Geochemical mechanisms controlling the chemical composition of groundwater and surface water in the southwest of the Pampean plain (Argentina) (original) (raw)
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Chemical characterization of aquifers with the same geological origin
Chinese Journal of Geochemistry, 2006
Physical characteristics of the Bicaz dammed lake are described as follows: water volume of 1.150x 109 m 3, 31.1 km in length, 2 km in width. The sluice is at 45 m above the maximal altitude of the lake. The Bistrita River is the main tributary of the lake: mean water contribution of 1.721x109 m3/a, mean suspended matter flow of 291000 t/a. This river drains a catchment rich in formerly mined mineralizations of polymetallic sulfides. The aim of this study is to determine if the lake can be considered as a sink toward trace elements. We analyzed major and minor elements, TOC, organic N, and some trace elements (e.g. As, Ba, Cd, Cr, Co, Cu, Mo, Ni, Pb, Sb, Sn, V, U, Zn) in filtered and bulk water samples. We worked on three locations, an upper site, a middle site, and a down site. Here we present the data for July and October 2005. Some trace elements have smaller dissolved concentrations in lake water than in the Bistrita River. Common associations can be defined in this lake such as: Co is associated with Mn; As is released in solution as Fe oxi-hydroxide is dissolved; V and U are following the same behaviour, etc. However, their distribution is not as regular as in a natural lake. The stratification of the water column at all 3 sampled sites is not as regular as expected. At the upper site (water depth of 33 m), the water column is homogeneous until 20 m, then the redox condition allows having Mn as Mn (+ II) and Fe as Fe (+III). For some elements a perturbation can be noticed at about 10 m. At the middle site (water depth of 59 m), there is a water section richer in dissolved and particulate Fe and Mn, with a dominant particulate form. This can assess this section, in between 30 to 50 m it is more oxidizing. At the down site, the reverse figure can be seen between 30 and 50 m depth. This redox anomaly is more noticeable for elements with a high solubility difference according to their oxidation rate. Other parameters do not follow this figure. This section could be linked to the sluice drawing off. In the whole lake, the stratification is more and more visible from the up to the down stream but it is not so pronounced than in natural lakes. Water column structuring seems to be disturbed by a lateral flow, induced by the sluice drawing off.
Geochemistry of groundwater in the alluvial plain of Tucumán province, Argentina
Hydrogeology Journal, 2001
The Salí River hydrogeological basin is one of the most productive artesian basins in Argentina. It is located in the southeastern part of the province of Tucumán, northwestern Argentina, and its groundwater resources are developed for water supply and irrigation. The chemical composition of the water is strongly influenced by the interaction with the basinal sediments and by hydrologic characteristics such as the flow pattern and time of residence. Three hydrochemical zones are defined in the study area and the processes that control the chemical composition of the water are manifestly different in each zone. The dissolution of halite, sodium sulphate, and gypsum explains part of the contained Na+, K+, Cl–, SO42–, and Ca2+, but other processes, such as cation exchange, calcite precipitation, weathering of aluminosilicates, and gas exchange with the atmosphere, also contribute to the water composition. The assessment of contamination indicators, such as pH, dissolved organic matter, dissolved oxygen, phosphate, and nitrate, indicates that the groundwater is suitable for human consumption. However, biological contamination has been detected in samples from some wells, especially those near the Salí River. Le bassin hydrogéologique de la rivière Salí est l'un des bassins artésiens les plus productifs d'Argentine. Il est situé dans la partie sud-est de la province de Tucumán, dans le nord-ouest de l'Argentine, et ses ressources en eaux souterraines sont exploitées pour l'alimentation en eau potable et pour l'irrigation. La composition chimique des eaux est fortement influencée par les interactions avec les sédiments du bassin et par les caractéristiques hydrologiques telles que les conditions d'écoulement et le temps de séjour. Trois zones hydrochimiques sont définies dans la région étudiée et les processus qui contrôlent la composition chimique des eaux sont manifestement différents d'une zone à l'autre. La dissolution de la halite, du sulfate de sodium et du gypse explique une partie des concentrations en Na+, K+, Cl–, SO42– et Ca2+, mais d'autres processus tels que l'échange de cations, la précipitation de calcite, l'altération d'aluminosilicates et des échanges gazeux avec l'atmosphère contribuent également à la composition chimique de l'eau. L'évaluation des indicateurs de contamination tels que le pH, la matière organique dissoute, l'oxygène dissous, les phosphates et les nitrates indique que l'eau souterraine convient bien à la consommation humaine. Toutefois, une contamination biologique a été détectée dans des échantillons provenant de certains puits, en particulier ceux proches de la rivière Salí. La cuenca hidrogeológica del Río Salí se encuentra ubicada en el extremo SE de la Provincia de Tucumán, Noroeste de Argentina, y constituye una de las cuencas hidrogeológicas