جستجوی مقالات مرتبط با کلیدواژه « Electrical conductivity » در نشریات گروه « زمین شناسی »

In recent decades, the growing population, limited water resources, and overexploitation of aquifers have caused irreparable damage to the quantity and quality of the country's aquifers. In the current study, geographical information system (GIS) models and machine learning (ML) techniques using available groundwater quality variables were applied for the prediction and zoning of salinity and SAR of groundwater in the Zahedan plain and then the accuracy of these methods was compared.The input data were based on water quality sampling in 2018 from 59 observation wells. The study of parameters showed that in Zahedan plain, EC, SAR, and TDS parameters had high variability (CV>41%) and acidity showed low variability (CV = 4.16%). The results of the geostatistical analysis showed that the IDW model represented better results with the power value of 2 for TDS and EC parameters while for pH and SAR parameters, the ordinary Kriging method revealed the best result with minimum RMSE in the test stage. Performance evaluation of ML models showed that all three models RF, ANN, and SVM showed acceptable results with R2 above 90% and NRMSE values below 15% for all parameters (except acidity). However, better estimations were observed in the training step than in the test step. A comparison of different GIS models and ML also revealed the notable superiority of ML models in estimating these parameters. Finally, it can be concluded that under a shortage of field facilities for the assessment of groundwater quality, data-driven methods can be a reliable alternative to water quality monitoring.

In this study, effectiveness of the intelligent method of ANFIS-FCM adaptive fuzzy neural inference system to predict the electrical conductivity in groundwater due to physical and chemical parameters in the Rayen plain was evaluated. To achieve this, 29 water samples were taken from wells and springs across the plain and the data were chemically analyzed in the laboratory. Descriptive statistics of data and the correlation matrix of the studied parameters were obtained using SPSS software. By forming a correlation matrix, it was found that the potassium (K+), sodium (Na+), calcium (Ca2+), magnesium (Mg2+), chlorine (Cl-), sulfate (SO42-), total soluble solids (TDS), total hardness (TH), compared to other available parameters, have the highest correlation with electrical conductivity (EC). Therefore, the model inputs included the mentioned parameters and electrical conductivity was also selected as the output according to the research purpose. After standardization, the data were entered into MATLAB environment and the electrical conductivity of groundwater was predicted using ANFIS-FCM method. In this method, 70% of the data (20 samples) were selected as the training data set and 30% of the data (9 samples) for the test data set. For the training data set of ANFIS-FCM model, R2 and RMSE values were 0.99994, 0.0001569, respectively, and also for test data set of ANFIS-FCM model, 0.9844 and 0.041652 were resulted for R2 and RMSE, respectively. Using the results of this model, it was found that the estimated electrical conductivity in the study area had very good accuracy and high correlation with the measured values. As a result, the ANFIS-FCM intelligent method is an effective, efficient and accurate method to estimate the electrical conductivity of water.

The aim of this study was to investigate the electrical conductivity of groundwater due to physical and chemical parameters of water using ANFIS-FCM method in Azarshahr, Ajabshir and Maragheh study areas of Urmia Lake catchment area. To achieve this goal, 82 water samples were taken from wells and springs in the plains and the data were chemically analyzed in the laboratory. Descriptive statistical data and correlation matrix of the studied parameters were obtained using SPSS software. By forming the correlation matrix, it was found that the four salinity parameters, soluble oxygen (DO), total soluble solids (TDS) and pH, have the highest correlation with electrical conductivity (EC) compared to other existing parameters. Therefore, the inputs of the model included the four mentioned parameters and the output was selected according to the purpose of the research, electrical conductivity.  After standardization, the data entered the MATLAB environment and using ANFIS-FCM method, the electrical conductivity of groundwater was predicted. In this method, 80% of the data (66 samples) were randomly selected for the training data set and 20% of the data (16 samples) were randomly selected for the test data set. For ANFIS-FCM training data set, R2, RMSE and VAF values were 0.9999, 0.0032399 and 0.99993, respectively, and also for ANFIS-FCM test data set, R2, RMSE and VAF values were 0.9998, respectively, 0.0029949 and 0.99972 were obtained. Using the results of this model, it was found that the estimated electrical conductivity in the studied areas had a very good accuracy and high correlation with the measured values. As a result, the ANFIS-FCM intelligent method is an effective, efficient and accurate way to estimate the physical and chemical parameters of water.

