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The Matusagaratí wetland in the Panamanian Darien is one of the largest and most biologically diverse wetland ecosystems in Central America. Despite this, no hydrological studies have been conducted in the area due to its remoteness and difficult access. The aim of this research is to define the relationship between surface water and groundwater through the field and laboratory data obtained from the first monitoring network installed in the Matusagaratí wetland. Variations registered in the isotopic relationships in surface water and groundwater show that the wetland receives contributions from rainfall as well as fluvial and estuarine water. There are areas of the wetland where one of these sources predominates, and others where they mix. In the wetland sector downstream the Tuira river, the groundwater presents a combination of freshwaters coming from Filo del Tallo and those coming from the Tuira river, whose high salinity reflects the estuary's influence. Meanwhile, in the upstream sector of the wetland, the groundwater is a mixture of river water and rainwater on the river´s levee but behind it, rainwater predominates. In all cases, groundwater has Rare Earth Elements patterns like those of the Tuira river, highlighting the importance of river flooding as a source and support system for the wetland groundwater. Hydrological research such as this, presents a valuable opportunity to provide sound scientific information to promote sustainable management and environmental conservation of this unique wetland that is rapidly being transformed to cattle pasture and palm and rice cultivation. Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Candanedo, Indra. Universidad Tecnologica de Panamá.; Panamá Fil: Saavedra, Sidney. Universidad Tecnologica de Panamá.; Panamá Fil: Arcia, Manuel. Universidad Tecnologica de Panamá.; Panamá Fil: Franco, Ana. Universidad Tecnologica de Panamá.; Panamá

El presente dossier de la Revista del Museo de La Plata reúne nueve de los artículos presentados en la V RAGSU, los cuales abordan distintas especialidades dentro de la geoquímica de la superficie.

El objetivo del trabajo es determinar los cambios en la química del agua subterránea y los procesos geoquímicos asociados en función de las variaciones geomorfológicas en el ámbito de la planicie costera del Río de la Plata en el sector litoral del estuario medio. Para ello se estableció una red de monitoreo que involucra puntos de muestreo de agua superficial y subterránea donde se determinó el contenido de iones mayoritarios, nitrato e isótopos estables de la molécula de agua. El contenido en isótopos ambientales registra, para el caso del agua subterránea, que el agua de lluvia infiltra sin previa evaporación y recarga al agua subterránea somera. Las muestras de agua superficial presentan porcentajes de evaporación menores al 10%. Estos bajos porcentajes pueden deberse a que el muestreo se realizó en un mes de excesos hídricos. En cuanto al contenido de iones mayoritarios se registran variaciones en función de la geomorfología. Así, la antigua llanura intermareal y la planicie con cordones de conchilla presentan facies que varían según la profundidad del muestreo entre bicarbonatada sódica y clorurada sódica. Estas variaciones estarían controladas por la composición original del agua meteórica y las reacciones químicas producto de la interacción con el sedimento. Particularmente, la química del agua subterránea de la marisma está regulada por los flujos mareales provenientes del Río de la Plata., The goal of this work was to determine changes in groundwater chemistry and associated geochemical processes as a function of geomorphological variations in the Río de la Plata coastal plain, within the littoral sector of the middle estuary. With this purpose, a monitoring network of groundwater and surface water was established for determining major ions, nitrate, and stable water isotopes. Isotopic analyses indicate that rainwater infiltrates with no previous evaporation, recharging shallow groundwater, and that surface water exhibits less than 10% of evaporation. These low percentages of evaporation might be related to the fact that the sampling was carried out in a month of water surplus. The chemical composition of major ions records variations as a function of geomorphology. The ancient intertidal plain and the plain with shell ridges exhibit facies that vary between sodium bicarbonate and sodium chloride according to depth of sampling. These variations would be controlled by the composition of meteoric water and the chemical reactions resulting from its interaction with the sediment. The chemical composition of the marsh groundwater is controlled by tidal flows from the Río de la Plata., O objetivo do trabalho é determinar as mudanças na química das águas subterrâneas e os processos geoquímicos associados em função das variações geomorfológicas, no âmbito da planície costeira do Rio da Prata no setor litoral do estuário médio. Para isso, foi estabelecida uma rede de monitoramento que envolve pontos de amostragem de águas superficiais e subterrâneas, onde foi determinado o conteúdo de íons majoritários, nitrato e isótopos estáveis da molécula de água. O conteúdo dos isótopos ambientais registra, no caso das águas subterrâneas, que a água da chuva infiltra sem evaporação prévia e recarrega as águas subterrâneas rasas. As amostras de águas superficiais mostram porcentagens de evaporação inferiores a 10%. Estas baixas porcentagens podem dever-se ao fato de que a amostragem foi realizada em um mês de excessos hídricos. Quanto ao conteúdo dos íons majoritários, foram registradas variações em função da geomorfologia. Assim, a antiga planície entremarés e a planície com cordões de conchas apresentam fácies que variam de acordo com a profundidade da amostragem entre contendo bicarbonato de sódio e cloreto de sódio. Estas variações seriam controladas pela composição original da água meteórica e pelas reações químicas resultantes da interação com o sedimento. Em particular, a química das águas subterrâneas da marisma é regulada pelos fluxos das marés provenientes do Rio da Prata., Dossier: Geoquímica y perspectiva ambiental de sistemas exógenos., Facultad de Ciencias Naturales y Museo

The most favourable locations for the development of saline lakes are in the rain-shadow of mountain ranges, which provide large areas of precipitation catchment while the base of the basin is under arid climate and exposed to evaporation. These conditions are found in Extra-Andean Patagonia under the rain-shadow generated by the Andean cordillera. There, an endorheic basin with two shallow and saline lakes, Cari Laufquen Chica (CLC) and Cari Laufquen Grande (CLG), was studied with the aim of analysing the factors that condition the hydrochemical processes acting in the formation of evaporites associated with these environments. A monitoring network was installed and five surface and groundwater survey campaigns were carried out at different points in the basin to define groundwater flow and also to extract samples. In situ pH, electrical conductivity and temperature and laboratory physicochemical determinations of major ions and stable isotopes of the water were measured. SEM-EDS and XRD analyses of saline crusts from the edge of the lakes and adjacent sediments were carried out. The obtained results allowed identifying that CLC and CLG saline lakes have different surface water-groundwater configurations. CLC is a flow-through shallow lake, while CLG is a discharge shallow lake. The analysis of the saline precipitates and the chemical facies of the water allows identifying cycles of dissolution, evaporation and precipitation in both saline lakes. However, the different groundwater flow between the two lakes is reflected in their salinity as well as in the evolution and development of saline precipitates. CLC saline lake shows a dissolution-precipitation trend of thenardite and Ca-Mg carbonates, whereas CLG saline lake displays a trend of dissolution-precipitation of halite, thenardite and trona with strong dominance of halite. The present study identifies for the first time the main factors conditioning hydrochemical processes in these saline lakes of extra-Andean Patagonia. Our results indicate that the hydrological configuration with respect to the groundwater flow is the prevailing factor setting the hydrochemical processes that trigger the formation of salt crusts.

Interactions and exchanges between surface water, groundwater, and the atmosphere are some of the most relevant functions that regulate environmental characteristics in wetlands. These functions depend on environmental attributes such as topography, geological-geomorphological setting and, in the case of coastal wetlands, the relationship with tidal flows. The aim of this work is to analyse the water flows in different landscape units of the wetland in the coastal plain of the Río de la Plata estuary within the Parque Costero del Sur biosphere reserve. For this purpose, monthly water balances and groundwater level measurements were compared with daily precipitation and tidal height data from the Río de la Plata estuary. The results show how water dynamics in the wetland responds to different geological-geomorphological and climatic controls. The main inlets and outlets of water, as well as the flow exchanges, vary according to the different landscape units, forming a complex system on which the main ecological features depend., Centro de Investigaciones del Medioambiente, Centro de Investigaciones Geológicas

Libro de Resumenes 3 de septiembre de 2019 Sala de Consejo Directivo, Facultad de Humanidades y Ciencias, Universidad Nacional del Litoral, Santa Fe, Argentina 9 de septiembre de 2019 Auditorio del Centro de Investigaciones Geologicas (UNLP-CONICET), La Plata, Argentina Comision organizadora Santa Fe: Natacha Bacolla Bernardo Carrizo Hugo Ramos Carina Giletta Laura Tarabella La Plata: Eleonora Carol Soledad Garcia Lerena Edoardo Melendi Lucia Santucci Carolina Tanjal Prologo En el marco del Proyecto ERASMUS 2019-20 el objetivo del taller es propiciar un espacio de intercambio comparativo de metodologias cientificas entre universidades e institutos de investigacion de Italia y Argentina sobre la interrelacion entre los ambientes fluviales y los asentamientos humanos. En el mismo participan docentes investigadores de la Universidad Ca´Foscari, la Universidad Nacional de Buenos Aires, la Universidad Nacional del Litoral, la Universidad Nacional de Rosario y la Universidad Nacional de La Plata. Este Workshop fue realizado en dos encuentros, el primero de ellos el 3 de septiembre en la Universidad Nacional del Litoral y el segundo el 9 de septiembre en la Universidad Nacional de La Plata.

