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The development of groundwater resources sustainability indicators is a process of scientific approach that presents the different characteristics of the groundwater systems in a simplified and understandable way. Although its use in such a system is relatively recent, their proper selection provides a valid basis to support coordinated actions in the process of resource operation, planning and management. The central area of Santa Fe province, Argentina, is one of the main producing regions of the province and the country, standing out for its dynamism in both the economic and socio-cultural aspects. In particular, the study area is characterized by strong agriculture-farming and industry activities. The grain and oilseed production has great preponderance in this area, which is complemented by dairies, meat and tanneries strengthened by the presence of the livestock sector. It also highlights the timber ventures, fine furniture stores, and provision of industrial and food systems. The natural quality of groundwater and the scarcity of exploitable surface water resources make groundwater exploited as the exclusive source of supply. This paper focusses on the use of groundwater sustainability indicators in an area of the Santa Fe province, Argentina, where groundwaters are the only source of supply to satisfy the demand for the various purposes. From the indicators used, the indicators of groundwater abstraction demonstrated that local recharge rate is not sufficient to meet the current demand in the area. Therefore, the identification of these indicators incorporates the high added value that they offer as a synthetic measure for the sustainability of groundwater exploitation. Besides, it is expected that the selected indicators contribute to the evaluation of the management of these water resources, to the development of new shares and/or the establishment of plans and projects for their proper management. [ABSTRACT FROM AUTHOR]

Landfills constitute potential sources of different pollutants that could generate human health and environmental problems. While some landfills currently work under the protection of a bottom liner with leachate collection, it was demonstrated that migration could take place even yet with these cautions. The purpose of this paper is to assess the pollution caused by a leachate plume from a municipal landfill that is affecting both groundwater and surface waters. The research was carried out at Pacará Pintado landfill in northwestern Argentina. Analysis of water samples indicates that leachate is affecting groundwater under the landfill area and an abandoned river channel hydraulically connected. In the center of the landfill area, the plume is anoxic and sulfate, nitrate, iron and manganese reduction zones were identified. Leachate plume presented high concentration of organic matter, Fe, Mn, NH, Cl and Cr reaching an extension of 900 m. The presence of a leachate plume in a landfill site with a single liner system implies that the use of this groundwater pollution control method alone is not enough especially if permeable sediments are present below. [ABSTRACT FROM AUTHOR]

This paper gives an account of the implementation of hydrochemical and isotopic techniques to identify and explain the processes that govern solute exchange in two groundwater-dependent shallow lakes in the Southeastern Pampa Plain of Argentina. Water samples (lakes, streams, spring water and groundwater) for hydrochemical and stable isotopic determination were collected and the main physical-chemical parameters were measured. The combination of stable isotope data with hydrogeochemical techniques was used for the identification of sources and preferential recharge areas to these aquatic ecosystems which allowed the explanation of the lake water origin. The hydrochemical processes which explain Los Padres Lake water chemistry are evaporation from groundwater, CO input, calcite dissolution, Na release by Ca and Mg exchange, and sulfate reduction. The model that best aligns with La Brava Lake hydrochemical constraints includes: mixing, CO and calcite dissolution, cationic exchange with Na release and Mg adsorption, and to a lesser extent, Ca/Na exchange. This model suggests that the fractured aquifer contribution to this water body is greater than 50 %. An isotopic-specific fingerprint for each lake was identified, finding a higher evaporation rate for La Brava Lake compared to Los Padres Lake. Isotopic data demonstrate the importance of these shallow lakes as recharge areas to the regional aquifer, becoming areas of high groundwater vulnerability. The Tandilia Range System, considered in many hydrogeological studies as the impermeable bedrock of the Pampean aquifer, acts as a fissured aquifer in this area, contributing to low salinity waters and with a fingerprint similar to groundwater isotopic composition. [ABSTRACT FROM AUTHOR]