Electrical conductivity increases in groundwater around the gypsum mines because of ions dissolution. this is a useful indicator in gypsum mines exploration, but not enough to that aim, so the elements with high concentrations involved in increasing EC should be identified. This study aims to investigate the efficiency of ANFIS-FCM method to exploration of salty gypsum mines using hydrogeochemical changes of groundwater, which was tested on a case: Anar salty gypsum mine. to this aim, 21 water samples were taken from wells across the plain and chemical analysis of samples was performed in the laboratory. Then, the resulted data were statistically analyzed and descriptive statistics of the data and correlation matrix of the studied parameters were obtained using SPSS software. Forming a data correlation matrix, it was found that in samples near the salty gypsum mine, some ions had the highest correlation with electrical conductivity (EC) including sodium, magnesium, calcium, manganese, selenium and lead, while the mentioned parameters had the highest correlation. The 6 mentioned elements selected as the model inputs and the electrical conductivity was the output according to purpose of the current research. After standardization, the data were entered into MATLAB and the electrical conductivity was predicted using ANFIS-FCM method. The measured electrical conductivity was used directly to compare with the electrical conductivity of the intelligent method. Based on the model results, the estimated electrical conductivity in the study area had very good accuracy and high correlation with the measured values. As a result, ANFIS-FCM intelligent method is an effective method to diagnose the salty gypsum mine. If this method is used in groundwater around other salty gypsum mines in Iran and a similar result be observed, its efficiency in diagnosing the salty gypsum mines is confirmed.

In arid and semi-arid regions, due to low rainfall and overexploitation of groundwater resources, and subsequent saltwater intrusion, the available fresh sources are reduced. Hydrological study and water budget are the first steps in identifying and assessing the region's water potential to provide management plans for the preservation of the fresh water aquifer. Recently Groundwater is becoming increasingly important as a source of drinking water, agriculture and industry activity. More than a hundred countries are facing water shortage of varying severity in the world. About 40% of the global population is situated in heavily water deficit basins. Estimating the terrestrial water balance is one of the main scopes of hydrology. Access to good quality of drinking water is the most basic of human needs, but these conditions are not always available in many of the arid and semi-arid regions. Arid regions are particularly sensitive to variability induced from climate changes. Investigation of water budget variables, such as precipitation (P), evapotranspiration (ET), stream flow and terrestrial water storage (TWS), provides improved understanding of water resources under a changing climate system. The Geysoor Plain is situated in the semi-arid region of Khorasan Razavi Province in the East of Iran. The area of the aquifer in Geysoor Plain is 11784 km2. The Salty plain exists in the northwest of the study area. Geysoor aquifer is located in Quaternary alluvial deposits and clay basins. The Geysoor plain is located in arid with hot and dry summers and cool winters, and has a low sporadic rainfall from 100 to 120 mm for each year, and this precipitation is the main recharge source of the groundwater in this area. This research investigates the hydrogeology and water budget of groundwater resources in this area.   To investigate the hydrological setting of the plain, the iso-potential map of the area was drawn using the data of 18 piezometer wells. Then, all of the water budget components including inputs (sub-surface flow, direct precipitation etc.) and outputs (groundwater flow, harvesting of wells, etc.) were calculated for a year.   The data from water level variations in 18 piezometer wells are used to study the hydrogeological properties. The aquifer is mainly recharged from south, southwest, and northwest and discharged toward the northeast of the plain. According to the iso potential map, the general groundwater flow direction is from west and south toward the northeast of the Geysoor plain. According to the EC map, the electrical conductivity is consistent with the direction of groundwater flow, so that in the southern and northwest parts of the area, the lowest EC value is measured at 989 µS/cm. The highest EC was observed in the central areas of the plain, with a value of about 16800 µS/cm, indicating an intrusion of salt water from salt plain. Based on long term drawdown of water level, the Geysoor plain is divided into three zones. Geysoor plain with negative groundwater balance, showed an average storage reduction of 4.12 Mm3 per year. This in result of a considerable groundwater level decrease of about 5.38 m during a 24-year period. Decreases in recharge and overexploitation could cause progressive depletion of the groundwater resources and more budget deficits.     Hydrogeological investigation is as the first step in identifying and assessing the water volume storage to provide management plans for the protection of available fresh water. In the study area, piezometric water level data and chemical features of the groundwater samples from the alluvial aquifer in the Geysoor plain were measured to assess the hydrogeological condition, groundwater balance and hydrochemistry characteristics of the aquifer. The decline of the piezometric heads in the study area is indicative of an imbalance between recharge and extraction of groundwater and points to the necessity for restriction on groundwater extraction from these aquifer systems to avoid adverse effects. The Geysoor Plain with a negative groundwater balance showed a considerable reduction in the groundwater level. Therefore, the overexploitation of the wells and consequent change in hydrologic regime is the main etiologic factor of the groundwater quality degradation in the central part of the plain. Along the direction of groundwater flow towards the outlet of the plain, the salinity has been reduced due to recharging by carbonate formation in the eastern regions. This detailed investigation is of a particular importance for sustainable management of these groundwater resources, especially in arid zones coupled with increasing exploitation for irrigation and domestic water supply which requires immediate attention.

