Subsurface Aquifer Research Articles

Vertical Electrical Sounding Analysis for Local Subsurface Water Bearing Identification Due to Isolated Hill. Case-study: Madurejo Village, Prambanan District, Yogyakarta Province, Indonesia

<p class="AbstractText"><span lang="EN-AU">In a subsurface aquifer, there is a ‘barrier like’ phenomenon that blocks the flow of water. It will create a subsurface water bearing/dam and potential source for water well drilling. The existence of clay-limestone in the isolated hill in Madurejo village, Prambanan district, Yogyakarta seems to act like a natural groundwater body which is interesting to be analyzed by means of vertical electrical sounding (VES). For this purpose, three VES points measured with 150 meters apart, creating a line from south to north. Maximum distance for AB is 200 meters. We found the shallow unconfined from surface to 4 m depth and confined aquifers from 6 m to 29 m. The geometry of the second aquifer in combination with the existence of isolated hill seems to have a water-bearing structure which is very potential for water resources.</span></p>

Aquifer analysis of Durensewu-Karangjati water source in Pandaan, Pasuruan using 2D resistivity method in identifying pollution of domestic waste

Conservation of the availability and guarantee of water quality from the spring is indispensable. One of the company as a provider of raw water in Surabaya made several efforts in maintaining the balance between quality and availability of water for sustainability . One method that can be used in aquifer monitoring of springs is the 2D Resistivity method. This study aims to describe the two-dimensional subsurface aquifers of Durensewu and Karangjati springs. The inversion result of 2D resistivity data shows the constituent rocks in the research area in the form of clay, sand, and loam clay with resistivity value 50-150 Ohm.m where sand rocks are identified as aquifer rocks at depths of 2-7 meters and a thickness of about 2-5 meters. The aquifers of Durensewu and Karangjati water sources are shown to have different systems. Escherichia coli contamination from domestic waste found in Durensewu springs is caused by aquifer connected to surface water flow, but not found in Karangjati spring.

Lipid analysis of CO2-rich subsurface aquifers suggests an autotrophy-based deep biosphere with lysolipids enriched in CPR bacteria

Sediment-hosted CO2-rich aquifers deep below the Colorado Plateau (USA) contain a remarkable diversity of uncultivated microorganisms, including Candidate Phyla Radiation (CPR) bacteria that are putative symbionts unable to synthesize membrane lipids. The origin of organic carbon in these ecosystems is unknown and the source of CPR membrane lipids remains elusive. We collected cells from deep groundwater brought to the surface by eruptions of Crystal Geyser, sequenced the community, and analyzed the whole community lipidome over time. Characteristic stable carbon isotopic compositions of microbial lipids suggest that bacterial and archaeal CO2 fixation ongoing in the deep subsurface provides organic carbon for the complex communities that reside there. Coupled lipidomic-metagenomic analysis indicates that CPR bacteria lack complete lipid biosynthesis pathways but still possess regular lipid membranes. These lipids may therefore originate from other community members, which also adapt to high in situ pressure by increasing fatty acid unsaturation. An unusually high abundance of lysolipids attributed to CPR bacteria may represent an adaptation to membrane curvature stress induced by their small cell sizes. Our findings provide new insights into the carbon cycle in the deep subsurface and suggest the redistribution of lipids into putative symbionts within this community.

A comparative study of methods for determining carbonate content in marine and terrestrial sediments

Abstract Carbonate can be produced in a variety of environments on the Earth's surface, such as shallow seas and deep oceans, continental lakes, soils and subsurface aquifers. The carbonate content of sediments is an important proxy in paleoceanography and paleoclimatology and is often used to reconstruct paleoenvironmental evolution of the earth. Many methods have been reported to measure the content of carbonate in sediments, but how those methods perform (e.g. degree of accuracy and precision, error-induced factors, operability, cost and time) remains understudied. Here, we employ three widely-used non-instrumental methods, including acid-base titration, gasometric method, and loss on ignition (LOI) based on muffle combustion, together with X-ray diffraction for mineral phase analysis, to compare the carbonate content data of sediments from deep ocean (water depths from 1218 m to 6147 m) of the western Pacific and Cenozoic sedimentary rocks from the Qaidam basin, northern Tibetan Plateau. The results show that data accuracies of most methods are closely related to mineral compositions in sediments (e.g. carbonate species and clay mineral contents) and analytical operations. Non-instrumental methods generally demonstrate low precisions (avg. RSD of 3.36%) in determining sediments with low carbonate contents (

