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Featured Application: Deep geoelectrical mapping of subsurface objectives. This work presents a case study of a geoelectrical exploration of understudied mud volcanoes in Romania, specifically the Pâclele Mici mud volcano from Buzău County. Using a geoelectrical technique facilitated by the distributed network of V-FullWaver equipment, we present, to our knowledge, the first deep 3D case study of a mud volcano in the country. The findings indicate that while geoelectrical surveys in such environments are met with important challenges in terms of soil conductivity, they nonetheless provide a viable approach to uncovering the complex structures and processes of mud volcanoes. We map a part of the mud volcano, showing that the active subsurface part corresponds only partly with what is visible on the surface, and suggest a framework for an in-depth analysis of the extensive mud volcano area. [ABSTRACT FROM AUTHOR]

Landslides are a significant hazard in mountainous regions, especially when influenced by construction activities such as tunnel excavation. In this paper, we aim to conduct a slope stability analysis as a result of tunnel blasts using quasi-3D subsurface models based on resistivity values. The study site is a construction area for the Jakarta-Bandung High-Speed Train tunnel, located in a mountainous region undergoing drill-and-blast excavation. This excavation method makes the area susceptible to landslides, which pose a threat to settlements in the Padalarang subdistrict, West Bandung Regency, Indonesia. Data was collected along four lines in 2D, and the dipole-dipole array was used to enhance resolution. Data modeling was carried out using ResIPy v3.2.3 software to create 2D and quasi-3D subsurface models based on resistivity values. The study findings indicate that the study area exhibits three resistivity ranges: low resistivity (0-30 Ωm), medium resistivity (31-49 Ωm), and high resistivity (>50 Ωm). Utilizing quasi-3D imaging, we were able to identify the dimensions and presence of slip surfaces, which can be categorized as shallow (1.5-5 m) and deep (5-20 m) criteria. This study successfully applied the quasi-3D geoelectrical approach in a susceptible environment to detect potential landslide zones.

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Uniaxial compressive strength is one of the most important mechanical characteristics of rocks, and its prediction is essential in most rock engineering projects. Recently, several types of research have been conducted regarding the relationship between the petrophysical and geomechanical properties of rocks and geophysical parameters, among which geoelectric and seismic methods have been the most utilized and efficient. In this research, the prediction of uniaxial compressive strength (UCS) has been investigated utilizing the geoelectrical method. In the present study, after sampling from the studied area, the core samples were saturated and by installing special electrodes, the changes in electrical resistivity during compressive stress loading were measured and monitored in the laboratory environment. Laboratory samples with various structures and textures indicated different electrical behaviors during the application of compressive stress which stresses the significant effect of the volume proportion of aggregates on petrophysical and geomechanical properties. In core samples prepared from fault breccias and alluvial materials with a volumetric block proportion (VBP) of 25–75%, a significant correlation was observed between the UCS and the measured electrical resistivity values. The neuro-fuzzy model presented with a decision factor (R2) of 99.7%, root sum of square error (RMSE) of 2.511, geometric mean error ratio (GMER) of 0.865, and relative improvement index (RI) of 71.08 can predict uniaxial compressive strength (UCS) more accurately than artificial neural network and multivariable regression methods. [ABSTRACT FROM AUTHOR]

This work presents a case study of a geoelectrical exploration of understudied mud volcanoes in Romania, specifically the Pâclele Mici mud volcano from Buzău County. Using a geoelectrical technique facilitated by the distributed network of V-FullWaver equipment, we present, to our knowledge, the first deep 3D case study of a mud volcano in the country. The findings indicate that while geoelectrical surveys in such environments are met with important challenges in terms of soil conductivity, they nonetheless provide a viable approach to uncovering the complex structures and processes of mud volcanoes. We map a part of the mud volcano, showing that the active subsurface part corresponds only partly with what is visible on the surface, and suggest a framework for an in-depth analysis of the extensive mud volcano area.

Groundwater Survey in Bolo District, Palibelo District, Woha District, Langgudu District, Wawo District, Sape District, Wera District, Bima Regency, and West Nusa Tenggara for drought mitigation has been implemented. The study area is located in the majority of hilly areas with soil vulnerable to drought. Water is abundant during the rainy season. However, during the dry season, the ground surface is cracked, and there needs to be more clean water. This situation is troubling the community and the Regional Government of Bima Regency. The study was conducted using the Schlumberger resistivity geoelectric configuration method. The measurement point is in seven sub-districts, with a total of 18 measurement points. Research location at 118,6305833 SL; -8,3008888889 EL up to 119,01925 SL; -8,704638889 EL or covers an area of ± 1,961 km2. The length of the path used is a maximum of 400 meters. Based on the results of geoelectric resistivity data, two types of aquifers are found, open aquifers with depths ranging from 1 m to 26 m and aquifers depressed with depths ranging from 70 to 115 m. In addition to geoelectric information data, drilling data is also used at points that can be reached by heavy equipment in Lanta Barat Village, Lambu District. At the drilling point, the presence of an aquifer layer is obtained at a depth of about 80 meters. Residents then use the discovery of the wellbore to meet their need for clean water.

