Vertical Electrical Resistivity Research Articles

The Result of Electrical Resistivity Investigation of Solid Waste Landfill Conducted at Nsukka Municipality Using Electrical Resistivity Measurments

Solid waste landfill management has been a significant issue for Nigerian urban areas and other developing countries across the globe.Similar to most other cities, Nsukka also generates waste on a daily basis, much of which is dumped in poorly designed and positioned dumping sites. The majority of the disposal sites are found on roadsides, at marketplaces, on farms, and in residential neighborhoods, among other places. The road infrastructure and groundwater are under danger, and the beauty of the impacted communities are not spared. Undoubtedly, the unchecked citation of boreholes as the source of potable water in the majority of our rural and urban communities—given that the government doesn't seem to be providing water to the people—has become a significant challenge. An investigation using electrical resistivity method was conducted around a solid waste dumpsite at Nsukka in Nsukka L.G.A of Enugu State, Nigeria with an aim to investigate the level of groundwater contamination and the objectives to determine the subsurface geoelectric layers, depth to water table, lithology delineation and map out the contamination zones. The scope of this study provides an overview of some of the approaches used to assess the aquifer vulnerability and aquifer potential using Vertical Electrical Sounding (Schlumberger array) and 2D resistivity imaging (Wenner array) in different locations around Nsukka municipality dumpsite. Both methods were used for this study in order to provide a geophysical database for exploration of the study area’s groundwater resources and also they are less expensive and less time consuming. VES has proved to be effective in solving groundwater problems in most places in Nigeria (Ezeh and Ugwu, 2010; Ugwu and Ezeh, 2012; Nzemeka et al. [1,2]. Electrical Sounding (VES) and 2D resistivity imaging were carried out with a digital read out resistivity meter (ABEM SAS 1000) to acquire data in the area and were interpreted using the Schlumberger automatic INTERPEX analysis software and the RES2DINV software respectively, which generates model curves using initial layer parameters and display the variations of electrical resistivities respectively. A total of eight (8) sounding and six (6) 2D resistivity imagings were carried out in the area. A contaminant leachate plume was delineated in 2D resistivity sections as low resistivity zones while the VES shows the depth of aquifer. In 2D pseudosections where bluish colours with low resistivities (less than 20.80\(\Omega\)m) with the depth ranging from 1.28m to 17.1m in the Line 1 and 2 are seen as contaminated zones. The rest of the lines are not contaminated because of their high resistivities (greater than 20.80\(\Omega\)m). The result of the electrical resistivity survey also showed 4 - 5 layers geo-electric sections and an AA and AK type sounding curves. The VES result shows that VES 1A, 1B, 2A and 2B which are carried out on line 1 & 2 of the wenner lines showed signs of contamination with low resistivity values less than 20.80\(\Omega\)m complementing the wenner results. The contamination has not yet got to where the aquifer is located on the lines. Since the depth to the aquifer ranges from 30.26m to 155.43m while maximum depth of contamination is 17.1m. It is believed that the leachate has not percolated down to the aquiferous zones as such aquifers are presumed to be free. As such, it is recommended that boreholes around the study area should not be less than 30m deep to avoid exploiting polluted water.

Aquifer vulnerability valorization via DRASTIC index-based assessment within litho-facies of a coastal environment

Determining the degree of an aquifer’s susceptibility to pollutants is an important tool for policy planning in subterranean water administration and conservation. In this work, subterranean water vulnerability was appraised with the use of DRASTIC methodology, which employs seven parameters: depth to groundwater (D); net groundwater recharge (R); aquifer media (A); soil media (S); topography (T); influence of vadose zone (I); and hydraulic conductivity (C). Different ratings were given to each parameter based on the hydro-geological and geo-electrical information obtained from the study area. Geo-electrostratigraphic data was acquired with vertical electrical soundings and electrical resistivity tomography surveys. The results demonstrated the existence of geoelectrical layers with variable resistivities ranging from high to low, with variable curve types. Longitudinal conductance measures indicated moderate subterranean water protective capacity. Analysis of DRASTIC vulnerability indices showed that the aquifer indicated moderate to high vulnerability to contamination. Vulnerability maps were generated to indicate locations of high vulnerability, the goal being to prevent indiscriminate haphazard and wildcat abstraction of groundwater in such locations. The quality category index (QCI) generated for the DRASTIC model indicated that underground water susceptivity is dependent on all 7 parameters employed in the model, with the most critical determinants being the depth to aquifer (D), net recharge (R), aquifer media (A), and impact of the vadose zone (I). The work recommends that anthropogenic activities that could contaminate groundwater resource be halted as the resource is indicated by DRASTIC models as being vulnerable.