Four salt marshes located in the Río de la Plata Estuary, Bahía Blanca Estuary, San Antonio Bay and Fracasso Beach in the Peninsula Valdés were studied. Water balances, tidal regime, geomorphology, anthropic modifications, salts in the soils and vegetation in each salt marsh were compared in order to determine how the natural and anthropic factors condition the salinization of the marshes. In addition, the way in which these factors affect the distribution of the communities of plants was studied. The climatic conditions are humid and arid along the northern and southern Argentine Atlantic coast. The tidal conditions were micro-tidal in the Ajó River associated with the Río de la Plata Estuary, meso-tidal in Bahía Blanca, and macro-tidal in San Antonio and Fracasso salt marshes. It is expected that, under natural conditions, the formation of salts in soils will present a higher increase in the south (arid and macro-tidal) than in the north (humid and micro to meso-tidal). However, the results obtained show that the anthropic factors associated with the construction of embankments in the northern marshes modify their hydrological functioning, and generate conditions which favour the processes of salinization, causing considerable changes in the distribution of the communities of plants. Thereby, future research should be aimed to improve the development of engineering structures that will not affect the salt marsh environments nor the ecosystem services the salt marshes provide. Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Idaszkin, Yanina Lorena. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Santucci, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

Contamination of groundwater in different parts of the world is a result of natural and/or anthropogenic sources, leading to adverse effects on human health and the ecosystem. In Península Valdés, where groundwater is the only source of supply, high concentrations of As and F- were registered. Since it is a region without industrial activity, an analysis of possible natural sources of contamination is necessary. The aim of this study is to analyse the hydrological processes that determines the presence and mobilization of those elements through the analysis of the mineralogy of the aquifer sediments and the ionic water relationships. The productive aquifer, dominated by psamites, coquinas and siltstone is located between 29 and 42 m below ground surface. The hydrochemistry studied from 105 sampling points, shows that groundwater is dominated by Na-Cl ions and, in the fresh water sectors, the ionic type is Na-HCO3 to Na-Cl. In 17 of these samples, Zn, Cr, Mn, As, V, Sr, Fe, F ions were measured and As and F contents above the potability limit were recorded. These contents vary between 0.01 and 0.40 mg/L in As and between 0.31 and 4 in F- which are both associated with elevated V values. The optical petrographic microscope observations and the X-ray diffraction measurements show that the sediments are dominated by volcanic lithic fragments, volcanic glass shards and quartz, plagioclase, pyroxenes and magnetite clasts. The scanning electron microscopy, combined with the energy dispersive X-ray analysis, shows that the highest concentrations of As are associated with volcanic shards and iron oxides. The combined analysis of all these elements leads to conclude that the processes which explain the presence of those ions are a result of the interaction of groundwater with the components of the aquifer sediments. At alkaline pH, the high solubility of the amorphous silica of vitreous shards allows the release of As, V and F- ions towards the solution. Thus, adsorption-desorption processes can also control the presence of these ions in groundwater. Both As and V (in solution in the form of oxyanions) can be adsorbed by iron oxides, while F- anions have more affinity to be adsorbed by the carbonate facies, some of them re-precipitated as a result of the increase in pH. The identified hydrogeological processes provide information for the planning of water purification measures that tend to improve the water resources management in a large arid region of Patagonia. Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina

Floods are one of the most common natural phenomena and represent a serious hazard when they affect human activities. Structural measures are commonly used to mitigate them; however, these do not always give good results, mainly in plain areas with scarce slope. In this sense, the generation of a flood hazard map contributes to adequate hazard management and disaster prevention. The aim of this work is to evaluate the flood hazard areas in hydrological plain basins with scarce slope, taking as a case study the Samborombón river basin located in the Pampean Plain, Argentina. For this, a flood hazard map was made based on the analytical hierarchy process and using a GIS, taking into account physical aspects of the terrain, observations, and field measurements. Likewise, the map was validated using satellite images and the inhabitants in danger in the basin were quantified. The results show that the flood hazard areas correspond mainly to the floodplain of rivers and tributaries, while the main and secondary divide zones have low flood hazard sectors. On the other hand, numerous urban settlements were identified within flood hazard areas, these being urban settlements in the vicinity of old urban centers and new gated communities with high value homes, quantifying 1961 inhabitants at flood hazard and showing poor territorial planning. The methodology proposed gives to the management agencies the possibility of generating land use maps, as well as designing mitigation and contingency plans after a large rainfall event., Facultad de Ciencias Naturales y Museo, Centro de Investigaciones Geológicas, Facultad de Ingeniería

Environmental liabilities have become one of the most important problems at environmental level, especially those located in urban areas. Within the area of the Rio de la Plata coastal plain, industrial waste abandoned by an ancient sulfuric acid industry in a sector of the petrochemical center constitutes an environmental liability composed mainly of fragments of native sulfur. The aim of this work is to evaluate, from laboratory tests, the generation of sulfate acid drainage in environmental liabilities associated with the ancient sulfuric acid industry in order to identify the waste spatial distribution and to determine the impacts that they impart on the quality of the soil and groundwater. The results obtained show that the native sulfur scattered in the environmental liability associated with the ancient sulfuric acid industry constitutes a potential source of sulfated acid drainage that locally affects the soil, groundwater, and underground structures of the industrial center, and also small adjacent ecosystems. The interaction between native sulfur and the rainwater causes the oxidation of the native sulfur releasing protons and sulfates, which reach the groundwater through the infiltration water process, generating the acidification of the environment. The results provide useful draft for the management of environmental liabilities, and also the monitoring data obtained could assist in prioritization of remediation options, which constitute a problem of relevance and whose regulations for management and mitigation are still a controversial issue., Centro de Investigaciones Geológicas

Las llanuras constituyen áreas de gran potencial para la producción agropecuaria afectadas frecuentemente por inundaciones. El objetivo del trabajo es utilizar una metodología que permita evidenciar bajo qué condiciones ocurren inundaciones en áreas de llanura con escasez de información base, tomando como caso de estudio a la cuenca del río Samborombón, situada en el centro-este de Argentina. Para esto fueron observadas imágenes satelitales Landsat y se realizaron balances hídricos diarios, para posteriormente realizar un análisis estadístico de recurrencia. Los resultados obtenidos evidencian que las inundaciones se ven influenciadas en gran medida por las condiciones hídricas previas del suelo. La metodología utilizada permite estimar períodos de retorno en cuencas de llanura de baja pendiente requiriendo solamente de imágenes satelitales de libre acceso y de datos de precipitación y temperatura media diaria, obteniendo resultados que reflejan el estado de la cuenca posterior a eventos de precipitación., The plains constitute areas of great potential for agricultural production frequently affected by floods. The objective of the work is to use a methodology that allows demonstrating under what conditions floods occur in plains areas with a shortage of basic information, taking as a case study the Samborombon River basin, located in the center-east of Argentina. For this, Landsat satellite images were observed and daily water balances were performed, to subsequently perform a statistical analysis of recurrence. The results obtained show that flooding is greatly influenced by previous soil water conditions. The methodology used allows estimating return periods in low-slope plain basins, requiring only satellite images of free access and daily average temperature and precipitation data, obtaining results that reflect the state of the basin after precipitation events., Centro de Investigaciones Geológicas

The watershed of El Pescado Creek has been established as a protected landscape; however, it is currently exposed to an intense land use and coverage change process, based on the conversion of grassland areas into greenhouse horticulture and urbanized areas. The aim of this work was to analyze hydrochemical modifications in this changing scenario, to identify parameter variations associated to water balance. The monitory network included surface water and groundwater samplings during winter, spring and summer of 2017. Daily water balance was estimated throughout the annual cycle. Electrical conductivity and pH were determined together with major ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, CO₃²⁻, HCO₃⁻, Cl⁻, SO₄²⁻ and NO₃⁻). The analysis of water stable isotopes (δ¹⁸O and δ²H) was performed for one sampling date. Water-balance variations during short-term periods affected surface water chemistry, although no relevant influence on deep groundwater was registered. Major ions variation in the surface water of the upper watershed might be related to runoff alteration caused by recently established impervious cover and by the dynamic of groundwater inputs. Isotopic analysis of surface water shows deviation from local meteoric line, with an isotopic enrichment following a tendency associated to evaporation processes. Deep groundwater samples express a recharge process by rainfall infiltration, with little or no previous evaporation (deuterium amounts were similar to those corresponding to local rainfall). Incipient evaporation processes are registered for shallow groundwater, possibly occurring before infiltration in the non-saturated zone, or right from the phreatic, when it is near the surface., Facultad de Ciencias Agrarias y Forestales, Facultad de Ciencias Naturales y Museo, Centro de Investigaciones Geológicas

