Chemical Analysis Of Groundwater Research Articles

Determination of redox potential of sulfidic groundwater in unconsolidated sediments by long-term continuous in situ potentiometric measurements

This study was undertaken to investigate the redox potential (Eh) of sulfidic groundwater in unconsolidated sediments. The Eh was determined by long-term (several days to several weeks) continuous in situ potentiometric measurements using a platinum (Pt) electrode. The Eh values measured in two monitoring campaigns were -259 and -202 mV, respectively. Chemical analysis of groundwater showed that the redox species in the groundwater were sulfide (S²⁻) and iron, respectively. The saturation indices calculated from the chemical analysis results indicated that FeS(am) and mainly mackinawite were close to equilibrium in the analyzed waters. Comparison of the measured Eh values with those calculated using different redox couples revealed that the Eh values measured in the first monitoring campaign were nearly equal to those calculated using HS⁻/SO₄²⁻, S²⁻/SO₄²⁻, FeS(am)/SO₄²⁻, and mackinawite/SO₄²⁻ redox couples; on the other hand, the Eh values measured in the second monitoring campaign were almost consistent with those measured using the FeS₂/SO₄²⁻ redox couple. The good fit between the measured Eh values and the theoretical calculated Eh values suggests that the sulfur system is related to the Eh value of sulfidic groundwater in unconsolidated sediments.

Combining geophysical data sets to study the dynamics of shallow evaporites in urban environments: application to Hamburg, Germany

SUMMARY Shallowly situated evaporites in built-up areas are of relevance for urban and cultural development and hydrological regulation. The hazard of sinkholes, subrosion depressions and gypsum karst is often difficult to evaluate and may quickly change with anthropogenic influence. The geophysical exploration of evaporites in metropolitan areas is often not feasible with active industrial techniques. We collect and combine different passive geophysical data as microgravity, ambient vibrations, deformation and hydrological information to study the roof morphology of shallow evaporites beneath Hamburg, Northern Germany. The application of a novel gravity inversion technique leads to a 3-D depth model of the salt diapir under study. We compare the gravity-based depth model to pseudo-depths from H/V measurements and depth estimates from small-scale seismological array data. While the general range and trend of the diapir roof is consistent, a few anomalous regions are identified where H/V pseudo-depths indicate shallower structures not observed in gravity or array data. These are interpreted by shallow residual caprock floaters and zones of increased porosity. The shallow salt structure clearly correlates with a relative subsidence in the order of 2 mm yr −1. The combined interpretation of roof morphology, yearly subsidence rates, chemical analyses of groundwater and of hydraulic head in aquifers indicates that the salt diapir beneath Hamburg is subject to significant ongoing dissolution that may possibly affect subrosion depressions, sinkhole distribution and land usage. The combined analysis of passive geophysical data may be exemplary for the study of shallow evaporites beneath other urban areas.

Relações Água-Rocha e a Hidrogeoquímica do Cromo na Água Subterrânea de Poços de Monitoramento Multiníveis de Urânia, SP, Brasil

Teores anômalos e naturais de cromo ocorrem nas águas subterrâneas do Aquífero Adamantina no município de Urânia (SP) e em uma ampla região do oeste do Estado de São Paulo, algumas vezes ultrapassando o limite de potabilidade (0,05 mg.L-1). Visando identificar as possíveis reações geoquímicas que justificam a ocorrência do cromo na água subterrânea em Urânia, foram realizadas perfurações com coleta de amostras contínuas de rocha para a condução de análises mineralógicas e químicas, construídos poços de monitoramento multiníveis e realizadas coletas e análises de amostras estratificadas de água subterrânea. Análises das amostras de testemunhos de sondagem indicaram a ocorrência de uma anomalia geoquímica de cromo (concentrações médias de 221 ppm), sendo o diopsídio cromífero provavelmente o mineral geoquimicamente mais reativo que contribui para esta anomalia, apresentando concentrações de cromo de 1.000 a 6.000 ppm. As análises químicas de amostras de água coletadas dos poços de monitoramento indicaram uma estratificação hidroquímica do aquífero: águas na base do aquífero apresentam pH anomalamente alcalino (superior a 10), enquanto águas mais rasas possuem pH neutro a ligeiramente ácido. O cromo ocorre predominantemente na forma hexavalente e alcança concentrações máximas de 0,13 mg.L-1. As reações geoquímicas que explicam a passagem do cromo da fase sólida para a água provavelmente envolvem a dissolução de minerais contendo Cr3+ (diopsídios), seguida de uma reação redox que oxida o Cr3+ para o Cr6+, provavelmente relacionada com a redução de óxidos de manganês presentes no aquífero. Adicionalmente, devem também ocorrer reações de adsorção, sendo que os ambientes de pH elevados favorecem a dessorção e mobilização do Cr6+ para a água

