Geological-geomorphological and geochemical control on low arsenic concentration in the Lerma valley groundwater between the two high arsenic geologic provinces of Chaco-Pampean plain and Puna

Argentina is known for having one of the most extensive areas with high arsenic (As) concentration in groundwater in the world. These areas correspond to two main geological provinces, the Puna plateau and the Chaco-Pampean plain. In this large territory, there are some specific environments where the As concentration in groundwater is lower, and in some cases within the recommended limits for drinking water. In our study, we analyze and interpret the low arsenic concentrations reported for the Lerma valley, the easternmost intermontane basin of the Cordillera Oriental, located between the aforementioned high-arsenic geological provinces. The groundwater from this valley is used for the consumption of more than 600.000 inhabitants in the city of Salta and nearby towns. The incipient development of the valley since the late Miocene and the subsequent tectonic and climatic evolution favored low As concentrations with respect to the Puna and the Chaco-Pampean plain. The high-energy sedimentary environments thatcharacterized the area during Plio-Quaternary times and the composition of the sediments have controlled the characteristics of sediments the multilayered aquifer. Moreover, the absence of geogenic arsenic sources, climate, high rain infiltration rate, near neutralpH,redox conditions, and wells construction with screens settledincoarse productive layers favor groundwater of good quality.The geological and tectonic evolution of the Lerma valley could be extrapolated to other similar valleys in the NW of Argentinaand can be useful as tool for exploration of good quality groundwater. This is of high importance in Latin American territories with high As concentration in groundwater such as Argentina.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina. University of Strasbourg; FranciaFil: Romero Orué, María Angélica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: López, Emilce de Las Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: García, Víctor. Geomap S.a.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universitat Potsdam; AlemaniaFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

Influence of extremophiles on the generation of acid mine drainage at the abandoned pan de azúcar mine (Argentina)

The risk of generation of acid drainages in the tailings of the Pan de Azúcar mine that closed its activities more than three decades ago, was evaluated through biooxidation studies using iron-and sulfur-oxidizing extremophilic leaching consortia. Most of tailings showed a high potential for generating acid drainage, in agreement with the results from net acid generation (NAG) assays. In addition, molecular analysis of the microbial consortia obtained by enrichment of the samples, demonstrated that native leaching microorganisms are ubiquitous in the area and they seemed to be more efficient in the biooxidation of the tailings than the collection microorganisms. The acid drainages detected at the site and those formed by oxidation of the tailings, produced a significant ecotoxicological effect demonstrated by a bioassay. These drainages, even at high dilutions, could seriously affect a nearby Ramsar site (Laguna de Pozuelos) that is connected to the Pan de Azúcar mine through a hydrological route (Cincel River).Fil: Plaza Cazón, Josefina del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Benitez, Leonardo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; ArgentinaFil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Kirschbaum, Pablo Enrique. Universidad Nacional de Salta. Facultad de Cs.naturales. Carrera de Geología; ArgentinaFil: Donati, Edgardo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Fermentaciones Industriales. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Fermentaciones Industriales; Argentin

Natural acid drainage in the Negra Muerta Caldera and its influence in surface water in the upper basin of Calchaquí River, Salta province, NW Argentina