Complete Genome of a Member of a New Bacterial Lineage in the Microgenomates Group Reveals an Unusual Nucleotide Composition Disparity Between Two Strands of DNA and Limited Metabolic Potential.

The candidate phyla radiation is a large monophyletic lineage comprising unculturable bacterial taxa with small cell and genome sizes, mostly known from genomes obtained from environmental sources without cultivation. Here, we present the closed complete genome of a member of the superphylum Microgenomates obtained from the metagenome of a deep subsurface thermal aquifer. Phylogenetic analysis indicates that the new bacterium, designated Ch65, represents a novel phylum-level lineage within the Microgenomates group, sibling to the candidate phylum Collierbacteria. The Ch65 genome has a highly unusual nucleotide composition with one strand of highly enriched in cytosine versus guanine throughout the whole length. Such nucleotide composition asymmetry, also detected in the members of Ca. Collierbacteria and Ca. Beckwithbacteria, suggests that most of the Ch65 chromosome is replicated in one direction. A genome analysis predicted that the Ch65 bacterium has fermentative metabolism and could produce acetate and lactate. It lacks respiratory capacity, as well as complete pathways for the biosynthesis of lipids, amino acids, and nucleotides. The Embden–Meyerhof glycolytic pathway and nonoxidative pentose phosphate pathway are mostly complete, although glucokinase, 6-phosphofructokinase, and transaldolase were not found. The Ch65 bacterium lacks secreted glycoside hydrolases and conventional transporters for importing sugars and amino acids. Overall, the metabolic predictions imply that Ch65 adopts the lifestyle of a symbiont/parasite, or a scavenger, obtaining resources from the lysed microbial biomass. We propose the provisional taxonomic assignment ‘Candidatus Chazhemtobacterium aquaticus’, genus ‘Chazhemtobacterium‘, family ‘Chazhemtobacteraceae‘ in the Microgenomates group.

Groundwater Aquifer Vulnerability Assessment using a Dar-Zarrouk Parameter in a Proposed Aboru Residential Estate, Lagos State, Nigeria

The need to build an automobile mechanic settlement, abattoir and a proposed meat processing factory at Aboru residential estate necessitated a geophysical assessment (using a Dar-Zarrouk parameter – longitudinal unit conductance, S) of the vulnerability of the subsurface aquifers in the study area against the expected long-term anthropogenic impacts of these facilities on the groundwater system. Thirteen (13) Vertical Electrical Sounding (VES) points and four (4) Dipole-Dipole resistivity profile lines were occupied on four traverse lines across the study area. Isoresistivity and Isopach maps were generated and Total Longitudinal Unit Conductance, S of the earth materials overlying the aquifer was computed and the aquifer protective capacity (APC) map was generated. The VES delineated four (4) geo-electric layers namely; topsoil, pebbly/lateritic sand, clay/clayey/silty sand and sandstone. The depth to the sandstone aquifer ranges from 30.6 – 39.4 m with resistivity values ranging from 851 – 1437 Ωm. The iso-resistivity and isopach maps reveal that the near surface lateritic materials with resistivity values ranging from 350 – 1150 Ωm and thicknesses ranging from 2 – 29 m are pervious. The Total Longitudinal Unit Conductance, S varies from 0.0164 - 0.1168 mhos indicating a poor to weak protective capacity rating across the study area and the APC map reveals that the north-eastern and western parts of the study area show areas with weak protective capacity ratings while other areas are characterized by poor protective capacity rating. As such, the establishment of the proposed service facilities in the study area is strongly discouraged as the nature of their operations has a high potential to contaminate and eventually pollute the sub-surface aquifers on the long-run. If however the inevitability of their establishment cannot be set-aside, then secondary measures must be taken to forestall a direct impact of their operations on the subsurface. Keywords : Aquifer, Dar-Zarrouk, Vulnerability, Longitudinal Unit Conductance

