Ecohidrología de un humedal intermareal antropizado: un estudio de caso en la Bahia de Samborombón (Argentina)

En los humedales intermareales los procesos hidrológicos y ecológicos están íntimamente conectados, razón por la cual los cambios en la hidrología derivados de las actividades humanas pueden modificar los ecosistemas. En el humedal de la marisma del río Ajó la expansión ganadera dio a lugar a la realización de numerosos terraplenes que cortan los canales limitando la propagación del flujo mareal. El objetivo del trabajo es analizar cómo los cambios hidrológicos ocasionados por el hombre en la marisma pueden afectar la ecohidrología del humedal en relación al desarrollo de la vegetación. Se estudiaron las características hidrológicas y ambientales en áreas naturales y antropizadas a partir de observaciones de campo y medición de variables hidrológicas. Para evaluar las modificaciones en la vegetación se efectuó una estimación de los cambios estacionales en la cantidad, calidad y desarrollo de la misma a partir del análisis del índice de vegetación de diferencia normalizada (NDVI) en imágenes Landsat. Los resultados obtenidos evidencian que cerca de un 18% del área de marisma está actualmente fuera del ciclo mareal debido a las alteraciones antrópicas. En estas zonas el funcionamiento hidrológico natural fue modificado afectando el desarrollo de la vegetación intermareal típica de este ambiente y en consecuencia la ecohidrología del humedal

El rol de la evapotranspiración en la geohidrología del humedal de la Planicie Costera de Ajó (provincia de Buenos Aires)

Fil: Carol, Eleonora Silvina. Cátedra de Hidrología General. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Kruse, Eduardo Emilio. Cátedra de Hidrología General. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Braga, Federica. Istituto di Scienze Marine. Consiglio Nazionale delle Ricerche. Venezia; ItalyFil: Tosi, Luigi. Istituto di Scienze Marine. Consiglio Nazionale delle Ricerche. Venezia; Ital

Respuesta hidrológica del Bañado de Maldonado en la planicie costera del Río de la Plata: eventos extremos de abril de 2013

On April 2, 2013 unprecedented flash floods due to extreme rainfalls (approximately 400 mm in a few hours) occurred in La Plata and its surroundings causing loss of human live and great socioeconomic harm. The southeastern part of La Plata was an important flooded area. The lack of hydrological data at regional scale represents a significant constraint to the water management planning. This work aims to evaluate the hydrological response to the extreme precipitation events. Herein, we analyzed the satellite images acquired on April 5 (ASTER), April 9 (SPOT5), April 13 (Landsat7) and May 21, 2013 (SPOT5) and the topographical setting of the coastal plain. We suggest that the quantification of the evolution of the stored water in the low flooded areas of coastal plain is an indirect way to know the response of the coastal plain to the extreme precipitation events

Identificación y delimitación de lentes de agua subterránea dulce en la planicie costera del Río de la Plata, Punta Indio, Buenos Aires, Argentina

El objetivo del trabajo fue identificar y delimitar las lentes de agua subterránea dulce presentes en la planicie costera en la zona litoral del partido de Punta Indio con el fin a futuro de evaluar sus reservas y establecer pautas de explotación sustentable. Para ello se analizaron datos de registros de sondeos eléctricos verticales y se realizó un censo de perforaciones donde se midió la conductividad del agua subterránea a distintas profundidades. Los datos fueron analizados conjuntamente confeccionándose mapas y diagramas tridimensionales que permitieron establecer los límites de las lentes de agua dulce. Los resultados señalan que el agua dulce está almacenada en lentes arenosos con un promedio de conductividad de 1320 μS/cm. El presente trabajo constituye el primer acercamiento tendiente a cuantificar las reservas de agua subterránea dulce en la zona a la vez que provee herramientas a la hora de planificar la realización de futuras perforaciones para abastecimient

Past, present, and expected hydro-morphologic evolution of the Bahia de Samborombon (Argentina) by remote sensing data