In salt marshes, there seems to be a trade-off between the presence of plants and some abiotic factors. Inparticular, it was observed that while groundwater salinity conditions the plant distribution pattern in certainsalt marshes, it does not do so in others. In the salt marsh of Fracasso beach (Península Valdes, Argentina) thegroundwater has a higher salinity than the seawater. Previous studies have proposed that salinization is aconsequence of the concentration and/or precipitation of salts as a result of partial evaporation/evapotranspirationof the tidal water that floods the salt marsh. However, the role of vegetation in the salinization process hasnot been thoroughly studied so far; therefore, this research work aims to explore this relationship. To this end, 10soils samples with plants and 10 soil samples without plants were taken from the unsaturated zone in Fracassomarsh. At the laboratory, the soil samples were centrifuged to obtain the interstitial water to determine theelectrical conductivity, the concentration of chloride, and the isotopic composition. Also, texture and moisture content were determined. The results indicate that fine fraction and moisture contents were higher in the patches with plants than in those without plants. Conversely, electrical conductivity, chloride concentration and δ18O and δ2H values were higher in the interstitial water of the non-vegetated samples. These results indicate that in patches without plants, the evaporation process is higher than in patches with plants. The presence of low permeability soils reduces infiltration favouring the evaporation of tidal water. Under these conditions, the distribution of vegetation within the salt marsh plays an essential role in attenuating evaporation. S. perennis has a shadow effect that locally attenuates water evaporation causing the soil beneath the vegetation canopy to have less salinity than the adjacent soil without vegetation. Fil: Idaszkin, Yanina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina

The aim of this work is to evaluate the nitrate content and its impact on groundwater quality used for supply in dairy farms in a sector of the Pampas Plain in relation to specific point sources of pollution. Samples were collected in nine dairy farms during the months of June, August and November 2017 and April 2018. In all the samples, electrical conductivity and pH were measured in situ with a portable multiparameter equipment and water samples were collected to determine nitrates content. In the April 2018 sampling, carbonates, bicarbonates, chlorides, sulphates, nitrates, sodium, calcium, magnesium, and potassium were also determined. Results show that groundwater is mainly sodium bicarbonate to magnesium calcium bicarbonate type with variable pH and salinity. Nitrates and hardness were above the limits for human and animal consumption. Nitrate contents are significantly correlated with pH, electrical conductivity and hardness, and tend to decrease in wells which are more distant from point sources of pollution. In turn, the incorporation of other ions into the aquifer is evidenced by the increase of chlorides and EC and their correlation with nitrates. It is interpreted that the nitrification process acidifies the medium, triggering the dissolution of carbonates present in the aquifer matrix which increases groundwater hardness. Water quality deterioration could not only put at risk farmers’ health but it also conditions animal production and the dairy farm machinery. This study is the first contribution to defining local guidelines to set a proper water management plan as well as to provide tools to address the problem in other dairy farms in this sector of the Pampas Plain and in other regions., Facultad de Ciencias Naturales y Museo, Centro de Investigaciones Geológicas, Facultad de Ciencias Agrarias y Forestales

A field as broad as geochemistry has evolved naturally to be subdivided, at various levels, into sub-disciplines. These sub-disciplines are distinguished from each other in several different ways and there is considerable overlap betweenthem in many cases. 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 (fresh, saline, residual, rain, superficial and groundwater), soils, minerals, sediments, rocks and air.The Argentine meetings of Geochemistry of the Surface RAGSU) have been held since 2009 with a periodicity of 2 and 3 years. The main research centers of the country participate in the organization and the groups that work specifically in the Geochemistry of the Surface can meet at these events. Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Santucci, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Botto, Irma Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina

Extra-Andean Patagonia, located in the south end of South America, is a wide arid region where the basaltic plateau landscape dominates. Associated with the basaltic plateaus, wet meadows and shallow lakes make up environments of relevance due to the ecosystemic services they provide. The aim of this work was to define the processes and factors that condition the hydrodynamics and hydrogeochemistry of wet meadows and shallow lakes in a sector of the Patagonian plateau basalts. For this, detailed geological and geomorphological studies were carried out and water was sampled at 29 points for the analysis of major ions and, in some samples, stable isotopes of the water molecule. Values of δ18O and δ2H similar to the local meteoric line in the water of wetmeadows indicate that rainwater quickly infiltrates through the fractures of the basaltic plateaus and stores in the underlying sediments. Groundwater discharge occurs in the scarp zone due to changes in sediment permeability. The weathering of silicates in basalts, ion exchange in the sediment clays, and the dissolution of soluble salts provided by the dust control water chemistry of this wetland.Water from wet meadows drains into saline endorheic basins of sodium chloride composition where the isotopic signal is indicative of evaporation percentages close to 95%. The high evaporation rates cause the precipitation of evaporitic salts at the edges of shallow lakes with carbonate, sulfate, and chloride species controlled by the dominance of sodium in the water. Fil: Melendi, Edoardo Luca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Tanjal, Carolina Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Borzi, Guido Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Raigemborn, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

The province of Buenos Aires located in Argentina contains numerous agricultural plain basins of world importance among which the Samborombon river basin stands out, where regular floods affect agricultural activities and urban expansion. This sector has large road works with approach embankments that obstruct the natural drainage, a poorly planned urban growth, and an increase in the rainfall regime in recent decades. The aim of this work is to carry out an analysis and assessment of the surface runoff conditioned by road works and urban settlements in large plain basins, taking the Samborombon river basin as a case study. Satellite images were used to define the floodplain and identify the main road works and urban settlements that develop within it. Subsequently, hydrological simulations were carried out to assess how these anthropic structures modify the surface runoff and the flooded areas. To validate the simulation results, the flooded areas obtained were compared with a similar flood event of a Landsat image. The results show that the road works embankments and urban settlements restrict the floodplain area of the river, generating an increase in the flooded area and delaying the water runoff. This problem, together with the rainfall increase, shows the need to generate a territorial management plan and adopt mitigation measures. The use of sacrificial embankments could be an economic alternative that would prevent the obstruction of water runoff, being able to use the basin as a pilot site for this innovative idea., Centro de Investigaciones Geológicas

The coastal plain of the Río de la Plata constitutes a large wetland which develops on the right margin of the river estuary. Anthropic activities such as intensive exploitation of groundwater carried out in the vicinity of the wetland can modify the natural hydrological regime. The aim of this work is to asses the effects of intensive aquifer exploitation in coastal wetlands using hydrogeological models. Such models allow to evaluate changes in the environmental conditions of wetland at regional level. The hydrogeological model exposed in this work shows how the intensive groundwater exploitation affects the wetland area, generating important variations both in the groundwater flows and in the salinity of the groundwater. Identification of these modifications to the environment is important to generate guidelines leading to minimize these affectations., Centro de Investigaciones Geológicas

