مجله تحقیقات آب و خاک ایران
سال پنجاه و چهارم شماره 11 (پیاپی 95، بهمن 1402)

Recognizing the effects of climate change in different sectors, as well as the integration of GCM models and the development of Ensemble Climate Models (ECM) are vital. In this study, the efficacy of the climate models from the CMIP5 in simulating atmospheric variables impacting the potential for water harvesting was assessed. These variables encompass mean air temperature, wind speed, relative humidity, and the feasible quantity of water harvested from air moisture. Also, assessing the efficiency of the optimization algorithm (Genetic Algorithm) in the development of an ensemble climate model was another goal of this research. It is noteworthy that the present investigation employed data from 16 synoptic stations situated in the northern and northwestern regions of Iran during the statistical period of 1991-2005. Results indicated that the performance of individual climate models in simulating variations in wind speed and relative air humidity is deemed poorly. Conversely, GA has yielded a reduction in both error magnitude and biases in climatic outputs in estimating wind speed and relative air humidity. Furthermore, the evaluation of the efficacy of climate models in estimating the water harvesting potential from air humidity indicates the acceptable performance of ECM in simulating changes in the amount of extractable water from air humidity. In general, the results showed that Manjil and Bandar-Anzali stations are the most suitable areas for the implementation of water harvesting projects from air humidity. Conversely, Arak and Hamedan stations exhibit the least potential for water harvesting. Based on the results, the average water that can be extracted from air humidity in the summer season for Manjil and Bandar-Anzali stations is estimated to be 1.56 and 1.78 (l/day.m2). Also, the seasonal changes of water harvesting potential from air humidity showed that the potential of extracting water in summer is more than the other seasons. This accentuates the urgency of water resource management and agricultural planning, prompting the implementation of substantial measures to use this water source. The potential applications of using this source encompass agricultural sectors, green space irrigation, and potentially catering to a portion of drinking water demands, contingent upon quantity and quality parameters.

The recent escalation of environmental concerns necessitates the development of computer models able to predict pollutant dispersal in natural aquatic systems, rendering them an absolute essentiality. Unlike physical models, the primacy of such computer models lies in their lower costs and facile adaptability to novel conditions. In order to resolve the pollution transport equation in rivers, both directly and inversely, the Group Preserving Scheme has been employed. As expeditious simulation of the pollutant intensity function is imperative, determining a technique to achieve this with celerity is essential. Solving the pollution transport equation in one time step utilizing GPS reduces computational duration and conserves time and resources. GPS constitutes a method for solving malignant problems. This method has been leveraged to solve the one-dimensional advection-dispersion equation with variable coefficients. This method is based on solving dynamic systems in positive and negative time intervals and deriving a general equation to solve ordinary differential equations in a one-step approach. In this study, three examples are shown to demonstrate the performance of the one-step solution of the direct and inverse Group Preserving Scheme. First, the pollutant concentration in the river was calculated using the forward solution with variable coefficients. Next, two different examples were used to simulate the pollutant intensity function at the initial time, employing the Backward Group Preserving Scheme. Afterward, the accuracy of the one-step and multi-step solutions was evaluated using statistical indicators.

The stabilization of a clay soil contaminated with glycerol was studied through a series of experimental tests. Contaminated soil was artificially prepared with percentages of 4,8 and 12% from the solution of glycerol with concentration of 50%. GGBS and activated GGBS with MgO or mixture of MgO and cement were used as agent materials. They were added and mixed with both natural and contaminated soil at percentages of 5,10 and 15%. Atterberg limits, compaction and unconfined strength tests (UCS) were performed on both soils with and without agents. The results showed that these parameters varied when adding glycerol or different agents and the extent of these changes were dependent on the percentage of glycerol and the type of agent. In addition, it was resulted that under constant conditions, strength values were dependent on the curing time. E50 (Elastic coefficient) for each strength test was calculated and the variations in its value corresponded to changes in strength. Comparing the results indicated that the effect of activated GGBS in increasing the strength and E50 of both soils were greater than that of GGBS alone. Based on the SEM results, it was revealed that the increase in the strength of stabilized soil is due to the production of chemical bonds between the particles of soil.