Hydrocarbon contamination occurs as a result of corrosion of buried pipelines, sabotage of oil and gas facilities and spills during petroleum product transportation. This study was undertaken to characterize hydrocarbon impacted sites in Erhoike community, Ethiope East local government area, Delta State, Nigeria using ten (10) transects were established in grid format to attain geoelectric data that were inverted to yield 2D resistivity structure and 3D depth slices respectively. The 2D results show that the hydrocarbon impacted zones are marked by very high resistivity values ranging from 637 ohm-m to more than 17000 ohm-m from the surface to a depth in excess of 31.9 m in places within the study area. In the same vein, the 3D result indicated that bulk of the contaminant has progressively moved to deeper depth with most of the plume found at between 25.0 – 33.7 m. The data obtained show that the site has been impacted by hydrocarbon contaminant. It also shows that the hydrocarbon moved downwardly at greater depth into the subsurface, through a porous medium - sandy layer. Finally, the study has demonstrated the effectiveness of the adopted geophysical techniques in delineating hydrocarbon contamination. [ABSTRACT FROM AUTHOR]

Ketersediaan air tanah di Kelurahan Hargomulyo, Kapanewon Gedangsari, Kabupaten Gunung Kidul, D. I. Yogyakarta belum bisa mencukupi dengan banyaknya jumlah penduduk yang ada. Maka dari itu, dibutuhkan suatu studi pendugaan air tanah guna mendeteksi keberadaan lapisan air tanah (akuifer) di wilayah penelitian. Studi ini terlaksana pada tanggal 7 Agustus 2021 dengan titik ukur sebanyak 3 titik. Pendugaan kedalaman akuifer dalam studi ini memakai metode VES (Vertical Electrical Sounding) dengan menggunakan susunan elektroda Schlumberger. Metode VES adalah salah satu metode tahanan jenis yang bisa dimanfaatkan untuk pendugaan lapisan litologi bawah permukaan seperti lapisan akuifer. Pengambilan data lapangan VES dilakukan dengan memakai dua buah elektroda arus stainless steel dan elektroda potensial tembaga. Panjang bentangan pada tiap-tiap titik ukur, yaitu 400 meter. Data sounding tiap titik pengukuran diinterpretasi dengan memakai perangkat lunak HIRA, kemudian hasil interpretasi ditampilkan dalam bentuk log tahanan jenis dengan memperlihatkan nilai tahanan jenis, kedalaman, serta ketebalan tiap-tiap lapisan. Berdasarkan hasil pengolahan data diperoleh 10 hingga 12 lapisan batuan. Hasil analisis dari korelasi antar titik pengukuran dalam tiap lintasan memperlihatkan bahwa di daerah penelitian ada dua jenis akuifer, yaitu akuifer dangkal dan akuifer dalam. Akuifer dangkal ditemukan pada kedalaman 5-16 meter dengan nilai resistivitas berkisar antara 12,79 sampai 12,83 ohm.m, sedangkan akuifer dalam ditemukan pada kedalaman 22-85 meter dengan nilai resistivitas berkisar antara 10,56 sampai 16,85 ohm.m.

Hydrocarbon contamination occurs as a result of corrosion of buried pipelines, sabotage of oil and gas facilities and spills during petroleum product transportation. This study was undertaken to characterize hydrocarbon impacted sites in Erhoike community, Ethiope East local government area, Delta State, Nigeria using ten (10) transects were established in grid format to attain geoelectric data that were inverted to yield 2D resistivity structure and 3D depth slices respectively. The 2D results show that the hydrocarbon impacted zones are marked by very high resistivity values ranging from 637 ohm-m to more than 17000 ohm-m from the surface to a depth in excess of 31.9 m in places within the study area. In the same vein, the 3D result indicated that bulk of the contaminant has progressively moved to deeper depth with most of the plume found at between 25.0 – 33.7 m. The data obtained show that the site has been impacted by hydrocarbon contaminant. It also shows that the hydrocarbon moved downwardly at greater depth into the subsurface, through a porous medium - sandy layer. Finally, the study has demonstrated the effectiveness of the adopted geophysical techniques in delineating hydrocarbon contamination.

Municipal solid waste (MSW) management is challenging as a whole. Global waste generation is expected to continue to increase in the coming years, and landfills are currently the primary destination. Therefore, the stability of these structures must be carefully evaluated to prevent failures and associated health and pollution risks, which implies the determination of waste properties using more reliable approaches. This paper presents a scoping review of field data from MSW landfills and outlines suggestions for future work. Studies published in the past twenty years were selected following a systematic search process in databases. Aspects discussed include (1) strength parameters and soil behavior type from in situ testing, (2) elastic moduli from seismic wave propagation, and (3) moisture content from geoelectrical measurements. Although the values of geotechnical parameters have varied due to waste heterogeneity and applied methods, the trends observed with depth and age could be compared. Research opportunities involve the spatial analysis of mechanical properties at a given site, seismic response of landfills with high organic content and saturation degree, interpretation of long-term resistivity monitoring, and combination of electrical properties to assess the degradation stages within the waste mass. [ABSTRACT FROM AUTHOR]