This paper gives an account of the implementation of a decision support system for assessing aquifer pollution hazard and prioritizing subwatersheds for groundwater resources management in the southeastern Pampa plain of Argentina. The use of this system is demonstrated with an example from Dulce Stream Basin (1,000 km encompassing 27 subwatersheds), which has high level of agricultural activities and extensive available data regarding aquifer geology. In the logic model, aquifer pollution hazard is assessed as a function of two primary topics: groundwater and soil conditions. This logic model shows the state of each evaluated landscape with respect to aquifer pollution hazard based mainly on the parameters of the DRASTIC and GOD models. The decision model allows prioritizing subwatersheds for groundwater resources management according to three main criteria including farming activities, agrochemical application, and irrigation use. Stakeholder participation, through interviews, in combination with expert judgment was used to select and weight each criterion. The resulting subwatershed priority map, by combining the logic and decision models, allowed identifying five subwatersheds in the upper and middle basin as the main aquifer protection areas. The results reasonably fit the natural conditions of the basin, identifying those subwatersheds with shallow water depth, loam-loam silt texture soil media and pasture land cover in the middle basin, and others with intensive agricultural activity, coinciding with the natural recharge area to the aquifer system. Major difficulties and some recommendations of applying this methodology in real-world situations are discussed. [ABSTRACT FROM AUTHOR]

This paper gives an account of the assessment and quantification of the water balance and the hydrogeological processes related to lake-groundwater interaction in the Pampa Plain by using hydrogeochemical, isotopic and flow numerical modeling techniques. La Salada is a permanent shallow lake, with an area of 5.8 km, located on the SE of Buenos Aires Province. A total of 29 lake water samples and 15 groundwater samples were collected for both hydrochemical analysis and environmental stable isotope determination. Water table depths were measured in wells closed to the lake. Groundwater samples appear grouped on the Local Meteoric Water Line, suggesting a well-mixed system and that rainfall is the main recharge source to the aquifer. Water evaporation process within La Salada is also corroborated by its isotopic composition. The model that best adjusts to La Salada Lake hydrochemical processes includes evaporation from groundwater, calcite precipitation with CO release and cationic exchange. The annual water balance terms for the lake basin indicates for each hydrological component the following values: 1.16 E m rainfall, 8.15 E m evapotranspiration, 1.90 E m runoff, 1.55 E m groundwater recharge, 6.01 E m groundwater discharge to the lake, 9.54 E m groundwater discharge to the river, 5.00 E m urban extraction and 4.90 E m lake evaporation. Integrated analysis of hydrochemical and isotopic information helped to calibrate the groundwater flow model, to validate the conceptual model and to quantitatively assess the basin water balance. [ABSTRACT FROM AUTHOR]

The Samborombon Bay wetland is located on the west margin of the Rio de la Plata estuary, in the Province of Buenos Aires, Argentina. This paper analyses the geological, geomorphologic, soil and vegetation characteristics of the southernmost sector of this wetland and their influence on surface water and groundwater. The study area presents three hydrologic units: coastal dunes, sand sheets and coastal plain. Coastal dunes and sand sheets are recharge zones of high permeability with well-drained, non-saline soils, and a few surface water flows. Changes in the water table are related to rainfall. Groundwater in coastal dunes is Ca–Mg–HCO3 to Na–HCO3, and of low salinity (590 mg/l). Groundwater in sand sheets is mainly Na–HCO3 with a salinity of about 1,020 mg/l. The coastal plain exhibits medium to low permeability sediments, with submerged saline soils poorly drained. Groundwater is Na–Cl with a mean salinity of 16,502 mg/l. A surface hydrological network develops in the coastal plain. Surface water levels near the shoreline are affected by tidal fluctuations; far from the shoreline water accumulates because of poor drainage. Both sectors have Na–Cl water, but the former is more saline. Human intervention and sea level rise may affect the wetland severely. [ABSTRACT FROM AUTHOR]