Appraisal of highly fluoride zones in groundwater of Kurmapalli watershed, Nalgonda district, Andhra Pradesh (India)

Fluoride (F) contamination study had been carried out to see its allocation in Kurmapalli watershed, Nalgonda district, Andhra Pradesh, India. The study area is located about 60 km SE of Hyderabad city. The groundwater is the main source of water for their living. The groundwater in villages and its surrounding are affected by fluoride contamination and consequently the majority of the people living in these villages has health hazards and is facing fluorosis. The purpose of this study is to identify the wells with high F, raise awareness in people, study the water chemistry, and also find out the source of F in groundwater. A total of 32 groundwater samples were collected from different wells in both shallow aquifers and deeper fractures zones during October 2004. The chemical analysis of groundwater has been done. Fluoride values vary from 0.7 to 19.0 mg/l. It is noted that the maximum value (19.0 mg/l) is one of the highest values found in groundwater in India and 78% of the total samples show F concentrations that exceeds the permissible limit value (1.5 mg/l). The highest value of F is found at Madanapur bore well which is located at central part of the watershed. The F value of this bore well was monitored from October 2004 to October 2006. During this period the F concentration varies from 17.8 to 21.0 mg/l with mean 19.3 mg/l. There is no correlation of F with chemical parameters except calcium. The Ca has shown inverse proportional with F. Water–rock interaction studies were also carried out to understand the behavior of F in groundwater at prominent F affected areas. Rock samples were collected and analyzed, and found their enrichment of F. The anthropogenic possibility of F is almost negligible. The rocks of this area are enriched in F from 460 to 1,706 mg/kg. It is indicated that the rock–water interaction is the main source of F in groundwater. The highest values of F are found in middle part of the region and are related to the occurrence of fluoride rich rocks and their chemical kinetic behavior with groundwater.

Influence of hydrostratigraphy and structural setting on the arsenic occurrence in groundwater of the Cimino-Vico volcanic area (central Italy)

Arsenic occurrence in groundwater near the Cimino-Vico volcanoes (central Italy) was analysed considering the hydrostratigraphy and structural setting and the shallow and deep flows interacting within the Quaternary volcanics. Groundwater is the local source of drinking water. As documented in the past, arsenic in the groundwater has become a problem, and the European maximum allowable contaminant level was recently lowered to 10 μg/L. Chemical analyses of groundwater were conducted, sampled over an area of about 900 km2, from 65 wells and springs representative of the volcanic aquifer and thermal waters. Considering the type of aquifer, the nature of the aquifer formation and its substratum, the hydrochemical data highlight that the arsenic content of the groundwater is mainly connected with the hydrothermal processes in the volcanic area. Thermal waters (54–60°C) fed from deep-rising fluids show higher arsenic concentrations (176–371 μg/L). Cold waters sampled from the volcanic aquifer are characterized by a wide variability in their arsenic concentration (1.6–195 μg/L), and about 62% exceed the limit of 10 μg/L. Where the shallow volcanic aquifer is open to deep-rising thermal fluids, relatively high arsenic concentrations (20–100 μg/L) are found. This occurs close to areas of the more recent volcano-tectonic structures.

