to recharge from the aquifer’s borders. The results of the transfer model showed that only one halo of pollution is forming in the Damaneh aquifer and it is spreading in the entire aquifer at an approximate speed of 15 m d-1.

According to the error values, it can be concluded that the mathematical model designed for the flow and transfer of pollution has a good match with the natural conditions of the aquifer and has well simulated the behavior of the hydrological system. It is suggested to prepare accurate and new statistics of the exploitation wells in the region, although it is very expensive at the level of plains such as the Doman plain, but the special conditions of this plain require more attention. Providing smart meters is the most effective harvesting control programs in the region.

Use of nitrate fertilizer to increase crop yield is a method used by many farmers. Once this ion enters the soil, it is converted to nitrate and easily leached. Using zeolite is one of the methods to prevent nitrate leaching has received much attention today; however, determining the exact amount of nitrate fertilizer when using zeolite is very important. Performing experiments in a classic way and taking into account the effect of all factors (factorial design) needs time and cost in performing experiments. For this reason, old research methods should be replaced by simple and standard methods such as Taguchi and central composite design. For this purpose, this study was conducted in a completely randomized as factorial design. Treatments consisted of zeolite (at three amount; zero, 2 and 6%) and nitrate application (at three levels; zero, 200 and 400 mg nitrate per kg of soil) with three replications. Taguchi and central composite designs were considered with 9 and 13 experiments, respectively. The results of complete factorial method showed that the amount of zeolite had a significant effect on nitrate leaching; however, nitrate fertilizer had no effect on nitrate leaching. According to Taguchi results, both zeolite and nitrate fertilizer were very important on nitrate leaching reduction from soil. Based on prioritizing the effect in the central composite design, it was observed that zeolite was the most important factor in reducing nitrate leaching. Based on the results, the application of 2% zeolite was the beginning of the effect of zeolite on nitrate leaching. Therefore, it can be expected that in amounts between 2 to 6% zeolite, a significant reduction in nitrate leaching occurs.

Groundwater in arid regions such as Iran plays a very large role in drinking water supply and agriculture. One of the threats to the future of groundwater exploitation, could be the contamination of these resources by harmful substances. At present, about 60% of the water consumption of Varamin plain region and the total volume of water consumption in the drinking sector is provided from groundwater sources. One of the best ways to prevent groundwater pollution is to identify vulnerable aquifer areas. The SINTACS model has been used to assess the vulnerability of the Varamin plain aquifer. This method consists of seven parameters that after combining the parameters, the vulnerability index map is obtained. The index of this method varies between 92 and 168.Results show that the north of the plain is very vulnerable and vulnerability is low in the south-eastern parts of Jalilabad village and downstream areas of the plain, while the rest of the plain has moderate vulnerability. A three-dimensional numerical model was used to evaluate the results of the model and the model was validated for a period of one year. The accuracy of the constructed model was evaluated as appropriate. In this model, nitrate contaminant was considered as an aquifer contaminant. In order to validate the inherent and special vulnerability of the SINTACS model, the nitrate output of the model was used, The correlation square of the results was about 65%, which shows a good agreement between the two models even thogh the numerical model is considered as micro- model compared to SINTACS one. Considering the role of the aquifer of Varamin plain in supplying the required water of the region, the quantitative and qualitative protection of this aquifer is a necessary and strongly recommonded. Also, in order to reduce the nitrate ion concentration in the study area, long-term solutions such as improving the agricultural structure and cultivation pattern of the area and constructing a collection network and wastewater treatment plant are proposed.

Watershed management strategies can be considered in mitigating water pollution issues. In this study, using SWAT as a semi-distributive hydrological model, runoff and nitrate amounts have been investigated according to management scenarios in Hashtgerd plain, Iran. After runoff simulation, three hydrometric stations were used for calibration in the period (1990-2013) and validation in the period (2014-2018). The results of R2 and NS statistical indices (greater than 0.6) show that the simulation results in this catchment have been done with good accuracy. The results also indicate that applying the first scenario (changing the crop pattern) and the second scenario (increasing irrigation efficiency) reduced the water usage in the agricultural sector from 85.3 MCM to 59.8 MCM in the present condition, which also will improve the fertilizing efficiency. It was demonstrated that changing the crop pattern can help reduce the deep percolation. On the other hand, using drip irrigation, the leaching requirement, and irrigation water loss will be reduced. Comparing the amounts of observed nitrate in the hydrometric station in the base period with the simulation results in the first scenario revealed that, by applying the first scenario, the amount of nitrate simulated has relatively a decreasing trend except in winter and early spring. The results of the second scenario show that by changing the irrigation method, the amount of nitrate leaching has decreased significantly compared to the base period. In general, the second scenario is more effective in reducing nitrate leaching and is recommended.

