Natural and anthropic perturbations to the chemical composition of the Colorado River (Tucum�n, Argentina) (original) (raw)
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Environmental Earth Sciences, 2004
Economic and urban development in the province of Tucumán is closely associated with its hydrological network. In spite of the regulatory efforts to preserve the quality of the water resources, the lower basins of the majority of the rivers are contaminated with organic effluents derived from sugar-mill and citrus industry. In this paper, the conditions of the Colorado River basin are described. At its headwater, the lithology and geology determine the chemical composition. Calcite and gypsum dissolution and silicate influence water composition, which is slightly perturbed a few kilometers downstream by geothermal waters discharged by a tributary. Close to the discharge into the Salí River, the Colorado River receives a high organic matter load from the highly polluted Calimayo stream, which produces an increase in the organic matter and depletion of dissolved oxygen with redox conditions that promote the reduction of sulfate to sulfide.
Chemical behavior of the Salí River, Province of Tucumán, Argentina
Environmental Earth Sciences, 2001
Major ionic composition and other chemical parameters were determined at five sampling stations on the Salí River (Province of Tucumán, Argentina). The heavy human usage of the river causes increased levels of dissolved ions, from the dissolution of halite and gypsum, and from the weathering of basic sediments. Correlations demonstrate that sodium chloride and sulphate, and calcium carbonate are the main contributors to dissolved ions in the river. In the polluted region, south of the Celestino Gelsi dam, the main source of calcium and sulphate is the dissolution of gypsum. Large amounts of halite are also dissolved. Weathering of biotite, K-feldspar and albite are suggested by the data. Conductivity, dissolved oxygen and organic matter all indicate severe contamination by organic matter (mainly from sugar-cane processing) in the lower course. The data also demonstrate a substantial improvement in water quality before the discharge of the river at the Río Hondo dam. Data from the Colorado (a tributary of the Salí River) and Medina rivers are also analyzed and compared.
Chemical behavior of the Salí River, Province of Tucumán, Argentina
Environmental Geology, 2001
Major ionic composition and other chemical parameters were determined at ®ve sampling stations on the Salõ Â River (Province of Tucuma Ân, Argentina). The heavy human usage of the river causes increased levels of dissolved ions, from the dissolution of halite and gypsum, and from the weathering of basic sediments. Correlations demonstrate that sodium chloride and sulphate, and calcium carbonate are the main contributors to dissolved ions in the river. In the polluted region, south of the Celestino Gelsi dam, the main source of calcium and sulphate is the dissolution of gypsum. Large amounts of halite are also dissolved. Weathering of biotite, K-feldspar and albite are suggested by the data. Conductivity, dissolved oxygen and organic matter all indicate severe contamination by organic matter (mainly from sugar-cane processing) in the lower course. The data also demonstrate a substantial improvement in water quality before the discharge of the river at the Rõ Âo Hondo dam. Data from the Colorado (a tributary of the Salõ Â River) and Medina rivers are also analyzed and compared.
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 of groundwater in the alluvial plain of Tucum�n 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.
Geosphere, 2008
A geochemical characterization of the middle Rio Conchos basin is presented based on two contaminants, salts (Ca and Na) and toxic metalloids (As and Sb). Their content in surface water and sediment samples was determined, and their spatial distribution was mapped to show the relationship to each other, to the geology and hydrology, and to other potential factors affecting their distribution (i.e., prevailing winds). Correlation analyses between salts, toxic metalloids, and associated elements, and their spatial distribution aided in determining their sources, which included mines, rock outcrops, urban centers, irrigation waste water, and agricultural runoff. The salinity of the Rio Conchos reached a critical level after receiving waters of its contaminated tributary Rio Chuviscar and irrigation drain returns from the Irrigation District 005, but further downstream the water quality improved when it mixed with Ca-rich water, signifi cantly reducing its Na concentration. Based on its spatial distribution, the content of As in alluvial material was found to be associated with the presence of Ag-Pb mines and to a lesser degree to Oligocene ignimbrites. A correlation of As with Sb, Cu, and Bi suggests that natural sources are the dominant contribution of As within the area, although concentrations above permissible level for water were found in river water samples at a few places where sewage was also present, suggesting an additional (anthropogenic) important source of As. A characterization of natural sources affecting the chemistry of surface waters is a fi rst step toward understanding the natural processes taking place and for documenting natural background levels that are needed to predict the response of the environment to various human activities.