Aplicação dos métodos eletromagnéticos indutivo, eletrorresistividade eip domínio do tempo em caracterização geoambiental

This project aims characterizing environmental problem generated in Serrana Landfill region, contained in Ribeirao Preto city (SP). In there, due to a huge soil cavity originated from sand extraction used in building site, the disposal of domestic, industrial and hospital residues started in mid 1970s. Nowadays, this landfill is saturated and without activity. However, damages caused by the inadequate residue disposition are still present, and the generated contamination plume still remains. The methodology used in this work consists in the integration of geophysical techniques efficient in the evaluation and characterization of environmental problems. The focus in here is to apply geophysical prospecting methods, such as resistivity, induced polarization related to time domains as well as electromagnetic inductive method, in geotechnical and environmental studies. The project was based on a compilation and reinterpretation of a large amount of pre-existent geophysical data as well as those collected during work conduction associated to surface geology and well data. In such way, with integrated information it attempted to study parameters to evaluate problems associated to tropical soil and groundwater contamination for urban residue landfill. This project accomplishment intends to achieve two main objectives. First of all it was application and interpretation of geoelectrical assays to a better geological characterization from the area. Geophysical data were linked to geological information from existent wells for a better local geology interpretation and definition. The second objective was the environmental problem characterization by using geophysical method and some water chemical analysis available by Ribeirao Preto City hall. In this context, it was also studied a geophysical parameter behavior of chargeability and time constant in digging delimitation filled out with residues from leachate shallow area and contamination plume inside of saturated area (deep area), once two mentioned parameter answers are not well known. This unknowing answer never happens with resistivity (and conductivity) case. The use of results obtained from electrical sounding has interpreted base on information about water monitoring wells and leachate collection, deep tubular wells, auger sounding, and surface geology made possible a better knowledge about landfill geology, which presents complex contact among three different geological units, and two types of aquifer. Since geological model establishment, results of electric profiling (resistivity and induced polarization) can be used in order to understand the association between residues and environment in landfill limits. Results of electromagnetic profile make possible a visualization of environmental impact in landfill zone and its surrounding as well as the establishment of hypothesis about format and way of contamination plume whose existence in the zone is verified by data from groundwater chemical analysis.

Assessment of groundwater contamination by landfill leachate: A case in México

In México, uncontrolled landfills or open-dumps are regularly used as "sanitary landfills". Interactions between landfills/open-dumps and shallow unconfined aquifers have been widely documented. Therefore, evidence showing the occurrence of aquifer contamination may encourage Mexican decision makers to enforce environmental regulations. Traditional methods such as chemical analysis of groundwater, hydrological descriptions, and geophysical studies including vertical electrical sounding (VES) and ground penetrating radar (GPR) were used for the identification and delineation of a contaminant plume in a shallow aquifer. The Guadalupe Victoria landfill located in Mexicali is used as a model study site. This landfill has a shallow aquifer of approximately 1m deep and constituted by silty sandy soil that may favor the transport of landfill leachate. Geophysical studies show a landfill leachate contaminant plume that extends for 20 and 40 m from the SE and NW edges of the landfill, respectively. However, the zone of the leachate's influence stretches for approximately 80 m on both sides of the landfill. Geochemical data corroborates the effects of landfill leachate on groundwater.

COMPORTAMENTO DE ÍONS DE CHUMBO ASSOCIADOS A ATERROS DOMÉSTICOS

This work was performed in an area with three domestic landfills where the groundwater, sedimentsand soil are seriously contaminated due to the ions of lead, most likely because of the landfill. In some sampling points,results from chemical analysis of groundwater were four times greater than the criteria established by environmentalagencies. The soil, due to its unfavorable capability to hold lead, is other risk factor to environmental disturbance in thearea. Analysis by Diffraction of X ray showed the tendency of caulinite and gibbsite, which combined with a low valor ofionized change capacity and organic matter, makes the soil not able to absorbed metal ion. On the other hands, to all thesefactors is added the human activities in the neighborhood. The population uses water from a shallow drinking well andbesides there is also farming and vegetable grown in the surroundings.