Eshtehard plain has been subjected to over exploitation of ground water in recent years and disregarding to the quality of ground water was led to pollution and salinity of aquifer. In this research the spatial distribution of some of the qualitative properties of ground water such as Electrical Conductivity, the concentration of sulfate and chloride and finally the drawdown of water table are studied. For this purpose, initially on the base of existing data in the field of water table during 1376-90 years, the graph of long-term changes in water levels in the aquifer is plotted and the average annual drawdown is calculated 0.69 meter. Also on the base of continuous measurement of groundwater level of the 16 wells in the study area, the map of iso-level groundwater is produced for the year of 1389-90. Then, 14 resources including 9 wells and 5 aqueducts are selected and two sampling is done in the 1389-90. After chemical analysis of samples, the concentrations of cations and anions suchas sulfate and chloride are determined and the maps of EC, SO4 and Cl are drawn. Also annual comograph of aquifer is produced using arithmetic average for 8 years period between 1382-90. Results showed that owing to limited recharges of the study area, unbalanced exploitation is led to drawdown of water table and changing the flow path in the aquifer. On the base of annual hydrograph, the average annual recharge is 29.7 m cubic meter and average annual drawdown of water table is 0.69 meter which shows the over exploitation of aquifer. The maps of EC, SO4 and Cl indicated that brackish waters has been spread from the north of plain to the southern parts of plain so the EC is increased from 4258.1 micromoss in the 1382-83 to the 6733.9 between 1389-90. Given that in the northern part of plain, the concentration of chloride is high, the infiltration of brackish waters with high chloride has had greater increase than sulfate. So the gradual salitinization of groundwater and the spreading of saltwater front into the fresh water front can be seen in this area as one of the consequences of continuous drawdown of water table or over exploitation. Therefore continuation of the current trend does not draw a clear vision for the plain.

The study of the physical properties (geophysical methods) of rocks associated with its mechanical properties has recently received lots of attention. Recent studies show that geophysical methods especially the seismic and geoelectric methods are able to estimate the mechanical parameters and recognize their spatial variations, including anisotropy. Meanwhile, electrical and seismic methods are the most used one. Electrical measurement is one of the non-invasive geophysical methods commonly used by engineers working in various fields such as mining, geotechnical, civil, underground engineering as well as oil and gas mineral explorations. This method can be applied both in laboratory and in the field. Numerous scientists have focused on the relation between resistivity and porosity. However, there is a very limited study on the relation between the electrical resistivity and the rock properties apart from porosity. In this paper, changes in the electrical conductivity of rocks during a uniaxial compression test were investigated in laboratory. The uniaxial compressive strength, elastic modulus, and density values of the samples were determined in laboratory. We installed special electrodes on seven nearly saturated core samples in order to measure the resistivity. Core samples had a 52-mm diameter and a 110-mm length. Two-electrode as well as four-electrode arrays were both used in resistivity monitoring in laboratory. Using a four-electrode array minimized the undesirable electrode polarization effects. In the four-electrode array, we used two non-polarizing Ag/AgCl electrodes mounted on the core sample. Our laboratory observations showed that there was not any electrode polarization effect. When we used a two-electrode array, the resistivity changes were less than 5 percent compared to a four-electrode array. In our laboratory investigation, we used different sedimentary core samples including sandstone, fossilioferous limestone and travertine. Maximum resistivity observed for the travertine core sample was less than 12 kohm. During the uniaxial compressive test, deformation measurements were made and the stress–strain curves were plotted. Tangent Young’s modulus values were obtained from stress–strain curves at a stress level equal to 50% of the ultimate uniaxial compressive strength. Sandstone core samples showed a resistivity increase in the whole strain range. On the contrary, the fossiliferous limestone samples (thin section showed that the sample was composed of tiny calcium fossils in a fine aggregate of micrite cementation) showed a resistivity decrease in the whole strain range. Travertine and limestone showed an intermediate behavior (resistivity increased in the lower strain and it decreased in the higher range). In other words, the onset of new crack formation occurs well inside the quasi-linear part of the stress-strain curve. The quasi-linear portion of the stress-strain curve was the result of a competition between closure of one population of cracks, and the growth of new propagation of the existing cracks. Resistivity behavior during a uniaxial compression load is closely related to the pores in the lower strain ranges and then to the new induced fractures in higher strains. Our results showed that the electrical resistivity may be a representative measure of the rock properties. Additionally, the effect of certain minerals on the rock’s resistivity must be taken into account. The results indicated that the rock structure had an important effect on the resistivity behavior during a mechanical loading.