Identification of groundwater potential through the characteristics of the aquifer layer is an important study. This is useful for knowing the availability of shallow groundwater in an area. Arjosari Village, Kalipare District, Malang Regency is an area that often experiences shortages in meeting daily water needs, especially during the dry season. The availability of groundwater at the research site is influenced by the area's topographical conditions, which range from flat to very steep.This study aims to identify the location of the aquifer and groundwater potential in Arjosari Village. This study uses the Schlumberger configuration to identify aquifers and groundwater. This method adheres to the basic principle that each rock layer has a different resistivity value. In addition to rock material type factors, the level of saturation and chemical composition in water affects the value of resistivity. The results showed that the aquifer characteristics and groundwater potential were different for each lithological condition, slope, soil type, and land use. In the research location, shallow aquifers were found less than 20 meters while there were also deep aquifers located more than 25 meters below the ground surface. Shallow aquifers can be used as a water source by the community, especially to meet their daily water needs. The results of this study are used for Geography learning on hydrological material. Identifikasi potensi airtanah melalui karakteristik perlapisan akuifer merupakan suatu kajian yang penting. Hal ini bermanfaat untuk mengetahui ketersediaan air tanah dangkal di suatu wilayah. Desa Arjosari, Kecamatan Kalipare, Kabupaten Malang merupakan wilayah yang sering mengalami kekurangan air dalam pemenuhan kebutuhan sehari-hari khususnya saat musim kemarau. Kondisi topografi wilayah yang bervariasi dari datar hingga sangat curam merupakan faktor yang mempengaruhi keterdapatan airtanah di lokasi penelitian. Penelitian ini bertujuan mengidentifikasi lokasi keberadaan akuifer dan potensi airtanah di Desa Arjosari. Penelitian ini menggunakan konfigurasi Schlumberger untuk mengidentifikasi akuifer dan airtanah. Metode ini berdasarkan prinsip dasar bahwa masing-masing perlapisan batuan mempunyai nilai tahanan jenis yang berbeda-beda. Selain faktor jenis material batuan, tingkat kejenuhan dan komposisi kimia dalam air mempengaruhi nilai tahanan jenis. Hasil penelitian menunjukkan bahwa karakteristik akuifer dan potensi airtanah berbeda pada setiap kondisi litologi, kemiringan lereng, jenis tanah, dan penggunaan lahan. Di lokasi penelitian ditemukan akuifer dangkal kurang dari 20 meter sementara terdapat pula akuifer dalam yang terletak lebih dari 25 meter di bawah permukaan tanah. Akuifer dangkal dapat dimanfaatkan sebagai sumber air oleh masyarakat khususnya untuk memenuhi kebutuhan air sehari-hari. Hasil penelitian ini dimanfaatkan untuk pembelajaran geografi pada materi hidrologi.

Increased groundwater extraction from aquifers in Holo-Quaternary rock formations in Lampung Bay has caused saltwater intrusion. This indication appears in several community wells and can spread further inland. Therefore, this study aims to identify the distribution of areas exposed to saline water and the boundaries of areas that have not, especially in the Holo-Quaternary Formation. This research uses the geoelectric method integrated with salinity data and the Soil Penetration Test (SPT) analysis at four drilling points. A total of 4 lines of Electrical Resistivity Tomography (ERT) and 8 points of Vertical Electrical Sounding (VES) have been acquired with a Schlumberger configuration with an AB/2 span of up to 200 meters. Meanwhile, the salinity data was measured directly from 60 samples from community wells. The ERT and VES analysis results show that the coastal aquifer in Lampung Bay is at a depth of 2–24 m. SPT analysis identified interbedded sand, silt, and clay which were interpreted as marine sedimentation from the Holo-Quaternary Formation layer. Groundwater is only in shallow aquifers (less than 24 m) but has experienced seawater intrusion with low resistivity values between 9–20 ohm m. The distribution of high salinity values up to 3,100 ppm has reached more than 1 km from the coastline. Furthermore, ERT results reinforce this finding, which shows low resistivity values of less than 10 ohm m in the shallow aquifer zone. VES data detects low resistivity values (18 ohm m) at a depth of 12–13 m.

A vertical electrical sounding survey was carried out in northern Gaza Strip (Gaza City, Jibalya, Bayt Lahya and Bayt Hanun), Palestine to study the groundwater conditions and evaluate its quality and distribution. The survey included twenty-six (26) traverses with variable lengths in the range 200-500 m. The geoelectrical survey revealed that the resistivity of the study area varies in a wide range mostly 9 to 850 Ωm, subdivided into three subsurface zones. The first zone represents the dry sandstone and alluvial that attains the highest resistivities (100-850 Ωm) with variable thicknesses in the range 26-80 m beneath the whole study area. This zone is characterized by the presence of thin layers of clay and silt in some localities that reduced the resistivity to 15-25 Ωm. The second zone represents the fresh water saturated calcareous sandstone (locally named Kurkur) with resistivities in the range 22 -39 Ωm). The thicknesses of this zone is about 55-70 m in the western part of the study area and increased to 110 m in the east. The surface of this zone shows a gentle westward gradient, which indicates a general flow of water towards the Mediterranean Sea. The third zone represents saline water saturation with low resistivities, mostly 9 Ωm -10 Ωm close to the Mediterranean shore, located at 60 m below sea level and 100 m beneath the eastern side of the study area. Beneath the eastern part of the study area, an anomalous low resistivity of 2-3 Ωm is observed within the fresh water zone, which indicates groundwater pollution near the buffer zone caused by agriculture activities and untreated pumped wastewater. [ABSTRACT FROM AUTHOR]