Mainly through BSi processing, shallow lakes regulate DSi retention, transport, and delivery to the ocean. However, these DSi fluxes in southern lakes are little known. This work evaluated the spatio-temporal variation and the main factors that affect DSi dynamics and retention in a temperate groundwater flow-through shallow lake in Argentina. Water samples from streams, the lake, and groundwater were collected from Los Padres Lake Watershed for DSi determination. DSi retention was calculated through a mass balance approach. The BSi pool from macrophytes was quantified using biomass, BSi production, and satellite images. The phytoplankton community was described by chlorophyll content, species quantification, and alpha diversity metrics. The contribution of Si-enriched water from groundwater (≈ 50 mg L−1) mainly controlled DSi concentrations in the inflow stream (≈ 54 mg L−1). Lake DSi concentration was lower than streams and groundwater, and increased over time (14–34 mg L−1). BSi contribution by macrophytes (≈1.4 Mg Si year−1) has little variation, therefore, the reduction of diatoms due to cyanobacteria increase is the most likely factor controlling DSi dynamics, influencing the role of the lake as a DSi sink/source. These biogeochemical processes regulated the DSi transfer from the lake to the outflow stream, and the delivery to the ocean (≈ 630 Mg Si year−1). Given the importance of small lakes in nutrient cycling and retention along flow paths within a watershed, in-lake Si processes and Si sources to these water bodies are critical to quantifying limnetic contributions to the global Si cycle. [ABSTRACT FROM AUTHOR]

Submarine groundwater discharge (SGD) is herein recognized as a significant pathway of material transport from land to the coastal SW Atlantic Ocean and thus, it can be a relevant factor affecting the marine biogeochemical cycles in the region. This paper focuses on the initial measurements of 226Ra, 228Ra and 222Rn made in Patagonia’s coastal zone of Chubut and Santa Cruz provinces (42°S-48°S, Argentina). 226Ra activity ranged from 2.9 to 73.5 dpm 100 L−1, and 228Ra activity ranged from 11.9 to 311.0 dpm 100 L−1 in groundwater wells. The radium activities found in Patagonia’s marine coastal regions and adjacent shelf indicate significant enrichment throughout the coastal waters. Groundwater samples presented the largest 222Rn activity and ranged from 2.66 to 1083 dpm L−1. Conversely, in the coastal marine environment, the 222Rn activity ranged from 1.03 to 6.23 dpm L−1. The Patagonian coastal aquifer showed a larger enrichment in 228Ra than in 226Ra, which is a typical feature for sites where SGD is dominant, probably playing a significant role in the biogeochemistry of these coastal waters. [ABSTRACT FROM AUTHOR]

Headwater streams play an essential role in catchment ecosystem processes and are particularly vulnerable to land use degradation and anthropic hydrological alterations. Considering that fish assemblages are reliable indicators of the ecological integrity of streams, we evaluated the ichthyofauna structure in four headwater Pampean streams located at catchment areas with contrasting land uses and hydrological man-made alterations. During autumn and spring of 2017 and 2018, fish assemblages were sampled and physicochemical and water table depth were measured. Specific richness, abundance, and diversity of fish assemblages were estimated. The degree of anthropic intervention of drainage networks and wetland coverage was estimated for each catchment. Statistical analyses assessed the differences between rural and periurban sampling sites in terms of environmental variables and fish assemblage structure, as well as the relationships between the biotic and abiotic variables. Results showed differences among headwater streams according to their land uses, hydrological alterations, and fish assemblage structure, evidencing a combined effect of land use and hydrologic alterations on fish assemblage. Changes in these communities can reflect not only alterations in water quality caused by local land use but also the influence of the catchment environmental integrity related to hydrological modifications and other phenomena that can occur simultaneously and at different geographical scales. [ABSTRACT FROM AUTHOR]

Some regions of Argentina are affected by high concentrations of molybdenum, arsenic and vanadium from natural sources in their groundwater. In particular, Mo levels in groundwater from Eduardo Castex (La Pampa, Argentina) typically exceed the guidelines for drinking water formerly established by WHO at 70 μg/L. Therefore, this study investigated the uptake of Mo in plants, using cress (Lepidium sativum L.) as a model using hydroponic experiments with synthetic solutions and groundwater from La Pampa. Cress grown from control experiments (150 μg/L Mo, pH 7) presented an average Mo concentration of 35.2 mg/kg (dry weight, d.w.), higher than the typical total plant range (0.7–2.5 mg/kg d.w.) in the literature. Using pooled groundwater samples (65.0–92.5 μg/L Mo) from wells of La Pampa (Argentina) as growth solutions resulted in significantly lower cress Mo levels (1.89–4.59 mg/kg d.w.) than were obtained for synthetic solutions of equivalent Mo concentration. This may be due to the high levels in these groundwater samples of As, V, Fe and Mn which are known to be associated with volcanic deposits. This research addressed the hitherto scarcity of data about the effect of various physicochemical parameters on the uptake of Mo in plants. [ABSTRACT FROM AUTHOR]

