مجله تحقیقات آب و خاک ایران
سال پنجاه و چهارم شماره 10 (پیاپی 94، دی 1402)

In recent years, environmental friendly methods have been considered for managing hazardous chemicals in landfill leachates to prevent their entrance to surface and groundwater resources. This research was done in 2022 at University of Guilan. An ureolytic bacterium with the ability to precipitate calcium carbonate was isolated from the Saravan landfill leachate (SLL) firstly. Then, its potential was investigated along with the indicator bacteria Sporosarcina pasteurii</em> in removing phosphate, calcium and fluoride ions from LLA through the calcium carbonate bioprecipitation process (MICP). The experiment was carried out as a 3 × 2 × 2 factorial in a completely randomized design with three replicates (36 samples). Factors include biocementing bacteria at three levels (no inoculation, inoculation with strain isolated from LLA and inoculation with S.  pasteurii</em>), urea at two levels (0 and 2% (v/v)), and calcium chloride at two levels (0 and 50 mM). The highest phosphate removal rate (93%) was observed in the presence of calcium chloride without bacteria inoculation, and urea addition. However, ureolytic bacteria were needed for fluoride removal where the treatments of indicator bacteria and isolated strain in the presence of urea and calcium chloride removed 77% and 48% of fluoride, which was 14.4 and 9 times greater than the control treatment, respectively. The calcium removal rate in treatments with indicator and isolated bacteria was 93% and 90%, respectively. Although the removal rate of phosphate, calcium and fluoride was higher in the presence of the indicator bacteria compared to the isolated strain, there was no significant difference between them. Therefore, considering the application of native microorganisms, in addition to reducing costs, also creates less environmental concern than the indicator bacteria, it can be used to remove hazardous chemicals from landfill leachates through the MICP process.

Drought, one of the most complex natural phenomena, causes significant direct and indirect damage to different sectors annually. The purpose of this study was to monitor drought, dust, and vegetation at five stations in the Khuzestan Province over a statistical period of 30 years (1990-2019). In this study, from the hourly data of horizontal visibility, the codes of the Meteorological Organization as well as the data of the synoptic station in the daily time frame were used to obtain the drought indices (SPEI and SPI) and the frequency variable of dust storms (DU) in time windows of 1, 3, 6, and 12 months. After calculating the indices of drought, dust and vegetation, they were combined with the empirical copula function method. The station that had the best correlation between the three climatic indices of dust-drought-vegetation was considered a representative station, and the three-variable coupling among the desired indices was investigated at that station. The results showed according to the SPI index, severe droughts occurred in the province from 1999 to 2003 and 2008 to 2012, which had a lot of negative effects on the soil of the region, as well as the formation of dust generating centers in the mentioned time period. Also, the results showed that the highest correlation was related to Bandar Mahshahr station between NDVI and SPEI (PM12) indices with Pearson and Spearman correlation coefficients of 0.44 and 0.46, respectively, and the highest negative correlation at Masjid Suleiman station between NDVI and DU06 occurred with Pearson and Spearman correlation coefficients of -0.37 and -0.47, respectively. The results obtained in Khuzestan Province are almost realistic as the drought index increased, the NDVI index increased, and as the dust increased, the NDVI value decreased.

Seepage is a crucial factor in the design of dams as it can lead to failure if not controlled. This study delves into the numerical modeling of seepage and investigates the effects of different sealing systems on the foundation and body of earthen dams under steady flow conditions. The study explores various sealing conditions ranging from optimal to critical, which include clay blankets, drains, and clay curtains in the foundation. In general, the combined effects have been studied by combining all types of defined elements without considering their geometric dimensions. The study reveals that the different seepage reduction systems have significant effects on reducing the flow within the dam body and foundation. The trend of seepage discharge increases with height and reaches a maximum between 38 to 46 meters before decreasing again. The combination of a drain, clay blanket, and clay curtain proved to be the most effective in ensuring the dam's stability. The study shows that this combination can reduce the flow rate by an average of 83%, the seepage rate by an average of 15.5%, and the water head by an average of 9.5% at downstream of the dam. The results of this study suggest that the diversity in the type of flow seepage reduction systems has a significant effect on reducing the flow inside the dam body and foundation. This finding underscores the importance of considering the combined effects of different sealing systems to ensure the stability of the dam.