Hydro-geomorphologic setting of coastal areas is the result of complex interactions between marine and continental processes. Lowland morphologies make coastlands the zones at highest hydrogeological risk because of flooding, land subsidence, and saltwater contamination (e.g., Pousa et al. 2007). As many studies have predicted a significant increase of eustacy, sea level rise (SLR) is the most relevant problem affecting coastal lowlands. The wetland of the Samborombon Bay (Argentina) is a Ramsar natural reserve affected to periodic floods due to rainfall, runoff, tidal fluctuations, and storm surges. In this work, we show preliminary results of a project aimed at understanding the effect of expected SLR scenarios on the hydromorphologic setting of the Samborombon Bay. In particular, the outcomes of the first step of the research, i.e., the remote sensing analysis, are illustrated

Trichoderma: Evaluation of Its Degrading Abilities for the Bioremediation of Hydrocarbon Complex Mixtures

Hydrocarbons can have very harmful effects on organisms and the environment, and conventional techniques for their removal are expensive and require the use of chemicals and long-term actions. Trichoderma is an ascomycete genus known to be active on different recalcitrant substrates, since it can produce a set of nonspecific extracellular enzymes generally involved in the degradation of lignin. However, the literature concerning the use of Trichoderma to degrade hydrocarbons is still limited. In this work we aimed to investigate the ability of Trichoderma to exploit used engine oil as its sole carbon source for prospective bioremediation of contaminated substrates. Four different strains belonging to Trichoderma asperellum and Trichoderma harzianum species were tested. The fungi were inoculated in direct contact with used engine oil, and after 45 days the samples were analyzed by gas chromatography/mass spectrometry (GC/MS). The results showed that all strains (except Trichoderma asperellum F1020) significantly changed the oil composition, decreasing the aromatic fraction in favor of the aliphatic one. T. harzianum F26, especially, showed a significant reduction of the BTEX (benzene, toluene, ethylbenzene, and the three xylene isomers) and alkylbenzenes fraction and an increase in short-chain aliphatics C1–C20. Enzymatic tests for laccase and peroxidase were also carried out, demonstrating that every strain seems to express a different mode of actio

Identification and delimitation of fresh groundwater lenses at the coastal plain of the Río de La Plata Estuary, Punta Indio, Buenos Aires, Argentina

El objetivo del trabajo fue identificar y delimitar las lentes de agua subterránea dulce presentes en la planicie costera en la zona litoral del partido de Punta Indio con el fin a futuro de evaluar sus reservas y establecer pautas de explotación sustentable. Para ello se analizaron datos de registros de sondeos eléctricos verticales y se realizó un censo de perforaciones donde se midió la conductividad del agua subterránea a distintas profundidades. Los datos fueron analizados conjuntamente confeccionándose mapas y diagramas tridimensionales que permitieron establecer los límites de las lentes de agua dulce. Los resultados señalan que el agua dulce está almacenada en lentes con un promedio de conductividad de 1320 μS/cm. El presente trabajo constituye el primer acercamiento tendiente a cuantificar las reservas de agua subterránea dulce en la zona a la vez que provee herramientas a la hora de planificar la realización de futuras perforaciones para abastecimiento.The aim of this study is to identify and delimitate the presence of valuable fresh aquifers in the coastal plain of the Punta Indio littoral in order to provide the indispensable information for a correct water management plan. To achieve this goal, Vertical Electrical Sounding (VES) and groundwater electrical conductivity measurements (EC) were performed and analyzed together. The whole dataset was processed to define the electro-stratigraphic model of the study area and to produce the map of the EC 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 the geomorphology of the littoral and the groundwater. Result points out that the freshwater is stored into sandy lens with an average EC of 1320 μS/cm. Although in this work we provide only preliminary outcomes, the information here included is still useful for a sustainable use of the groundwater resources.Centro de Investigaciones Geográfica

El rol de la evapotranspiración en la geohidrología del humedal de la Planicie Costera de Ajó (provincia de Buenos Aires)