Aquifer vulnerability valorization via DRASTIC index-based assessment within litho-facies of a coastal environment

Determining the degree of an aquifer’s susceptibility to pollutants is an important tool for policy planning in subterranean water administration and conservation. In this work, subterranean water vulnerability was appraised with the use of DRASTIC methodology, which employs seven parameters: depth to groundwater (D); net groundwater recharge (R); aquifer media (A); soil media (S); topography (T); influence of vadose zone (I); and hydraulic conductivity (C). Different ratings were given to each parameter based on the hydro-geological and geo-electrical information obtained from the study area. Geo-electrostratigraphic data was acquired with vertical electrical soundings and electrical resistivity tomography surveys. The results demonstrated the existence of geoelectrical layers with variable resistivities ranging from high to low, with variable curve types. Longitudinal conductance measures indicated moderate subterranean water protective capacity. Analysis of DRASTIC Vulnerability Index showed the aquifer indicated moderate to high vulnerability to contamination. Vulnerability maps were generated to indicate locations of high vulnerability, the goal being to prevent indiscriminate haphazard and wildcat abstraction of groundwater, especially in locations with high vulnerability to contaminators. The quality category index (QCI) generated for DRASTIC indicated that underground water susceptivity is dependent on all 7 parameters employed in the DRASTIC model, with the most critical determinants being the depth to aquifer (D), net recharge (R), aquifer media (A), and impact of the vadose zone (I). The work recommends that anthropogenic activities that could contaminate groundwater resource be halted as the resource is indicated by DRASTIC models as being vulnerable.

Właściwości fizyczne zbiorników łupkowo-piaskowych: Pole Szafranowe, Delta Nilu, Egipt

The Saffron gas Field is in the Scarab-Saffron Development Lease in the offshore Nile Delta. It was discovered by the Saffron-1 exploration well drilled in 1998 and appraised by Saffron-2 and Sapphire-3 wells. Saffron is a stacked channel system and consists of 6 different reservoirs with differing levels of connectivity between them. It can be interpreted as deep-water canyon fill deposits on a delta-front slope. Some physical properties of 4 full diameter core samples (approximatly164 core plugs) obtained from the Saffron-2 borehole were petrophysically analysed. Helium porosity, horizontal and vertical permeability, grain density and electrical resistivity were laboratory measured. Several bivariant plots were accomplished such as porosity- permeability; grain density, formation resistivity factor; cementation exponent and Winsaur’s multiplier (a) as well. Several regression line equations with robust coefficient of correlations were obtained to be used for reservoir characterization. On the other hand, numerous frequency histograms were built for most of the measured reservoir parameters to determine their type of distribution and other statistical parameters. Some important relations like cementation exponent versus multiplier (a) are performed which improves Archie’s general equation and subsequently the reservoir fluid saturation (Sw and/or Sh). The lack of stratification in sedimentary section represented by core numbers 4&5 of Saffron-2 well have severe consequences on measured reservoir parameters especially exposed by the porosity- permeability relation.

Groundwater potential assessment in parts of Nnewi Industrial Zone: Implications for sustainable development and conservation