Contaminant transport forecasting in the subsurface using a Bayesian framework

In monitoring subsurface aquifer contamination, we want to predict quantities—fractional flow curves of pollutant concentration—using subsurface fluid flow models with expertise and limited data. A Bayesian approach is considered here and the complexity associated with the simulation study presents an ongoing practical challenge. We use a Karhunen–Loève expansion for the permeability field in conjunction with GPU computing within a two–stage Markov Chain Monte Carlo (MCMC) method. Further reduction in computing costs is addressed by running several MCMC chains. We compare convergence criteria to quantify the uncertainty of predictions. Our contributions are two-fold: we first propose a fitting procedure for the Multivariate Potential Scale Reduction Factor (MPSRF) data that allows us to estimate the number of iterations for convergence. Then we present a careful analysis of ensembles of fractional flow curves suggesting that, for the problem at hand, the number of iterations required for convergence through the MPSRF analysis is excessive. Thus, for practical applications, our results provide an indication that an analysis of the posterior distributions of quantities of interest provides a reliable criterion to terminate MCMC simulations for quantifying uncertainty.

Cometabolic biotransformation of 1,4-dioxane in mixtures with hexavalent chromium using attached and planktonic bacteria

Biological treatment of 1,4-dioxane, a probable human carcinogen and a recalcitrant contaminant of concern, is often complicated by the presence of inhibitory co-contaminants. Due to its use as a solvent, wetting agent, and stabilizer for chlorinated solvents employed in metal vapor degreasing, 1,4-dioxane has often been found to occur with a variety of co-contaminants, including heavy metals such as hexavalent chromium [Cr(VI)]. Cr(VI) also occurs naturally in groundwater due to geological formations, but also has sources that can coincide with 1,4-dioxane from anthropogenic activities such as metal vapor degreasing. Biodegradation of 1,4-dioxane can be accomplished by microbes that use it as a source of carbon or energy as well as those that cometabolize it after growth on other organic substrates. A propanotroph, Mycobacterium austroafricanum JOB5, was grown in planktonic pure cultures and biofilms to determine its ability to cometabolize 1,4-dioxane in the presence of varying concentrations of Cr(VI). 1,4-Dioxane cometabolism by JOB5 planktonic cells was uninhibited by Cr(VI) at levels up to 10 mg/L, while biofilms were only mildly inhibited at 10 mg/L. As an important part of the biofilms commonly found in subsurface aquifers and engineered systems, extracellular polymeric substances (EPS) were found to play an important role in preventing Cr(VI) exposure to cells. We observed that soluble EPS were able to bind to Cr(VI) and theorize that biofilm-associated EPS additionally served to impede penetration of the biofilm structure by Cr(VI), thus mitigating exposure and toxicity. These findings suggest that bioremediation would be a viable treatment strategy for 1,4-dioxane-contaminated waters that contain elevated levels of Cr(VI) in natural and built environments.

Transport and retention of hydrochar-diatomite nanoaggregates in water-saturated porous sand: Effect of montmorillonite and phosphate at different ionic strengths and solution pH