Groundwater is an appreciated and vital natural resource in the world, and it is of the utmost essential for the growth and development of a country. Nevertheless, assessing the groundwater potential and its recharge region is still ambiguous due to the nature of groundwater. In this study, the groundwater potential of the Weserbi Guto Laga Qawe Catchment Sululta area was assessed using VES and GIS methods. For the model, thematic layers were generated from the geophysical investigation, existing maps, and field survey results and were integrated into the GIS environment to delineate the groundwater potential zones. Factors such as lineament density, drainage density, elevation or topography, slope gradient, aquifer resistivity, and lithology were derived, reclassified, and scaled to common ranges and assigned with appropriate weights. The groundwater potential zonation model of the site was produced by the multicriteria evaluation method. Accordingly, the geometrical interval method was utilized to classify the index into three zones (high, moderate, and low) to produce the map. The model result revealed that a large part of the study area fell into the high zone with 50.14 % (3669.99ha). whereas 35.85% (262.72ha) and 14.01% (1024.95ha) show moderate and low groundwater potential, respectively. The resulting map was validated using eleven existing water level data points and the result was found to be in good agreement with the model.

Today, the use of underground dam technology is considered as one of the efficient methods of rainwater harvesting systems and flood management in order to eliminate the shortage of water resources in arid and semi-arid regions. Underground dams block the subsurface flow of water across the river and stores it in the riverbed. The construction of an underground dam, while helping the environment, will compensate for surface water and expand cultivated lands. The content of water extracted from these dams depends on the hydraulic and hydrodynamic of alluvial sediments. The aim of the present study was to determine the hydrodynamics of the riverbed deposits of the Meshnaqeh underground dam in the north of Lake Urmia. Feasibility study and location of the dam axis was done using ArcGIS system. Three options were determined and finalized after a geophysical evaluation of the location of the main alluvium with a thickness of 14 m. Engineering studies showed that the sedimentation of bed was in gravel and sandy soils in UNIFIDE division with more than 78% of sand, and according ASTM method, were in the GC and GM. Lefranc experiment showed that alluvial sediments had a permeability of 0.0012 cm/s and a porosity above 35%. According to the special discharge, 163,800 m3 of water can be harvested in each flooding period. Drinking water and sanitation of the region is provided hundreds of kilometers away through Zarrinehroud water transmission line. The construction of this dam with a realistic view of the real value of water and its role in human societies, will have constructive environmental effects requiring independent study.

Self-Potential methods that have advantages in providing more extensive and integrated information to better ensure that geothermal areas have potential geothermal resources. This study discusses the geothermal system in the Ijen volcano area based on the value of resistivity and potential different from the subsurface structure. The stages in the implementation of research programs are (1) literature study, carried out to obtain accurate and up-to-date information, (2) data retrieval, carried out to obtain primary and secondary data, (3) data search, data processing, and data interpretation, carried out using Res2div and Surfer software to obtain subsurface structure mapping (4), evaluation, was carried out as a monitoring of geothermal resource potential mapping research. The modeling results were obtained from the subsurface layer in Blawan geothermal manifestation consisting of 3 zones with upper resistivity zones (> 10 ohm to 50 ohm meters), reservoir zones (> 50 ohm meters to 100 ohm meters) and heat source zones (> 100 ohm meters, based on the isopotential contour map, that the Blawan region is a destructive zone.

Abstract Through time, the large ceremonial centers of the Peruvian pre-Hispanic coast have played an important role as Pachacamac, renowned for its famous oracle, which was an important site for cult and pilgrimage, where the use of water entered largely into ritual functions during Inca age and before. The sanctuary’s landscape included sea, valley and lomas (ecosystem of grassy, seasonal knolls), and a complex and elaborate system of springs and canals which seem to use both the natural water table and the waters of the nearby Lurin river. In this sacred landscape there are over fifty buildings associated to springs and canals, built during a long occupation spanning over a 1000 years. This entire system must have been connected to Urpiwachaq lagoon, located to the northeast and only a few kilometers away from the sea. The origins of the lagoon and its relationship with the archaeological site evoke creation myths for the waters and marine species of the central coast. In this paper we discussed the results obtained from the geophysical investigations performed to define the water management system in the sanctuary and their connection with the lagoon. In particular, geo-electric, geomagnetic and ground penetrating radar prospections were carried out in the monumental area to determine the trajectory of the waters that drained into the lagoon from a series of ponds and canals. The interdisciplinary work in both the lagoon and monumental area provided a valuable source of information useful to better understand the history and function of the Pachacamac sanctuary in prehispanic times.