Integrated field geological and geophysical (Vertical Electrical Sounding VES and 2D Electrical Resistivity Tomography ERT) investigations were carried out in the Nnewi Industrial Zone, SE Nigeria to identify and characterize productive aquifer, aquifer hydraulic properties, and aquifer vulnerability. Data acquired from 17 VES points and across a profile line of about 800 m for the 2D ERT were processed, interpreted, and modeled. Results from the geologic mapping showed that the outcropping units are mainly the sandstone, shaly-sandstone, and less commonly shale of the Nanka and Ogwashi-Asaba Formations which are relatively permeable and offer poor protective cover to the underlying aquifer. Models from the resistivity data showed that the depth-to and thickness of the aquifer vary from 38.60 to 98.80 m and 30.10–177 m, respectively. Aquifer properties estimated from the geophysical data gave values ranging from 0.611127 m2/day to 246.6576 m2/day and 0.1609 m/day to 5.6325 m/day for transmissivity and hydraulic conductivity, respectively, and suggestive of low – moderate aquifer potential. Aquifer Protective Capacity APC distribution modeled from the longitudinal conductivity values, and the aquifer vulnerability modeled using the DRASTIC method indicate that the study area is characterized by poor – moderate APC and low – moderate – high aquifer vulnerability, respectively. Analysis shows that the modeled aquifer parameters, APC, and aquifer vulnerability have similar trend which tends to improve towards the southern and more specifically southeastern parts of the study area, suggesting that even though aquifer units were identified all through the study area, the southeastern parts are best suited for the development of groundwater exploitation schemes. Also, aquifer vulnerability model results recommend that proper and efficient waste disposal schemes are put in place to conserve groundwater quality from pollution from industrial waste since the aquifer in the area is relatively vulnerable.

Geophysical exploration to assess leachate percolation and aquifer protectivity within hydrogeological units at a major open dump in Eket, Nigeria

Leachate contamination was investigated with geo-electrical methodologies at a major open dump in Eket, Southern Nigeria. The open dump is heavily polluted, degrades the environment, and has released toxins into the atmosphere. To model leachate percolation, vertical electrical soundings (VES) and electrical resistivity tomography (ERT) surveys, constrained by well lithological information, were undertaken at the site. The field equipment used for the geo-electrical investigations was the ABEM Terrameter SAS 1000 and its accessories. WINRESIST software was employed to process the sounding data and RES2DINV was employed to generate 2D tomograms indicating subsurface heterogeneity. Results obtained from sounding data showed that the subsurface had three lithological units (motley topsoil, fine sand and coarse sand), with coarse sand being the main hydrogeological unit comprising water-bearing formations. The first layer’s resistivity ranged from 84.9 – 625.4 Ωm with a mean of 360.4 Ωm; the second layer’s resistivity ranged from 7.5 – 1008.1 Ωm with a mean of 142.9 Ωm, and the third layer’s resistivity values ranged from 11.6 – 745.6 with a mean of 205.5 Ωm. The 2D resistivity tomograms indicated that leachate had percolated into groundwater resources. This is concerning as groundwater is the major water resource within the area. Measures of the Dar-Zarrouk indices and electrical reflection co-efficient indicated that the highly heterogenous region had moderate aquifer protective capacity and moderate aquifer potentiality. To mitigate contamination at the site, sanitary landfills, phyto-remediation, impermeable liners, or impermeable earth materials should be employed to diminish the rate of leachate percolation.

Combination of Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT) techniques for hydrogeological reconnaissance in the Guigou plain, Tabular Middle Atlas, Morocco

The study site is located in the Guigou plain, which is situated on the south-eastern edge of the Tabular Middle Atlas and is characterised by a particular geology within the mountainous region. Unlike the Tabular Middle Atlas, which is generally covered by Lias carbonate formations, the Guigou plain is characterised by the presence of a different type of cover formed by basaltic flows of plioquaternary age, forming a surface layer that is used extensively for agricultural activities. The main objective of our study is to detect the different geoelectric levels both at the surface and at depth, thus providing indications of the specific aquifer formations in the region studied. The analysis of the results obtained highlighted the presence of a superficial resistant level, attributed to basalts of Plio-Quaternary age, with an estimated thickness of between 30 and 100 m, forming the superficial aquifer of the plain. Next, a conductive level was identified, associated with alternating marl and marl-limestone of Pliocene age, in keeping with the local geology. Finally, at a depth of 225 m, a very resistant level was identified, corresponding to Lias limestone, which becomes a deep aquifer on the Guigou plain. This study provides essential vertical hydrogeological reconnaissance and highlights the need to carry out numerous tomographic profiles as well as electrical boreholes. These combined approaches are crucial to enriching our understanding of the particular geological and hydrogeological characteristics of this region, which forms a transition zone between the MAT and the MAP.