In coastal wetlands, the interaction between groundwater, surface water and marine or estuarine water determines the water chemistry; variations in the water balance may be of influence as well. The objective of this work was to assess how the rainfall regime affects the hydrological and geochemical processes that regulate the quality of surface and groundwater in the Samborombón Bay coastal wetland. We analyzed the water balances and chemical data of surface and groundwater during a dry and a wet period. Results show that the rainfall regime regulates water quality in the three hydrological units defined for the region (i.e., groundwater in the coastal plain, groundwater in the shell ridges and surface water in the coastal plain). In the water balance corresponding to a dry period, real evapotranspiration is similar to precipitation. In such conditions, in the coastal plain, the halite and gypsum salts precipitate. Subsequently, the rain or the tidal flow dissolves them, and they enter the water table by infiltration. The lowering of the water table favors the oxidation of sedimentary pyrite and the contribution of sulfates. The oversaturation of calcium carbonates in groundwater causes their precipitation, both in the coastal plain and in the shell ridges. The chemistry of surface water depends on the influence generated by the tidal inflow and groundwater discharge. During the wet periods, precipitation is higher than real evapotranspiration, leading to the infiltration of water excess toward the water table and the increase in surface runoff; this causes a decrease in the concentration of ions dissolved by dilution. This rainfall regime hinders the formation of evaporite salts (gypsum and halite) and leads to the undersaturation of groundwater with respect to calcite, allowing the dissolution of carbonates. As regards the chemical composition of the surface water in the coastal plain, the surface runoff in the drainage basin is more significant than the groundwater discharge and the tidal inflow. It can be concluded that the alternation of dry and wet periods in the Samborombón Bay wetland causes the rainfall regime to be a determining factor in the different hydrological and geochemical processes affecting the quality of surface and groundwater. [ABSTRACT FROM AUTHOR]

The iron and manganese content in groundwater on the northeastern coast of the Buenos Aires Province, Argentina, was analyzed. Borehole sampling and chemical analyses were performed and evaluated based on the hydrogeological characteristics of the phreatic aquifer located in the coastal barrier, which is the only supply source to the population. Fe concentrations in groundwater fluctuate between 0.03 and 3.5 mg/L, with a mean value of 0.33 mg/L, whereas Mn varies between 0.03 and 1.20 mg/L, with a mean value of 0.24 mg/L. There is a relationship between the geomorphological environments and the distribution of major ions, except the case of Fe and Mn. The sand that constitutes the aquifer contains pyroxenes, amphiboles, biotite, Fe oxides and hydroxides, and volcanic groundmass stained by hydroxides, all of which are the source of Fe and Mn-whose concentrations are unrelated to each other, to Ph or to Eh due to a state of redox disequilibrium. Possible health risks due to Fe and Mn excess in water are considered. According to the international guidelines for Fe, 38 % of the samples exceed the acceptable values, while 33 % exceed the Argentine standards. As regards Mn, the samples with excess Mn are 53 and 38 %, respectively. Further groundwater quality monitoring and chemical studies are necessary, especially regarding the evolution of Fe and Mn contents. To offer an adequate supply of drinking water to the population, it is necessary to remove Fe and Mn so that the concentrations are within the drinking water guidelines. [ABSTRACT FROM AUTHOR]