Hydrochar, a solid hydrate with a high energy density, is produced by hydrothermal carbonization of lignocellulosic biomass and is widely applied in agriculture as a soil amendment. The fate and transport of hydrochar when applied to soil need to be investigated. The major components of soil, clay and phosphate, likely interact with hydrochar in the subsurface. This study investigated the cotransport behavior of hydrochar and diatomite (D) through water-saturated quartz sand in the presence of montmorillonite (M) and/or phosphate in NaCl (1–50 mM) solutions at pH 6.0 and 9.0. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images and zeta potential (ZP) results showed that hydrochar-D nanoaggregates formed preferentially due to surface charge heterogeneity. M inhibited the transport of hydrochar-D in sand columns regardless of the solution pH mainly because the organo-mineral clusters of hydrochar-D with M were prone to filling the pores of the sand medium. Moreover, fine M particles preferentially attached to sand could decrease the ZP of the sand surface and subsequently decrease the repulsive forces between hydrochar-D and sand. The copresence of M and phosphate slightly facilitated hydrochar-D transport at pH 6.0 due to phosphate adsorption, whereas a negligible effect on transport occurred at pH 9.0. Thus, phosphate played a predominant role in the transport of hydrochar when clays were also present. A two-site kinetic retention model suggested that k1d/k1 and k2 are responsible for hydrochar-clay aggregate deposition in sand. Our findings relate to the potential risks posed by hydrochar in subsurface soils and aquifers where clay and phosphate ubiquitously co-occur.

Efficient Simulations for Contamination of Groundwater Aquifers under Uncertainties

AbstractAccurate modeling of contamination in subsurface flow and water aquifers is crucial for agriculture and environmental protection. Here, we demonstrate a parallel method to quantify the propagation of the uncertainty in the dispersal of pollution in density‐driven flow. We solve an Elder‐like problem, where we use random fields to model the limited knowledge on the porosity and permeability. The uncertain solution, mass fraction, is approximated via low‐cost generalized polynomial chaos expansion (gPCE). Parallelization is done in both the physical and parametric spaces.

Sphingobacterium puteale sp. nov., isolated from a deep subsurface aquifer.

A bacterial strain M05W1-28T was isolated from a well that collected water for irrigation from a deep aquifer at a depth of 400 m. Cells were observed to be rod-shaped, non-motile, aerobic, stained Gram-negative. Optimal growth was obtained at pH 7.0 (range: 6.0-9.0), 28 °C (range: 15-37 °C) and 0 % NaCl (range: 0-1.5 %, w/v) in modified tryptic soy broth (mTSB) without added NaCl and R2A. The cells were found to be positive for catalase and oxidase activities. The major fatty acids (>10 %) were identified as summed feature 3 (C16 : 1 ω7c / C16 : 1 ω6c) and iso-C15 : 0. The major polar lipids were phosphatidylethanolamine, glycolipid, phosphoglycolipids, phospholipids, and unidentified lipids. The major respiratory quinone was menaquinone-7 (MK-7). The genomic G+C content of strain M05W1-28T was 40.7 %. Based on similarities of 16S rRNA gene sequences, strain M05W1-28T was affiliated with the genus Sphingobacterium, exhibiting the highest sequence similarities with S. multivorum LMG 8342T (97.5 %), S. ginsenosidimutans THG07T (97.1 %) and less than 97.0 % to other members of the genus. The average nucleotide identity (ANI) and digital DNA-DNA hybridisation values (dDDH) between M05W1-28T and S. multivorum LMG 8342T were 78.1 and 22.5 %, respectively. Phenotypic characteristics including enzyme activities and carbon source utilisation differentiated the strain from other Sphingobacterium species. The phenotypic, chemotaxonomic and phylogenetic properties suggested that strain M05W1-28T represented a novel species within the genus Sphingobacterium, for which the name Sphingobacterium puteale sp. nov. is proposed. The type strain is M05W1-28T (=CGMCC 1.13711T=KCTC 72027T).

Integrated Geophysical Investigation in Delineating Extent of Pollution Caused by Poultry Waste at Ilora Area, Southwestern Nigeria