Study of vertical electrical resistance changes in reservoir beds of Tournaisian oil deposits

The article proposes a method for rapid assessment of the initial position of oil-water contacts, oxidized oil zones, transition zones, zones of high and decreasing resistance in the Lower Carboniferous Tournaisian oil deposits at one of the oilfields of the Republic of Tatarstan. As initial data, the values of electrical resistivity of effective interlayers from the catalog of geological and geophysical data, determined from induction logging curves, were used. Well log data for more than 200 wells drilled in elevation areas were used in analysis. The change in the electrical properties of deposits vertically is considered using the average resistivity values of effective interlayers averaged over all wells. Conclusions are based on the results of the done work: according to the resistivity values in massive carbonate deposits of the Tournaisian age, it is possible to distinguish various zones of oil saturation along the vertical; initial oil saturation does not grow exponentially, as in the Leverett function, but linearly in each zone.

Hydrostratigraphy and hydrogeophysical studies to delineate fresh and saline aquifer boundaries in Lesser Cholistan of Pakistan.

The differentiation of saline water and fresh water interfaces is a key objective in ground water exploration and management. Bahawalpur is the twelfth biggest metropolitan area of Pakistan situated in south Punjab near the bank of River Sutlej and lies at 29°59'55" N latitude and 73°15'12" E longitude at an elevation of 521 ft AMSL in the Cholistan area close to the Thar abandon. The study area comprised of Lesser Cholistan experiencing acute shortage of water for inhabitants and livestock as well. The occurrence of fresh water is also challenging because of high salinity in groundwater. The present study is intended to identify hotspots of fresh groundwater zones. To achieve the goal, vertical electrical resistivity and borehole data are used to mark fresh and saline interfaces in groundwater. To achieve the results 230 vertical electric sounding were performed in the study area. A total of 3 to 5 geo-electric layers are identified with modeling along with the processing and interpretation of resistivity data. In the study area, resistivity values are classified as very high (>230 Ω-m), high (230-100 Ω-m), medium (100-40 Ω-m), low (40-20 Ω-m) and very low (<20 Ω-m). Borehole data is used to interpret subsurface lithologies and to calibrate the modeled resistivity curves. The electric resistivity data indicates that thick layers of Quaternary sediments is present in the subsurface that is primarily composed of clay, silt, sand, gravels and some kanker. Inversion technique is applied to generate 2D subsurface resistivity maps to delineate fresh and saline water zones. The generated 2D resistivity maps at variable depth above and below water table and formation resistivity maps are successfully utilized to differentiate fresh and saline water zones. The identification of a saline water aquifer within sediments rich in clay was made possible by the observation of very low resistivity measurements in the southern region. Conversely, the detection of relatively high resistivity values, coupled with the presence of sand and gravel deposits in the northern section of the lesser Cholistan area, provided compelling evidence of the existence of fresh groundwater. These findings have significant implications for the management of water resources in the region, as they provide valuable insights into the distribution and availability of groundwater resources for future use.

Lithologic characterization of Iguosa erosion site using geoelectrical techniques

Considering the devastating menace of gully erosion for which lithology is one amongst several other agents that drives soil loss and gully erosion, Vertical Electrical Sounding (VES) and Electrical Resistivity (ERT) techniques were adopted to investigate subsurface lithology in Iguosa gully erosion site. PASI 16GL model resistivity meter was used in acquiring data for VES and ERT in the area under investigation. VES data acquired were processed both qualitatively and quantitatively, and geoelectric sections were generated using AUTOCAD software by combination of two or more interpreted VES results along a profile. ERT data were processed using Res2dinv software to an inverse model resistivity section. The geoelectric image generated were interpreted to obtain lithology of the subsurface. The analysis and interpretation of the subsurface image reveals presence of topsoil, sand, dry sand, clayey sand and coarse sand. The subsurface lithology within the study location is predominantly sandy. The result obtained from the resistivity of all profiles shows that erodibility increases with depth within this study area with corresponding high resistivity values. Due to the fact that sand within the study area is loose coarse and silty, which can give rise to high resistivity and causes erosion.