One of the sectors supporting the economy of Indonesia is the mining industry. In East Kalimantan, coal mining activity has been done widely. Coal-mining open-pit activities play a significant role in the economic growth and the advancement of technology for Indonesia. Therefore, it is necessary to study every critical aspect including the hydrological and hydrogeological studies but especially aquifers, so that mining activities can be well managed and the impact on the environment can be overcome. The study of the aquifer from the study area was based on the resistivity value of the materials obtained through one of the geophysical methods that are the geoelectrical resistivity method, by using Wenner-Schlumberger configuration. In this study, geoelectrical resistivity method was performed in order to find out the condition of the subsurface by injecting two electrodes into the soil using direct current (DC) with certain distance so that potential difference can be known and resistivity information of subsurface layers can be obtained. The obtained resistivity value of the material was then interpreted so that the type of aquifer in the study area can be known. The interpretive results of the resistivity values of the materials in the study area showed that the distribution of aquifers based on measurement of a geoelectrical line of line number one, two and three, ware semi-confined aquifers. Meanwhile, the distribution of aquifers of line number four was confined aquifers. Based on the results of hydrological studies, the area of study has an annual rainfall of 3,053.704 mm/year with a watershed area of 16.586 km2. The evapotranspiration value of the study area is 1,784.21 mm/year, the surface run-off is 913.51 mm/year, and groundwater recharge is 355.98 mm/year.

The subsurface is made up of distinct geologic materials existing at various depths. In a basement complex terrain, the lithologic unit that can be noticed is made up of the weathered layer, weathered/fracture basement and fresh basement. This research work was carried out at Ozalla community in Owan West Local Government Area of Edo State Nigeria, The study area is a basement complex area with some parts as transition zone, two dimensional geoelectrical resistivity survey was use to determine the subsurface resistivity distribution of the subsurface and interpreted with Res2Divn software to determine the subsurface Lithology and the mineral composition of the study area. The result from the study shows some buried subsurface minerals from the tomography images of the subsurface shows that at a depth between 10 m to 12 m reveals the composition of Alluvium soil, Shale, Slate, Sandstone, while at a depth between 13 m to the last depth of investigation reveals Quartz, Marble, Basalt, and Granite with apparent resistivity values ranging from 50 Ωm to 1500 Ωm. From the obtained results, slightly weathered/schist formation are the aquifer zone which shows that borehole drilling in this area is achievable at the depth of 40m, which allow big reservoir within the aquifer unit and overburden is thick enough for aquifer to accommodate high ground water potential due to presences of permeable rock. Keywords: Geoelectrical, Subsurface, Resistivity, Imaging

The subsurface is made up of distinct geologic materials existing at various depths. In a basement complex terrain, the lithologic unit that can be noticed is made up of the weathered layer, weathered/fracture basement and fresh basement. This research work was carried out at Ozalla community in Owan West Local Government Area of Edo State Nigeria, The study area is a basement complex area with some parts as transition zone, two dimensional geoelectrical resistivity survey was use to determine the subsurface resistivity distribution of the subsurface and interpreted with Res2Divn software to determine the subsurface Lithology and the mineral composition of the study area. The result from the study shows some buried subsurface minerals from the tomography images of the subsurface shows that at a depth between 10 m to 12 m reveals the composition of Alluvium soil, Shale, Slate, Sandstone, while at a depth between 13 m to the last depth of investigation reveals Quartz, Marble, Basalt, and Granite with apparent resistivity values ranging from 50 Ωm to 1500 Ωm. From the obtained results, slightly weathered/schist formation are the aquifer zone which shows that borehole drilling in this area is achievable at the depth of 40m, which allow big reservoir within the aquifer unit and overburden is thick enough for aquifer to accommodate high ground water potential due to presences of permeable rock. [ABSTRACT FROM AUTHOR]

Electrical Resistivity Tomography (ERT) was used to map and detect the subsurface contaminant plumes from the cassava effluents in the various cassavas processing mill in Ozalla Area of Edo North, Edo State, Nigeria. The result from the 3D resistivity images shows clearly the distribution of the plumes from all the profile lines in the surveyed area. From the results it is evident that at a depth of 2.5 m - 21.9 m with resistivity values between 6.2 Ωm -13.1 Ωm the plumes were observed. The results thus point out the need for environmental Education and proper management/ location of cassava processing sites by the relevant agencies of Government. Keywords: Geoelectrical, Mill, Contaminant Plume, Cassava effluent, Imaging

The grey wolf optimizer (GWO) is a novel bionics algorithm inspired by the social rank and prey-seeking behaviors of grey wolves. The GWO algorithm is easy to implement because of its basic concept, simple formula, and small number of parameters. This paper develops a GWO algorithm with a nonlinear convergence factor and an adaptive location updating strategy and applies this improved grey wolf optimizer (improved grey wolf optimizer, IGWO) algorithm to geophysical inversion problems using magnetotelluric (MT), DC resistivity and induced polarization (IP) methods. Numerical tests in MATLAB 2010b for the forward modeling data and the observed data show that the IGWO algorithm can find the global minimum and rarely sinks to the local minima. For further study, inverted results using the IGWO are contrasted with particle swarm optimization (PSO) and the simulated annealing (SA) algorithm. The outcomes of the comparison reveal that the IGWO and PSO similarly perform better in counterpoising exploration and exploitation with a given number of iterations than the SA. [ABSTRACT FROM AUTHOR]