A geophysical and geochemical approach for seawater intrusion assessment in the Acquedolci coastal aquifer (Northern Sicily)

Vertical electrical sounding (VES’) surveys and chemical analyses of groundwater have been executed in the coastal plain of Acquedolci (Northern Sicily), with the aim to circumscribe seawater intrusion phenomena. This urbanized area is representative of a more general problem interesting most of Mediterranean littoral areas, where intensive overdraft favors a heavy seawater intrusion through the coastline. Aquifer resistivity seems decisively to be conditioned by the chlorine and magnesium content in the main aquifer of the region. Schlumberger VES’, together with piezometric and chemical–physical information of groundwater, allowed us to perform hydrogeological and geophysical elaborations, to propose the occurrence of a relatively narrow belt marked by fresh–salt water mixing. In the considered plain, pollution risk studies have been already realized by authors with the proposal to identify—by parametric and synthetic zoning of significant hydrogeological elements—the most vulnerable sectors. In detail, an intrinsic vulnerability mapping has been already performed, applying the well-known SINTACS system. This paper intends to give—in this sector of Sicily—an example of integration of different methodologies, showing the role of geophysics to describe the degradation of aquifers on the whole as well as to assess their pollution risk better.

Chemical analysis of ground water collected from different areas of Antiri and some nearby villages, Gwalior (M.P.)

Water is most essential to life next to air only .Ground water is most important for water supply for irrigation, industries and drinking purpose. Safe drinking water is primary needs of every person. Most of person mainly depends upon ground water sources. Some of these have problems such as excess hardness, sodium, fluoride etc. The natural quality of ground water tends to be degraded by human activities and geo environmental changes. Physico -chemical analysis of bore wells& hand pumps, drinking water has been done in winter season. Different parameters of water has been analyzed and assessed the suitability of drinking water in public hygiene scenario. Some parameters are prescribed by ISI and WHO while other are beyond the limits. 2+ ,Ca 2+ , Na + , K + Cl - , NO 3 - , F - , E.C., T.D.S.

Chemical analysis of groundwater at some selected sites in Jaipur

The results of a 16-month continuous study on the chemical analysis of groundwater with respect to pH. conductivity and concentrations of Ca 2+ , Mg 2+ , NO - 3 Na + , K + , Cl - , HCO - 3 SO 2- 4 , F-, SiO 2 and heavy metals viz. Fe, Co, Cu, Pb, Ni, Zn, Mn at five selected sites in Jaipur are presented. Although at four sites the nitrate concentrations exceed the permissible limits recommended for potable water, at one site the nitrate concentration is unusually high.

Tracing leachates at waste sites using geophysical and geochemical modelling

Tracing leachates at landfills is usually carried out using either geophysical methods or chemical analyses of groundwater. There are often problems with fingerprinting pollution sources or clarifying the spreading pattern due to a wide variety of possibilities giving similar anomalies. The aims of the project were to evaluate the advantages of combining results from multigeophysical modelling and statistical/chemical modelling in order to identify pollution sources and the spreading pattern and to test a new technique for chemical fingerprinting. The project was carried out at a landfill in central Sweden using geophysical measurements and modelling of CVES, GPR and VLF as well as chemical modelling using M3 (multivariate mixing and mass balance calculations). The results indicate that by combining geophysical modelling and chemical calculations, the possibilities of fingerprinting the origin of pollution as well as delineating the spreading pattern are significantly increased.

Integrated geophysical and chemical study of saline water intrusion.

Surface geophysical surveys provide an effective way to image the subsurface and the ground water zone without a large number of observation wells. DC resistivity sounding generally identifies the subsurface formations-the aquifer zone as well as the formations saturated with saline/brackish water. However, the method has serious ambiguities in distinguishing the geological formations of similar resistivities such as saline sand and saline clay, or water quality such as fresh or saline, in a low resistivity formation. In order to minimize the ambiguity and ascertain the efficacy of data integration techniques in ground water and saline contamination studies, a combined geophysical survey and periodic chemical analysis of ground water were carried out employing DC resistivity profiling, resistivity sounding, and shallow seismic refraction methods. By constraining resistivity interpretation with inputs from seismic refraction and chemical analysis, the data integration study proved to be a powerful method for identification of the subsurface formations, ground water zones, the subsurface saline/brackish water zones, and the probable mode and cause of saline water intrusion in an inland aquifer. A case study presented here illustrates these principles. Resistivity sounding alone had earlier failed to identify the different formations in the saline environment. Data integration and resistivity interpretation constrained by water quality analysis led to a new concept of minimum resistivity for ground water-bearing zones, which is the optimum value of resistivity of a subsurface formation in an area below which ground water contained in it is saline/brackish and unsuitable for drinking.