Joint Electromagnetic-Terrain Conductivity and DC-Resistivity Survey for Bedrock and Groundwater Characterization at the New Al-Obour City, Egypt

A multi-spacing electromagnetic–terrain conductivity survey profile and vertical electrical resistivity soundings were carried out at New Al-Obour City, Northeastern Cairo. The chief purpose of this survey was to characterize the bedrock, and groundwater occurrence, and hence to image both the surface and subsurface structures. The water is used mainly to meet the demands of the agricultural sector in the area. Accordingly, a set of sixteen Multi Spacing Electromagnetic Terrian Conductivity profiles and 11 vertical electrical soundings were done from September 2018 to March 2019. The data sets were transformed–inverted comprehensively with regard to stitched one-dimensional (1D) electrical resistivity smoothed-earth models. These sets were used efficiently in the interpretation of the geologic sequence of bedrock through successive conductive anomalies and electrically resistive. Remarkably, the obtained subsurface electrical resistivity structures are coincident with the mapped field geologic faults. The current study proved that a comprehensive Multi Spacing Electromagnetic Terrian Conductivity and vertical electrical sounding resistivity survey could help optimize geotechnical exploratory work. The results of the interpretation of geoelectrical data indicate that the elevation of the top of the groundwater aquifer ranges from 60-70 m above sea level.

Application of Geoelectric Technique in Groundwater Protection of Quaternary Aquifer in Wadi El Natrun, Egypt

Qualitative and quantitative interpretations of the accessible geoelectrical resistivity data were conducted in the area located to the west of Nile Delta on both sides of the Cairo-Alexandria desert road, between latitudes 30.190816° and 30.745892° N and longitudes 29.797607° and 30.702070° E, in the northern Western Desert of Egypt. The study area is covered by thick sedimentary exposures ranging from the Miocene to the Quaternary period. Geological factors such as lithology and geological structures significantly influence the groundwater in the study area. The Quaternary, Pliocene, and Miocene eras make up the majority of strata in the study region that require water.&#x0D; The study conducted twenty-three vertical electrical resistivity soundings using the Schlumberger array to define the shallow subsurface geological inferences and investigate the possibilities of finding underground water accumulations and its contamination with clay lenses. The examination of the obtained electric resistivity values revealed the segmentation of the examined section into five geoelectrical units with lateral variations in thicknesses, lithologies, and features. The five geoelectrical units had different compositions, with the first surface unit consisting of silt clay and relatively high resistivity sands and gravels that have been altered laterally. After the surface unit, resistivity ranges from relatively modest to high. Intercalation of sand and clay occurs in the second unit, followed by lenses of relatively medium-resistance coarse sand and clay in the third and fourth units, possibly forming an aquifer, and finally relatively low-resistance sand and clay in the fifth unit.&#x0D; Due to the haphazard drilling of hundreds of water wells, significant hydrogeological and environmental issues, such as soil salinization, water head decline, and groundwater salinity deterioration, have occurred. These issues have attracted significant expenditures in the field of land reclamation, both on small and large-scale projects. The study area is divided into five main geoelectrical layers observed along this cross area, as follows:&#x0D; The first surface geoelectrical layer (layer A) is characterized by relatively high resistivity ranging from 8.21 to 595.3 Ohm.m. The thickness of this layer varies from 2.1 to 8.86 m. This layer represents the dry surface cover of the area and consists of gravel, sand, and silt clay.&#x0D; The second geoelectrical layer (layer B) represents the dry layer lying above the water-bearing formation. It generally consists of sand and clay intercalation. The resistivity of this layer varies from 3.49 to 91.18 Ohm.m, and the thickness of this layer ranges from 17.13 to 38.3 m.&#x0D; The third geoelectrical layer (layer C1) is the water-bearing formation that generally consists of coarse sand and clay. The resistivity of this layer varies from 4.41 to 37.5 Ohm.m, and the thickness ranges from 10.38 to 54 m.&#x0D; The fourth geoelectric layer (layer C2) represents the lower part of the water-bearing formation. It consists of clayey sand and clay. The resistivity of this layer varies from 1.83 to 30.1 Ohm.m, and the thickness ranges from 17.78 to 31.35 m.&#x0D; The last geoelectric layer (layer D) represents the lower layer of investigation, consisting mainly of clay. The resistivity of this layer is generally low, varying within a narrow range of 26.7-39.8 Ohm.m.&#x0D; Finally the current study highlights the necessity of conducting in-depth geomorphological assessment studies before developing new reclamation projects, in addition to soil and water assessment.