Research of the groundwater in Pakel, Bandung and Besuki Subdistricts, Tulungagung District has been implemented. The research area is located in the rice field area, previously an area of annual flooding inundation during the rainy season. This situation troubles the community and local government of Tulungagung District. During the dry season, the mud cracks, making it difficult as agricultural land. The research was done using Geoelectrical Resistivity Schlumberger configuration method. The measurement point is located in the three Subdistricts with a total of 19 measurement points. The study location is at 111.75988880 EL; -8.2264166670 SL to111.84541670 EL; 8.1309166660 SL or covers an area of 101 km². The length of the track used is a maximum of 600 meters. Based on the results of the geoelectrical resistivity data, it was found two types of aquifers, which are open aquifers in depth ranging from 6 m to 21 m and a confined aquifer in depth ranging from 90 to 115 m. In addition to the geoelectrical information data, drilling was done at an accessible point by heavy equipment in the Gempolan Village, Pakel Subdistrict. At the drilling point, artesian wells were obtained at a depth of 108 meters and can rise to 2 meters above the soil surface. The discovery of artesian wells is then used by residents to meet the needs of clean water considering that in this area most wells are smell and iron contain. [ABSTRACT FROM AUTHOR]

Electrical Resistivity Tomography (ERT) was used to map and detect the subsurface contaminant plumes from the cassava effluents in the various cassavas processing mill in Ozalla Area of Edo North, Edo State, Nigeria. The result from the 3D resistivity images shows clearly the distribution of the plumes from all the profile lines in the surveyed area. From the results it is evident that at a depth of 2.5 m - 21.9 m with resistivity values between 6.2 Om -13.1 Om the plumes were observed. The results thus point out the need for environmental Education and proper management/location of cassava processing sites by the relevant agencies of Government. [ABSTRACT FROM AUTHOR]

Subsoil evaluation within a proposes site for civil engineering structure by using geoelectrical and geotechnical methods of investigation carry out. The study aims to provide information on the stratigraphy, thickness, nature, and competence of the subsoil. Eighteen (18) Vertical Electrical Sounding (VES) stations using Schlumberger configuration occupy and complement with geotechnical analysis of eighteen (18) soil samples collect at all the VES points at depth not exceeding 1m within the study area. The VES interpretations delineate four main geoelectric sequences which comprise of the top soil, mixture of clay and sand, gravely sand and sandy gravel. The top soils are generally thin (< 2 m) and majorly composes of clayey silt/ silty clay /sandy clay/ clayey sand/ fill materials. The layer resistivity ranges from 0.75-19.6 Ωm for topsoil, 1.71 - 6.7 Ωm for clay and sand mixture, 0.01 – 2.69 Ωm for saturated gravelly sand layer and 4.23- 4.61 Ωm for saturated sandy gravel layer. Low resistivity values at the study area are due to moisture and clay content within deposits at the study area. The geotechnical results show that the soil is relatively high clay content, intermediate to high moisture content and high plasticity. It concludes from the combined results above, that the topsoil is generally geotechnically less competence soil and may not serve as a good foundation material, therefore shallow foundation may not be feasible in studied area and, for engineering structure to be erected on such soil there is need for soil improvement or pilling to the sand layer.

A DC resistivity survey of Oba Akoko in southwestern Nigeria was carried out over the three major rock units of the Migmatites; granite, granite-gneiss and grey-gneiss underlying the study area. The objectives of the study included the delineation of the subsurface geological/geoelectrical sequences and aquifer unit(s) and types with a view to assessing prospective site for groundwater potential rating of the area. Fifty nine Schlumberger vertical electrical sounding data were acquired. The inter-electrode spacing (AB/2) varied from 1 to 100 m with maximum spread length of 200 m. The ground resistance measurements were made with ABEM SAS 1000 resistivity meter. Seven distinctive sounding curve types were obtained from the data inversion/interpretation techniques. These included H, A, HA, AA, HK, QH and AK curve types. Maximum of four geological/geoelectric layers were delineated; the top-soil, clay/clayey sand/sandy clay weathered basement, partly weathered/fractured basement and fresh basement with resistivity values that ranged from 20 - 360 Ωm, 25 - 850 Ωm, 476 - 979 Ωm and infinity ohm-m respectively, while the thickness values ranged from 0.4 - 3.8 m, 1 - 17 m, 4 - 17 m respectively, and depth to rock head of 24.9 m. Isopach maps of the weathered layer and overburden showed spatial distribution of the thickness with a relatively thick weathered/fractured basement not less than 10 m as basement depressions or pockets of closures. The thickness pattern showed uneven basement bedrock interface. It may, therefore, be concluded that groundwater potential of the study area is generally low arising from shallow depth to basement or thin regolith and few fracture density in places in the area. The localized fractured bedrocks and weathered basement columns/basement depressions arising from the deep weathering of the parent rocks may have constituted the main sustainable aquifer/groundwater storage units for consumption via borehole groundwater abstraction in the area. [ABSTRACT FROM AUTHOR]

Vertical Electrical Sounding (VES) proved to be an important tool for mapping the freshwater-saltwater interface. Seawater intrusion is serious problem especially in coastal areas. 14 Vertical electrical soundings with Schlumberger array were carried out (perpendicular to the coast) in southern part of the coastal aquifer in Gaza Strip (Khan Younis and Rafah Governorates) to study the subsurface geologic formation and delineation of seawater intrusion into freshwater aquifer. Lithology and hydrochemistry data from 12 bore holes were used to integrate the results. The results reveals that 50% of the total sounding are interpreted of 3 layer modes, while the other 50% are of 4 layers model. Interpreted 2D geoelectrical models (in two cross sections parallel to the coast line) showed that seawater intrusion with electrical resistivity less than 2Ωm is dominant along the section parallel to coast line at 400m east of it and for shallow depths (3-10m depth), while in the other section (1000m) east of the coast line seawater intrusion is detected in some places while the other parts still have brackish/fresh groundwater with resistivity more than 10Ωm at different depths (26-50m). [ABSTRACT FROM AUTHOR]