En la zona de alteración hidrotermal de Cu-Pb-Zn y Au-Mo de la caldera Negra Muerta se observa la generación de drenaje ácido de rocas por la interacción de aguas meteóricas con sulfuros. En el Manantial Ácido el pH es bajo (2,92) con concentraciones de metales elevadas para la región, debido a la presencia de pirita y otros sulfuros y a la influencia del clima árido. La elevada evaporación favorece la formación de sales solubles sulfato-metálicas que pueden transformase en ocres de hierro formando ferricretas. La mezcla de aguas termales con manifestaciones de drenaje ácido de rocas daría origen a las aguas del río Blanco, tributario del río Calchaquí, el cual tiene sus nacientes en esta zona. En el río Blanco altas concentraciones de Cl-, Na+, B y Li de origen termal permanecen en solución mientras que los metales aportados por el drenaje ácido de rocas precipitan en fases amorfas de Fe y Al. El río Calchaquí presenta pH circum-neutro y la descarga del Manantial Ácido genera un incremento en Al, Mn, Cu, As, Co, Se, Ag, Cs y Ba. Sin embargo, el río Calchaquí ya posee anomalías en metales y sulfatos por la oxidación de sulfuros de la Caldera Negra Muerta aguas arriba de la zona de estudio. La descarga del río Blanco en el río Calchaquí genera un incremento en Cl-, Na+, B y Li. En la zona de estudio las aguas del río Calchaquí solo son aptas para bebida de ganado y su contenido en B podría limitar su uso para riego dependiendo del tipo de cultivo.The interaction of meteoric waters with sulfides in the hydrothermal alteration zone of Cu-Pb-Zn and Au-Mo at the Negra Muerta Caldera generates acid rock drainage. Acid rock drainage in the Manantial Ácido has low pH value (2.92) and its metals concentrations are high for the region due to the presence of pyrite and other sulfides under arid climate conditions. High evaporation favors the formation of metals-sulfate soluble salts that can transform into iron oxides forming ferricretes. Thermal waters mix with acid rock drainage at Blanco River, which is an important tributary of the Calchaquí River. In the Blanco River high concentrations of Cl- , Na+, B and Li of thermal origin remain in solution while the metals from acid rock drainage precipitate in amorphous Fe-Al phases. The Calchaquí River has circum-neutral pH and the Manantial Ácido discharge generates an increase in Al, Mn, Cu, As, Co, Se, Ag, Cs and Ba. However, the Calchaquí River already has metals and sulfates anomalies due to the oxidation of sulfides upstream of the study area. The discharge of Blanco River in Calchaquí River generates an increase in Cl- , B and Li. In this area Calchaquí River, waters are only suitable for livestock drinking and its content in B could limit its use for irrigation depending on the kind of crops.Fil: Galvan Claros, Federico Eduardo. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Chiodi, Agostina Laura. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Pereyra Hafner, Ricardo Eduardo. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

Wet precipitation in northern Argentina: chemical characterization of soluble components in the Lerma Valley, Salta.

La depresión del valle de Lerma se ubica geográficamente en el centro sur de la Provincia de Salta y geológicamente en la Provincia Cordillera Oriental, en el noroeste de Argentina. Dentro de esta unidad geomorfológica,se ubicaron dos sitios para la colección de muestras de agua de lluvia en el período 2009 a 2012: uno en la localidad deVaqueros y otro en la Ciudad de Salta. El objetivo de este trabajo fue caracterizar la composición química del agua delluvia de la región e inferir las posibles fuentes que aportan a la misma. También este estudio propone evaluar la posibleinfluencia de las zonas con mineralizaciones polimetálicas, ubicadas al oeste del área de estudio, sobre la composicióndel agua de lluvia para cada muestra se analizó pH, conductividad eléctrica, concentración de aniones (Cl-, NO3- y SO42-),cationes (Na, Mg, K y Ca) y elementos traza (Al, Mn, Co, Cu, Zn, As, Sb, Ba y Pb). Para la interpretación de los resultadosse aplicaron técnicas estadísticas multivariadas y cálculos del factor de enriquecimiento, utilizando como valor dereferencia análisis químicos de polvo atmosférico recolectado en el área. El agua de lluvia local presenta enriquecimientosignificativo en las concentraciones de Ca, Cu, Zn, As, Sb y Pb y, de acuerdo con análisis estadísticos, una correlacióndirecta entre los mismos. La asociación de elementos encontrada es similar a las paragénesis de las mineralizacionespolimetálicas de la Puna-Altiplano, aflorantes al oeste del área de estudio. Imágenes satelitales y trabajos científicosdocumentan intensa deflación de la región Puna-Altiplano con componentes de transporte dominantemente hacia el E,donde se encuentra el Valle de Lerma. Se infiere que este fenómeno otorga una impronta particular a la química delagua de lluvia de este valle. Este trabajo corresponde al primer registro de la composición química del agua de lluviade esta región. Como la ciudad de Salta no registra una contaminación atmosférica significativa ni importantes fuentesde aporte antrópico, se define además el nivel de base del agua de lluvia del Valle de Lerma.Wet precipitation in northern Argentina: chemical characterization of soluble components in the Lerma Valley, Salta. Soluble components in rainwater were studied in Valle de Lerma (Salta-Argentina). The studied area is located in the central south area of Salta Province in the Cordillera Oriental region, Northwest Argentina. The largest urban area corresponds to Salta city, where sample collection and analysis of rainwater were performed between 2009 and 2012 periods. Conductivity and pH were measured on each sample, and major (Cl-, NO3-, SO42-, Na, Mg, K, Ca) and trace elements (Al, Mn, Co, Cu, Zn, As, Sb, Ba and Pb) were analyzed. Multivariate statistical calculation and enrichment factor were applied to the obtained data. Atmospheric dust collected on the same sampling stations were used as reference for enrichment factors calculations. The local rainwater presents significant enrichment in Ca, Cu, Zn, As, Sb and Pb while statistical analyses indicate a direct correlation between them. The association of elements in the rainwater is similar to those for the polymetallic ore deposits outcropping in the Puna-Altiplano region, which are located to west of the study area. Satellite images as well as previous research indicates transport of atmospheric dust from the Puna-Altiplano to the East, where Valle de Lerma is suited. We conclude that this phenomenon gives a particular print to the chemistry of the rainwater in this area. This work corresponds to the first study of the rainwater’s chemical composition in this region. As Salta city lacks of significant air pollution or major sources from anthropogenic activities, the data on this paper establish the background of the Valle de Lerma rainwater geochemistry.Fil: Romero Orué, María Angélica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Gaiero, Diego Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Paris, Marta del Carmen. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; ArgentinaFil: Formica, Stella Maris. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: de la Hoz, Gonzalo Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: López, Emilce de Las Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