más importantes del país. Sus recursos son intensamente explotados para el abastecimiento de agua potable y para riego. La composición química de estas aguas está fuertemente influida por su interacción con los sedimentos y por algunas características hidrogeológicas tales como velocidad de infiltración, patrones de flujo y tiempo de residencia en el acuífero. En el área de estudio se pudieron distinguir tres zonas hidroquímicas, en cada una de las cuales los procesos que controlan la composición química del agua se manifiestan en forma diferente. Entre los procesos identificados, la disolución de halita, de sulfatos de sodio y de yeso, explica en parte los contenidos observados de Na+, K+, Cl–, SO42– y Ca2+. También participan en la regulación de la composición del agua otros procesos, como el intercambio catiónico, la precipitación de calcita, la meteorización de aluminosilicatos y el intercambio gaseoso con la atmósfera. De acuerdo con los indicadores de contaminación analizados (pH, materia orgánica disuelta, oxígeno disuelto, fosfato y nitrato), estas aguas son aptas para consumo. Sin embargo, algunos pozos próximos al Río Salí presentan contaminación bacteriológica.
Geochemistry and the understanding of ground-water systems
Hydrogeology Journal, 2005
Geochemistry has contributed significantly to the understanding of ground-water systems over the last 50 years. Historic advances include development of the hydrochemical facies concept, application of equilibrium theory, investigation of redox processes, and radiocarbon dating. Other hydrochemical concepts, tools, and techniques have helped elucidate mechanisms of flow and transport in ground-water systems, and have helped unlock an archive of paleoenvironmental information. Hydrochemical and isotopic information can be used to interpret the origin and mode of ground-water recharge, refine estimates of time scales of recharge and ground-water flow, decipher reactive processes, provide paleohydrological information, and calibrate ground-water flow models. Progress needs to be made in obtaining representative samples. Improvements are needed in the interpretation of the information obtained, and in the construction and interpretation of numerical models utilizing hydrochemical data. The best approach will ensure an optimized iterative process between field data collection and analysis, interpretation, and the application of forward, inverse, and statistical modeling tools. Advances are anticipated from microbiological investigations, the characterization of natural organics, isotopic fingerprinting, applications of dissolved gas measurements, and the fields of reaction kinetics and coupled processes. A thermodynamic perspective is offered that could facilitate the comparison and understanding of the multiple physical, chemical, and biological processes affecting ground-water systems. La géochimie a contribué de façon importante à la compréhension des systèmes d'eaux souterraines pendant les 50 dernières années. Les avancées ont portées sur le développement du concept des faciès hydrochimiques, sur l'application de la théorie des équilibres, l'étude des processus d'oxydoréduction, et sur la datation au radiocarbone. D'autres concepts, outils et techniques, ont aidé à l' élucidation des élucider les mécanismes d'écoulement et de transport dans les systèmes d'eaux souterraines, et à la compréhension des archives informations paléo-environnementales. Les informations hydrochimiques et isotopiques peuvent être utilisées pour interpréter l'origine et le mode de recharge des eaux souterraines, affiner l'estimation des temps de recharge et d' écoulements, déchiffrer les processus de réaction, apporter une meilleure information paléohydrogéologique et calibrer les modèles d'écoulement des eaux souterraines. Beaucoup de progrès ont besoin d'être réalisés pour obtenir des échantillons représentatifs. Des améliorations sont nécessaires dans l'interprétation des informations obtenues, et dans la construction et l'interprétation de modèles numériques utilisant des données hydrochimiques. La meilleure approches arsurément un processus itératif optimisé entre la collection de données de terrain et l'analyse, l'interprétation, et l'application d'outils de modélisation statistique, inverse et direct. Des avancées sont anticipées par les dans le demeine des études microbiologiques, dans la caractérisation des matières organiques naturelles, le marquage isotopique, les mesures de gaz dissous, les réactions cinétiques la compréhension des couplages. Une perspectives thermodynamique pourraient faciliter la comparaison et la compréhension des multiples processus physiques, chimiques et biologiques qui affectent les systèmes hydrogéologiques. La geoquímica ha contribuido significativamente al entendimiento de los sistemas de aguas subterráneas durante los últimos 50 años. Entre los avances históricos puede incluirse el desarrollo del concento de facies hidroquímicas, la aplicación de la teoría de equilibrio, investigación de los procesos oxidación-reducción, y datación con radiocarbono. Otros conceptos, herramientas y técnicas hidroquímicas han ayudado a esclarecer los mecanismos de flujo y transporte en sistemas de agua subterránea, y han ayudado a descifrar un archivo de información paleoambiental. Información hidroquímica e isotópica puede utilizarse para interpretar el origen y modo de recarga de agua subterránea, descifrar procesos reactivos, aportar información paleohidrológica, y calibrar modelos de flujo