Irrigation networks are the main infrastructures for water conveyance and distribution in agricultural sector. Chemical damage of concrete is one of the main limiting factors for service life of irrigation networks. The main target of this research was to investigate and compare the risk of chemical detriments on concrete structures of Golestan and Kausar-Nomal irrigation networks. In this regard, in June 2022, water samples were collected from different points of the studied networks and the laboratory tests were performed. Then, the results of the water-quality parameters in tandem with the previously available monthly water quality data of the studied networks, were analyzed based on credible international criteria and using water corrosiveness indices. The Ryznar index values, for both Golestan and Kausar-Nomel networks, during October 2021-June 2022, were beyond the threshold of water corrosiveness (6.8). The average values of Ryznar index for the water samples of Golestan and Kausar-Nomel networks were 7.45 and 8.15, respectively, which means the corrosiveness intensity of Kausar-Nomel network’s water is significantly higher. Also, the concentration of dissolved-CO2 in the water of Kausar-Nomel network, in June 2022, was equal to 31.7 mg/l, which means that there has been a risk of cement decomposition. On the other hand, during the nine studied months, the sulfate-ion concentration values in the Golestan network’s water were recorded more than 150 mg/l, which is more than the minimum required for reaction with concrete. In four months out of the nine studied months, the magnesium-ion concentration values in the Golestan network’s water were more than 100 mg/l which are the beyond of threshold risk in concrete chemical damages.

The decline in quality and quantity of water resources has created a great challenge in the production of greenhouse agricultural products in Iran. Considering the increasing use of water desalination systems in the greenhouses, a research was conducted in Isfahan province (Falawarjan, Isfahan, Mobarakeh and Shahreza counties). Therefore, after visiting and observing various aspects of the use of these devices, samples were taken from well water, desalinated water and the condensed effluent of desalination systems and the methods of effluent disposing of the devices were studied. The results showed that the highest amount of well water salinity was observed in Falawarjan, with an average of 12.41 dS/m and the lowest in Shahreza, with an average of 4.09 dS/m. For condensed effluent of devices, the highest amount of salinity was also observed in Falawarjan, with an average of 16.63 dS/m and the lowest in Shahreza, with an average of 5.41 dS/m. The average salt removal from feed water (returned salt) in all investigated greenhouses in Isfahan province was 73%. In addition, the values of Sodium Absorption Ratio (SAR), Calcium-Magnesium Ratio, Chlorine and Bicarbonate level in water samples was also carried out. Regarding the condensed effluent discharge, the main option with 46% belonged to the release of effluent in the surrounding lands (environment), followed by combined use with well water for open-air agriculture with 27%, discharge to local wells with 18%, and discharge to trenches and the infiltration ponds with 9%, respectively. Due to the lack of monitoring of the implementation and use of these devices and the lack of consideration in waste disposal, a suitable situation was not observed, and with the continuation of the current process, the spread of contamination of water and soil resources is not far from expected.

In order to determine the nitrogen requirement of rice (cv. Guilaneh) using the nitrogen nutrition index and chlorophyll meter, an experiment was conducted as a randomized complete block design with three replications in the research field of the Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran in 2016. Experimental treatments consisted of six nitrogen fertilizer levels (0, 60, 120, 180, 240, and 300 kg N. ha-1; Urea source). Evaluation of the relationship between nitrogen nutrition index and chlorophyll-meter readings at three stages of plant growth (maximum tillering, booting, and heading) to predict grain yield in response to nitrogen fertilizer showed that the equation of the critical nitrogen concentration in Guilaneh was Nc = 3.99W -0.36. The correlation between chlorophyll-meter readings and nitrogen nutrition index was positive and significant at each plant growth stage. The results showed that the mature lower leaves were more sensitive than the younger higher leaves in response to nitrogen fertilizer and were more suitable for detecting plant nitrogen status, especially during the booting and heading stages. The highest correlation was found between the nitrogen nutrition index and chlorophyll-meter (r=0.95*) and relative chlorophyll-meter (the ratio of chlorophyll-meter readings in each treatment to nitrogen saturated treatment) (r=0.96**) in the third leaf and booting stage. The overall results of this experiment showed that the nitrogen nutrition index and chlorophyll meter may consider reliable indicators for evaluating the nitrogen status of rice (cv. Guilaneh) during the growing season.

In this study, the accuracy of estimating shallow aquifer recharge values in Astane-Kouchsefahan using two models: SWAT (a surface water hydrological model) and MODFLOW (a groundwater flow model) was evaluated. Then the need for using SWAT in the modeling of groundwater flow, which is typically done by MODFLOW, was evaluated. For this purpose, the simulation of the Astane-Kouchsefahan aquifer was done by MODFLOW using GMS graphical user interface. Then the SWAT model was built for the Astane-Kochsefahan watershed and calibrated by the SUFI2 algorithm in SWAT-CUP software. In the following, after determining the two models' common spatial and temporal range, the aquifer recharge amounts were compared according to the outputs of the two models. MODFLOW results showed that the total aquifer recharges including recharge from the river in 1391-1392 were equal to 102.71 and 23.71 million m3, respectively. The highest and the lowest amounts of aquifer recharge occurred in December and April, respectively. The results of SWAT showed that the amounts of aquifer recharges including recharge from the river are estimated to be 138.34 and 35.09 million m3, respectively. So, the highest and the lowest recharge amount occurred in December and September, respectively. Based on the regional circumstances, SWAT offers more dependable estimates of the groundwater recharge parameters by considering surface water parameters and factors like the influence of dams and water transfer channels, soil characteristics, land use, climatic and meteorological data, and information regarding agriculture and irrigation management. Consequently, integrating the precise recharge results from SWAT into groundwater models such as MODFLOW leads to enhance and more reliable evaluations of the aquifer's state.