Flooding and drainage cycles affect the biological and chemical characteristics of the soil in paddy fields and play an important role in cadmium (Cd) availability. In this study, the effect of biochar (B), hematite (H), and their simultaneous application (HB) on pH, Eh, and calcium chloride extractable Cd was investigated in a Cd-contaminated soil during a flooding and drainage period. Also, the Cd fractionation at the end of the incubation period was studied. The pH value increased during the flooding period and decreased with the beginning of the drainage period. The Eh value decreased from the beginning of the flooding and showed an increasing trend during the drainage period. Calcium chloride extractable Cd decreased during the flooding period, while at the beginning of the drainage increased with a slight slope and followed a decreasing trend up to the end of the drainage period. Cd concentration reduced at the end of the flooding period in the B, H and HB treatments compared to the control by 16.8%, 20.5%, and 25.7%, respectively. Also, the reduction in Cd concentration compared to the control treatment at the end of the drainage period was 18.2, 23.1 and 28.2% respectively. HB treatment reduced the Cd availability by reducing the soluble and exchangeable fractions and increasing organic, iron, and manganese oxides fractions. The results indicated that the application of amendments can reduce Cd availability in paddy fields and its uptake by the rice plant.

The present study was devoted to investigate the concentration of lead (Pb) in the tailings of Tang-e Douzan lead–zinc mine then determine the growth factors and the lead accumulation in metallicolous and non-metallicolous populations of Marrubium cuneatum in 2018 at the university of Isfahan. The both plant populations were transferred to hydroponic mediums and after proper vegetative growth, they were exposed different treatments of lead for 14 days. The results showed the highest Pb concentration in the tailings of mine (1968 mg/kg) was more than 72-fold the global average and by increasing lead concentration, the growth factors  decreased, but this reduction in growth was always greater in the non-metallicolous population, so that at the 200 mg/L treatment of lead, relative water content and shoot weight loss of the metallicolous population was 66.8 and 32.2%, respectively but they were 58.9 and 84.9% in non-metallicolous population in comparison with their control. With increasing the concentration of Pb in the medium, the accumulation of Pb in the roots and shoots of both populations are enhanced and lead accumulation was constantly more in the metallicolous population. The highest concentration levels of Pb were in the roots and shoots of the metallicolous population (15.2 and 0.9 mg per plant) which were 3.1- and 3.6-fold accumulation Pb in the non metallicolous population. The accumulation of lead in the roots was 15-folds more than the one in the shoots in both populations. The metallicolous population had an efficient antioxidant system which can grow with more accumulation of Pb and enhance the ratio of shoot to root, therefore, it can be used for phytoremediation.

Digital Soil Mapping (DSM) encompasses a variety of methodologies that can yield precise spatial information about soil by establishing quantitative relationships between environmental covariates (predictors) and soil classes or properties. In this study, Artificial Neural Networks (ANNs), Decision Tree (DT), Multinomial Logistic Regression (MLR), and Random Forest (RF) algorithms were used to predict the soil map of downstream lands of Azad dam with an area of approximately 178.3 ha in the northwest of Sanandaj city in Kurdistan province. A random soil sampling method was used to determine the location and distribution of the 84 soil profiles in the study area. After recording soil morphological attributes, sampling of all horizons was conducted for required laboratory analysis. Afterward, the soil profiles were classified up to the family taxonomic level based on US classification system. Based on the soil taxonomy classification system, Inceptisols and Entisols order were observed by frequency, two Suborder, three Great groups, five Subgroups, and Family. To calculate the predictor variables, a digital elevation model (DEM) with a 10 m spatial resolution and Sentinel 2-B satellite images were used in the study area. To check the prediction accuracy of the models the Overall accuracy (OA), Kappa Index (K), and Brier Score (BS) were used. The best result was obtained by the ANN model (OA=0.65, K=0.53, and BS=0.16, respectively). The weakest predictions were found by DT model with OA, K, and BS of 0.38, 0.22, and 0.87, respectively.

