Search

ArGIS was used to obtain the knowledge of spatial variability of macronutrients and Chlorophyll a in different p arts of Bahía Blanca Estuary (BBE). Dissolved inorganic nitrogen, phosphorous and silicates associated with the seasonal pattern of Chlorophyll a, in the inner and the middle estuary of Bahia Blanca, are evaluated in this paper. During November 2008-September 2011, continuous samples of seawater were taken aboard the institutional boat, in the main Channel. Twenty-one stations in the inner and middle zone were studied. Physicochemical parameters were in situ measured. Surface water samples for nutrients, Chlorophyll a and phaeopigments analysis were collected. Phosphates levels increase during spring (3.24 μmol L) in the outer station and minimum values were observed during winter in the inner stations (0.93 μmol L). The maximum value of Chlorophyll a was observed in winter (13.17 µg L) at middle stations, associated with minimum values of phosphates. Several changes have been observed in chemical and biological parameters found in the intermediate zone of BBE during the coldest months of the year. [ABSTRACT FROM AUTHOR]

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]

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 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]

This paper estimates CO fluxes in a municipal site for final disposal of solid waste, located in Gualeguaychu, Argentina. Estimations were made using the accumulation chamber methods, which had been calibrated previously in laboratory. CO fluxes ranged from 31 to 331 g m day. Three different populations were identified: background soil gases averaging 46 g m day, intermediate anomalous values averaging 110 g m day and high anomalous values averaging 270 g m day. Gas samples to a depth of 20 cm were also taken. Gas fractions, XCO < 0.1, XCH < 0.01, XN ~0.71 and XO ~0.21, δC of CO (−34 to −18‰), as well as age of waste emplacement, suggest that the study site may be at the final stage of aerobic biodegradation. In a first approach, and following the downstream direction of groundwater flow, alkalinity and δC of dissolved inorganic carbon (−15 to 4‰) were observed to increase when groundwater passed through the disposal site. This suggests that the CO generated by waste biodegradation dissolves or that dissolved organic matter appears as a result of leachate degradation. [ABSTRACT FROM AUTHOR]

Suquía River is a medium-sized hydrological system (basin area of ~7,700 km) that supplies fresh water to Córdoba city, a town of ~1,500,000 inhabitants in central Argentina. This paper examines the present-day hydrochemistry of Suquía River urban catchment analyzing its major and minor dissolved components, and the nutrients variability by means of QUAL-2K modeling software. The Suquía River has bicarbonate-type waters upstream the city and sulfate-type waters right downstream, whereas they exhibit a mixed-to-alkali-type cationic composition. The seasonal analysis of its major dissolved constituents clearly showed a dilution process during the wet season (i.e. austral summer). In the last 20 years, the Suquía River has modified its anionic composition, now showing higher relative concentrations of SO as a consequence of urban activities. However, trace elements dissolved concentrations do not evidence a strong pollution effect. Nutrients [nitrogen species, total phosphorous (TP)] and related parameters, such as biochemical oxygen demand (BOD), and dissolved oxygen (DO), evidence a clear influence of human activities. The QUAL-2K model was used to evaluate the spatial behavior of selected nutrients and associated variables, (i.e. TP, N-NH, N-NO, DO, BOD). Nutrient concentrations are affected by point sources of contaminants, particularly domestic waste and sewage, as well as by diffuse agricultural pollution. A calibrated QUAL-2K modeling exercise clearly shows the impact of the Córdoba city's municipal wastewater treatment plant on the Suquía River water quality. [ABSTRACT FROM AUTHOR]

