Abstract:

Pyroclastic materials dispersed in recent volcanic eruptions in Northern Patagonia were analysed in order to characterize the volcanic provenance by the geochemical fingerprint. The volcanic products studied were dispersed by eruptions of volcanoes Calbuco in 1961, Chaitén in 2008, and Cordón Caulle Volcanic Complex (CCVC) in 1960 and 2011. The geochemical characterization was based on the determination of 35 major and trace elements by Instrumental Neutron Activation Analysis, including geochemical tracer such as Rare Earth Elements (REE). The study of the pyroclastic products also included the morphological analysis by petrographic and scanning electron microscopy, and the mineralogical characterization by X-ray diffraction.Geochemical tracers determined in the glass fraction of the dispersed pyroclastic materials allowed a clear discrimination of the three volcanoes that gave origin to the tephras, the three of them with different evolution degree. Tephras from 1960 and 2011 CCVC eruptions showed the same geochemical signature. The geochemical parameters providing the differential characterization are the normalized REE and multi-element patterns, the Eu anomaly, the heavy to light and medium to light REE normalized ratios, and the Cs, Sc, Rb, Ta and Th concentrations. The bulk glassy fraction showed the same composition for each volcanic eruption in samples collected even in distant sites (from 100 to 220km in Chaitén, 2008, and from 80 to 650km in CCVC 2011), attesting to be the most reliable material for correlation purposes.According to the mineralogy, cristobalite was found in volcano Chaitén tephra as an indicator of such origin. Arsenic, an element of environmental interest, exhibited concentrations ranging from 6 to 16μgg-1, with the highest values corresponding to Puyehue-Cordón Caulle and Chaitén products.

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina

Author affiliation: Ribeiro Guevara, Sergio. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Analisis Por Activación Neutronica; Argentina

Author affiliation: Poire, Daniel Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. 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; Argentina

Author affiliation: Arribere, Maria Angelica. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

Abstract:

Chironomid communities were studied in a sediment core collected from Lake Moreno Oeste, located in Nahuel Huapi National Park. A major change in midge assemblages occurred at ∼AD 1760, which was characterized by a decrease of “cold taxa” including Polypedilum sp.2 and Dicrotendipes, and an increase of “warm taxa” including Apsectrotanypus and Polypedilum sp.1. These taxa are likely related to climatic conditions concurrent with the end of a cold period at ∼AD 1500–1700 and the beginning of a drying climate at ∼AD 1740–1900 in northern Patagonia. Coarse tephra layers had low midge diversity; however they did not disrupt the climatic trend as the community recovered rapidly after the event. Since AD 1910, after the increase in suburban housing, fish introduction, and the construction of a road, there was an increase in the relative abundances of taxa typically associated with the littoral zone, such as Parapsectrocladius, Riethia, Apsectrotanypus, and some Tanytarsini morphotypes. The main change in the chironomid community appears to be associated with long-term climate change. At the beginning of the 20th century, other site-specific environmental factors (catchment change and fish introduction) altered the chironomid assemblages, making it more difficult to understand the relative importance of each driver of assemblage change.

Author affiliation: Williams Velázquez, Natalia Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina

Author affiliation: Rieradevall, Maria. Universidad de Barcelona; España

Author affiliation: Añón Suárez, Diego Alejandro. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Author affiliation: Rizzo, Andrea Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina

Author affiliation: Ribeiro Guevara, Sergio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina

Author affiliation: Arribere, Maria Angelica. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

Abstract:

After 54 years since its last major eruption in 1961, Calbuco Volcano (Ensenada, Southern Chile) reawakened with few hours of warning on 22 April 2015 at 18:05 local time. The main explosive eruption consisted of two eruption pulses (lasting ~1.5 and 6 h each one) on 22 and 23 April, producing stratospheric (>15 km height) eruption columns. The erupted materials correspond to porphyritic basaltic andesite (~55 wt.% of SiO2). The tephra fall affected mainly the area northeast of the volcano and the finest ash was deposited over Southern Chile and Patagonia Argentina. We studied the tephra fall deposits of both pulses in terms of stratigraphy, distribution, volume, emplacement dynamics and eruption source parameters. Here, we show field observations that have been made 5-470 km downwind and distinguish five layers (Layers A, B, B1, C and D) representing different stages of the eruption evolution: eruption onset (Layer A; pulse 1), followed by the first paroxysmal event (Layer B; pulse 1), in some places interbedded by layer B1, tentatively representing the sedimentation of a secondary plume during the end of pulse 1. We recognized a second paroxysm (Layer C; pulse 2) followed by the waning of the eruption (Layer D; pulse 2). The total calculated bulk tephra fall deposit volume is 0.27 ± 0.007 km3 (0.11-0.13 km3 dense rock equivalent), 38% of which was erupted during the first phase and 62% during the second pulse. This eruption was a magnitude 4.45 event (VEI 4 eruption) of subPlinian type.

