Using isotope data to characterize and date groundwater in the southern sector of the Guaraní Aquifer System

The Guaraní Aquifer System (SAG) is the largest transboundary aquifer in Latin America, extending beneath parts of Brazil, Paraguay, Argentina, and Uruguay. This paper presents the results of recent hydrogeological studies in the southern portion of the SAG. Locally, the abundance of surface water bodies precluded the use of conventional hydrological tools to characterize groundwater flows. Geological, hydrochemical and environmental isotope investigations were integrated to postulate a revised hydrogeological conceptual model. The revised geological model has provided a better definition of the geometry of the aquifer units and outlined the relevance of regional faults in controlling flow patterns. The new potentiometric map is consistent with groundwater flow from the SAG outcrops to the centre of the Corrientes Province, where upwards flows were identified. Hydrochemical and isotope data confirmed the widespread occurrence of mixing. Noble gas isotopes dissolved in groundwater (4He and 81Kr/Kr) provided residence times ranging from recent recharge up to 770 ± 130 ka. Groundwater age modelling confirmed the role of the geological structures in controlling groundwater flow. The southern sector of the SAG is a multilayer aquifer system with vertical flows and deep regional discharge near the Esteros del Iberá wetland area and along the Paraná and Uruguay rivers.The different works were founded by the International Atomic Energy Agency, the Argentina National Agency for Scientific and Technological Promotion (Project PICT2008-2071), the Spanish Ministry for Economy and Competitivity (Project CGL2009- 12910-C03-03, REDESAC), and the Instituto de Hidrología de Llanuras (CONICET, Azul). The authors are indebted with Dr. Pradeep Aggarwal (formerly at the IAEA) for facilitating the research, with Drs Roberto Kirchheim and Didier Gastmans (Rio Claro University, Brazil) for performing the noble gases sampling, and with the Provincial Directorate of Parks of the Corrientes Province for their strong support with personnel, vehicles, and boats, making possible most of fieldwork. The authors would like to thank the anonymous reviewers for their useful comments and suggestions

Trabajo cooperativo como herramienta en el proceso de enseñanza/aprendizaje de los impactos ambientales en la Educación Secundaria Obligatoria

Trabajo Fin de Máster que gira en torno al uso de el trabajo cooperativo como herramienta en el proceso de enseñanza/aprendizaje de los impactos ambientales en la ESO. La propuesta didáctica se puso en práctica en el IES San Alberto Magno de Sabiñánigo en dos grupos de 3º ESO y otro de 4º ESO Diversificación Curricular. Se trabajo mediante grupos de expertos

Extrinsic calibration of a camera-robot system under non-holonomic constraints

A novel approach for the extrinsic calibration of a camera-robot system, i.e. the estimation of the pose of the camera with respect to the robot coordinate system, is presented. The method is based on the relative pose of a planar pattern as seen by the camera, estimated along with a predefined set of simple robot motions. This set has been generated so as to exploit the kinematic constraints imposed by the robot architecture and the relative pose between the pattern and the camera coordinate system. The resulting calibration procedure is very simple, making it suitable to be used in a broad range of applications. Experimental evaluations on both synthetic and real data demonstrate the validity of the proposed method.Sociedad Argentina de Informática e Investigación Operativ

Relaciones entre aguas superficiales y subterráneas en la región hídrica de los Esteros del Iberá (Corrientes, Argentina)

El 222Rn se ha utilizado, con otros trazadores ambientales, para estudiar la descarga de aguas subterráneas a cuerpos de agua superficial en los Esteros de Iberá y su entorno hasta el río Uruguay. Se realizó un estudio químico regional y mediciones de 222Rn en lagunas, ríos y pozos. Todas las aguas superficiales y muchas subterráneas estudiadas tienen características químicas e isotópicas coherentes con la lluvia. En cambio las actividades de 222Rn medidas en aguas subterráneas y superficiales son significativamente diferentes. Los resultados no sugieren la existencia de descarga de agua subterránea en los lugares medidos, al menos en magnitud notable. No obstante, algunas medidas locales relativamente altas apuntan cierta contribución de agua subterránea: en el río Uruguay al S de Misiones y al S de la laguna Iberá. Una segunda medición en ésta última no reprodujo los valores de la primera vez, debido a que la detección de la descarga depende de muchos factores.222Rn activity was used, with other environmental tracers, to assess the existence of groundwater discharge to surface water bodies in the Esteros de Iberá and its surrounding towards the Uruguay River. A regional chemical study has been performed together with 222Rn measurements in lagoons, rivers, and wells. All surface water samples and many groundwater samples are poorly mineralized and their chemical and isotope properties are coherent with rain water. 222Rn activities measured in groundwater and surface water are significantly different. The results do not suggest the existence of generalized and relevant groundwater discharge to the measures surface waters. However, some local measurements with relatively high activities could indicate groundwater discharge: this is the case of the Uruguay River in S Misiones and at the S of the Iberá lagoon. A second measurement in the last place did not reproduce the first results, but detecting groundwater discharge depends on many factors.Universidad Nacional de La Plat