Organic matter is a fundamental factor in the biogeochemical cycle of carbon; it influences the chemical, physical, and biological properties of the soil. The aim of this paper is to determine the organic fractions in the three predominant morphologies of aggregates found in Typical Argiudolls of the Buenos Aires southeastern area and to link them to different soil uses, as possible indicators of soil quality. The study was carried out in the basin de Los Padres Pound (General Pueyrredón, Buenos Aires). We analyzed the first 5 cm of mollic epipedons of plots with different soil uses: (a) cultivated plots, (b) pine and eucalyptus forests, (c) pastures, and (d) a natural plot in the de Los Padres Pound Reserve as a reference. The percentage of soil organic carbon (SOC), light organic carbon (LOC), fulvic acids (FA), humic acids (HA), and humins (H) in elongated, quadrangular and spherical aggregates were determined. The results show slight variations in SOC (7.2-8.6%) in the spherical aggregates of all the plots and a greater variability in elongated and quadrangular aggregates (5.6-10% and 6.9-13.6%, respectively). HA are minimal in the agroecosystems with extreme values of 0.02% in the spherical aggregates of cultivated plots, and maximal in the elongated and quadrangular aggregates of natural plots (0.3-0.5%). Fulvic acids display a similar behavior, while H decrease slightly with the morphologies and the different practices. The substantial decrease of humic substances in cultivated plots translates into a lower biologic activity; this, in turn, influences the aggregation, thus lowering the structural stability of these plots, which have been under agro-horticultural management for more than 50 years. [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]

Global warming and the intensification of extreme temperature events have been significant issues around the world in recent decades. The Pampas region in Argentina is one of the essential areas worldwide because of its agricultural productivity. Therefore, this study aimed to assess daily temperature events trends to identify warming signals during the last 6 decades. Thus, climatic information from 50 weather stations was analyzed to calculate cold and hot extreme events. Trends analysis was carried out with a Mann–Kendall test. As a result, we identified that maximum, minimum, and mean temperatures increased more than 1 °C in most of the Pampas from 1960 to 2018. The hot and cold extreme events demonstrated the existence of warming signals since warm days, warm nights, summer days, tropical nights, and both the coldest days and nights presented a significantly positive trend (2.3 °C, 0.7 °C, 43.6 days, 17.1 days, 0.9 °C, and 1.9 °C in the 59 years, respectively). Contrarily, frost days and cold nights and days had negative trends (12.3 days, 3.2 °C, and 2.4 °C in the 59 years, respectively). The results allow us to conclude that a high daily temperature variability characterizes the region. This knowledge is crucial for generating management policies focused on the sustainability of agricultural economic activities in Pampas. [ABSTRACT FROM AUTHOR]

Sedimentological connectivity is associated with the degree of linkage between sediment sources and downslope areas. In this study, a connectivity index is proposed to estimate the contribution of different parts of a basin as sources of sediments and to assess the pathway of sediment flux. A small granitic basin located on the eastern slope of the Comechingones Ranges (Córdoba Province, Argentina), was selected as a case study. The semi-quantitative connectivity index is defined by the equation CI = T + Dd + C–B, in which T is the variable toposequences that represents the types of storage and lateral links; Dd is the drainage density and it is used to evaluate the longitudinal links; C corresponds to the number of connections between channels of different order in a basin and it complements Dd in the longitudinal links analysis; and B connotes barriers associated with the number and type of disconnections in the drainage network, thus its sign is negative. From cartographic and field data, a detailed lithological–geomorphological survey was carried out; storage and toposequence types were described, and the barriers were classified according to the type, size, and position in the basin. The CI was determined for each secondary and main sub-basin of the Arenoso stream. Therefore, five connectivity classes were defined from the CI values obtained. This methodology allows arising acceptable results in research associated with the spatial heterogeneity of basin connectivity. The CI developed, in this first approach, showed satisfactory results and is applicable to analysis of small mountain basins, being based mainly on geological–geomorphological–hydrographic maps coupled with detailed fieldwork. [ABSTRACT FROM AUTHOR]