Author affiliation: Romero, J. E.. Universidad de Atacama; Chile

Author affiliation: Morgavi, D.. Università di Perugia; Italia

Author affiliation: Arzilli, F.. University of Manchester; Reino Unido

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Author affiliation: Caselli, Alberto Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Negro; Argentina

Author affiliation: Reckziegel, Florencia Mabel. 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; Argentina

Author affiliation: Viramonte, Jose German. 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; Argentina

Author affiliation: Díaz Alvarado, J.. Universidad de Atacama; Chile

Author affiliation: Polacci, M.. University of Manchester; Reino Unido

Author affiliation: Burton, M.. University of Manchester; Reino Unido

Author affiliation: Perugini, D.. Università di Perugia; Italia

Abstract:

Mercury is released to the environment from natural and anthropogenic sources, and through atmospheric transport is distributed globally. Lake Futalaufquen (42.8°S) is an oligotrophic lake located in Los Alerces National Park (Northern Patagonia), providing a remote and unpolluted study system. A lacustrine sedimentary sequence revealed 1600 years of Hg deposition, identifying natural baselines and marked peaks not correlated with long-range atmospheric transport. Organic matter and catchment erosion were discarded as Hg drivers. Natural background, pre-1300 CE Hg concentrations, ranged between 27 and 47 ng g-1 (accumulation rates from 8 to 15 μg m-2 y-1). From 1300 CE on, the Hg background profile did not follow the generally increasing Hg pattern observed in both Southern and Northern Hemisphere since pre-industrial times. It was not until the last century that a 1.6-fold increase is observed in the Hg accumulation rate, considered among the lowest increments in southern South America. Noteworthy local/regional sources of Hg for this area, along with global transport, are forest fires and volcanic activity. Between approx. 1340 and 1510 CE, sharp increase in Hg concentration and accumulation rate (up to 204 ng g-1 and 51 μg m-2 y-1, respectively) were clearly associated with extended fire episodes. Furthermore, high Hg peaks during the last 300 years were associated with volcanic eruptions in northernmost Patagonia together with fairly irregular fire episodes, caused by anthropogenic burning by settling population in the Andes.

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Author affiliation: Ribeiro, Sergio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Author affiliation: Pavlin, Majda. Jožef Stefan Institute; Eslovenia

Author affiliation: Rizzo, Andrea Paula. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Author affiliation: Lojen, Sonja. Jožef Stefan Institute; Eslovenia. University of Nova Gorica; Eslovenia

Author affiliation: Vreca, Polona. Jožef Stefan Institute; Eslovenia

Author affiliation: Horvat, Milena. Jožef Stefan Institute; Eslovenia

Author affiliation: Arribere, Maria Angelica. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

Abstract:

In regions with limited knowledge of the historical volcanic record, like remote areas in the Andean Southern Volcanic Zone, the definition of reliable age-depth models for lake sequences represents a valuable tool for tephra layers dating. In Lake Futalaufquen (42.8°S), Northern Patagonia, a short sedimentary sequence was extracted after the AD 2008 Chaitén eruption with the purpose to analyze the records of volcanic eruptions at these poorly studied latitudes. The sequence was dated by 210Pb, 137Cs, and 14C techniques. Five tephras were identified for the last 1600 years, restricted to the last 5 centuries. Sedimentology, morphology, and geochemical properties allowed the characterization of the tephras and their correlation with tephras recently identified proximal to the sources, mainly from Chaitén and Huequi volcanoes, and Michinmahuida accessory cones, representing the first distal records reported of these tephras. Furthermore, tephras modeled ages obtained by the sequence age-depth model shrink the ages for the volcanic events, like a potential cycle of activity from Michinmauida accessory cones during AD 1530 ± 55, one eruption from Huequi volcano at AD 1695 ± 50, and a possible recent eruption from Chaitén at AD 1775 ± 40. Additionally, the work contributes to improve the regional volcanic records knowledge, basic for volcanic hazard assessment.