The North China Plain (NCP) is one of the global hotspots of groundwater depletion, groundwater is almost the only source of water for agricultural, industrial and drinking water in this region. After long-term's over-exploitation of deep groundwater, there appeared several deep groundwater depression cones, such as Cangzhou cone, Dezhou cone, Hengshui cone, Tianjin cone, etc., in which the Cangzhou cone is one of the typical cones for its special geography and hydrogeology conditions. In this study, the authors intended to analyze the evolution characteristics and influence factors of deep groundwater depression cone in Cangzhou region, especially the No. III aquifer depression cone, which is the main exploitation zone in this region. Analysis of the evolution of the groundwater depression cone of the No. III aquifer group in Cangzhou region showed that this process can be divided into four stages, namely, development, stable development, rapid expansion, and gradual recovery. The shape and evolution characteristics of the depression cone at different stages are described by analyzing the evolution of the −30, −40, and −50 contours of the groundwater table, for example the closed area of water table contour of −50 m has been enlarged from 95 km in 1985 to 6 528.5 km in 2005. The dominant factors that affect the evolution characteristics at different stages are proposed. The results showed that relatively long dry periods with less precipitation, special geological and hydrogeological conditions, and sharply increased water consumption for industrial and agricultural development are the main factors that cause the formation of deep groundwater depression cones. Meanwhile, an environmental response against groundwater exploitation is presented, and rational solutions are suggested to avert water crisis. [ABSTRACT FROM AUTHOR]

The Pampa in Argentina is a large plain with a quite obvious dependence on agriculture, water availability and its quality. It is a sensitive environment due to weather changes and slope variations. Supplementary irrigation is a useful practice for compensating the production in the zone. However, potential negative impacts of this type of irrigation in salinization and sodification of soils are evident. Most conventional methodologies for assessing water irrigation quality have difficulties in their application in the region because they do not adjust to the defined assumptions for them. Consequently, a new GIS-based methodology integrating multiparametric data was proposed for evaluating and delineating groundwater suitability zones for irrigation purposes in flat areas. Hydrogeological surveys including water level measurements, groundwater samples for chemical analysis and electrical conductivity (EC) measurements were performed. The combination of EC, sodium adsorption ratio, residual sodium carbonate, slopes and hydraulic gradient parameters generated an irrigation water index (IWI). With the integration of the IWI 1 to 3 classes (categories of suitable waters for irrigation) and the aquifer thickness the restricted irrigation water index (RIWI) was obtained. The IWI′s index application showed that 61.3 % of the area has 'Very high' to 'Moderate' potential for irrigation, while the 31.4 % of it has unsuitable waters. Approximately, 46 % of the tested area has high suitability for irrigation and moderate groundwater availability. This proposed methodology has advantages over traditional methods because it allows for better discrimination in homogeneous areas. [ABSTRACT FROM AUTHOR]

Prosopis flexuosa trees dominate woodlands in the Central Monte Desert (Mendoza, Argentina), with <200 mm rainfall, exploiting the water table recharged by Andean rivers, and also growing in dunes with no access to the water table. Prosopis woodlands were extensively logged during development of the agricultural oasis, and surface and groundwater irrigation could lower the depth of the water table in the future. We evaluated tree populations with decreasing access to the water table: valley adult trees, valley saplings, and dune adult trees, in order to assess their ecophysiological response to water table accessibility. High and seasonally stable pre-dawn leaf water potentials (−2.2 ± 0.2 to −1.2 ± 0.07 MPa) indicated that valley adults utilize larger and more stable water reservoirs than valley saplings and dune adults (−3.8 ± 0.3 to −1.3 ± 0.07 MPa), with higher midday leaf conductance to water vapor (valley adults ~250; dune adults <60 mmol m s), potentially higher CO uptake, and increased radial growth rate (valley adults 4.1 ± 0.07; dune adults 2.9 ± 0.02 mm year). Trees with poor access to the water table exhibited drought tolerance responses such as midday stomata closure, leaflet closure, and osmotic adjustment. Stomata density decreased in response to drought when leaf expansion was restricted. The combination of phreatophytism and drought tolerance would enlarge P. flexuosa habitats and buffer populations against changes in rainfall dynamics and water table depth. [ABSTRACT FROM AUTHOR]