222Rn is widely used as a tracer to detect and calculate submarine groundwater discharge in coastal zones, rivers and lakes. Relatively few investigations, however, have used this element for other applications in hydrogeology. We analyze the relationship between 222Rn activity in groundwater and variations in the water cycle in the sandy aquifer of Buenos Aires coast, Argentina. Groundwater levels, electrical conductivity and 222Rn activity were measured in situ in wells in March 2016 and November 2018, representing two different hydrological conditions. Groundwater flow maps were drawn, hydrological gradients and flux velocities were calculated. An inverse correlation between 222Rn activity and recharge conditions was found. Lower water surplus shows higher 222Rn activity and vice versa, potentially due to dilution of high 222Rn activity water with 'newer' lower activity recent recharge. A variability in 222Rn spatial distribution was identified along the sand dune barrier. A correlation between 222Rn and groundwater electrical conductivity was not observed. [ABSTRACT FROM AUTHOR]

The multinational Paraná River (drainage basin ~ 2.6 × 106 km2; current discharge ~ 540 km3 y−1) has in its middle and lower stretches a long (~ 1200 km) and wide (~ 30 – 50 km) flood valley mantled with riparian vegetation and fully carved with lentic and lotic water bodies. Most of the wetland (~ 50000 Km2) holds myriad water bodies which, following the seasonal variation of the prevailing discharge regime, exchange water, dissolved chemical species, sediment, and biological materials with the Paraná's main stem. Exceptional hydrological events (e.g., strong El Niño-triggered floods) sporadically inundate almost totally the flood valley's expanse. The examination of chemical data collected in the main channel during the 1982–1983 event showed: (a) TDS was diluted to almost ¼ of the original concentration during the high flood; (b) water pH decreased to ~ 6.5, and CO2 partial pressure increased up to ~ 16000 ppmv during the overbank stage and afterwards; (c) throughout the event water remained within the medium dilute/dilute water types (375 > TZ+ > 1500 µeq L−1); and (d) dissolved inorganic carbon (DIC)—along with other variables—reached the highest concentrations in the descending limb, when the floodplain was drained. Dissolved organic carbon (DOC) showed an uneven variability pattern, seemingly unrelated to DIC, but definitely influenced by the significant lentic–lotic exchange. A 10-year long (1965–1975), uninterrupted series of alkalinity measurements allowed probing into the mechanisms that contributed to determine the observed alkalinity variability. Such variation appeared controlled by several biogeochemical processes occurring in the wetland (e.g., photosynthesis/respiration), sporadically impacted by changing hydrological stages. [ABSTRACT FROM AUTHOR]

Geochemistry involves the study of the distribution, proportion, and association of chemical elements of the earth’s crust that are present in different matrices such as water (sweet, saline, residual, rain, underground), soils, minerals, sediments, rocks, and air. Initially, this discipline was only used to study the composition and formation of rocks, but nowadays simultaneously relates geology to chemistry. [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]

Three combined approaches were used to study the arsenic (As) occurrence in carbonate-rich unsaturated zone from a large plain environment (Pampean plain, Argentina). A sequential extraction procedure (SEP) was used to identify the As-bearing phases and distribution along a 2-m-long unsaturated zone profile, whereas XRD and SEM/EDS were used to determine the mineralogical features of the sediments. In this hydrogeologic environment, groundwater levels tend to be close to the surface (<5 m) and hydrogeochemical processes that develop during infiltration and recharge through the unsaturated zone may release the As hosted in the sediments to shallow aquifers. According to SEP results, the unsaturated zone was divided in an upper and a lower zones. Disregarding the As contained in the silicates, low crystalline Fe(III) oxyhydroxides were the main As-bearing minerals in the upper zone. Its presence was confirmed by SEM/EDS analysis. In the lower zone, carbonates were the main As-bearing minerals, also supported by XRD analysis. The chemical composition from the resulting water-extractable step of the SEP was constrained using geochemical inverse modeling (PHREEQC) to elucidate those potential geochemical processes that may control the As release or retention during, for instance, an infiltration event. They showed that Na/Ca exchange promoted the calcite dissolution which, in turn, raised the pH as a result of proton consumption. High pH and HCO contents favored the As desorption from low crystalline Fe(III) oxyhydroxides in the upper zone, where they were present in higher proportion. [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 short and medium-term coastal evolution of Necochea Municipality, Buenos Aires province (Argentina) was studied. The medium-term evolution study was based on aerial photographs from 1967 and 1984, and satellite images from 2004, using the dune or cliff toe as coastline indicator. The short-term evolution was studied from February 2006 to December 2009 by means of seasonal beach profiles and sediment sampling. Results showed that in the medium-term at Necochea, the coastline has remained stable or has advanced. Whereas in the short-term, the analysis has evidenced incipient erosion processes. On the other hand, at Quequén the retreat of the coastline and the negative sedimentary balances (medium and short-term) are clearly indicating an accentuated erosion process. The different degrees of coastal erosion are related in part to beach vulnerability to wave storms but mainly to anthropogenic actions, which have affected the beach sediment supply. These results evidence the necessity to develop a coastal management programme. [ABSTRACT FROM AUTHOR]