Due to the association of some heavy metals with petroleum hydrocarbons, the use of native degrading bacteria of surfactant-producing oil that is resistant to heavy metals is one of the priorities of bioremediation technology. For this purpose, in this study, 39 alkane-degrading and biosurfactant-producing strains were used (isolated from saline soils contaminated with oil in the oil-rich areas of southern Khuzestan province) belonging to the soil microbiology laboratory gene bank of Tehran University. Then, the sensitivity of the isolates to different concentrations (40 to 80 ppm) of heavy metals (chromium, lead, copper, nickel, and cadmium) was tested. The results showed that only three strains Ochrobactrum lupini</em> strain SH23, Ochrobactrum lupini</em> strain SH24, and Bacillus subtilis</em> subsp. Inaquosorum</em> strain SH34 could grow in the presence of all heavy metals. The effects of different concentrations of heavy metals on the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of selected bacteria showed that Ochrobactrum lupini</em> strain SH23 had the highest tolerance to heavy metals. The evaluation of the ability to degrade petroleum hydrocarbons in the presence of heavy metals by selected bacteria showed that the microbial consortium (SH23, SH24, and SH34) and Ochrobactrum lupini</em> strain SH23 were able to degrade 71 and 64% of crude oil with a concentration of 0.5% (v/v), respectively after 10 days of aeration at 30 0C. The findings of this research proved that by conducting additional environmental studies, the bacterium Ochrobactrum lupini</em> strain SH23 can be used in the treatment of water and wastewater contaminated with petroleum hydrocarbons and heavy metals.

Researchers consistently seek methods that minimize data requirements and decrease soil quality assessment costs. Soil pores are recognized as indicators of soil physical quality due to their environmental sensitivity. This study identified key parameters related to soil pores and physico-chemical properties to assess their potential as indicators of soil physical quality. Conducted between 2020 and 2022 at the University of Tehran's Soil Sciences Department Micromorphology Laboratory, the study used image analysis to determine the parameters related to pores resulting from 126 experimental units, including ammendments, removals and disruptive experimental treatments and affected by 22 cycles of wetting and drying which were determined in two types of soils, sandy loam and silty clay. Parameters included sphericity, elongation, area, and compactness. The first two principal components (PC1 and PC2) represent more than 70% of the variations in the studied soils. Parameters like sphericity (81% and 80% correlation with PC1 and PC2) and elongation (77% and 83% correlation with PC1 and PC2) in loamy sand, and elongation (53% and 87% correlation with PC1 and PC2) and pore area (48% and 68% correlation with PC1 and PC2) in silty clay loam were identified as quality indicators. Comparing soil quality based on pores in different treatments with control showed 32% and 18% differences in loamy sand and silty clay loam, respectively, demonstrating indicator efficacy in reflecting soil quality changes. The microscopic features of pores that possess fractal properties were successfully utilized in this study for assessing soil quality. Based on this method, it is possible to employ this approach for determining soil quality on a field scale.

Antibiotics as emerging pollutants, potentially affect the environment and human health and their entry into the environment has created great concerns. To study the ciprofloxacin hysteresis phenomenon in the soil, the adsorption process was done with different concentrations of ciprofloxacin (0–1 mmol L-1) on a calcareous soil system. Then, the reversibility of the adsorption process was assessed through desorption experiments of ciprofloxacin-loaded soil samples. The concentration of ciprofloxacin was determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS). The experimental data were analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherms. The results demonstrated the experimental data followed the Redlich-Peterson isotherm model due to the lowest value of error (SE= 0.24) and the highest value of correlation coefficient (R²=0.99). The exponent value of this equation (g) was less than one, so the adsorption surfaces are heterogeneous. Ciprofloxacin adsorption increased with increasing initial concentrations. The highest adsorption and desorption efficiency of ciprofloxacin was obtained at concentration 1 mmol L-1, 96% and 2%, respectively. The hysteresis index was 0.89 indicating low reversibility of the adsorption process or hysteresis phenomenon. The strong bind of the ciprofloxacin to the soil components leads to less degradability in soil and forms stable residues in the soil environment.