Caracterización hidroquímica e isotópica de las aguas subterráneas del entorno de los Esteros de Iberá (Corrientes, Argentina)

Se han caracterizado química e isotópicamente las aguas subterráneas del entorno de los Esteros de l Iberá. Las aguas tienen mineralizaciones muy bajas a medias; las más salinas son de los sondeos más profundos (>1000 m). Hacia el centro, N y NE de la zona las aguas son principalmente bicarbonatadas sódicas, mientras que al S son bicarbonatadas cálcicas. Los dos pozos más profundos, Oberá (SO Misiones; 1050 m) y Monte Caseros (SE Corrientes; 1250 m), tienen aguas sulfatadas sódicas. El primero capta formaciones del SAG; el segundo formaciones salinas infrayacentes al SAG. En el entorno cercano a la laguna Iberá hay cuatro pozos de unos 100 m de profundidad que tienen agua clorurada sódica levemente salina, la cual parece ser mezcla del SAG y de otras formaciones. Varias aguas de distintas profundidades tienen actividades de 14C bajas. La combinación de δ18O, Cl y 14C sugiere que hay dos componentes antiguas que darían lugar a dos grupos de aguas mezcla.A chemical and isotopic characterization of the groundwaters around the Esteros del Iberá has been carried out. All groundwater samples have low to medium mineralization, except the two deepest samples (>1000 m). To the center, N and NE parts of the study area sodium-carbonate waters dominate; to the S and SE they are mostly calcium-carbonate. The two deepest samples, one in Oberá (SW Misiones; depth: 1050 m) and the other one in Monte Caseros (SE Corrientes; depth: 1250 m) belong to sodium-sulphate type. In the first case groundwater comes from GAS formations; in the second one deep saline groundwater comes from pre-GAS formations. In a small area close to the Iberá lagoon there are four wells around 100 m deep having sodium-chloride water, which is attributed to the GAS formations. Some groundwaters from different depths have low 14C activities. The combined study of δ18O, Cl and 14C suggests the presence of two different old components which would result on two groups of mixed waters.Universidad Nacional de La Plat

Balancing precision and throughput of δ17O and Δ’17O analysis of natural waters by Cavity Ringdown Spectroscopy

δ17O and Δ’17O are emerging tracers increasingly used in isotope hydrology, climatology, and biochemistry. Differentiating small relative abundance changes in the rare 17O isotope from the strong covariance with 18O imposes ultra-high precision requirements for this isotope analysis. Measurements of δ17O by Cavity Ringdown Spectroscopy (CRDS) are attractive due to the ease of sample preparation, automated throughput, and avoidance of chemical conversions needed for isotope-ratio mass spectrometry. However, the CRDS approach requires trade-offs in measurement precision and uncertainty. In this protocol document, we present the following: • New analytical procedures and a software tool for conducting δ17O and Δ’17O measurements by CRDS. • Outline a robust uncertainty framework for Δ’17O determinations. • Description of a CRDS performance framework for optimizing throughput, instrumental stability, and Δ’17O measurement precision and accuracy

Global and local meteoric water lines for δ 17O/δ 18O and the spatiotemporal distribution of Δ′17O in Earth’s precipitation