The Argentine shore of the Rio de la Plata estuary and its southwards adjacent maritime front are normally affected by extratropical positive and negative storm surges that affect human activities seriously. Positive surges can raise the water level in the estuary by more than 3 m over the predicted tide; thus, flooding the coastal plain where over 13 million people live and causing extensive property damage. Sometimes, there has been loss of life too. Although less populated than the coastal plain, the maritime front has many important tourist resorts and also undergoes severe beach erosion processes and loss of property owing to positive surges. Negative surges are particularly troublesome in the Rio de la Plata because they critically affect navigation safety and drinking water supply by lowering the predicted water level in an amount that sometimes reached more than 4 m. A remarkable point is that the same storm event can simultaneously give rise to a positive surge on the maritime front and a negative one in the Rio de la Plata. The environmental impacts of positive storm surges are strongly aggravated by human intervention. At the same time, sea level rise due to global climatic change has also its influence. [ABSTRACT FROM AUTHOR]

The phreatic aquifer beneath the Pampean plain, in eastern central Argentina, constitutes a relevant source of water supply in the area. The objective of this work was to assess the significance of the cation exchange processes in the hydrochemical evolution of this aquifer, based on a study case located in the middle and upper basin of the El Pescado creek. Results indicate that Ca/Na exchange is the main process determining the evolution of groundwater from the recharge areas (Ca-HCO) towards the local discharge areas (Na-HCO), as well as representing a source of Na contribution to the water in the aquifer. This hydrochemical characteristic is central to the identification of local discharge areas within a plain environment which extends regionally. The ion exchange capacity of these discharge areas has environmental importance, due to its influence on groundwater quality and potential groundwater uses. These results may be applied to any aquifer sharing similar hydrogeological characteristics. [ABSTRACT FROM AUTHOR]

The area studied includes a little-known portion on the Dry Andes of the San Juan Frontal Cordillera, Argentina, where the hydrological significance of glaciers and rock glaciers was earlier never studied. The surveyed sector includes Cerro El Potro (5,870 m ASL) and nearby mountain chains (28°S). The predominant landforms in these areas were shaped in a periglacial environment superimposed on an earlier glacial landscape. These regions comprise abundant rock glaciers, a noteworthy rock glacier zone in the world, of which little is known in South America. This work employs geomorphological mapping to analyze the distribution of active rock glaciers in relation to altitude, aspect and slope using optical remote sensing techniques with GIS. Statistical estimation techniques were used based on a Digital Elevation Model (DEM) and aerial photos and Spot images interpretation. The specific density of rock glaciers' estimation in the surveyed area (Argentine border) is 1.56% with corresponds to 38 rock glaciers with an area of 5.86 km and 0.12 km of water equivalent. Furthermore, the analytical results show that elevations >4,270 m ASL, a southeast-facing aspect, and slope between 2° and 40° favor the existence of rock glaciers, Finally, a comparison with glacier water equivalent, which covers an area of ~16 km and 0.9 km of water equivalent, shows that glaciers are the main stores of water at 28°S (Cerro El Potro Glacier). However, the importance of rock glaciers as water reserves in this portion of Argentina should not be underestimated. [ABSTRACT FROM AUTHOR]