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Ribeiro, Sergio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Arribere, Maria Angelica. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

Abstract:

In contrast with the extensive palaeolimnological studies carried out in North America and Europe, relatively few studies have described the anthropogenic and/or climate impacts in Patagonian lakes. We addressed these issues by analysing geochemistry, lithology, pigments and chironomid remains from sediment cores collected from Lake Hess (41°22 20 S, 71°44 0W) located in the Nahuel Huapi National Park in northern Patagonia. The aim of this study is to provide a palaeoenvironmental and climate reconstruction of the past ca. three centuries for this cold oligotrophic, quasi-pristine lake which receives meltwaters from the Tronador ice cap. Chronology was based on 137Cs and 210Pb measurements of the upper sediments, and the inferred sedimentation rate of 23.2 mg cm-2 y-1 (0.15 cm y-1) was consistent with both sets of measurements. The sediment from Lake Hess was rich in tephra deposits particularly evident in the lower part of the cores. Tephras are valuable to use for core correlation and can be traced through peaks in the magnetic susceptibility (MS) profiles. Results from the multiproxy analyses in the longest core (83 cm) identify three main phases of change. From the bottom up to 42 cm (ca. ad 1800), the sediment is composed of light-grey organically rich clays. Both pigments and chironomids suggest variable trends in productivity and precipitation regime. At the end of the Little Ice Age chronozone (ad 1770-1850), pigment concentrations were very low. From 42 cm to ca. 25 cm (ad 1800-1940), the sedimentary record is composed of alternating black and dark organic-matter rich mud with variable amounts of macrophyte remains. Pigment concentrations and chironomid head capsule counts were also very low. These facies are composed of very fine plastic sediments with some faintly laminated intervals and an organic matter composition gradually decreasing towards the top of the zone. A sharp change occurs at 25 cm (ca. ad 1940) showing a strong increase in organic matter content, algal nutrients and plant pigments together with a change in the chironomid assemblages. This might document a change in the trophic condition of the lake associated with changes in erosion/deposition rates. Although there are records of human impact in the area studied, involving the use of fires, most of the observed chemical and biological changes in Lake Hess sediment sequence were interpreted in terms of climate changes, especially to changes in moisture balance brought about by variations in the strength of the westerlies.

Author affiliation: Guilizzoni, Piero. Consiglio Nazionale delle Ricerche; Italia

Author affiliation: Massaferro, Julieta. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina

Author affiliation: Lami, Andrea. Consiglio Nazionale delle Ricerche; Italia

Author affiliation: Piovano, Eduardo Luis. 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; Argentina

Author affiliation: Ribeiro Guevara, Sergio. Comisión Nacional de Energía Atómica; Argentina. Consiglio Nazionale delle Ricerche; Italia

Author affiliation: 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; Argentina

Author affiliation: Daga, Romina Betiana. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear; Argentina

Author affiliation: Rizzo, Andrea Paula. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear; Argentina. Consiglio Nazionale delle Ricerche; Italia

Author affiliation: Gerli, Stefano. Consiglio Nazionale delle Ricerche; Italia

Abstract:

The limnological conditions during the past 700 yr were reconstructed based on multiproxy analysis of a short sedimentary sequence from El Toro Lake (~40°S, 70°W). Mineralogical and geochemical features, as well as ostracods and chironomids, record hydrologic changes in the El Toro Lake basin. The ostracod Limnocythere rionegroensis var. 1, a reliable indicator of high salinity, and Eucypris fontana, a euryhaline species with preferences for moderate-salinity waters, are studied as paleolimnological proxies. The chironomid fauna indicates less saline conditions in the mid-twentieth century. These salinity changes are interpreted in terms of negative-positive hydrologic balance. High lake level and low salinity between AD 1500 and 1700 match with the wetter and colder climate during the second pulse of the Little Ice Age in northern Patagonia. High-salinity conditions occurred during the late nineteenth century, corresponding to the driest period during the past 400 yr in northeastern Patagonia. An increase in the precipitation around the middle of the twentieth century, in contrast to the records from the Chilean side of the mountains, correlates with a positive phase of the Southern Annular Mode. This is associated, in turn, with a strengthening, poleward shift of the midlatitude westerlies, possibly enhancing easterly moist air flows into central-north Patagonia.