La marisma del arroyo Jabalí forma parte de la Reserva Natural Provincial de Uso Múltiple Bahía San Blas y se encuentra ubicada al sudeste de la provincia de Buenos Aires, Argentina. El objetivo del trabajo es analizar los principales procesos geohidrológicos que regulan la química del agua superficial y subterránea de este humedal y su relación con las características geomorfológicas y pedológicas. Para ello se realizó una caracterización geomorfológica en base a la cual se diseñó una red de monitoreo del agua superficial y subterránea. Se construyeron 14 freatímetros a lo largo de 3 transectas perpendiculares al arroyo y se recolectaron muestras de agua en las que se analizó in situ el pH y la conductividad eléctrica y se determinó en laboratorio el contenido de iones mayoritarios. Los datos fueron analizados mediante gráficos de relaciones iónicas y diagramas de clasificación de aguas. A su vez en cada sector estudiado se efectuaron calicatas para la descripción de los perfiles del suelo y características texturales de los sedimentos superficiales. Los resultados obtenidos muestran que tanto la química del agua del canal Jabalí como la subterránea de la marisma son dominantemente cloruradas sódicas, existiendo un enriquecimiento en el contenido iónico asociado a una mayor distancia con respecto a la boca del canal y una posición topográfica más elevada. El principal proceso que condiciona la química del agua subterránea es la disolución de especies minerales formadas en la superficie de los suelos por evaporación del agua de mar y la posterior incorporación en el acuífero por infiltración. Estos procesos se ven favorecidos por el clima semiárido, la menor recurrencia de inundación por posición topográfica elevada, y por la textura fina de los suelos. A su vez, la oxidación de sulfuros pedogenéticos y la consecuente acidificación del medio son propuestos como otros mecanismos que condicionan la química del agua., The marsh of the Jabalí stream lies within the Reserva Natural Provincial de Uso Múltiple Bahía San Blas and is located in the southeast of Buenos Aires province, Argentina. The aim of the work is to analyze the main geohydrological processes that regulate the chemistry of groundwater and surface waters in this wetland, and the link of these chemical characteristics to local geomorphological and pedological features. For this purpose, a geomorphological characterization was performed and used as basis for establishing a surface and groundwater monitoring network. Fourteen phreatimeters were built along 3 transects perpendicular to the stream; the water samples collected were analyzed in situ for pH, electrical conductivity, temperature and dissolved oxygen, while major ion contents were determined in the laboratory. The data were analyzed through diagrams of ionic relationships and water classification diagrams. In each sector, soil pits were dug for the description of soil profiles and textural characteristics of the surface sediments. Results show that the chemistry of both the water from the Jabalí channel and the marsh groundwater are predominantly sodium chlorinated, with an enrichment of ionic content associated to greater distance to the mouth of the channel and more elevated topographic position. The main processes that condition groundwater chemistry are the dissolution of mineral species such as halite, gypsum and carbonates that occur as surface crusts on the soil, resulting from the total or partial evaporation of seawater and their subsequent incorporation into the aquifer through infiltration. These processes are facilitated by the semiarid climate, the lower recurrence of flooding due to the high topographic position, and the fine texture of the soils. In turn, the oxidation of paedogenetic sulphides and the consequent acidification of the medium are proposed as additional mechanisms that condition water chemistry., A marisma do arroio Jabalí faz parte da Reserva Natural Provincial de Uso Múltiplo Bahía San Blas, e está localizada a sudeste da província de Buenos Aires, Argentina. O objetivo do trabalho é analisar os principais processos geo-hidrológicos que regulam a química das águas superficiais e subterrâneas deste terreno úmido e sua relação com as características geomorfológicas e pedológicas. Para isso, foi realizada uma caracterização geomorfológica com base na qual foi projetada uma rede de monitoramento de águas superficiais e subterrâneas. Foram construídos 14 freatímetros ao longo de três transectos perpendiculares ao arroio, e foram coletadas amostras de água nas quais foram analisados in situ o pH e a condutividade elétrica, e foi determinado em laboratório o conteúdo dos íons majoritários. Os dados foram analisados por meio de gráficos de relações iônicas e diagramas de classificação de águas. Por sua vez, em cada setor estudado foram escavados poços para descrever os perfis do solo e as características texturais dos sedimentos superficiais. Os resultados obtidos mostram que tanto a química da água do canal Jabalí quanto a subterrânea da marisma contém predominantemente cloretos de sódio, havendo um enriquecimento no conteúdo iônico associado a uma maior distância da boca do canal e uma posição topográfica mais elevada. O principal processo que determina a química das águas subterrâneas é a dissolução de espécies minerais formadas na superfície dos solos por evaporação da água do mar e subsequente incorporação no aqüífero por infiltração. Estes processos são favorecidos pelo clima semiárido, pela menor recorrência de inundações devido à posição topográfica elevada, e pela textura fina dos solos. Por sua vez, a oxidação de sulfetos pedogenéticos e a conseqüente acidificação do meio são propostas como outros mecanismos que condicionam a química da água., Dossier: Geoquímica y perspectiva ambiental de sistemas exógenos., Facultad de Ciencias Naturales y Museo

La cuenca del arroyo El Pescado, ubicada en el noreste bonaerense, desde principios de siglo atraviesa un proceso de cambio en el uso del suelo. El objetivo del trabajo fue realizar un diagnóstico sobre la distribución y cuantificación de elementos traza en el recurso hídrico de la cuenca, en relación con los diferentes usos del agua. Se utilizó una red de monitoreo de agua superficial y agua subterránea somera y profunda. Se determinó el contenido de elementos traza mediante un equipo ICP-MS. Las mayores concentraciones de elementos traza correspondieron al agua subterránea somera y las menores al agua subterránea profunda. En el acuífero freático el As y el Fe superaron los límites permitidos para abastecimiento de agua potable. En tanto que el V y el Zn superaron los límites para uso agropecuario en el acuífero freático y agua superficial. En las aguas superficiales el Cu, Pb y Zn excedieron los límites de protección para la vida acuática en todos los sitios, mientras que el V sólo en la cuenca media y parte de la cuenca baja., The watershed of El Pescado Creek, located in the northeast of the Buenos Aires province, has been undergoing a process of land use change since the beginning of this century. The aim of this work was to evaluate the distribution and concentration of trace elements in the water resource, with regard to different water uses. We used a monitory network for surface water and groundwater (including deep and shallow groundwater wells). Trace element content was determined by inductively coupled plasma mass spectrometry (ICP-MS). The highest trace element concentrations corresponded to shallow groundwater and the lowest concentrations to deep groundwater. Regulatory limits of As and Fe for drinking water were exceeded in the phreatic aquifer. Moreover, V and Zn limits for livestock consumption were exceeded both in the phreatic aquifer and in surface water. In all sampling sites along the watershed, concentration of Cu, Pb and Zn exceeded limits for protection of aquatic life in surface water; meanwhile V concentration only exceeded established limits in the middle watershed and part of the lower watershed., A bacia do arroio El Pescado, localizada no nordeste de Buenos Aires, passa por um processo de mudança no uso do solo desde o início do século. O objetivo do trabalho foi realizar um diagnóstico sobre a distribuição e quantificação de elementos traço nos recursos hídricos da bacia, em relação aos diferentes usos da água. Foi utilizada uma rede de monitoramento de águas superficiais e subterrâneas rasas e profundas. O conteúdo de elementos traço foi determinado por meio de um aparelho de ICP-MS. As maiores concentrações de elementos traço corresponderam às águas subterrâneas rasas, e as menores às profundas. No lençol freático, As e Fe excederam os limites permitidos para o abastecimento de água potável. Já V e Zn excederam os limites para uso agropecuário no lençol freático e nas águas superficiais. Nas águas superficiais, Cu, Pb e Zn excederam os limites de proteção para a vida aquática em todas as localidades, enquanto V excedeu apenas na bacia média e parte da bacia baixa., Dossier: Geoquímica y perspectiva ambiental de sistemas exógenos., Facultad de Ciencias Naturales y Museo

Wet meadows in mountainous areas are important environments for the ecosystem services provided, mainly those associated with the water supply to local people. In the region of the Patagonian Andes wet meadows are spatially associated with rock glaciers and other related periglacial landforms. The aim of this work was to determine the hydrological significance of these geoforms as sustenance of wet meadows in La Hoya watershed, located in Northern Patagonian Andes. We carried out a geomorphological mapping of the depositional units, wetlands, springs and streams located in the area. During fieldwork, we checked and completed this information, together with sedimentological analysis of the morphosedimentary units and hydrodynamic and salinity measurements on streams and springs. Finally, we performed hydrogeological schemes to outline the geological and geomorphological controls regulating water flows and the development of wet meadows. Results obtained show a constant flow from rock glaciers and solifluction lobes towards wet meadows during the driest period. The principal contribution of water comes from snowmelt and rain, constituting a short and intermediate-term water input. Rock glaciers and solifluction lobes constitute effective water storage depositional units, and the groundwater discharged from these landforms is constant, even during the dry season, which keeps wet meadows moist and evergreen year-round.

Arid and semi-arid regions constitute an area where approximately 20% of the global population lives and the groundwater represents the only source of fresh water supply in many cases. In Extra-Andean Patagonia, located in the south extreme of South America, the landscape dominated by basaltic plateaus is associated with wet meadows, which are the only source of fresh water for rural inhabitants in a region characterized by arid conditions. The aim of this work was to define the geological and geomorphological controls that condition the formation of wet meadows associated with basaltic plateaus in a sector of the Extra-Andean Patagonian. For this, fieldworks were carried out that included geological profiles, rock sampling and geomorphological description of the sectors associated with wet meadows. The perennial character of wet meadows is supported by lithostratigraphic, structural and geomorphological controls that regulate the recharge, storage, flows and discharge of the groundwater that sustains them. The subhorizontal position of the basaltic plateau and the presence of fractures allow the rapid infiltration of rainwater that recharges the aquifers. The lithology, structure and paleorelief of the underlying rocks to the basalts determine the storage and flow of groundwater. Despite the great extension of the basalt plateaus and their homogeneity, there are different geological-geomorphological combinations in the underlying rocks that give rise to a great variety of controls of the water flows that sustain the wet meadows. The data obtained provide new information for the knowledge of wetlands and water resources in arid environments such as Extra-Andean Patagonia, where wet meadows provide water supply of local people, livestock and vegetation, constituting a relevant ecosystem service.