Environmental pollution and its harmful consequences for the population's health derived from coal production in the locality of Ensenada (Argentina) is studied by magnetic and non-magnetic means. Coke is used for the production of industrial coal. This is a final product obtained in petroleum refineries. Coke is a non-magnetic material showing values of magnetic susceptibility close to zero. Conversely, the magnetic susceptibility of the coal released from factory chimneys is considerably enhanced due to the building of magnetic fibers and spherules inside the furnace, used for coal production. Due to this property, the magnetic content of coal can be used as environmental proxy for studying the environmental impact caused by coal industries in urban areas. The values of magnetic susceptibility decrease as the distance from the contamination source increases. This indicates that magnetic concentration is lower. The grain size of magnetic particles also decreases according to the distance, which is seen when analyzing the grain size parameters. According to the different non-magnetic approaches applied, the particles released by the industry, which affect the region, fall within the rank of breathable particles (<2.5 μm). Besides, inhalable particles are also found (2.5-10 μm). Such determinations are consistent with inter-parametric ratios applied in the study of grain sizes. The undesirable dust of the local coal industry also carries heavy metals which are dangerous for the population's health, like Zn, Cu, Pb and V. [ABSTRACT FROM AUTHOR]

Chemical studies on 19 lakes of the Argentine sector of the Patagonian Tierra del Fuego Island were performed. These lakes are placed in two geological provinces, Extra Andine (northern) and Fueguian Cordillera (southern). Range of the results obtained, pH (5.80–8.60), TDS (29.5–10,232 mg/l), ionic composition (from calcium bicarbonate to sodium chloride type), Secchi disc depth (0.05–12 m), total inorganic nitrogen (20–237 μg N/l), orthophosphate (5–498 μg P/l), total phosphorus (5–3,800 μg P/l) and chlorophyll a (0.1–63.0 μg/l), indicated the presence of a wide variety of aquatic ecosystems. According to Gibbs model, the mechanisms that control the water chemistry are mainly rock dominance and evaporation–crystallization processes. [ABSTRACT FROM AUTHOR]

The aim of this study was to contribute to the understanding of the hydrogeological system of the Argentine Patagonia Extra-Andina region, focused on the Atlantic coastal area at 46° south latitude. The hydrogeochemical aspects of this aquifer system were taken into consideration for this purpose. The database includes 193 chemical analyses of major ions obtained through standard laboratory methods. A statistical analysis of the data, as well as the realization of hydrochemical models using PHREEQC software, was performed. The regional groundwater flows from west to east, with the recharge water being a sodium–chloride–bicarbonate type, and the discharge of water is typified as a sodium–sulfate–chloride type. The hydrogeochemical evolution of the aquifer shows a general augmentation of salinity and major ions in the groundwater-flow path, except for HCO3−. Inverse hydrochemical modeling showed that gypsum dissolution with calcite precipitation, Ca2+/Na+ and Mg2+/Na+ ionic exchange, and dedolomitization are the main processes along the groundwater flow pathway. [ABSTRACT FROM AUTHOR]

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]

This work presents the results of a soil erosion study using the 7Be technique. This technique estimates the water erosion/deposition from the comparison between 7Be soil content of a reference site and an eroded or sedimented site. The soil samples were collected from an agricultural area of the semiarid region of Argentina near San Luis City, which has a marked rainfall season. The area has been used for crop cultivation, being subjected to plowing practices. The 7Be in the Reference Site was in the first centimeter of soil, showing the typical exponential decreasing of 7Be soil content with depth, with the 7Be inventories value being 340 ± 50 Bq m−2 for the dry season and 571 ± 48 Bq m−2 for the rainy season. The 7Be technique was applied to a potential eroded site subjected to traditional tillage practices (plowing). A net soil erosion value of 13.5 t ha−1 (1.35 kg m−2) was obtained. From the assumptions of the applied technique, we can draw the inference that this erosion was caused by rains produced in the month prior to the date of soil sampling. [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]