Today, human activities are one of the most important challenges in issues related to the quality of water resources, which is currently considered one of the management threats in the exploitation sector. This issue will require the identification and evaluation of water resources from different perspectives, of which the vulnerability of water resources is one. This study evaluates the vulnerability of water resources by combining two DRASTIC vulnerability indices in the aquifer sector and WRASTIC vulnerability index in the upland sector of Astana-Kuchsefahan region. In this study, after assessing the vulnerability with the relevant indicators, two methods of entropy and hierarchical analysis were used for scaling based on maximizing the correlation with nitrate concentration. The results showed that the most importance in both indices based on recalibrated weights include industrial use in the WRASTIC index and underground water depth in the DRASTIC index. The analysis of the calibration results showed that the correlation of nitrate with the DRASTIC vulnerability index using the AHP method was 0.61 and with the WRASTIC index was 0.58 using the Shannon entropy method. Also, the measurement results showed that the WRASTIC index ranges from 17 to 46 and the DRASTIC index ranges from 119 to 180. Based on the consolidated results in the western and eastern parts of the highlands, the level of vulnerability using the WRASTIC index is lower and there is a higher vulnerability in the western part of the aquifer compared to the eastern part.

In this study, the concentration of heavy metals in water and sediments in four stations of Chabahar Lagoon was investigated. Ecological risk index (RI), pollution load index (PLI), and land accumulation index (Igeo) were used to evaluate the ecological risk of heavy metals in the sediment environment. To evaluate the risk of these metals to human health, the hazard index (HI) for two age groups, adults and children  was used. The results showed that the highest value of the ecological risk index occurred in station 4 with a value of 38.73 and the lowest value occurred in station 1 with a value of 21.36. The calculated RI values for all stations were less than 150, indicating that they are in the low-risk range. The highest value of the pollution load index also occurred in station 4 with a value of 0.59, which shows that the sediments of all four stations were not polluted. However, Igeo values were less than zero, which indicates that the studied sediments are in the non-polluted range. Only station 4 had a value greater than zero and less than 1 for chromium, which is in the range of pollution, not polluted to moderate with this metal. Also, risk index values for minors and adults were calculated at each station. The highest value for minors and adults occurred at station 4 with values of 0.89 and 0.59, respectively. Although HI values are less than 1, minors are more exposed to these metals than adults. These results are very worrying for minors who are a vulnerable group in society.

Climate change is a phenomenon that affects many natural processes, including the hydrological cycle. Evapotranspiration is also an important part of the hydrological cycle, which is crucial in water resource management and agricultural planning. Since the estimation of evapotranspiration is always associated with uncertainties, this study examines the effects of climate change on the evapotranspiration process at the Crumbed station in Preston province. The study uses the SAP1-2.6, SAP2-4.5, SAP3-7.0, and SAP5-8.5 scenarios according to the Sixth Assessment Report (AR6) in three future time periods: near future (2023-2048), mid future (2049-2074), and far future (2075-2100). The reference evapotranspiration for the base period and future periods is calculated using the Hargreaves method. The results show that the maximum temperature at the Crumbed station will increase by an average of 0.26 to 6.3 degrees Celsius by the year 2100, compared to the base period (1988-2014). The minimum temperature will also increase by an average of 0.32 to 4.9 degrees Celsius during the same period. Additionally, the average evaporation-transpiration in all periods will increase compared to the base period. The average evaporation-transpiration in the near future will range from 4.69 to 4.82, in the mid-term future from 4.7 to 4.94, and in the far future, from 4.72 to 5.04

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.