La planicie costera de Ajó en la Provincia de Buenos Aires conforma un humedal cuyas características hidrológicas se diferencian según se trate de sectores de marisma influenciados por los flujos mareales o que se encuentren fuera del ciclo mareal. El objetivo del trabajo es evaluar el rol de la evapotranspiración en el funcionamiento geohidrológico del sector del humedal que se sitúa fuera del ciclo mareal. Para tal fin se analizaron imágenes satelitales Landsat visible-infrarrojo cercano (VNIR), datos de precipitaciones, de temperatura y de niveles y química (iones mayoritarios e isótopos) del agua superficial y subterránea entre septiembre de 2005 y marzo de 2006, abarcando un periodo húmedo y uno seco. Los resultados muestran que en la transición del periodo húmedo al seco se produce una disminución del área inundada, un descenso de los niveles freáticos y un aumento en la salinidad y contenido iónico del agua superficial y subterránea. Los balances hídricos y el contenido en cloruros e isótopos muestran la relevancia de la evapotranspiración que se encuentra evidenciada en la dinámica y calidad del agua del humedal.The wetland of the Ajó coastal plain in the Province of Buenos Aires shows different hydrological characteristics depending on whether the sector is influenced by the tidal flow or not. The aim of this work is to assess the role of evapotranspiration in the geohydrological behaviour of the sector of the wetland which remains out of the tidal cycle. Landsat visible and infrared (VNIR) satellite images, rainfall, temperature, chemical data (major ions and isotopes) and water level of surface and groundwater were analysed. The study includes a wet and a dry period between September 2005 and March 2006. A decrease in the flooded area, a deepening of the water table and an increase in the salinity of the surface water and groundwater were observed in the transition of the wet period to the dry period. The water budgets and the chloride and isotope contents indicate the relevance of evapotranspiration, which is demonstrated by the hydrodynamic and hydrochemical conditions of the wetland.Universidad Nacional de La Plat

Asymmetric Synthesis of Spirooxindoles via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts

Taking into account the postulated reaction mechanism for the organocatalytic epoxidation of electron-poor olefins developed by our laboratory, we have investigated the key factors able to positively influence the H-bond network installed inside the substrate/catalyst/oxidizing agent. With this aim, we have: (i) tested a few catalysts displaying various effects that noticeably differ in terms of steric hindrance and electron demand; (ii) employed α-alkylidene oxindoles decorated with different substituents on the aromatic ring (11a-g), the exocylic double bond (11h-l), and the amide moiety (11m-v). The observed results suggest that the modification of the electron-withdrawing group (EWG) weakly conditions the overall outcomes, and conversely a strong influence is unambiguously ascribable to either theN-protected orN-unprotected lactam framework. Specifically, when the NH free substrates (11m-u) are employed, an inversion of the stereochemical control is observed, while the introduction of a Boc protecting group affords the desired product12vin excellent enantioselectivity (97:3er)

Environmental isotopes applied to the evaluation and quantification of evaporation processes in wetlands: a case study in the Ajó Coastal Plain wetland, Argentina

In the Ajó coastal plain, which occurs in the south of the Samborombón Bay, Argentina, certain sectors of the wetland are influenced by the tidal flow, whereas others are not. In the tidally restricted Ajó wetlands, the evapotranspiration process is one of the most important components of the water balance due to fact that the flat morphology and low soil permeability make the flow of surface and groundwater difficult. Although evaporation is an important component of evapotranspiration, a quantitative estimation of this process is still lacking or poorly known. In this work, we quantify the evaporation term in the tidally restricted wetlands by applying isotopic modelling and assessing the hydrological response of the wetland by means of other methodologies, such as satellite imaging and level measurements. The results show that during deficit periods, the total evaporation ranges between 10 and 33 % of the local precipitation. In groundwater samples, it fluctuates between 2 and 13 %, whereas in surface water it varies between 8 and 20 %. Analyses of the water budget, satellite images and water level time series provide evidence on how evaporation processes regulate the hydrology of the wetland. The water balance suggests the occurrence of a deficit period, in which the satellite images show a reduction of the waterlogged areas and lakes, and a lowering in surface and groundwater level is recorded.Facultad de Ciencias Naturales y Muse