The South Atlantic coast in Argentine Patagonia is an area where semi-arid to arid conditions predominate and coastal populations present serious water supply problems. The aim of the work was to evaluate the factors that condition the salinization processes of coastal aquifers from a hydrochemical and isotopic analysis of the groundwater located in Pleistocene and Holocene littoral ridges in the northern sector of Patagonia in Bahia San Blas. A geomorphological characterization of the area was carried out using digital elevation models, satellite image interpretation and field surveys. Groundwater chemistry was analyzed in 40 shallow wells and 2 tidal water samples. At each point, electrical conductivity, temperature and pH of water were measured and samples were taken for analysis of major ions and stable isotopes. The salinization processes were analyzed by means of ionic and isotopic relationship graphs and were subsequently modeled using free software. The results obtained allowed the identification of the factors that determine the salinization of coastal aquifers. Particularly in the Pleistocene coastal ridges, the cementation of the most superficial sediments reduces permeability conditioning rainwater infiltration. This, together with the presence of soluble salts on the surface and the mixing with sea water, determines the salinization of the groundwater. In contrast to these, in the Holocene coastal ridges without cementation, rainwater infiltrates forming freshwater lenses where salinization processes occur only at the edges of the lenses where the saltwater wedge is located. The data provided in this paper are useful in prospecting freshwater sources along the arid coast of Patagonia where freshwater availability is scarce. They can also be extrapolated to other sectors worldwide with similar geological and climatic environments.

Heavy metal pollution that affects salt marshes is a major environmental concern due to its toxic nature, persistence, and potential risk to organisms and to human health. Mining waste deposits originated four decades ago, by the metallurgical extraction of heavy metals, are found near to the San Antonio salt marsh in Patagonia. The aim of the work was to determine the geochemical processes that control the distribution and concentration of Cu, Fe, Pb and Zn in the soils of this Patagonian salt marsh. A survey of the mining waste deposits was carried out where three dumps were identified. Samples were collected to determine soil texture, Eh pH, organic matter and metal contents and the soil mineralogical composition. The results shows that the soils developed over the mining waste deposits are predominantly reddish constituted mainly by iron oxide, hydroxide and highly soluble minerals such as Zn and Cu sulphates. The drainage from these deposits tends to move towards the salt marsh. Within the salt marsh, the highest concentrations of Cu, Pb and Zn occur in the sectors closest to the mining wastes deposits. The sulphide oxidation and the dissolution of the Cu, Pb and Zn sulphates could be the mainly source of these metals in the drainage water. The metals in solution that reach the salt marsh, are adsorbed by the organic matter and the fine fraction of the soils. These adsorbed metals are then remobilized by tides in the lower sectors of the marsh by desorption from the cations present in the tidal flow. On the other hand, Fe tends to form non soluble oxides, hydroxides and sulphates which remain as altering material within the mining waste deposit. Finally, the heavy metal pollutants recorded in the San Antonio salt marsh shows that the mining waste deposits that were abandoned four decades ago are still a source metal contamination. Fil: Idaszkin, Yanina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia; Argentina Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

Freshwater lenses associated to shell ridges and sand sheets exist on the coastal wetland of Samborombón Bay. As they constitute one of the most vulnerable aquifer systems, it is the aim of this study to determine the hydrogeochemical processes that condition the chemical quality of its groundwater and to assess their present and future capability as sustenance of native woods and local villagers. To achieve this, hydrogeomorphological field surveys were made and groundwater samples were taken. Results show that lenses have a mean thickness of 12 m and its chemical quality depends on the dissolution of CO2(g) and carbonates, weathering of silicates and ion exchange. Lenses can be affected by long-term climatic variability and mining. The study of morphology and geochemistry of the freshwater lenses bring lights into important information about the management of water resources and conservation of the environment., Centro de Investigaciones Geológicas

The aim of this work was to analyze the hydrologic effects on surface runoff and infiltration of changes in land use and land coverage. The periurban-flatland watershed of El Pescado Creek (Argentina) was the study site investigated. We used Geographic-Information-System techniques together with the curve-number method (CN) to estimate the surface runoff in five land-use scenarios having increasing levels of anthropic impact (years 1986, 1996, 2006, 2016, and 2026) considering two rainfalls and the antecedent-runoff conditions (ARC) defined by that methodology. We identified three hydrologic-soil Groups (B, C, and D) and five land uses (grassland, forest, urbanization, greenhouses, and poultry farms). Land use and land coverage change process increased CN values, and consequently the estimated surface runoff, especially in the upper watershed. Changes towards impervious (687 ha with greenhouses and poultry farms) or semi-impervious land coverage (800 ha with urbanizations) affected infiltration. The most contrasting results were related to the ARC I, II, and III weighted-average infiltration of the watershed that diminished from above 93.0%, down to 88.5% and finally to 50.4%, respectively (calculated with data from the 55.8-mm rainfall), and from 86.6%, to 58.3%, and to finally 28.8% (calculated with data from the 117.8 mm rainfall). Simulating a near-future land-use scenario (year 2026) enabled us to estimate the watershed pattern by adding new area containing semi-impervious and impervious land coverage. The estimated weighted-average infiltrations (ARC II) were 81.3% and 54.9%, for the above 55.8-mm and 117.8-mm rainfalls, respectively. Changes concerning infiltration might be disturbing the natural recharging process of aquifers, carrying out modifications in the hydrodynamics of the watershed, and also affecting water supply for human activities in the territory. Fil: Delgado, María Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Ficología; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Casco, Maria Adela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Ficología; Argentina

Groundwater geochemistry and dynamics are both among the main controlling factors of environmental features in wetlands. Coastal wetlands in particular are complex environments in which groundwater geochemistry is linked to a large number of controls, such as tidal action, landforms and interactions between groundwater and surface water. The Parque Costero del Sur Biosphere Reserve is part of a larger wetland zone that extends along the right margin of the Río de la Plata estuary. The environmental characteristics present in such area are strictly connected to the geomorphological setting of the coastal plain. The aim of this study is to understand the hydrogeochemical processes which determine groundwater quality in this biosphere reserve. Major ions and environmental isotopes of groundwater were analyzed together with water balances, water table measurements and a geological and geomorphological characterization of the coastal plain in order to analyze the hydrogeochemical and hydrodynamic processes present in the wetland. Results point out that the groundwater hydrogeochemical and hydrodynamic characteristics vary over the different landforms that form the Río de la Plata coastal plain, with particular chemical facies for each one. The principal hydrogeochemical mechanisms acting in groundwater are controlled by processes which include rainfall recharge, dissolution of CO2(g), carbonates, halite and gypsum, and Na+/Ca+2 exchange. Water is one of the main conditioning factors in wetlands and this study is the first attempt to understand the mechanisms that rule groundwater geochemistry in this remote area. This research contributes to a better understanding both the hydrology and hydrogeochemistry of the biosphere reserve and future investigations will benefit from our results. In particular, this work provides the basic knowledges on surficial water - groundwater interaction necessary to develop an integrated coastal management plan aimed to guarantee the ecosystem protection through a sustainable use of the natural reserve. Fil: Cellone, Francisco Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Tosi, Luigi. Consiglio Nazionale delle Ricerche; Italia. Institute of Geosciences and Earth Resources; Italia

The Samborombón River basin, which has eminently rural characteristics, develops within the Pampean plain along with other basins with serious contamination problems due to the growth of the industrial activities and the absence of a proper groundwater management. Considering that the knowledge of the natural baseline quality is important to measure an imposed environmental change, the aim of this work was to study the mechanisms that control the natural composition of groundwater and superficial water in the Samborombón River basin. In order to achieve this, detailed analysis of the minerals forming the aquifer matrix along with the data obtained from isotopes, major and trace elements were performed. Geochemical processes that define the chemical characteristics and contribute to the evolution of both surface and groundwater are associated with rainwater infiltration, carbonate dissolution, cation exchange and evaporation. Additionally, the low concentration of heavy metals may respond to natural background levels. Comprehending the hydrochemical processes governing groundwater and superficial water quality, particularly in a rural area where water supply is vital for the development of human activities, is essential to prevent environmental deterioration and thus, enhance socio-economic growth. Fil: Borzi, Guido Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Tanjal, Carolina Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Santucci, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

El área de estudio comprende el sector S. de la Bahía de Samborombón (Partido de General Lavalle, Provincia de Buenos Aires). Dentro del área y directamente relacionado con la línea de costa de la bahía, se encuentra el humedal de la Bahía de Samborombón. Los recursos hídricos del sector adquieren una alta significación en el desarrollo socioeconómico y en la preservación de sus características ambientales. El objetivo general fue evaluar los procesos hidrológicos y costeros que participan en la dinámica y conservación del humedal. Los objetivos particulares fueron: caracterizar la dinámica hidrológica y costera, definir las particularidades hidrodinámicas e hidroquímicas, analizar las variaciones del contenido de nutrientes (fósforo y nitrógeno) en los sedimentos y formular un modelo conceptual del comportamiento hidrológico y de su relación con la dinámica costera. Se estudió el comportamiento del ciclo del agua en distintas escalas espaciales y temporales. En primera instancia, a partir de un análisis global en un marco regional, y luego en sucesivas aproximaciones de mayor detalle. Las actividades desarrolladas incluyeron tareas de campo, gabinete y laboratorio.