Abstract Recently, δ 17O and its excess (Δ′17O) have become increasingly significant “triple-oxygen-isotope” indicators of distinctive hydrological processes in hydrology and climatology. This situation mirrors the research regarding δ 18O and δ 2H in the 1960s towards a solid theoretical base and a surge in application examples and field studies worldwide. Currently, systematic global measurements for δ 17O in precipitation are still lacking. As a result, attempts have been made to define a Global δ 17O/δ 18O Meteoric Water Line (GMWL), often by using regional or local datasets of varying systematicity. Different definitions of the global reference slope (λ ref) for determining Δ′17O values have been proposed, by ongoing debate around a proposed consensus value of 0.528. This study used worldwide samples archived in the IAEA Global Network of Isotopes in Precipitation (GNIP) to (a) derive a δ 17O/δ 18O GMWL based on four-year monthly records from 66 GNIP stations, (b) formulate local δ 17O/δ 18O meteoric water lines (LMWL) for these stations’ areas, and (c) evaluate regional and seasonal variations of Δ′17O in precipitation. The GMWL for δ 17O/δ 18O was determined to be δ′17O = 0.5280 ± 0.0002 δ′18O + 0.0153 ± 0.0013, in keeping with the consensus value. Furthermore, our results suggested that using a line-conditioned 17O-excess is a viable alternative over the global λ ref in the context of regional hydrology and paleoclimatology interpretations; however, without challenging the global λ ref as such

Unravelling groundwater and surface water sources in the Esteros del Iberá Wetland Area: An isotopic approach

In the Esteros del Iberá Wetland Area (EIWA, NE Argentina), the southern sector of the transboundary Guarani Aquifer System (SAG) is overlain by the Ramsar listed Iberá Wetlands and several rivers, that combined extend across 37,930 km2 and represent one of the largest freshwater systems on the South American continent. Previous hydrogeological studies encompassing the entire SAG proposed preferential discharge of groundwater of various origins and ages to the EIWA. In this study, a multi-tracer study using major ionic species, δ18O, δ2Hand222Rn was conducted in lagoons, rivers, wells, and boreholes in the EIWA to confirm if discharge from the transboundary SAG is contributing to the sur-face water system. End-member Mixing Analysis (EMMA) determined the existence of four main end-members: groundwater from the SAG, more saline groundwater from the deeper Pre-SAG, and two poorly mineralised end-members from shallow, Post-SAG. EMMA calculations clearly illustrated complex binary and ternary mixing patterns involving the four end-members and highlighted the role of geological structures, specifically regional steep faults, in controlling the mixing patterns. 222Rn activities allowed in-situ identification of preferential deep groundwater dis-charge into both surface waters and shallow groundwaters. These findings provide strong evidence for the widespread existence of upward flows along major faults in this sector of the SAG, inducing complex mixing flow patterns and explaining the presence of old groundwater in shallow aquifers. Mapping the sources of water and the hydrological interactions are relevant for improving water balance estimates and develop management policies towards the preservation of these wetlands.The data from various projects between 2011 and 2015: International Atomic Energy Agency, project "The role of wetlands and rivers in the discharge of groundwater from the Guaraní aquifer in NE Argentina"; Ministry of Economy and Competitiveness of Spain, MICINN-REDESAC project CGL2009-2910-CO3, "Aquifer recharge and discharge processes"; and Ministry of Science, Technology and Productive Innovation of Argentina (PICT project 2008/2071). The authors would like to thank the comments and corrections of two anonymous reviewers that contributed greatly to improve the manuscript

Proficiency testing of 78 international laboratories measuring tritium in environmental waters by decay counting and mass spectrometry for age dating and water resources assessment

Rationale Tritium (3H) is an important hydrological tracer that has been commonly used for over 60 years to evaluate water residence times and water dynamics in shallow/recent groundwaters, streams, lakes and the ocean. We tested the analytical performance of 78 international laboratories engaged in low‐level 3H assays for water age dating and monitoring of environmental waters. Methods Seven test waters were distributed by the IAEA to 78 international tritium laboratories. Set 1 included a tritium‐free groundwater plus three ultra‐low 3H samples (0.5–7 TU) for meeting groundwater dating specifications. Set 2 contained three higher 3H‐content samples (40–500 TU) suitable for testing of environmental monitoring laboratories. Results Seventy of the laboratories used liquid scintillation counting with or without electrolytic enrichment, seven utilized 3He accumulation and mass spectrometry, and one used gas‐proportional counting. Only ~50% of laboratories demonstrated the ability to generate accurate 3H data that was precise enough for water age dating purposes. Conclusions The proficiency test helped identify recurrent weaknesses and potential solutions. Strategies for performance improvements of 3H laboratories include: (a) improved quantification of 3H detection limits and analytical uncertainty, (b) stricter quality control practices in routine operations along with care and recalibration of 3H standards traceable to primary NIST standards, (c) annual assessment of tritium enrichment factors and instrumental performance, and (d) for water age dating purposes the use of electrolytic enrichment systems having the highest possible 3H enrichment factors (e.g. >50×)