A large amount of hydrocarbon reservoirs in the world are in the secondary recovery stage and improving this step in the exploitation of these reservoirs would greatly benefit the oil industry. Secondary recovery involves injecting brine in some wells in order to maintain reservoir pressure. The injected water moves mainly through the channels with higher permeability of the reservoir rock. The identification of these channels would allow the development of technical strategies to close them. In this context, the ability to detect brine flow pathways after injection is a goal of this work. Given the high electrical conductivity of brine, the use of geoelectrical methods can be useful to detect and monitor flow evolution. The limitations in the application of this method are due to the characteristics of the target: a very conductive fluid is usually contained in paths with dimensions that are much smaller than the depth at which it is located. Therefore, our objective is to overcome these constraints in order to find the strategies required to successfully detect and eventually monitor the movement of brine flowing from injection wells. In this work, we studied the feasibility of detecting brine in an oil reservoir with surface-downhole electrical measurements. To achieve this, we designed an electrical model of the reservoir from well data and numerically simulated the forward geoelectrical response to determine the conditions under which the anomaly, i.e., the accumulation of brine, can be identified. Our results show that once the initial location of the brine is known, by installing potential electrodes in a single well the direction of brine migration can be determined, even in unfavorable conditions with relatively few surface measurements. In the case of a well equipped with permanent electrodes, this could be an efficient method to monitor the evolution of the brine plume. [ABSTRACT FROM AUTHOR]

Highlights: [•] The study covers the virgin hydrogeological setting of southern Benue Trough. [•] Delineate architecture of different aquifers using an integrated approach. [•] Estimation of aquifer parameters from pumping test, grain size and resistivity. [•] Processes controlling groundwater chemistry using cross plots and ratios. [•] Assessment of groundwater for irrigation application. [ABSTRACT FROM AUTHOR]

Groundwater is an appreciated and vital natural resource in the world, and it is of the utmost essential for the growth and development of a country. Nevertheless, assessing the groundwater potential and its recharge region is still ambiguous due to the nature of groundwater. In this study, the groundwater potential of the Weserbi Guto Laga Qawe Catchment Sululta area was assessed using VES and GIS methods. For the model, thematic layers were generated from the geophysical investigation, existing maps, and field survey results and were integrated into the GIS environment to delineate the groundwater potential zones. Factors such as lineament density, drainage density, elevation or topography, slope gradient, aquifer resistivity, and lithology were derived, reclassified, and scaled to common ranges and assigned with appropriate weights. The groundwater potential zonation model of the site was produced by the multicriteria evaluation method. Accordingly, the geometrical interval method was utilized to classify the index into three zones (high, moderate, and low) to produce the map. The model result revealed that a large part of the study area fell into the high zone with 50.14 % (3669.99ha). whereas 35.85% (262.72ha) and 14.01% (1024.95ha) show moderate and low groundwater potential, respectively. The resulting map was validated using eleven existing water level data points and the result was found to be in good agreement with the model., Competing Interests: The authors declare no conflict of interest., (© 2022 The Author(s).)

Abstract: Nanoparticles have grown in importance over the last decade with significant consumer and industrial applications. Yet, the behavior (fate and transport) of nanoparticles in the environment is virtually unknown. Research is needed to identify, characterize, and monitor nanomaterials in the subsurface. Here, we investigate the spectral induced polarization (SIP) response of nanometallic powders (nZVI, nAg, nTiO2, nZnO, and nCeO2) in porous geologic media. Our main objective is to determine the sensitivity of the SIP response (0.1–10,000Hz) to the presence of nanoparticles (metals and metal oxides) in porous media. The SIP response was tested under various conditions: increasing particle concentration under constant solution chemistry; varying solution molarity (0.0M–1.0M), and varying solution valence (+1, +2, +3 valence) under constant particle volume. We examine the results in terms of phase shift and resistance magnitude. Our data suggest that the oxide nanoparticles do not show SIP responses to increasing particle concentration, solution valence, and molarity, while the metallic particles show a clear response to increasing particle concentration, and frequency. Silver was the only material to show any significant response to increasing solution molarity, valence, and frequency. Because of the high propensity of the nanoparticles to form aggregates, they essentially behave as colloidal and clay particles allowing us to apply conventional SIP theory to our interpretation. We suggest that the oxidation state of the metals diminishes their SIP response consistent with more recent studies that have documented that polarization decreases with oxidation of metallic particles. We infer from our results that nanoparticle crystalline composition and aggregation effects control the SIP response of nanoparticles in porous media. [Copyright &y& Elsevier]