An integrated VLF-Electromagnetic and Electrical Resistivity survey was carried out in Odo Abata, Ilora area of Southwestern Nigeria in order to investigate the possible extent of groundwater contamination caused by an indiscriminate accumulation of poultry fecal droppings in a seasonal stream. The poultry fecal accumulation solidifies during the dry season and the percolating water plays a significant role in leachate generation and infiltration during the wet season. When in contact with the subsurface aquifer, the leachate forms a plume which diffuses into the pore spaces of aquifer with high rate of infiltration. Field data were collected using ABEM WADI VLF- EM equipment and campus Tigre Terrmeter. A total of eight VLF profiles, four electrical imaging profiles and two VES points were obtained in the vicinity of the study area. Control profiles and VES point were obtained at 500 m away from the study area. Field data were interpreted using KHFFilt program version 1.1a for VLF, Dipro software for electrical imaging and Winresist version 1.0 for VES data. Interpretation of VLF data showed conductive near surface layers and some fractures at depth. Electrical imaging data however revealed a near surface very low resistivity region which is due to the surface fecal accumulation. VES results showed that the overburden is clayey, and the basement is fractured. Depth to basement ranges from 9.3 – 12.8 m. Poultry fecal accumulation with leachate is mostly restricted to the topmost 6 m of the soil and if not controlled, leachate infiltration may reach the shallow basement with time and contaminate the groundwater system of Odo Abata area. Keywords: Very Low Frequency Electromagnetic (VLF-EM), Electrical Resistivity, Contamination, Leachate, Fracture DOI : 10.7176/JEES/9-10-09 Publication date :October 31 st 2019

DNA- and RNA- Derived Fungal Communities in Subsurface Aquifers Only Partly Overlap but React Similarly to Environmental Factors.

Recent advances in high-throughput sequencing (HTS) technologies have revolutionized our understanding of microbial diversity and composition in relation to their environment. HTS-based characterization of metabolically active (RNA-derived) and total (DNA-derived) fungal communities in different terrestrial habitats has revealed profound differences in both richness and community compositions. However, such DNA- and RNA-based HTS comparisons are widely missing for fungal communities of groundwater aquifers in the terrestrial biogeosphere. Therefore, in this study, we extracted DNA and RNA from groundwater samples of two pristine aquifers in the Hainich CZE and employed paired-end Illumina sequencing of the fungal nuclear ribosomal internal transcribed spacer 2 (ITS2) region to comprehensively test difference/similarities in the “total” and “active” fungal communities. We found no significant differences in the species richness between the DNA- and RNA-derived fungal communities, but the relative abundances of various fungal operational taxonomic units (OTUs) appeared to differ. We also found the same set of environmental parameters to shape the “total” and “active” fungal communities in the targeted aquifers. Furthermore, our comparison also underlined that about 30%–40% of the fungal OTUs were only detected in RNA-derived communities. This implies that the active fungal communities analyzed by HTS methods in the subsurface aquifers are actually not a subset of supposedly total fungal communities. In general, our study highlights the importance of differentiating the potential (DNA-derived) and expressed (RNA-derived) members of the fungal communities in aquatic ecosystems.

Radiometric and electromagnetic investigations of the Olushosun dumpsite Lagos, Southwest, Nigeria

Abstract The Olushosun dumpsite is one of the largest dumpsites in Nigeria, and variety of waste materials are often deposited on the dumpsite. Therefore, radiometric and electromagnetic (EM) investigation of the dumpsite was embarked upon to assess the radioactive status and the extent of leachate contamination. A well calibrated portable radiometric spectrometer nuclear radiation monitoring metre (Model BG0-Super-SPEC RS 230) and the Geonics EM 34 measuring instruments were used to achieve this objective. The mean activity concentration of 40K measured along all the profile lines ranged from 0.22% to 1.19% (68.86–372.47 Bq/kg), while that of 238U and 232Th ranged from 0.88 ppm to 2.02 ppm (10.87–24.95 Bq/kg) and from 4.87 ppm to 15.61 ppm (19.65–63.38 Bq/kg) respectively. The results of the radiation dose rate measurement showed that the overall mean absorbed dose rate measured in the study area were comparable to those reported around some cities in Nigeria. The radiation level along some points on the profile lines, even though high, did not exceed the safe limit of 70 μSvyr−1 as recommended by UNESCO on effect of Atomic Radiation. This implies that the inhabitants around this area are not exposed to radiological risk, and the dumpsite when reclaimed in future, could be used for the construction of buildings without any form of restrictions. However, continuous exposure to these radiations may have long term consequences on human health. Results from the EM data set along traverses on the dumpsite show that the subsurface is characterised by high conductivity (60–680 mS/m) up to a depth of 60 m. The high terrain conductivity signature here may be attributed to leached contaminats migrating into the subsurface and contaminating shallow aquifers. The descriptive statistical analysis of the measured EM data sets showed higher level of correlation among parameters measured along control lines outside of the dumpsite. Generally, correlation between the entire EM data on the dumpsite was poor, but reasonably better for the control data. This could be attributed to the heterogeneous properties of waste materials deposited on the dumpsite.