Author affiliation: Coviaga, Corina Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Author affiliation: Rizzo, Andrea Paula. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina

Author affiliation: Perez, Alejandra Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Author affiliation: Daga, Romina Betiana. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina

Author affiliation: Poire, Daniel Gustavo. 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

Author affiliation: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Author affiliation: Ribeiro Guevara, Sergio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Abstract:

El volcán Copahue presenta un registro de erupciones históricas de limitada intensidad cuyo carácter ha sido analizado principalmente a partir de los eventos de las últimas décadas. Hacia fines del año 2011 comenzaron a observarse cambios significativos en diversos parámetros asociados a la actividad del volcán hasta que, luego de doce años de quietud, en julio de 2012 comenzó un nuevo ciclo eruptivo. En este trabajo se presenta la caracterización de los productos piroclásticos emitidos durante el evento del día 19 de julio de 2012, el cual tuvo una dispersión limitada, pero resulta de importancia para la definición del carácter de la fase inicial del ciclo eruptivo. Una alta proporción de litoclastos y la presencia de vitroclastos juveniles primarios, los cuales son estudiados en detalle, permiten caracterizar el mecanismo eruptivo, consistente con una erupción hidromagmática. La particularidad de la tefra generada está dada por la presencia de azufre piroclástico. Si bien este tipo de partículas ha sido identificado en erupciones previas, su presencia resulta de importancia ya que refleja la existencia de azufre fundido por debajo del lago de cráter. La participación de este material precipitado permitiría inferir la influencia del mismo en el mecanismo eruptivo.

Copahue volcano has a record of historical eruptions of low intensity which have mainly been characterized from the events ob-served in last decades. Significant changes in several parameters associated with the volcano activity were observed since the end of 2011. After 12 years of quiescence, on July 2012, the volcano started a new eruptive period. In this work, the characterization of the pyroclastic products emitted on 19th July 2012 is presented. Although the limited dispersion of the event, its study is central in the definition of the character of the initial phase of the eruptive cycle. A high proportion of lithics and the presence of juvenile first-cycled vitroclasts studied in detail allow us to characterize the eruptive mechanism, consistent with a phreatomagmatic erup-tion. A distinctive feature of the tephra is the presence of pyroclastic sulfur. Although these kinds of particles have been identified in previous eruptions, its presence is crucial revealing the existence of molten sulfur under the crater lake. The participation of this precipitated material allow us to infer its influence in the eruptive mechanism.

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina

Author affiliation: Caselli, Alberto Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina

Author affiliation: Ribeiro Guevara, Sergio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutrónica; Argentina

Author affiliation: Agusto, Mariano Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas. Grupo de Estudio y Seguimiento de Volcanes Activos; Argentina

Abstract:

At the beginning of the 21st century, digital imaging technology replaced the traditional silver-halide film photography which had implications in Ag contamination. Lake Nahuel Huapi is a popular Patagonia tourist destination impacted by municipal silver (Ag) contamination from photographic processing facilities since 1990's. Silver concentrations in a dated sediment core from the lake bottom showed a 10-fold increase above background levels in the second half of the 20th century, then a decrease. This trend corresponds well with published annual global photography industry demand for Ag, which clearly shows the evolution and replacement of the traditional silver-halide film photography by digital imaging technology. There were significant decreases in Ag concentrations in sediments, mussels and fish across the lake between 1998 and 2011. Lower trophic organisms had variable whole-body Ag concentrations, from 0.2–2.6 μg g−1dry weight (DW) in plankton to 0.02–3.1 μg g−1DW in benthic macroinvertebrates. Hepatic Ag concentrations in crayfish, mussels and predatory fish were significantly elevated relative to muscle which often have Ag concentrations below the detection limit (0.01–0.05 μg g−1DW). Trophodynamic analyses using δ15N and whole-body invertebrate and muscle Ag concentrations indicated food web biodilution trends. High sedimentation rates in conjunction with the reduction of silver waste products discharged to the lake, as a result of the change to digital image processing technologies, are resulting in unplanned but welcome remediation of the Ag contamination in Lake Nahuel Huapi.

Author affiliation: Juncos, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Campbell, Linda. Saint Mary's University; Canadá

Author affiliation: Arcagni, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Daga, Romina Betiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Rizzo, Andrea Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Arribere, Maria Angelica. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina

Author affiliation: Ribeiro Guevara, Sergio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; Argentina