Sedimentary characteristics and geophysical architecture of the Cretaceous Bambalo claystone formation (Mayo Oulo-Lere Basin, North Cameroon)

• Depth and spatial development of Bambalo sedimentary sequences during the Cretaceous. • The Bambalo Formation described in terms of lithostratigraphy, VES and ERT. • Fluvio-lacustrine deposits including claystone, siltstone and limestone. • Sequences dominated by retrogradational sequences in a lacustrine environment. The Mayo-Oulo-Lere Basin, with an overall surface area of 122 km 2 is located in northern Cameroon between the western extension of the Doba Basin and the eastern edge of the Benue Trough. This study maps the depth and spatial development of Bambalo sedimentary sequences in the Mayo Oulo-Lere Basin that were deposited during the Cretaceous. The depositional sequences present an exposure of crocodile fossils and plants evidenced by superficial alteration. The Bambalo Formation is described in terms of lithostratigraphy, vertical electrical sounding (VES) and electrical resistivity tomography (ERT) to provide a better understanding of stratigraphic evolution and setting conditions during sedimentation. Sedimentary deposits in the Mayo Oulo-Lere Basin are mainly fluvio-lacustrine deposits consisting of alternating claystone, siltstone and limestone. The lithostratigraphic log of Bambalo for the subsurface geology up to 25 m presents three main depositional sequences named S1, S2 and S3. S1 presents ripples marks and desiccation cracks that are directly observed on the surface outcrop. The separation between S1-S2 and S2-S3 is marked by unconformity surfaces. The sedimentary sequences are dominated by retrogradational depositional trends that describe short sequences of fining-upwards successions. The ERT image results obtained from geophysical analysis using Res2Dinv display local features associated with folding in the aforementioned sedimentary thickness of approximately 30 m. Additionally, the VES analyses using ipi2win software show that the upper 78 m part of the Bambalo formations is composed of four layers (L1, L2, L3 and L4) distinct by resistivity. L4 Layer correlated with the top of lithostratigraphic log S3, while L3 is a semiresistive set of 78 Ω·m layering S1 and S2 lithostratigraphy sequences. Layer L2 corresponds to a conductive set with resistivity of approximately 27 Ω·m above the lower layer L1, a resistive sequence with resistivity greater than 1000 Ω·m. The combination between the major rifting faults (N70°, N110° and N130°E), syntectonic sedimentation and Barremian-Aptian age attributed to sediments of Bambalo demonstrate clearly that the sediments were deposited during or few time after the rifting phases. The sediments are resulting from a rapid filling of the basin characterised with retrogradational sequences that are controlled by the evolution between accommodation space created after each tectonic phase and the base water level rise within the basin. The rapid elevation of water and sedimentation might be one of the reasons of the massive death of crocodilians. The results of this study demonstrate that the combination of ERT and lithostratigraphic analysis is a powerful tool for a better understanding of the Bambalo sedimentary process and basin evolution. The lateral and vertical evolution of the layers being proven, a future deep excavation will certainly make it possible to bring to light new types of fossils from these deposits and in the neighbouring basins.

GLOBAL OPTIMIZATION VERY FAST SIMULATED ANNEALING INVERSION FOR THE INTERPRETATION OF GROUNDWATER POTENTIAL

This study examines the inversion modelling of one-dimensional Schlumberger configuration resistivity data using the Very Fast Simulated Annealing (VFSA). Detailed identification and mapping of aquifer conditions is very important for the sustainable development of groundwater resources in an area. Vertical electrical sounding (VES) and surface electrical resistivity surveys have proven very useful for studying groundwater due to their simplicity and cost effectiveness. Global optimization inversion method also provides an inversion solution that is not expected to be trapped in a local minimum solution, so that it will get results that are closer to the actual situation. The VFSA method is inspired by phenomena in metallurgy related to the formation of crystals in materials caused by thermodynamic processes. This inversion scheme was tested initially with free noise synthetic data and with noise 5%. Furthermore, the program is applied to field data that has been measured in Ambon City, Maluku, Indonesia. The results of the VFSA inversion on field data obtained four layers consisting of top soil (141.2 ± 0,61 m) with a thickness of 1.43 m, andesite breccia rock (355.90 ± 0.46 m) with a thickness of 4 m, lapilli tuff (93.40 ± 0.31 m) with 30 m thick, then the last is the coarse tuff layer (34.30 ± 0.15 m) which is estimated as an aquifer.