de agua subterránea. Necesita avanzarse en la obtención de muestras representativas. Se necesitan mejoras en la interpretación de la información obtenida y en la construcción e interpretación de modelos numéricos que utilizan datos hidroquímicos. El mejor enfoque asegurará un proceso iterativo optimizado entre toma y análisis de datos de campo, interpretación, y la aplicación de herramientas de modelizado estadísticas, directas, e inversas. Se anticipan avancesa partir de investigaciones microbiológicas, la caracterización de orgánicos naturales, caracterización isotópica, aplicaciones de mediciones de gas disuelto, y los campos de cinética de reacción y procesos acoplados. Se ofrece una perspectiva termodinámica que podría facilitar la comparación y entendimiento de los múltiples procesos físicos, químicos, y biológicos que afectan sistemas de aguas subterráneas.
Arsenic, Fluoride, and Vanadium in surface water (Chasicó Lake, Argentina)
Frontiers in Environmental Science, 2014
Chasicó Lake is the main water body in the southwest of the Chaco-Pampean plain. It shows some differences from the typical Pampean shallow lakes, such as high salinity and high arsenic and fluoride levels. The aim of this paper is to analyze the trace elements [arsenic (As), fluoride (F −) and vanadium (V)] present in Chasicó Lake. Surface and groundwater were sampled in dry and wet periods, during 2010 and 2011. Fluoride was determined with a selective electrode. As and V were determined by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Significant correlation in surface water was only found for As and F − (r = 0.978, p < 0.01). The As, F − and V concentration values were higher and more widely dispersed in surface water than in groundwater, as a consequence of evaporation. The fact that these elements do not correlate in surface water may also indicates that groundwater would not be the main source of origin of As, F − and V in surface water. The origin of these trace elements is from volcanic glass from Pampean loess. As, F − and V concentration were higher than in national and international guideline levels for the protection of aquatic biota. Hence, this issue is relevant since the silverside (Odontesthes bonariensis) is the most important commercial species in Chasicó Lake. This fish is both consumed locally and exported to other South-American countries through commercial and sport fishing.
Speciation studies in understanding high As content in ground water
Mineralogical Magazine, 2008
Two sites with five wells in the Danube-Tisza interfluvial were studied in order to help understand the genesis of the high-As content of shallow ground water. Separation of As species was carried out in the field as it proved to be the best method by which to preserve the As species. Different geochemical environments could be separated by the speciation studies which correlate with the concentrations of oxyanion-forming elements such as V, Se, Mo, U and W.
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Hydrogeochemical analysis on Italian bottled mineral waters: Effects of geology
Journal of Geochemical Exploration, 2010
The use of bottled mineral waters use is increasingly becoming popular and the need for better knowledge of their chemical composition is a key issue for defining their quality, particularly for those elements that are not monitored on a regular basis. The link between geology and water chemistry is well known and can lead to extreme differences in element distribution and is an issue that needs to be addressed. Such an opportunity has been provided by a project of the EuroGeoSurvey Geochemistry Expert Group aimed at the characterization of groundwater geochemistry using bottled mineral waters purchased in supermarkets all over Europe. On these waters pH, conductivity and concentrations of 69 elements and ions were measured at the BGR geochemical laboratories. On a total of 1785 "samples", 158 represent waters bottled in Italy in 126 different sites scattered throughout the country. Most of the purchased mineral water is packaged in PET bottles. In this paper, the dataset concerning Italy has been used to provide an overview on the relationship between natural concentration of the determined chemical elements in groundwater and geo-lithological features. These relationships have been investigated mostly taking into account the surface geology and other information available on water sources. Application of R-Mode factor analysis to the data set allowed the determination of the possible relationship between the distribution of individual elements and lithology or other surface enrichment phenomena. In particular waters draining through volcanic rocks are enriched in elements such as As, B, Br − , Cl − , Cs, I, K, Li, Na, NO 3 − , PO 4 3− , Rb, Sc, SiO 2 , Sr, Te, Ti, and V up to 3 orders of magnitude higher than waters draining through other lithologies. REE and Y show significant difference in median concentration due to interaction of waters with plutonic rocks. Many elements have a large spread of concentrations, which reflects natural variations and interaction with particular lithologies. One of the five Rmode factor analysis associations, recognized as being representative of elements analysed shows high nitrate and V loadings along with As, PO 4 3− and Se. The latter association probably reflects a sign of anthropogenic contribution in some aquifers in volcano-sedimentary or silico-clastic deposits and in intensively cultivated areas.