Uncertainties related to sampling and their impact on the chemical analysis of groundwater

It is necessary to take into account the impact of the field stages on the chemical analysis of natural water, in terms of both sampling representativeness and spatial and temporal variability. We demonstrated this need in studies conducted at two industrial sites, which involved groundwater contaminated with metals and organochlorine compounds. We developed a methodology for estimating the uncertainties linked to the entire analytical chain — from sampling to handing over results to the client. This methodology is based on the use of groundwater chemical logs acquired in the field for evaluating field heterogeneity and identifying water levels to be sampled. We validated the methodology through specifically-designed repeatability and reproducibility tests carried out in the field. The results illustrated that a geochemical understanding of the natural environment and the changes it undergoes is possible, but requires an international consensus on the methodology best suited to application in field tests. If not, major inconsistencies and/or erroneous interpretations may arise in environmental monitoring programs.

Characterization of the hydrogeologic environment at a petroleum hydrocarbon contaminated site in Korea

The hydrogeologic environment of a petroleum hydrocarbon contaminated site in Korea is characterized by hydrogeologic field work and chemical analyses of groundwater. Quaternary alluvium is the main aquifer contaminated by petroleum hydrocarbons, mainly TEX (toluene, ethylbenzene and xylenes). Contamination at this site was derived from the leaking of petroleum storage tanks. The aquifer is highly permeable, but vertically heterogeneous. Water-table fluctuations reach up to 2 m during heavy rains. Contaminants migrated to the northwest along the main groundwater-flow direction. The concentration of hydrocarbons in groundwater is particularly high downgradient from the source area. The ubiquitous distribution of TEX was caused by the heterogeneity of the aquifer material and the significant fluctuation of the water-table. Chemical properties of the contaminated groundwater and field parameters indicate that intrinsic biodegradation, including aerobic respiration, nitrate reduction, iron reduction, manganese reduction, and sulfate reduction, occurs at this site. The dilution and mixing due to new groundwater recharge from rainfall is also identified as one of the major attenuation processes of TEX.

Flowpath Delineation and Ground Water Age, Allequash Basin, Wisconsin

AbstractAn analysis of ground water flowpaths to a lake and creek in northern Wisconsin shows the flow system in a geologically simple basin dominated by lakes can be surprisingly complex. Differences in source area, i.e., lakes or terrestrial, combined with the presence of intervening lakes, which may or may not capture underflowing ground water as water moves downgradient from recharge areas, contribute to a complex mix of flowpaths. The result is water of different chemistry and vastly different ages may discharge in close proximity. Flowpaths, travel times, and capture zones in the Allequash Basin in northern Wisconsin were delineated using particle tracking based on a calibrated steady‐state ground water flow model. The flowpath analysis supports the conclusions of Walker et al. (2003) who made inferences about flowpath characteristics from isotope and major ion chemistry. Simulated particle tracking agreed with Walker et al.'s measurements of water source (lake or terrestrial recharge) in the stream subsurface and also supported their assertion that ground water with a high calcium concentration in the lower basin of Allequash Lake is derived from long flowpaths. Numerical simulations show that ground water discharging in this area originates more than 5 km away in a source area located upgradient of Big Muskellunge Lake, which is upgradient of Allequash Lake. These results graphically illustrate that in settings with multiple sources of water with different age characteristics and converging flowlines (like the Allequash Basin) it may be difficult to obtain accurate estimates of ground water age by chemical analyses of ground water.

Ground water quality assessment using multi-rectangular diagrams.