The Argentine Atlantic coast constitutes an extensive area where numerous wetlands develop under humid, semi-arid and arid conditions, in which there are also variations in relation to tidal influence with estuarine, mixing and marine areas. The aim of this work is to conduct a comparative study on the processes controlling the groundwater salinity in medium to high latitudinal coastal wetlands of four natural reserves with contrasting hydrological and climatic conditions. In each study area a monitoring network was established where the content of CO32−, HCO3−, Cl−, SO42−, Ca2+, Mg2+, Na+, K+, δ2H and δ18O of the water were determined. The results show a saline groundwater increase along a latitudinal gradient with electrical conductivities varying from 0.3 mS/cm at 34°47′ S to 154 mS/cm at 42° 25′ S. The results obtained show that the ionic contents in groundwater are partially controlled by the salinity of the tidal flood water whose electrical conductivity varies from 0.3 mS/cm in the Río de la Plata estuary to 52 mS/cm in the sea water of the southern study area. In the southern wetlands, where an increase of aridity is also registered, there is a clear increase in groundwater ionic concentrations, which occurs without isotopic enrichment indicating processes of salts dissolution of the sediments. The evaporites precipitation occurs due to the total evaporation of the tidal water that floods the wetlands in spring high tides. The salinization of groundwater responds to natural processes inherent to the hydrological, climatic and lithological characteristics of each wetland. Given that the areas studied correspond to natural reserves, the results generate databases that will allow the identification of future changes in salinity associated with anthropic influences or changes in hydrological and/or climatic conditions as a result of climate change. Fil: Galliari, Maria Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Santucci, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Misseri, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, María del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina

The formation of evaporites associated with the final stages of the precipitation sequence, such as the case of halite, is frequent in marshes in arid areas, but it is not to be expected in those humid climates. This work, by means of the study of the hydrological, climatic and land use conditions, identifies the factors that allow the formation of saline precipitations in a marsh located in a humid climate area. The results obtained show that the exclusion of the marsh as a result of the embankment is the main reason for the presence of halite. It is to be expected that in the future the growth of the embanked marsh areas, together with the climatic and tidal condition tendencies recorded, will favour a higher rate of formation of evaporite salts. The identification of these factors makes it possible to set basic sustainable management guidelines to avoid soil salinisation. Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Borzi, Guido Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

Population growth and industrialization involve environmental problems, such as metal pollution, and coastal environments are particularly susceptible to such issues. Within this framework, we aimed: (i) to determine the levels of trace metals in soils and Spartina densiflora tissues in rocky shore marshes of Central Patagonia; (ii) to relate metal concentration patterns in the different soil-plant complex fractions to environmental conditions; and (iii) to investigate whether geographical metal concentration patterns can be explained with anthropogenic influences and sources and/or by local prevailing biogeochemical processes. For this purpose, soil samples and associated vegetation were collected in five rocky shore marshes located at different distances from an urban or industrial area. The concentration of Al, Cd, Cr, Cu, Fe, Ni, Pb, and Zn in soils (pseudototal and bioavailable) and in plants (roots and shoots) was determined. Then the enrichment factor, bioaccumulation and translocation factor were calculated. The soil mineralogy and the behavior of these metals according to different soil variables were discussed. The results showed different behavior and level of anthropic impact according to the metal considered. Salt marshes located on the southern edge of the Nuevo Gulf showed the highest concentrations of metals. Fe, Al, Cu and Zn showed mostly a natural origin. Fe and Al were mainly in soils rather than in plants, while Cu and Zn were similarly distributed in both matrixes. Although Cd in soils showed enrichment, it would have a natural origin. Also, it was scarce in the soil and was mostly concentrated in Spartina’ roots. Pb, Cr and Ni showed anthropic enrichment too, being mainly derived from the port and industrial activities. Pb had significant representation in all soil-plant subsystems and showed the highest bioavailability in soils. Cr and Ni, were found in high concentration in the soil and showed a high bioaccumulation in roots. The human impact level in rocky shore marshes of the Nuevo Gulf in Central Patagonia associated to the trace metals pollution varies from being scarce to significantly important, with the marshes located in its southern margin showing the worst scenarios. Fil: Idaszkin, Yanina Lorena. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Barcia Piedras, José M.. No especifíca; Fil: Bouza, Pablo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Mateos Naranjo, Enrique. Universidad de Sevilla; España

Coastal lagoons and marshes are among the most fluctuating and productive ecosystems in the world, which provide a wide range of ecosystem. The objective of this work was to evaluate the factors and processes that condition the hydrogeochemical dynamics in salt marshes associated with the development of small coastal lagoons located at the southern end of the outer estuary of the Rio de la Plata, where it confluences with the Atlantic Ocean. Four samplings were carried out where major ions composition was determined in seawater, surface water of the lagoon and tidal channel, and in groundwater of the marsh, measuring in situ water pH and the electrical conductivity (EC). The chemical data were analyzed considering the conditions and processes associated with both water balance and tidal regime. The coastal lagoon develops within a sandy spit with dunes which is connected to the sea by a narrow tidal channel where the entry of the tidal flow is limited. The tide that enters has strong chemical variability, reflected in EC ranging from 19.1 to 37.5 mS/cm, depending on the dominant source (ocean or estuary). In periods with evapotranspiration domain, tidal water in the lagoon evaporates resulting in soluble salts precipitation such as gypsum and halite. The subsequent tidal flood dissolves these salts causing that in these periods both surface water of the lagoon and groundwater in the marsh present EC values between 8.4 and 57.1 mS/cm. Conversely, when evapotranspiration is low, surface water of the lagoon and tidal channel and groundwater of the marsh have EC between 3.5 and 18.1 mS/cm, and freshwater discharge from the dune sector where the rain preferentially infiltrate becomes relevant. The results obtained show the strong chemical variability that this type of coastal wetlands presents, providing the basis for its conservation andmanagement of natural reserve areas. Fil: Galliari, Maria Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Tanjal, Carolina Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

Arsenic (As) is an important component in thermal springs, which can reach water sources constituting an important hazard for both the environment and people. For this reason, the aim of this paper is to analyze the geologic and geochemical processes that determine the presence and concentration of As in wet-meadows associated to a geothermal field in Patagonia (Argentina) which is used as water supply. To achieve this, during field surveys temperature, pH and electrical conductivity were measured and water and rock samples were taken. Major ions and stable isotopes were determined in water samples while As content was analyzed in both water and rock samples. Due to geological control and chemical analyses, three areas were recognized with respect to major streams in the geothermal field: wet-meadows at headwaters, thermal springs at mid basin and wet-meadows at down basin. Even though, water in wet-meadows have the same origin the obtained results evidence how thermal springs at mid-basin influence the chemistry of these wetlands, particularly those at down basin. In the latter, As raises over two orders of magnitude than the ones at headwaters which surpasses the reference limit, proving that thermal springs are also responsible for the increase of the As content in water changing its quality as a source of potable water. The concentration of this metalloid could be higher but it is retained in travertine and sinter deposits formed near the geothermal discharge area. Understanding processes controlling water quality and the chemistry of As in this type of wetlands is of vital importance, mainly in an arid region where water supply sources are scarce.