Applied Geochemistry, 1999
Owens Lake in SE California became essentially dry by the 1920s after the Los Angeles Aqueduct was constructed and diversion of water from the Owens River began. Frequent dust storms at Owens Lake produce clouds of eorescent salts which present human health hazards as a result of their small particle size and elevated concentrations of As and SO 4 . This study was conducted to characterize the evolution of major elements in ground water in eastern Owens Lake and to examine the factors controlling the concentrations of dissolved As and F. Evapoconcentration of shallow ground waters at the lakebed surface produces high pH, high alkalinity brines with major ion compositions that are consistent with those predicted by the Hardie±Eugster Model. Evaporite minerals identi®ed in the surface salts using XRD were halite (NaCl), thenardite (Na 2 SO 4 ), trona (Na 3 H(CO 3 ) 2 Á2H 2 O), pirssonite (Na 2 Ca(CO 3 ) 2 Á2H 2 O), and nesquehonite (MgCO 3 Á3H 2 O). Signi®cant correlations between both As and F with Li in shallow ground waters indicate that As and F are not partitioned into surface salts until very high salinities are reached (>9.0 m). Leaching experiments show that As and F can be readily released from lakebed salts when exposed to natural precipitation. Conservative behavior of As and F results from the high pH values and low Ca activities of shallow ground waters that contribute to: (1) redox stability of As(V) even at moderately reducing conditions, (2) a decrease in the adsorption anities of As and F to mineral surfaces, (3) undersaturation with respect to¯uorite (CaF 2 (s)). #
CATENA, 2018
The Pampean aquifer, in south east Argentina, is mainly constituted of loess-like sediments. These are clastic sediments mainly composed of quartz and aluminosilicates and calcrete concretions. Its hydrochemistry is generally studied assuming a chemical equilibrium between mineral phases and the aqueous fluids. The phases forming the matrix of this aquifer are considered to be the reactive phases responsible for the chemistry of the groundwater. In the present study, batch dissolution experiments were performed on calcrete and loess to better understand the source of the Pampean aquifer water chemistry and to measure the benefit of applying waterrock interaction models that use kinetic rate laws instead of thermodynamic equilibria. The different minerals composing the loess and calcrete samples were calculated using quantitative Rietveld refinement of X-ray powder diffraction (XRD) patterns. This analysis showed that the major phases of loess are quartz (~30 wt%) and feldspars (~70 wt%). The main components of calcrete are calcite (~95 wt%) and quartz (~5 wt%). Scanning electron microscopy with energy dispersive X-ray microanalysis (SEM/EDXS) was used to provide detailed information about the chemical composition of the powder samples, revealing the presence of traces of minerals like halite, barite and fluorapatite, which were not detected by XRD. The kinetic code KINDIS was used to carry out simulations using the minerals identified previously in their relative proportions to identify the signature of those geochemical phases on water chemistry. Experimental data from batch dissolution experiments were compared to simulated data. This investigation showed that water reached pseudo steady state concentrations due to the presence of fast dissolving phases like halite, barite, gypsum, plant phytolith. These phases appeared to be of major importance in controlling the chemical composition of the Pampean groundwater. Furthermore, this work showed that the KINDIS software can be used on all kinds of aquifers as it is very easy to modify the parameters of the simulation to adapt it to numerous situations. The modeling is a very important tool for thermodynamic and kinetic studies of groundwater chemistry; it enables the prediction of water quality and can help to understand the impact of anthropic or natural contamination on the groundwater.