A new graphical technique is proposed here for classifying chemical analyses of ground water. In this technique, a diagram is constructed using rectangular coordinates. The new diagram, called a multi-rectangular diagram (MRD), uses adjacent multi-rectangles in which each rectangle represents a specific ground water type. This new diagram has the capability to accommodate a large number of data sets. MRDs have been used to classify chemical analyses of ground water in the Chaj Doab area of Pakistan to illustrate this new approach. Using this graphical method, the differentiated ground water types are calcium bicarbonate, magnesium bicarbonate, sodium bicarbonate, and sodium sulfate. Sodium bicarbonate emerges as the most abundant ground water type. MRDs also offer a visual display of the Chebotarev sequence of ground water quality evolution.

Factors affecting the distribution of hydrocarbon contaminants and hydrogeochemical parameters in a shallow sand aquifer

The distributions of hydrocarbon contaminants and hydrogeochemical parameters were investigated in a shallow sand aquifer highly contaminated with petroleum hydrocarbons leaked from solvent storage tanks. For these purposes, a variety of field investigations and studies were performed, which included installation of over 100 groundwater monitoring wells and piezometers at various depths, soil logging and analyses during well and piezometer installation, chemical analysis of groundwater, pump tests, and slug tests. Continuous water level monitoring at three selected wells using automatic data-logger and manual measuring at other wells were also conducted. Based on analyses of the various investigations and tests, a number of factors were identified to explain the distribution of the hydrocarbon contaminants and hydrogeochemical parameters. These factors include indigenous biodegradation, hydrostratigraphy, preliminary pump-and-treat remedy, recharge by rainfall, and subsequent water level fluctuation. The permeable sandy layer, in which the mean water table elevation is maintained, provided a dominant pathway for contaminant transport. The preliminary pump-and-treat action accelerated the movement of the hydrocarbon contaminants and affected the redox evolution pattern. Seasonal recharge by rain, together with indigenous biodegradation, played an important role in the natural attenuation of the petroleum hydrocarbons via mixing/dilution and biodegradation. The water level fluctuations redistributed the hydrocarbon contaminants by partitioning them into the soil and groundwater. The identified factors are not independent but closely inter-correlated.

Natural chromium contamination of groundwater at León Valley, México

Chromium in groundwater resulting from natural sources has been detected in León Guanajuato Valley, Central-México. The aim of this work was to assess the types of rocks and the geochemical processes responsible for the chromium presence in the water. Superficial and groundwater chemical analyses, X-ray diffraction and EDS determinations in rock samples from the polluted area were performed. Leaching experiments with various types of rocks including SEM/EDS and petrographic observations were used to identify the minerals with higher possibilities to liberate chromium. To the East of León valley the chromium comes from the Sierra de Guanajuato ultramafic units and their alteration products. Recent and past tectonic and hydrothermal events have enhanced the chromium release. Among the studied rocks, the serpentinites showed the highest water pollution potential. Disintegration of exsolution borders appeared to be the main geochemical process for derived chromium.

Intrinsic bioremediation of a petroleum hydrocarbon-contaminated aquifer and assessment of mineralization based on stable carbon isotopes.

This study presents a stepwise concept to assess the in situ microbial mineralization of petroleum hydrocarbons (PHC) in aquifers. A new graphical method based on stable carbon isotope ratios (delta 13C) was developed to verify the origin of dissolved inorganic carbon (DIC). The concept and the isotope method were applied to an aquifer in Student, Switzerland, in which more than 34,000 liters of heating oil were accidentally released. Chemical analyses of ground water revealed that in this aquifer locally, anaerobic conditions prevailed, and that PHC mineralization was linked to the consumption of oxidants such as O2, NO3-, and SO4(2-) and the production of reduced species such as Fe2+, Mn2+, H2S and CH4. However, alkalinity and DIC balances showed a quantitative disagreement in the link between oxidant consumption and DIC production, indicating that chemical data alone may not be a reliable assessment tool. delta 13C ratios in DIC have been used before for bioremediation assessment, but results were reported to be negatively influenced by methanogenesis. Using the new graphical method to display delta 13C data, it was possible to identify anomalies found in methanogenic monitoring wells. It could be shown that 88% of the DIC produced in the contaminated aquifer originated from microbial PHC mineralization. Thus, the new graphical method to display delta 13C ratios appears to be a useful tool for the assessment of microbial hydrocarbon mineralization in a complex environment.