Nowadays, the use of effluent in irrigation and especially drip irrigation systems has increased. The findings uncovered that drip irrigation is assumed as the only method which is capable of overcoming specific problems caused by wastewater usage. In this study, the efficiency of sand and geotextile filters with zeolite on wastewater properties and their application in the filtration of the drip irrigation system was investigated.
This study was conducted to investigate the changes in important chemical properties in the municipal wastewater of a university after passing through sand filters, geotextiles, and zeolites in the drip irrigation filtration system. A factorial experiment was performed in a completely randomized design with three replications. Treatments included sand filter (control-CTRL treatment), geotextile filter (G), sand filter with zeolite (SZ), and geotextile filter with zeolite (GZ). The sand used in this study was the usual silica sand which was in three sizes of 3-5, 5-8, and 8-12 mm. In order to remove any contamination and soil particles and increase the accuracy of the measurement of suspended solids in the effluent, the sands were washed several times with water before usage. The geotextiles used in this study had three types with weights of 300, 500, and 1000 grams per cubic meter. The zeolite used in this study was clinoptilolite modified with hydrochloric acid. The wastewater used in this study was obtained from the effluent of Shahrekord University. System flow rate, Pressure, nitrate, suspended solids, sodium, calcium, magnesium, electrical conductivity, effluent pH were measured before and after entering the filters at different hours. Statistical analysis was done by SAS software and the Duncan test was used to compare the means of the data.
The results showed that the sand-zeolite treatment had a good performance in terms of pressure and the geotextile-zeolite treatment was able to provide pressure for a short time. The amount of nitrate in the wastewater of the sand filter was not significantly different from the amount of inlet, but in other filters was significantly reduced. The amount of nitrate input of all treatments was 26 mg/l.The average output nitrate in the sand filter was about 25 and in the other filters was less than 20 mg/l. The average amount of suspended solids in the effluent was about 110 mg/l, while the average amount of suspended solids in the wastewater was reduced to less than 72 mg/l. The sand and sand-zeolite treatments increased the total amount of calcium and magnesium in the wastewater more than geotextile and geotextile-zeolite treatments, respectively. The average Ca + Mg of effluent in the total operating hours of the system was higher than the average input in all filters. The percentage of EC changes in total hours increased about 4% in sand and geotextile treatments and 14% in geotextile- zeolite and sand -zeolite filters. The highest percentage of pH changes was related to sand-zeolite filter, which reduced the pH of incoming wastewater by about 4.5%. After that, geotextile- zeolite filter reduced the pH of the incoming wastewater by 4%. The average pH of the effluent of all filters is lower than the average of their inlet.
Sand and geotextile filters alone cause pressure drop and dropper clogging. However, the sand-zeolite treatment has performed well in this regard. The geotextile-zeolite treatment has the potential to be used in terms of supplying the necessary pressure for a short period by applying special treatment measures before this filter. These conclusions are only in terms of pressure drop due to the ability of filters in practical use and do not refer to their ability to filter the parameters and provide the desired flow. All treatments, especially zeolite treatments, significantly reduced nitrate, and these filters can be used to reduce effluent nitrate in cases where the amount of nitrate is more than allowed. However, since the sand filter had no effect on nitrate reduction, the effluent must be treated for nitrate before using sand filters. The geotextile filter had a higher percentage of suspended solids removal at all hours. The addition of zeolites to both geotextile and sand base filters reduced their ability to treat suspended solids. Therefore, geotextile filters can be a good alternative to ordinary sand filters in terms of this parameter. All treatments increased Ca + Mg relative to the input. The sand- zeolite treatment reduced the pH of the incoming wastewater more than other treatments (about 4.5%). Also, desalination of salts from zeolite treatments increased the EC of effluent in the sand-zeolite and Geotextile- zeolite treatments. According to this study, the use of sand-zeolite in terms of reducing nitrate and suspended solid, increasing calcium and magnesium, and reducing pH and no pressure drop is recommended.