Geochemical composition of Volcanic rocks with published As data: Altiplano-Puna region

This tabla contain compiled geochemical data for volcanic rocks with arsenic data in the Altiplano-Puna region. This compilation was made in the frame of the project funded by the International Geoscience Programme (IGCP) UNESCO. IGCP-707: Origin, Distribution, and Biogeochemistry of Arsenic in the Altiplano-Puna plateau of South America.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

The Unique Altiplano-Puna Plateau: Environmental Perspectives

The Altiplano-Puna is a distinctive plateau and pristine environment to study geochemical, ecological, and climatic phenomena. It is the second highest plateau on Earth after Tibet and contains the largest endorheic system of South America. Nevertheless, water is a vital resource in the region, and surface water and groundwater are essential sources of drinking water for inhabitants. Environmental characterizations in the Altiplano-Puna plateau are fairly new and increasingly important due to climate change, the sustained decrease of surface water bodies (e.g. Lake Poopó), as well as anthropogenic and natural contaminants (e.g. arsenic) which can pollute the scarce water resources. Despite extreme and unique climatic, hydrologic, and geochemical conditions of the Altiplano-Puna plateau, some indigenous populations and biota have adapted. This Special Issue presents seven original research papers covering a wide range of topics in the Altiplano-Puna related to hydrogeochemical, climatic, and anthropogenic processes on the origin and mobility of economically important elements and contaminants, as well as environmental issues and bioindicators of ecological conditions in surface waters. Its aim is to present new and comprehensive analyses with interpretations in this extreme, yet pristine area which has been scarcely characterized from an environmental perspective, and also inspire future studies in the region.Fil: Tapia, Joseline. Universidad Católica del Norte; ChileFil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta-Jujuy. Instituto de Bio y Geociencias del Noroeste Argentino. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto de Bio y Geociencias del Noroeste Argentino; ArgentinaFil: Ormachea Muñoz, Mauricio. Universidad Mayor de San Andrés; BoliviaFil: Bhattacharya, Prosun. Royal Institute of Technology; Sueci

Silicic volcanic rocks, a main regional source of geogenic arsenic in waters: Insights from the Altiplano-Puna plateau, Central Andes