Wildfire Effects on Cryosols in Central Yakutia Region, Russia

Forest fires are one of the most significant types of disturbance on a global scale, affecting biodiversity and biogeochemical cycles and playing an important role in atmospheric chemistry and the global carbon cycle. According to a remote monitoring information system, forest fires in Yakutia were the largest wildfires in the world in 2021. In this regard, mature pale-yellow soils unaffected by fire were investigated in comparison with the same soils that were strongly affected by surface fire in 2021 in the area surrounding Yakutsk, Yakutia region. Data obtained showed an intensive morphological transformation of the topsoil layers, increase of total organic matter and slight increase of pH, and apparent decrease of basal respiration and content of microbial biomass. A slight accumulation of Zn and Ni in soils due to wildfires was recorded, as well as alteration in the distributions of heavy metals in the soil profile. Moreover, an electric resistivity study was carried out during field studies. An influence of forest fire on the electrical resistivity value was not reliably found, but the vertical electrical resistivity sounding provided precise data regarding the degree of soil-permafrost layer homogeneity and/or heterogeneity.

English

Vertical electrical sounding (VES) and 2D electrical resistivity tomography (ERT) employing the Schlumberger and Wenner configurations respectively were combined for groundwater exploration in parts of Enugu metropolis. The area is underlain by Enugu Shale and Mamu Formation. A total of twenty (20) VES and four (4) 2D ERT traverses were acquired in the study area. VES and 2D ERT data were processed and interpreted using INTERPEX 1X1D and RES2DINV respectively. Sounding curves shows dominant decrease in resistivity with depth while 2D ERT inverse model shows lateral variation in resistivity of the rock layers with lower resistivity at increasing depth. VES geoelectric layer sections show top sideritic clay - clay/shale sequence. Resistivity curve analysis also shows predominance of Q and K curve types. 2D map of aquifer layer resistivity, thickness and depth were constructed. Aquifer layer resistivity range from 2.00 to 190 ?m, while the thickness range from 10 to 75 m and a depth range of 23 to 150 m. The 2D ERT shows layer resistivity range of 0.1 to 250 ?m. Based on the combination of the two techniques for groundwater exploration in the study area, a water table depth of 18 m with a maximum drill depth of about 100 m was determined. However, it is recommended that the selection of point of drill should be on the low saturated regolith as observed on the 2D ERT sections.&nbsp;&nbsp; Key words: Aquifer, groundwater, VES, 2D ERT, resistivity.

Fabrication and simulation study for vertical micro-TEGs based on printed circuit board manufacturing processes

The development of fabrication procedures for micro-thermoelectric generators (µTEGs) based on low-cost fabrication technologies, appropriate for mass production is discussed and demonstrated in this study. Simulations were carried out, two manufacturing processes were tested, and device performance is compared to simulation results for vertical µTEGs. The substrate for this device is a printed circuit board, and the thermoelectric materials are self-developed Bi0.5Sb1.5Te3 (p-type) and Bi2Te2.7Se0.3 (n-type) pastes. A square µTEG (15 mm × 15 mm × 500 µm) with eight thermocouples (TCs) was fabricated. The characterization of the fabricated 8-TC-µTEG was carried out and a power output of 1.23 µW was obtained for the fabricated 8-TC-µTEG. The measurement results of this 8-TC-µTEG closely match simulation results as well. Moreover, a novel vertical electrical contact resistance measurement setup is designed and implemented into the final evaluation of µTEG production to have a more accurate assessment. The simulation study is also applied for the designed electrical contact resistance measurement setup. As a result, the contact resistivity of Bi2Te3/Cu was calculated as 5.65 × 10−4 Ωcm2.