Environmental liabilities have become one of the most important problems of the last years, especially those of contaminated sites located in urban areas which have been abandoned by pollution intensive industries. Such sites may contain hazardous materials that pose risks to human health and the environment. Industrial waste from the ancient sulfuric acid industry is scattered in a local area at the petrochemical pole in a sector of the Río de la Plata coastal plain. The aim of this work is to define the geochemical processes that determine the alteration of waste in the old sulfuric acid industry (OSAI) area and to study the migration of soluble pollutants to groundwater. A survey of soil and waste deposit was carried out and samples were examined by X-ray diffraction, under a scanning electron microscope and a polarizing microscope. Surface water and groundwater samples, both to the unconfined and semi-confined aquifers, were collected to determine electrical conductivity, pH and major elements. The results show the presence of minerals composed of sulfur associated with jarosite and iron oxides on superficial sediments. The detailed study of soil sediments together with that of the water physicochemical characteristics make it possible to understand the geochemical processes developed in soil that cause the high concentrations of sulfates in groundwater. Furthermore, high SO4 −2 concentration registered in the semi-confined aquifer due to its infiltration from the unconfined aquifer shows that the industrial pollution has an important impact at local level. These results may contribute to the understanding of chemical processes and pollutants distribution in highly industrialized coastal plain areas. Fil: Santucci, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Tanjal, Carolina Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

Drinking-water supply is one of the main issues that populations face in many coastlands. Shallow coastal aquifers are often characterized by the presence of lens-shaped freshwater floating on the saline groundwater plume of marine origin. These groundwater lenses are commonly associated with landforms, such as littoral ridges and dunes and in many cases they represent the main source of water supply in remote coastal areas. At the right side of the middle Río de la Plata estuary (Argentina) the aquifer system is generally saline. Elongated and thin sandy beach ridge systems emerging from the general flat morphology of the marsh-flood plain are capable of storing precipitations forming freshwater lenses, which to date are the main freshwater supply for inhabitants. The aim of this study is to identify and delimitate the presence of such valuable freshwater reserves in order to provide the first necessary guidelines for the water management plan in this area, which has never been implemented since, to the Authors' knowledge, no specific investigation had been carried out before this study. To achieve this goal, Vertical Electrical Sounding, groundwater electrical conductivity measurements, water balances and groundwater chemical analyses were performed and interpreted together. The whole dataset was processed to define the electro-stratigraphic model of the study area and to produce the map of the electrical conductivity of the shallow aquifer. In addition, a three-dimensional model of the fresh water reservoir has been implemented for a better understanding of the relationship between geomorphology and groundwater. Results point out that a total freshwater volume of 78,259,700 m3 is stored into a continuous lens and the annual average recharge from precipitation amounts to 6,303,500 m3. Although preliminary, this work provides the basic knowledge on the potential fresh groundwater lenses and provides important information for addressing a sustainable use of the freshwater resource. Fil: Cellone, Francisco Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Tosi, Luigi. Consiglio Nazionale delle Ricerche; Italia. Istituto di Scienze Marine; Italia Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

The processes regulating the relationship between tidal fl ows and shallow groundwater dynamics, temperature and salinity in a coastal wetland in an arid climate are analysed in a detailed fi eld study carried out in the marsh located at Playa Fracasso (Argentina). The continuous records of groundwater level, temperature and electrical conductivity from a transect perpendicular to the coastline were studied during a period ranging from summer to winter, together with the information obtained in hydro- geomorphological fi eld surveys and soil pro fi les. An assessment of the processes conditioning marsh hydrology was carried out contemplating seasonal (summer e winter) and periodical variations caused by tidal fl ows. The study showed that the dynamics of groundwater in relation to tidal fl ows depends almost exclusively on the in fi ltration of tidal water when the marsh is fl ooded during spring tides (syzygy), with an increase in the groundwater discharge level at the onset of syzygy. The differences in temperature between sea and continental water were very useful in de fi ning the origin of the different contributions. Groundwater salinity is mainly associated with the leaching of the soil salts that enter with the sea water in fi ltrating during fl ood events. The presence of saline soils in the marsh is regulated by the evapo- transpiration predominating in arid zones. The conceptual hydrological model suggested may help in the understanding of the hydrological processes in other similar marshes of Patagonia, as well as in coastal wetlands of arid zones worldwide. Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Hernández, Mario A.. Universidad Nacional de La Plata; Argentina Fil: Bouza, Pablo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina

Coastal wetlands are complex hydrogeological systems, in which saline groundwater usually occurs. Salinity can be attributed to many origins, such as dissolution of minerals in the sediments, marine contribution and evapotranspiration, among others. The aim of this paper is to evaluate the processes that condition the hydrochemistry of an arid marsh, Playa Fracasso, located in Patagonia, Argentina. A study of the dynamics and geochemistry of the groundwater was carried out in each hydrogeomorphological unit, using major ion and isotope (18O and 2 H) data, soil profiles descriptions and measurements, and recording of water tables in relation to the tidal flow. Water balances and analytical models based on isotope data were used to quantify the evaporation processes and to define the role of evaporation in the chemical composition of water. The results obtained show that the groundwater salinity of the marsh comes mainly from the tidal inflow, to which the halite and gypsum dissolution is added. These mineral facies are the result of the total evaporation of the marine water flooding that occurs mostly at the spring high tides. The isotope relationships in the fan and bajada samples show the occurrence of evaporation processes. Such processes, however, are not mainly responsible for the saline content of groundwater, which is actually generated by the dissolution of the typical evaporite facies of the arid environment sediments. It is concluded that the evapotranspiration processes condition groundwater quality. This is not only due to the saline enrichment caused by the evapotranspiration of shallow water, but also because such processes are the main drivers of the formation of soluble salts, which are then incorporated into the water by groundwater or tidal flow. Fil: Alvarez, Maria del Pilar. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina Fil: Dapeña, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentina

The coastal plain of the middle estuary of the Río de la Plata is a highly industrialized area and is densely populated by sectors. The main human activity in the sector encompassed between the cities of Ensenada and Berisso is associated with the petrochemical industry. In this work, hydrogeochemical and isotopic characteristics of surface and groundwater in the impacted area are analyzed and the results are contrasted with those obtained in an undisturbed protected area. Major and trace elements were determined using standardized methods while the stable isotopes δ18O y δ2H were analyzed by mass spectroscopy. Human impact is evidenced by the occurrence of large variations in the major chemical composition of water, and also by the elevated concentrations of some trace elements that are not contributed from natural sources. These results may contribute to the understanding of chemical processes and pollutants distribution in highly industrialized coastal plain areas., Centro de Investigaciones Geológicas

The attenuation of the acid mine drainage is one of the most important environmental challenges facing the mining industry worldwide. Mining waste deposits from an ancient metallurgical extraction of heavy metals were found near to the San Antonio marsh in Patagonia. The aim of this work was to determinate which mechanisms regulate the mobilization and retention of metals by acid drainage. A geological and geomorphological survey was carried out and samples from the mining waste deposits and the marsh were collected to determine soil texture, Eh pH, organic matter, Cu, Pb, Zn and Fe content, and soil mineralogical composition. Metals in marsh plants were determined in above- and below-ground structures. In the mining waste deposits polymetallic sulphides were recognized where the oxidation and formation of oxy-hydroxides and sulphates of Fe, Cu, Pb and Zn occurs. Then, by the alteration of those minerals, the metals enter in solution and are mobilized with the surface drainage towards the marsh where adsorption in the soils fine fraction and organic matter and/or by plants occurs. Locally, in the mining waste deposits, the precipitation/dissolution of Cu, Pb, and Zn sulphates take place in small centripetal drainage basins. In topographically lower portions of the marsh desorption and removal of metals by tidal flow could also be happen. The results allow to concluding that the marsh adjacent to the mining waste deposits is a geochemically active environment that naturally mitigates the contamination caused by acid drainage. Fil: Idaszkin, Yanina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; Argentina

The variability in dynamics and salinity of the coastal alluvial aquifer on which the city of Lisbon is located was evaluated. Such an evaluation was based on the analysis of level and groundwater electrical conductivity fluctuations depending on the tide in the Tagus River. The results obtained made it possible to recognize three sectors. First, a littoral sector where the variations in level and salinity are larger on the coast and decrease towards the innermost sections of the alluvial fan. Second, a sector close to the docks where there is greater dynamic and salinity variability than in the coastal sectors, as the excavations of the docks favour the tidal propagation towards the aquifer. And third, a sector located towards the apex of the alluvial fan associated with the dynamics of the stormwater channel. In this sector, the largest periodical water table fluctuations in the aquifer occur, since the freshwater that cannot drain towards the river enters the aquifer at high tide, causing a slight decrease in salinity content. On the basis of these results, conceptual models of hydrogeological behaviour were used to describe the spatial and temporal variations in the hydrodynamic and salinity characteristics of groundwater., Facultad de Ciencias Naturales y Museo