Volcanic rocks are a common, worldwide source of geogenic arsenic (As) that can affect water quality detrimentally. Nonetheless, variations of As concentration within different types of volcanic rocks and questions related to the original source of As in magma are not yet fully understood. We compiled published As data from the abundant Cenozoic volcanic rocks of the Altiplano-Puna plateau, considered the main source of As for waters in the region. These data indicates that volcanic rocks in the Altiplano-Puna have a mean As concentration of 9.1 mg/kg, which is almost 2 times higher than the upper continental crust. Arsenic increases within the more silicic compositions such as dacites and rhyolites as well as from mafic monogenetic volcanic edifices to stratovolcanoes of intermediate composition, silicic calderas and ignimbrite fields. The rate and composition of crustal assimilation by the magmas (enhanced by the crustal thickness up to >70 km) strongly influence the As concentration in volcanic rocks. The assimilation of argillaceous shale-type sediments represents the most important source of As in the magmas. The eruption dynamics has an enormous effect on As concentration. The higher the explosivity of an eruption, the higher the amount of ash that will be formed. Arsenic can be sorb onto ash particles so that fall deposits produced during explosive volcanic eruptions are prone to high As concentrations. Large volume ignimbrites formed after caldera collapses in the Altiplano-Puna are often the result of sustained explosive eruptions related to low, dense pyroclastic fountaining eruptions where highly concentrated pyroclastic density currents (PDC, flowing pyroclastic mixtures of particles and gas) are able to maintain high temperatures for long periods. Then As released from volatiles may remain for longer time in the emplacing PDC and can be sorbed onto ash particles, resulting in deposits with a higher As concentration. Post eruption hydrothermal alteration and sulfide mineralization produce As enrichment up to 100 times in the volcanic rocks (957 mg/kg) of the region, but can be very heterogeneous. Volcanism and its related products are the main source of As in the region. Once As is released from the volcanic sources, the semiarid climate, the occurrence of Na-HCO3 water types, and alkaline pH further enhance As concentrations in surface water and groundwater.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Guzman, Silvina Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Tapia, Joseline. Universidad Católica del Norte; ChileFil: Nordstrom, D. Kirk. No especifíca

Seasonal fluctuations and geochemical modeling of acid mine drainage in the semi-arid Puna region: The Pan de Azúcar Pb–Ag–Zn mine, Argentina

Pan de Azúcar is an inactive Pb–Ag–Zn mine in the semi-arid Puna region of NW Argentina at 3600 m above sea-level. The mine is situated in Los Pozuelos basin, which is a UNESCO Biosphere Reserve. Substantial pyrite and few carbonate minerals are present in the tailings. The generated acid mine drainage (AMD) has low pH (1.92–4.06) and is mainly Fe–Zn–SO4 type water with high concentrations of metals that in order of relative abundance vary as: Al ≫ Cd > As(T) > Ni > V > Cu > Co > Sb > Cr > Pb > Sn > Ag. The strong annual cycle of dry and wet seasons in the Puna generates a significant influence on AMD geochemistry. In the dry season, there is no runoff and AMD drains mainly in the form of seepages with low pH (1.92–2.21), high concentrations of metals, and the formation of metal-rich soluble efflorescent salts is favored by strong evaporation. At the beginning of the wet season, the efflorescent salts rapidly dissolve and metals concentrations in AMD increase significantly, creating the most hazardous period for the surrounding fluvial environment. At the end of the wet season the pH increases (3.44–4.06) and the concentration of metals decreases, especially arsenic associated with ferric iron precipitates. As a consequence of the DC3 dam restoration, a large volume of AMD is retained forming an acid pond, in which processes of AMD mixing, secondary minerals precipitation, and sulfide oxidation were quantified by inverse modeling with mixing. Jarosite and schwertmannite precipitates in the surface of the pond and favors the attenuation of As and Pb. However, subaqueous oxidation of sulfide minerals, hydrolysis of silicates, and mixing with upstream AMD seepage increases the concentrations of SO42-, Fe(II), and the other metals in the seepage of the pond that migrates downstream. The results of this study indicate the necessity to improve the remediation methods of Pan de Azúcar mine. It is expected that other sulfide mines in the Puna region will have a similar variability of the AMD geochemistry, which should be considered for mine closure, remediation, and monitoring of water quality in mining.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Nordstrom, Darrel Kirk. United States Geological Survey; Estados UnidosFil: Dold, Bernhard. Pontificia Universidad Católica de Perú; Perú. Sustainable Mining Research & Consultancy ; ChileFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