International Journal of Salt Lake Research, 1994
Rivers and streams originating in the surrounding mountainous area are the major sources of salt in the Salinas Grandes basin (Crrdoba, Argentina). These rivers infiltrate when they reach the sandflat or in the fringes of the mudflat, feeding springs which often form shallow lakes. Presently, the lakes are distant from the playa edge, thus allowing inflow waters to dissolve ancient (Pleistocene?) evaporite beds. In the sandflat environment, two dominant types of water have been recognized (SO]--C1--HCO~--Na +, and C1--SO] --HCO~--Na +), both considered as original members of the brine in the saline complex. Two main sources of solutes were distinguished, one related to the waters supplied by the southern sector and another to waters of the eastern sector. As a result of the chemical evolution in the playa environment, all brines belong to the neutral type (C1--SO]--Na+). Following model, waters from the southern sector should evolve towards an alkaline brine (C1--SO 2--HCO~--Na+), whereas those from to the eastern sector should evolve towards a neutral one (C1--SO]--Na+). A computer simulation was carried out to model the chemical evolution of source waters. The results obtained by this methodology showed the same dichotomy (alkaline vs, neutral) established by model. The deficit in alkalinity could not be explained by any of the mechanisms published until now. Gypsum dissolution is the most likely mechanism which accounts for the chemical evolution of the waters investigated. When such a process is included in the computations, the Ca 2+ supplied by gypsum beds generates an increase in the ion activity product (aCa+2.aCO] -) and produces a significant change in the 2Ca+2/(2CO~ -+ HCO3) ratio, switching from values less than 1 to values greater than 1. This process determines the precipitation of calcite, and leads to a decrease in alkalinity, which in turn would explain the existence of a neutral brine in the saline complex. An intermediate salinity brine was detected in the mudflat, which, according to the model , should evolve towards a SO ]--free neutral brine (CI--Na+--Ca2+). The absence of this type of brine may be explained through mixing processes.
1977
Thermodynamic evaluation of the ion speciation of the major chemical constituents from the anomalous spring and surface waters showed gypsum to be supersaturated in these anomalous spring waters. Downstream from the spring, the loss of the springs carbon dioxide in attaining equilibrium with the atmospheric carbon dioxide, resulted in the surface waters being supersaturated with respect to the carbonate minerals, such as calcite, aragonite, magnesite and dolomite. Therefore, the mixing of the characteristic Ca•Mg•HCO 3 •SO 4 groundwater from the underlying bedrock, appeared to be the principal effect upon the spring water contamination of the major constituents in the North Creek waters. Downstream from the spring, the minor constituents such as, the heavy metals, are co-precipitated with CaCO 3 , complexed with the sulphate radical and other inorganic ligands and form aquo metal complexes. In relation to time, the relative heavy metal concentrations in these anomalous surface waters showed direct relationships with respect to precipitation and the surface water discharge of the North Creek waters. This briefly summarized the origin and the geochemical history of the abnormality of the high metal values. The source of these high heavy metals are derived naturally from the dissolution of the bedrock mineral deposits, thus contaminating the groundwater discharge in the North Creek waters. The contribution of man's activities as a source of heavy metal contamination in these natural waters appeared to be negligible, since the implication of atmospheric pollution was proven to be relatively minute.
Hydrogeochemical Variability of the Acidic Springs in the Rio Tinto Headwaters
Water, 2021
Peña de Hierro, located in southwest Spain, encompasses the springs and headwaters for the Rio Tinto River that emerge above normal faults and has been mined for its rich sulfide ore since 2500 BC. The springs are typically characterized by an orange coloration, typical pH of ~2.33, and contain elevated concentrations of heavy metals that are produced by acid rock drainage (ARD). ARD is a natural phenomenon that results from chemolithoautotrophs metabolizing the sulfide ore. Mining has amplified the magnitude of the acidity and concentrations of heavy metals evidenced within sedimentary cores from the Huelva estuary. Acidity, redox state, hydrochemistry and isotopic analyses were examined for the purpose of characterizing the subsurface flows and determining the interconnectivity of the groundwaters. Previous studies have documented the geochemistry of the springs, dating a select few, yet many springs remain uncharacterized. Acidity presented spatial variability throughout the fiel...
2016
A chemometric study on physico-chemical variables of Calera River basin waters located to the northeast of the province of Tucumán, Argentina was carried out. This underground resource is an important alternative for water supply, and agricultural and cattle activities in this area. A physico-chemical analysis of 44 (forty-four) underground and Calera River water samples was carried out. Chemometric tools were used to determine which variables are more relevant and their possible associations, and also to identify the drillings whose waters are more representative of the area under study. Principal Component Analysis (PCA) and Cluster Analysis (CA) were applied for this purpose. The PCA allowed us to establish that the most important variables in this region are bicarbonate, sulfate and sodium. These ions are the main constituents of the minerals and rocks which form the geological structure of this region since there are limestone deposits (calcium carbonate), gypsum (calcium sulfate dihydrate) and halite (sodium chloride) irregularly distributed all over the region. Besides, an association between bicarbonate with sodium and sulfate with calcium variables was determined by means of CA. The most representative wells of the region under study were also selected by applying PCA. Based on these data, a regional hydrogeochemical model considering the chemical characteristics of waters and their possible interactions with the environment in which they circulate was carried out. The dissolution and/or hydrolysis of minerals present in rocks were established as important chemical processes in the area.