Coastal wetlands rank among the most endangered ecosystems since they are affected by the sea level rise and by anthropogenic activities. The continued loss and degradation of these valuable environments requires that a great deal of attention be given to groundwater?surface water exchange, as the ecological function of coastal wetlands greatly depends on it. Hydrological research carried out in the lower part of the Samborombón Bay coastland (Río de la Plata estuary, Argentina) by remote sensing revealed the presence of a meandering channel system, which does not appear in modern maps. The analysis of SPOT satellite images, the interpretation of historical maps and in situ surveys confirmed that this structure is part of an ancient river system, the palaeo-Rincón de Ajó River, at present almost completely silted up. In addition, multispectral satellite data provided the information to develop a conceptual hydrological model, as well as evidence that a significant hydrologic landscape shift occurred due to man-made interventions. The palaeo-Rincón de Ajó River disappeared because the water flow in its upper course was intercepted by man-made canals, and in its lower course the embankments built for the construction of roads and to prevent the flooding of the wetlands from the Río de la Plata estuary excluded the surface flow from the estuary to the mainland and vice versa. The silting up in the lower course and in the vicinity of the mouth cancelled the original structure of the ancient river. Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Braga, F.. Istituto di Scienze Marine; Italia Fil: Donnici, S.. Istituto di Scienze Marine; Italia Fil: Kruse, Eduardo Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Cátedra de Hidrología General; Argentina Fil: Tosi, L.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina

We provide a model for the genesis of Holocene coralligenous buildups occurring in the northwestern Adriatic Sea offshore Venice at 17-24 m depth. High-resolution geophysical surveys and underwater SCUBA diving reconnaissance revealed meandering shaped morphologies underneath bio-concretionned rocky buildups. These morphologies are inferred to have been inherited from Pleistocene fluvial systems reactivated as tidal channels during the post-Last Glacial Maximum transgression, when the study area was a lagoon protected by a sandy barrier. The lithification of the sandy fossil channel-levee systems is estimated to have occurred at ca. 7 cal. ka BP, likely due to the interaction between marine and less saline fluids related to onshore freshwater discharge at sea through a sealed water-table. The carbonate-cemented sandy layers served as nucleus for subsequent coralligenous buildups growth., Contiene material complementario: consultar en https://www.nature.com/articles/s41598-017-01483-z#Sec5, Centro de Investigaciones Geológicas

On the Samborombón Bay coastline, located in the Río de la Plata estuary in Buenos Aires province (Argentina), a complex hydrological system has developed at the interface between continental and estuarine water, where significant wetlands develop. The main hydrogeological units, namely the shell ridges, the tidal plain and the marsh areas, have been identified using geomorphological criteria. Water table, hydrochemical and isotopic data have been used to determine their hydrological features, as well as those of the streams and canals. Evaporation processes, in particular, have been considered when depicting chemical and isotopic changes in surface waters in streams and marsh areas. The shell ridges represent a hydrogeological unit in which rainwater is stored, constituting a lens-shaped freshwater aquifer. In this unit, just as in the tidal plain, carbonate dissolution and ion exchange are the main processes regulating water chemistry. On the other hand, in the marsh and surface waters, processes such as mixing with estuarine water and evaporation predominate. These processes control water fluxes and the salinity of the wetland areas and, consequently, their ability to preserve the existing biodiversity. This study shows the importance of knowledge of hydrochemical processes in any proposal concerning the management and preservation of this type of wetland. Fil: Carol, Eleonora Silvina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mas Pla, Josep. Universidad de Girona; España. Instituto Catalán de Investigaciones en Agua; España Fil: Kruse, Eduardo Emilio. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Evaporites are mineral facies frequently occurring in salt marsh environments in arid climates. Considering that groundwater and soil salinity play an important role in the development of salt marsh ecosystems, the aims of this work are to study the occurrence and precipitation/dissolution processes of evaporites of marine origin and to evaluate how such processes influence groundwater chemistry in the Fracasso Beach salt marsh (Península Valdés, Argentina). Groundwater and seawater samples were collected for isotopic and chemical analysis. Ionic speciation and saturation indices were estimated, and the modelling of theoretical seawater evaporation was undertaken. The estimation of the isotopic variations due to evaporation was carried out according to an analytical model. To study the evaporites, soil salt crust samples were collected in the different sectors of the marsh and then observed in a scanning electron microscope with an X-ray energy-scattering micro-analyzer. The evaporite minerals occurring in different areas of the salt marsh show that there are changes in the dominance and type of evaporites depending on the topographic height. In the most elevated areas, abundant halite and gypsum/anhydrite precipitates are registered, accompanied by epsomite and bischofite, whereas in the lower salt marsh, mainly halite can be observed and, to a lesser extent, gypsum and scarce epsomite. The dissolution of all the evaporites is verified in the groundwater chemistry; the results show that the process of precipitation/dissolution of marine evaporites is the main determinant of groundwater salinity in the Fracasso Beach salt marsh. The variation in ion content registered within the salt marsh is related to the recurrence of the tidal flooding in each sector, as it renews the groundwater. This indicates that in the highest sectors the evaporation percentages are higher, and it confirms that the occurrence of evaporite minerals is determined by their closeness to the sea, the topographic height and, therefore, by the flooding frequency. Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Bouza, Pablo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina

The hydrochemistry of minor elements and traces such as bromide, lithium, strontium, uranium and selenium, together with the chemical analysis of major ions, has been used in the study of salinization process. This process occurs in a semi-confined aquifer that corresponds to a Pliocene–Pleistocene fluvial environment. The semi-confined aquifer is located in the littoral of the cities of Ensenada and Berisso, in the region of the middle Río de la Plata estuary, Argentina. Groundwater salinization was detected in the semi-confined aquifer in the coastal plain area, with salt contents that increase from the loess plain towards the river. The content of major ions that predominate in sea water (Cl−, Na+ and Mg2 +), as well as the Cl−/Br− and U vs. Cl− ratios, demonstrates that such salinization is related to sea water, which shows no correspondence with estuary water. In the salinized area, Li, Sr and Se enrichments occur, and are used as tracers of the average time that a substance remains in solution in sea water in the aquifer. The study of such minor ions together with the geological evolution of the area made it possible to recognize that the salt water in the semi-confined aquifer corresponds to a palaeo-intrusion of sea water associated with the Pleistocene–Holocene ingressions caused by the climate changes occurring during the Quaternary. Fil: Santucci, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Kruse, Eduardo Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Hidrología General; Argentina

Salt marshes are some of the most important wetlands in many regions of the world. Soil and groundwater salinity plays an important role in coastal wetland ecosystems because of the differences in tolerances of plant species to salinity and tidal inundation. Given that the salinity of these environments is mostly dominated by the chloride anion, it is the aim of this study to identify the geochemical processes that regulate its content in groundwater. A comparison of two intertidal wetlands under different environmental conditions was carried out in Peninsula Valdés and in Samborombón Bay, both on the Atlantic coast of Argentina. The tidal influence over the groundwater marsh dynamics was analyzed from continuous records of groundwater levels and electrical conductivity. Besides, major ion and environmental isotope data were used to identify the geochemical processes that determine the chloride content, based on the study of ion ratios and analytical models. The results show that, despite the hydrological differences between the two studied marshes, the processes regulating the Cl− contents are similar: evaporation, transpiration and halite dissolution. Among them, evaporation/transpiration are the processes that could continuously increase the chloride concentration. However, it is expected that those are not processes that greatly increase the groundwater saline content if compared to the dissolution of halite. Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Alvarez, Maria del Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina

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 Samborombon 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 Samborombon 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., Facultad de Ciencias Naturales y Museo

Many worldwide coastal wetlands are facing erosion, severely putting at risk their noteworthy ecological functions. The Punta Indio coast, which bounds the Argentinean side of the middle Rio de la Plata Estuary, is experiencing noticeable shoreline retreat, as clearly shown by the occurrence of erosive features and wetland loss. The first step in understanding the causes of the coastal erosion is estimating the long-term historic evolution of the coastal changes. In order to overcome the unavailability of historical topographic data, we have used remotely sensed imagery (aerial photos and satellite images) to retrieve the multiple shoreline positions over the period 1943–2013. The rates-of-change and net shoreline movements have been computed by a statistical approach based on the Digital Shoreline Analysis System. Results point out that severe shoreline retreats (up to −7.4 m/yr) affect wide wetland sectors, especially where the natural intertidal vegetation is absent. In these areas, the native vegetation has been cut in the last century, and human activities such as tourism and settlements building experienced a strong development over the last decade. The simulated evolution of the coastline changes for the next 50 years shows that shoreline retreatments will take place very fast, about 4 m/yr. A general warning concerning possible consequences of severe degradation of the wetlands is given, while a remediation strategy, in conjunction with a coastal protection plan, are discussed. Fil: Cellone, Francisco Aldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Carol, Eleonora Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina Fil: Tosi, Luigi. Consiglio Nazionale delle Ricerche; Italia