Assessment groundwater occurrences using VES/TEM techniques at North Galala plateau, NW Gulf of Suez, Egypt

Water resources assessment is important for urbanization and industrial projects in remote areas. As the area is far from the Nile and characterized by rarity of rainfall, the main source of freshwater is groundwater. Vertical Electrical Sounding (VES) and Time Domain Electromagnetic (TEM) methods are chosen. To overcome the ambiguity, TEM station no.1 was conducted close to a borehole. The information from the borehole includes lithology and producing aquifer zones. The processing started with the inversion of VES data then use the models obtained as the primary model for TEM inversion. The last models from VES and TEM were further used to construct 3 geoelectrical profiles and 8 contour maps illustrating subsurface water-bearing aquifers electric resistivity. From the results, two aquifers are found divided by a highly conductive clay unit. The shallow one is consisting of coarse sand with silt. It displays moderate to low resistivity, depth ranging from 6 m to 33 m underground surface and a thickness of 15–35m. On the other hand, the deep one shows low resistivity values that may show brackish to fresh water with depths to the upper surface ranges from 58m to 118m and thickness distribution of 26–80m. In general, the groundwater flow is expected to be from southwest to northeast towards Suez Gulf as indicated by the elevation trending of the aquifers. According to the resistivity distribution, the direction of seawater intrusion is the northeast in the directions of Suez Gulf.

Biased Estimation of Groundwater Velocity from a Push-Pull Tracer Test Due to Plume Density and Pumping Rate

The single-well push-pull tracer test is a convenient and cost-effective tool to estimate hydrogeological properties of a subsurface aquifer system. However, it has a limitation that test results can be affected by various experimental designs. In this study, a series of laboratory-scale push-pull tracer tests were conducted under various conditions controlling input tracer density, pumping rate, drift time, and hydraulic gradient. Based on the laboratory test results, numerical simulations were performed to evaluate the effects of density-induced plume sinking and pumping rate on the proper estimation of groundwater background linear velocity. Laboratory tests and numerical simulations indicated that the actual linear velocity was underestimated for the higher concentration of the input tracer because solute travel distance and direction during drift time were dominantly affected by the plume density. During the pulling phase, reasonable pumping rates were needed to extract the majority of injected tracer mass to obtain a genuine center of mass time (tcom). This study presents a graph showing reasonable pumping rates for different combinations of plume density and background groundwater velocity. The results indicate that careful consideration must be given to the design and interpretation of push-pull tracer tests.

Mobility and transport behavior of lead in agricultural soils

Abstract The description of contaminant transport behavior in porous media is essential to optimally manage soils and subsurface aquifers, and to deal with chemical pollution in these resources. This study was conducted to examine the transport behavior of Pb through soil columns at different concentrations of Pb. Soil columns were collected from three different agricultural fields, namely, close canopy cocoa (CCC), open canopy cocoa (OCC) and an arable field grown with maize. The soils from all the three fields had a loamy sand texture. Soil from the CCC field had the best structure as evinced by the high total porosity (f), macroporosity (fm), soil organic carbon (SOC), and saturated hydraulic conductivity (Ks), and low bulk density (BD). The results indicated that high concentrations of applied Pb resulted in high concentrations of Pb in the effluents. In addition, the transport of Pb through the soil columns were found to be significantly affected by SOC, f, fm, Ks, and BD. The highest rates of Pb leaching at all application concentrations were observed in the CCC soil, and the least in the arable field.