Groundwater in the central part of Argentina contains arsenic concentrations that, in most cases, exceed the value suggested by international regulations. In this region, Quaternary loessical sediments with a very high volcanic glass fraction lixiviate arsenic and fluoride after weathering. The objectives of this study are to analyze the spatial distribution of arsenic in different hydrogeological regions, to define the naturally expected concentration in an aquifer by means of hydrogeochemistry studies, and to identify emergent health evidences related to cancer mortality in the study area. The correlation between arsenic and fluoride concentrations in groundwater is analyzed at each county in the Cordoba Province. Two dimensionless geoindicators are proposed to identify risk zones and to rapidly visualize the groundwater quality related to the presence of arsenic and fluoride. A surface-mapping system is used to identify the spatial variability of concentrations and for suggesting geoindicators. The results show that the Chaco-Pampean plain hydrogeologic region is the most affected area, with arsenic and fluoride concentrations in groundwater being generally higher than the values suggested by the World Health Organization (WHO) for drinking water. Mortality related to kidney, lung, liver, and skin cancer in this area could be associated to the ingestion of arsenic-contaminated water. Generated maps provide a base for the assessment of the risk associated to the natural occurrence of arsenic and fluoride in the region. [ABSTRACT FROM AUTHOR]

The objective of this study is to analyze the geochemical conditions associated with the presence of arsenic (As) and fluoride (F) in the phreatic aquifer of Coronel Moldes, in the central sector of the Argentine Chacopampean plain. The studied aquifer is composed of silty sand sediments of aeolian origin, typically loess-like sediments. The geochemical composition of water varies from sodium bicarbonate to sodium sulfate-chloride water. As contents range from low concentrations, below detection level, to 250 μg/l. High values of F (up to 12 mg/l) were recorded. A high As–F correlation was found ( R2 = 0.84). The pH varied from 7.31 to 8.85 and the nitrates reached concentrations up to 200 mg/l, indicating an oxidant environment. The highest values of As and F agreed with sodium bicarbonate waters as well as with the highest values of pH recorded. There was a high correlation between As and F− as well as between As and the Na/Ca ratio. The composition and texture of loess, low permeability and hydraulic gradients together with the geochemical features of sodium bicarbonate waters are proper conditions for the mobilization of As and F in groundwater in the central area of Argentina. [ABSTRACT FROM AUTHOR]

The concentrations of dissolved cadmium, lead, chromium and níquel were determined in surface water column and pore water, collected from the extensive tidal plain at Bahía Blanca estuary, Argentina. Three different polluted areas were selected to study the spatial variation of these metals. The concentration ranges within the water column were slightly variable (Cd: 0.18–2.48 μg L−1; Pb: 0.38–7.53μg L−1; Cr: 0.89–5.83 μg L−1; Ni: 0.81–3.49 μg L−1), and displayed a clear gradient respect to the industrial area. Significant differences (contrast tests) between sites were detected for Cd, Pb and Ni. Very similar concentrations of Cd (0.18–3.41 μg L−1), Pb (0.38–5.83 μg L−1), Cr (0.89–9.37 μg L−1), Ni (0.81–6.56 μg L−1) were found in the porewater at all sites. The results suggested that both environmental compartments (water column and tidal flats porewater) may be affected by similar point and non-point heavy metal sources. [ABSTRACT FROM AUTHOR]