Origin and geochemistry of arsenic in surface and groundwaters of Los Pozuelos basin, Puna region, Central Andes, Argentina

Los Pozuelos is a closed basin in the Puna region of NW Argentina, Central Andes. This is a semi-arid region where closed basins are the most important feature for the hydrologic systems. The center of the basin is occupied by a fluctuating playa lake called Los Pozuelos lagoon, which constitutes a UNESCO Biosphere Reserve. This is one of the most populated closed basins in the Argentinian Puna and residents use groundwater for drinking and cooking. Lowest concentrations of As and dissolved solids are in the headwaters of the rivers (1.46–27 μg/L) and the highest concentrations are in the lagoon (43.7–200.3 μg/L). In groundwater, arsenic concentrations increase from the outer ring aquifer (3.82–29.7 μg/L) composed of alluvial-alluvial fan sediments to the inner lacustrine aquifer (10–113 μg/L) that surround the playa lake. Moreover, high concentrations of As during the dry season (90.2 and 113 μg/L), Na/K mass ratios (0.2 and 0.3), and formation of Na-rich efflorescent salts suggest that high evaporation rates increases As concentration, while rainwater dilutes the concentration during the wet season. As(V) is the dominant species in all the water types, except for the lagoon, where As(III) occasionally dominates because of organic matter buildup. There are at least three potential sources for As in water i) oxidation of As sulfides in Pan de Azúcar mine wastes, and acid mine drainage discharging into the basin; ii) weathering and erosion of mineralized shales; iii) weathering of volcanic eruptive non-mineralized rocks. Because it is a closed basin, the arsenic released from the natural and anthropogenic sources is transported in solution and in fluvial sediments and finally accumulates in the center of the basin where the concentration in water increases by evaporation with occasional enhancement by organic matter interaction in the lagoon.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina. Université de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Nordstrom, Darrel Kirk. United States Geological Survey; Estados UnidosFil: Dold, Bernhard. Luleå University of Technology; SueciaFil: Romero Orué, María Angélica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

Arsenic solid speciation in tailings of the abandoned Pan de Azucar mine, Northwestern Argentina

In the Argentina Puna region there are several metal sulfide mines that ceased their activity twenty years ago without a proper closure plan. The exposure of the waste rocks and tailing impoundments to weathering led to sulfide oxidation and generation of highly acid solutions rich in metal(oid)s, that react with the unaltered waste rocks, partitioning into different solid phases. The As speciation along a 120 cm depth oxidation profile described in the Pan de Azucar mine tailings was studied by standarized sequential extraction procedures. Results show that the highest As concentration remain in the bottom unaltered layer mainly associated with primary and secondary sulfides. In the upper layers, the total As concentrations are ?î40 to 70% lower than that of the bottom layer, and most As is associated with amorphous and cristalline oxides. More bioavailable forms of As (exchangeable and soluble) account for less than 1.5% of the total As concentration.Fil: Murray, Jesica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Bio y Geociencias del NOA; Argentina.Fil: Murray, Jesica. Universidad Nacional de Salta. Museo de Ciencias Naturales; Argentina.Fil: García, María Gabriela. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales; Argentina.Fil: García, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Borgnino, Laura. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales; Argentina.Fil:Borgnino, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Mendez Guimaraes, Edi. Universidad de Brasilia. Laboratório de Rayos X; Brasil.Fil: Kirschbaum, Alicia Matilde. Universidad Nacional de Salta. Museo de Ciencias Naturales; Argentina.Fil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Bio y Geociencias del NOA; Argentina.Otras Ciencias de la Tierra y relacionadas con el Medio Ambient