Complete Genome Sequence of an Uncultured Bacterium of the Candidate Phylum Bipolaricaulota

Bacteria of the candidate phylum Bipolaricaulota, previously known as OP1 and Acetothermia, have been identified in various terrestrial and marine ecosystems as a result of molecular analysis of microbial communities. To date, none of the members of Bipolaricaulota has been isolated in a pure culture. We assembled the complete closed genome sequence of the bacterium of this phylum from the metagenome of a subsurface thermal aquifer and used the genomic data to analyze the phylogenetic position and metabolic potential of this bacterium. Analysis of the genome of this bacterium, designated Ch78, revealed various transporters of sugars and peptides and limited capacities for the extracellular hydrolysis of polysaccharides. Reconstruction of the central metabolic pathways suggested that the bacterium Ch78 is an anaerobic organotroph capable of fermenting sugars and proteinaceous substrates. Known pathways of aerobic and anaerobic respiration, as well as of autotrophic carbon fixation, were not found in the Ch78 genome. In the subsurface aquifer Bipolaricaulota probably consume low-molecular weight organic compounds and produce hydrogen and acetate. Based on the results of phylogenetic and genomic analysis, classification of the novel bacterium as “Candidatus Bipolaricaulis sibiricus” is proposed.

Behavior of rare earth elements in an aquifer perturbed by CO2 injection: Environmental implications

Three cubic-meters of CO2-saturated water was injected into a subsurface fractured aquifer in a post-mined area, using a push-pull test protocol. Groundwater samples were collected before and after CO2-injection to quantify geochemical changes. CO2-injection initially reduced the pH of water from 7.3 to 5.7, led to the enrichment of major ions (Ca2+, Mg2+, and alkalinity), and dissolved trace metals (including Fe, Mn, As, and Zn) in the groundwater. Rare earth elements (REE) and yttrium concentrations were also measured in these samples before and after CO2 perturbation, to evaluate their behavior. An enrichment of total Y plus REE (REY) occurred. REY fractionation was observed with higher heavy REE (HREE) enrichment compared to light REE (LREE), and significant variations in La/Yb and Y/Ho ratios were observed following CO2 perturbation. Enrichment by a factor of three was observed for Y, Lu, and Tm, and by nearly one order of magnitude for Dy and Yb. A geochemical model was used to evaluate the amount of REE aqueous ions complexed throughout the experiment. Modeling of the results showed that speciation of dissolved REE with carbonate, along with desorption from iron oxyhydroxide surface were the main factors controlling REE behavior. This study increases an understanding of dissolved REE behavior in the environment, and the potential use for applying iron oxides for REE recovery from mine drainages. Furthermore, the description of REE fractionation patterns may assist in surveying CO2 geological storage sites, surveying underground waste disposal sites, and for understanding the formation of ore deposits and fluid inclusions in geological formations.

Hydrogeologic Characterization of a Fault-Related Dome Using Outcrop, Borehole and Electrical Resistivity Data

Geological structures introduce heterogeneity along deformed strata, which in turn exert a strong control on regional groundwater occurrences and water flow. We developed and applied procedures of structural, borehole and direct current resistivity (DCR) data to (1) figure out a reliable structural model of a fault-related dome, (2) visualize the relationship between structural complexity and aquifers geometry and (3) characterize the fault damage zones and its related sealing potentialities. The present approach was applied at the northern Eastern Desert, Egypt, considering its complex deformation history. To alleviate the uncertainties and artifacts in solving the DCR inverse problem, advanced and non-conventional inversion schemes were applied. Moreover, fault seal potentialities were assessed by applying the shale gouge ratio (SGR) estimation to predict the groundwater pathway flow. The main findings include: (a) The DCR measurements can be considered as a complementary tool to visualize the relationship between subsurface structures and aquifers geometry at highly deformed areas; (b) detailed surface structural data analysis combined with sophisticated inversion algorithms application can increase the reliability of the constructed geo-electrical cross sections for deep and large-scale geological surveys; and (c) the structural modeling of geological units and faults distribution contributes to clarify hydrogeological settings and aquifers connectivity. The approach can be readily applied elsewhere, as long as detailed structural analysis, geometric parameters and high-resolution DCR resistivity data are available.