Geoelectric and mineralogical studies for foundation soil characterization in new Luxor city, Upper Egypt

The new Luxor city was proposed by the Egyptian government as a new constructional and building site in order to face the increasing population density around the two banks of the river Nile. It is important prior construction of buildings to characterize the foundation soil. So, vertical electrical resistivity survey and mineralogical investigation were conducted for this purpose. The results obtained from the interpretation of the sounding data indicate that the lithological succession of the study area consists of four geoelectric layers. The top layer corresponds to the surface loose sediments of conglomerate, gravel, and sand. The second geoelectric layer is composed of sand and gravel. The third layer is composed of silty clay, sandy clay, and clayey sand. The fourth geoelectric layer is composed of dry sandstone. The X-ray diffraction (XRD) results of samples collected from the clay-rich layer revealed the presence of smectite mineral as predominate clay minerals which is characterized by its swell potentiality on wetting. Accordingly, the clay zone recorded within the third layer must be taken into consideration during designing the foundations at new Luxor city especially this layer was located at shallow depth range between 1.6 and 7.5 m and attains a relatively big thickness that reach up to 33.5 m in some parts. This study emphasizes the importance of the integration of geophysical investigation and mineralogical analysis of the foundation soil for optimal characterization of a site.

Geoelectric investigation for aquifer characterization in Boi and Environs, Bauchi State, Northeast, Nigeria

A total of thirty eight (38) Vertical Electrical resistivity Sounding (VES) were used to characterize aquifers in Boi and its environs, Bogoro Area of Bauchi State, Northeastern, Nigeria. The purpose of the study is to characterize the aquifer system in the area using Schlumberger configuration. Because there are multiple failed wells and boreholes in the vicinity, the research is justified. A total of 38 vertical electrical sounding (VES) were carried out, with a maximum electrode spacing of 100 m. The sounding curves acquired were three layer earth models, and the curve types were H, Q, A, and K respectively. The following lithologies were discovered in the area: topsoil with a resistivity of 81ῼm to 264.21ῼm and a thickness of 0.56m to 3.77m, laterite with a resistivity of 526.43ῼm to 999.71ῼm and a thickness of 1.93m to 3.47m, weathered/fracture basement with a resistivity of 10.62ῼm to 238ῼm and a thickness of 2m to infinite depth, and the fresh basement with a resistivity of 1000.33ῼm to 1821ῼm. The longitudinal conductance (S), transverse resistance (T), reflection coefficient (RC), and resistivity contrast (FC) were used to assess the area's groundwater potentials. The area's aquifer protection capacity found to be moderate, weak, and poor, while the groundwater potentials categorized as high, medium, low and very low. According to the results of the evaluated parameters, the area has a predominantly good to moderate groundwater potential. The numerous occurrences of failed/aborted boreholes in the area could be linked to a variety of factors, including poor data quality, lack of technical know-how, incorrect point selection, and poor drilled hole development, all of which are common in Basement Complex terrains. The VES 5 and 10 results showed a dramatic decline in resistivity, indicating that the water likely heavily polluted, particularly by anthropogenic chemicals, or that it was an ancient dumpsite.

Archaeo-Geophysical Investigation of Simulated Settlement: Case Study in a Part of Basement Complex of Nigeria

We have used the 2D Vertical Electrical Sounding method and Electrical Resistivity Tomography (ERT) method to map buried artifacts in a simulated settlement, and have shown how the geographical information system could aid future research. Stones, bones, metals, cement bricks, and cement-and-sand mixtures were locally constructed to fit into an African-archaeological setting. Parameters such as the materials’ composition, width, electrical resistivity, height, age, and depth of burial were taken into account before this investigation. The integrated methods employed collected data over the study area along with a pre-calculated dense network of parallel profiles. A total of eight (8) VES points and six (6) ERT profiles were obtained. The analysis and interpretation revealed that the VES yielded poor resolution for small-scale archaeological anomalies and could only be used fractionally for prospection whilst the ERT results were more suitable for delineation due to the high spatial resolution they provided. The field values correlated with other literature values. This research suggests that rapid significant prospection information, of any area under investigation, can easily be obtained from Google Earth time-lapse images and that its results will serve as a thorough reconnaissance in the search of prehistoric activities.