Historically, the arid conditions of La Rioja, Argentina have been the main controlling factor in its development. The shortage of surface water, which is fully used, makes groundwater a potential source for development. The government encouraged investment in early 1979, resulting in a 20-fold increase of groundwater extraction by 1998 (0.076–1.450 m3/s, respectively) to cover related needs of agriculture, industry and population growth. This extraction created unjustified uncertainties derived from negative results obtained in hydrological balances. However, a 0.5 m lowering of the water-table surface was experienced. A knowledge of groundwater functioning was required to establish a reliable frame of reference for development and, at the same time, to find possible scenarios of feasible economic activities in harmony with accessible water resources and aptitude of the environment. The flow regime was found to be composed of three main systems: a regional, an intermediate and several local. The intermediate system provides water for the extraction boreholes, and discharges naturally in Salina La Antigua. From the chemical perspective the intermediate system has three groundwater groups. Group I has an outstanding fluoride concentration (1.98–3.10 mg/l) defined to the north of the City of la Rioja and the highest temperature (26.8–33.0°C), the lowest lithium content (0.029–0.059 mg/l) and moderate arsenic (≤0.038 mg/l). Group II has the moderate arsenic content (≤0.38 mg/l) detected to the south of the City of La Rioja and high lithium (0.024–0.085 mg/l), Group III has the lowest TDS (456–931 mg/l) and arsenic (0.007–0.012 mg/l) and the highest lithium (0.067–0.141 mg/l). to A regional flow is represented by Group IV with one order of magnitude higher strontium (4.870 mg/l), lead (0.021 mg/l) and uranium (0.362 mg/l) content than the other groups. Results provide evidence to eliminate several well-established hydro-myths such as “the boreholes are getting dry” and “boreholes are getting saline water”. The aquifer (granular Tertiary and Quaternary material) thickness (≈750m) was defined with the aid of the geological framework, geothermometers and Modflow modelling. The aquifer extent extends far beyond the limits of the study area. Several economic activities were found to be feasible with available groundwater resources and without bordening the environment (fish farming, bottled-water marketing, SPA activities and farming of endangered species). [ABSTRACT FROM AUTHOR]

Analyzes the hydrogeological behavior of an alluvial aquifer in the River Mojotoro basin site in the Province of Salta, Argentina. Characteristics of the study area including coarse-grained sediments with high infiltration capacity; How the groundwater flow velocity field is computed; Data suggesting the migration of chloride shows patterns, which are affected by the litologic heterogeneities of the aquifer and the regional groundwater flow.

Submarine groundwater discharge (SGD) is a complex hydrological process which occurs at the continent–ocean interface and plays an important role in coastal dynamics. The main objective of this study was to detect groundwater discharge from the sandy freshwater aquifer towards the Atlantic Ocean along the western coast of Buenos Aires Province (Argentina) using multiple methods. 222Rn as a tracer, electrical resistivity tomography (ERT), and hydrogeological information were applied to detect and quantify SGD. 222Rn activity was measured in wells, at the beach (tidal pools and surf zone) and along a transect ~ 200 m from the coastline coincident with geoelectrical measurements. Groundwater depth was measured in wells, and from these data, groundwater contour maps were made. 222Rn activity in wells varies from 16 and 173 dpm/L; at the beach, the values are between 28 and 48 dpm/L; and along the coastline, they oscillate between 1.3 and 20.5 dpm/L. The ERT shows a high resistivity layer close to 3–4 m depth from the sea floor indicating the presence of freshwater. Groundwater contour maps show discharge toward the continental plain to the west and toward the sea to the east. There is no precedent related to the application of these methodologies in the study area which results of interest for the knowledge of the coastal hydrodynamics. [ABSTRACT FROM AUTHOR]

High levels of fluoride in drinking water affect millions of people due to health problems associated with water consumption. Fluoride concentrations in groundwaters from the unsaturated and saturated zones of a watershed located in the Chaco-Pampean Plain of Argentina are reported and investigated to evaluate the mechanism that controls these concentrations. Two hypotheses were formulated: (a) the adsorption hypothesis, which assumes that fluoride is controlled by adsorption/desorption processes on mineral oxides, and (b) the dissolution hypothesis, which assumes that the solubility of fluorite is the controlling process. Calculations with the CD-MUSIC surface complexation model to test the adsorption hypothesis rendered very poor results. The affinity of fluoride for surface sites is so low that it is easily displaced by carbonate, and thus the calculated fluoride-carbonate trends are very different to the experimentally found with the studied water samples. On the contrary, a comparison of reaction quotients, Q, with equilibrium constants, K, for fluorite dissolution, calcite dissolution and a combination of both processes indicates that fluorite and calcite are in equilibrium or close to equilibrium with their corresponding ions in solution, giving strength to the dissolution hypothesis. This hypothesis can also explain, at least qualitatively, why fluoride correlates positively with arsenate and carbonate. The conclusions could be extrapolated to many other systems worldwide, which present these positive correlations. [ABSTRACT FROM AUTHOR]