A series of 2D apparent resistivity data were generated over two synthetic models representing different geological or environmental conditions commonly associated with geophysical applications for hydrogeological, environmental and engineering investigations. The apparent resistivity data were generated for the following arrays: Wenner-alpha (WA), Wenner-beta (WB), Wenner-Schlumberger (WSC), dipole-dipole (DDP), pole-dipole (PDP) and pole-pole (PP) arrays, which were paired such that apparent resistivity data for 2D profiles in a parallel direction are obtained with a particular array type and those in a perpendicular direction are observed with a different array type. The 2D apparent resistivity data for the orthogonal paired-arrays were then collated to 3D data sets. The effectiveness and efficiency of the orthogonal paired-arrays in 3D geoelectrical resistivity imaging were evaluated by determining the mean absolute anomaly effects of the electrode configurations on the synthetic models. The results show that DDP-PDP, DDP-PP, DDP-WSC, PDP-PP, DDP-WB, PDP-WB and WB-WSC orthogonal paired-arrays produced higher anomaly effects on the synthetic models. This indicates that DDP-PDP, DDP-PP, DDP-WSC, PDP-PP, DDP-WB, PDP-WB and WB-WSC orthogonal paired-arrays are more sensitive to 3D features of the geologic models than the other orthogonal paired-arrays investigated. [ABSTRACT FROM AUTHOR]

Abstract: During the past two decades, the diagnosis and monitoring of polluted sites have become more important. Urban sites are particularly difficult to study, because they are contaminated with various pollutants, and there is a large physical and chemical heterogeneity. The heterogeneity comes from the landfilling of various solid wastes and remolded soil (endogenous or exogenous) from which they were constituted over time. Traditional techniques such as wells monitoring, are often insufficient to evaluate the extension of soil contamination. This is why we proposed a geoelectrical methodology from the fastest to the most information rich technique, showing all carry out and acquisition times: electromagnetic low frequency conductivity mapping, electrical resistivity profiles, chargeability profiles and spectral induced polarization (SIP) soundings. This strategy has been successfully applied to an urban site located in the Paris Basin (France). A conductivity map in relation with geochemical and lithological informations should provide us information to implement electrical resistivity and chargeability profiles. The latter allowed us to differentiate 3 main anomaly zones that have been determined. As interpretation of chargeability profiles is difficult, because it integrates polarization mechanisms with different relaxation times, we add spectral induced polarization soundings that provide us information concerning the contaminant nature. We determined the extension of an organic phase, and of 2 highly mineralized zones that could be linked to biodegraded and/or with pyrite areas. That theory is consistent with groundwater analysis and SIP data. The conclusion is that the suggested methodology is well suited to the study of urban contaminated sites including several different pollutants. [Copyright &y& Elsevier]

Orthogonal set of 2D geoelectrical resistivity field data, consisting of six parallel and five perpendicular profiles, were collected in an investigation site using the conventional Wenner array. Seven Schlumberger soundings were also conducted on the site to provide ID layering information and supplement the orthogonal 2D profiles. The observed 2D apparent resistivity data were first processed individually and then collated into 3D data set which was processed using a 3D inversion code. The 3D model resistivity images obtained from the inversion are presented as horizontal depth slices. Some distortions observed in the 2D images from the inversion of the 2D profiles are not observed in the 2D images extracted from the 3D inversion. The survey was conducted with the aim of investigating the degree of weathering and fracturing in the weathered profile, and thereby ascertaining the suitability of the site for engineering constructions as well as determining its groundwater potential. [ABSTRACT FROM AUTHOR]

Abstract: The self-potential method can be applied to evaluate the degree of water seepage into earth or rockfill dams. Spatial distribution of measured self-potential data can indicate possible anomalous water flow. Phenomena, such as piping, can be modelled as cylindrical bodies. Internal erosion can develop structures, which can be represented by a sphere or point source. Differential settlement in the dam structure occasionally creates horizontal fractures, which require equivalent geometrical body formula. An equation, which allows the calculation of a self-potential profile over a horizontal contact, was developed. This equation can also be applied to the inspection of water flow into horizontal drainage filters. When inverse interpretation returns bodies of relatively small amplitudes, then their probability can be tested statistically. A test, based on cross-correlation between a modelled curve and field data, can be used to evaluate their existence at a given probability level. An acceptance criterion is computed, using the concept of likelihood coefficient. The equation was applied to two case histories. The first is an example of water flow evaluation into a horizontal drainage filter. Several anomalous bodies were interpreted from residual self-potential data, i.e. from the difference between the theoretical response of the filter and the measured self-potential values, then, most of the interpreted bodies were statistically tested. The second case deals with detection and evaluation of a horizontal fissure. The interpreted parameters of the detected body corresponded well to a horizontal fracture found when the water level in the reservoir was lowered. [Copyright &y& Elsevier]

One of the main problems of modern karst investigations is to forecast a place and time of possible depression formation. A solution to this problem requires investigations of karst dynamics by different methods, including geophysical methods. Karst dynamics is determined, in general, by movement of underground waters. At the same time, it is known that electric fields and electric properties of rocks are very sensitive to variations of fluid amounts and their characteristics. Thus, geoelectrical methods of monitoring are useful for investigation of karst dynamics in general and for forecasting karst depressions in particular. Authors have introduced two methods of geophysical monitoring: geoelectrical and seismo-electrical. The main features of instruments and methods of measurement are explained, and the results of the field investigations are shown. The possibilities of the application of these methods to karst dynamics investigations are discussed. [ABSTRACT FROM AUTHOR]