Ezeiza, Argentina
Ezeiza, Argentina

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Villafane V.E.,Estacion de Fotobiologia Playa Union | Villafane V.E.,CONICET | Banaszak A.T.,National Autonomous University of Mexico | Guendulain-Garcia S.D.,National Autonomous University of Mexico | And 5 more authors.
Limnology and Oceanography | Year: 2013

The effects of temperature and ultraviolet radiation (UVR; 280-400 nm) on seasonal succession in phytoplankton assemblages of Patagonia (Argentina) were studied in the context of global change. Samples collected during pre-bloom, bloom onset, bloom, and spring were exposed to in situ and increased (+4°C) temperatures and solar radiation with and without UVR. Daily cycles of effective photochemical quantum yield exhibited a pattern of high values in the morning, decreasing towards noon, and increasing in the afternoon. The decrease in yields towards noon as the season progressed increased from 30% in the pre-bloom to 80% in the spring; in the latter there were significant differences between radiation treatments under both temperature conditions. The highest inhibition rates were during the bloom, whereas the highest recovery rates were during the spring. Inhibition rates were generally higher in treatments exposed to UVR in comparison to photosynthetically active radiation-only treatments and some stages of the succession exhibited an additional temperature effect. Increasing temperatures had little effect on pre-bloom communities but helped to counteract the magnitude of the yield decrease during the bloom onset. However, during the bloom and in the spring, temperature and UVR acted synergistically, increasing the overall photochemical inhibition. Feedback mechanisms of increased temperatures causing a shallower mixing depth will expose phytoplankton to higher radiation, which will have a negative effect on the bloom and on spring assemblages. Due to the differential effects of solar UVR and increased temperature on phytoplankton, future studies should consider the repercussions on higher trophic levels. © 2013, by the Association for the Sciences of Limnology and Oceanography, Inc.

Romagnoli M.,Centro Universitario Rosario Of Investigaciones Hidroambientales | Garcia C.M.,National University of Cordoba | Lopardo R.A.,Instituto Nacional del Agua
Journal of Hydraulic Engineering | Year: 2012

This note presents experimental results on an error analysis of acoustic Doppler velocimeter (ADV) turbulence measurements in free hydraulic jumps incorporating a recent ADV signal processing technique. The work aims to quantify the influence of each error source in acoustic Doppler measurements (i.e., presence of spikes, Doppler noise, and filtering effects due to the ADV sampling strategy) on variance and integral time scale computations as well as to define the corresponding confidence interval for each reported value. Experiments were conducted for an upstream Froude number of 3.0. The relative error contribution of each source to both raw longitudinal variance and raw longitudinal integral time scale decreases downstream. Inside the zone where aeration effects and high turbulence levels are relevant, Doppler noise constitutes the most important error source. Further downstream, where aeration effects and turbulence levels diminish, the error produced by the presence of spikes can be neglected, whereas the effects of both Doppler noise and ADVs' sampling strategy are balanced. The relative confidence interval for corrected longitudinal variance ranges between 30 and 10%, whereas the relative uncertainty level for the corrected longitudinal integral time scale varies from 80 to 50%. The results of this study point out the requirement for an adequate signal postprocessing technique and uncertainty analysis of ADV turbulence measurements. © 2012 American Society of Civil Engineers.

Areco M.M.,University of Buenos Aires | Hanela S.,Instituto Nacional del Agua | Duran J.,Instituto Nacional del Agua | dos Santos Afonso M.,University of Buenos Aires
Journal of Hazardous Materials | Year: 2012

Many industries have high heavy metals concentrations in their effluents that should be treated before disposal in drains or natural watercourses. When adsorption process is evaluated to generate and implement an efficient, economical and sustainable method suitable for heavy metals removal from contaminated effluents, it is necessary to develop an experimental setup that contains the adsorbent. Ulva lactuca, a marine green alga, was studied as a natural biosorbent for heavy metals at acid pH conditions. Adsorption experiments were carried out in glass columns and in batch where the alga was suspended or fixed in an agar matrix. Langmuir and Freundlich models were applied to the experimental results. Langmuir model best describes the adsorption isotherms in all analyzed cases. The adsorption capacity increases with pH. Kinetic studies demonstrate that, in most studied cases, the adsorption follows a pseudo second order kinetics model. Removal efficiencies of the biomaterial supported in agar or fixed in columns were: fixed in columns > suspended in batch mode > fixed in agar. Finally, the effect of the presence of two sorbates, Cd and Pb, in the solution was measured and results demonstrate that adsorption of both metals are diminished by co/adsorption. © 2012 Elsevier B.V.

The objective of this work is to study the ability of the Simulator for Water Resources in Rural Basins - Water Quality (SWRRB-WQ) model to estimate the load of nitrogenous fertilizer transported by surface runoff in a sub-basin of the Tapalqué River (Buenos Aires Province, Argentina). Also discussed is the impact of the climatic variability resulting from El Niño Southern Oscillation (ENSO) phases on runoff and fertilizer load. The SWRRB-WQ model consists mainly of a representation of the hydrology and water quality associated with a hydrometeorological variables generator. Precipitation data from the meteorological station located in Azul was used for the period 1961-1990 as input to the SWRRB-WQ in order to analyze the variability of surface runoff and nitrate load in a control section located at the outlet of the basin under study. The results of this analysis show the effect of the variability observed in the precipitation associated with ENSO phases on surface runoff and transported nitrate loads at different time scales.

Re M.,Instituto Nacional Del Agua | Kazimierski L.D.,University of Buenos Aires | Menendez A.N.,University of Buenos Aires
Tecnologia y Ciencias del Agua | Year: 2014

A numerical modeling methodology for sedimentation in navigation channels is used to evaluate effects of Climate Change, through consideration of potential changes in the river discharge. This methodology, which is explained in detail, is illustrated through its application to a 'paso' of the Parana River (South America), validating its results with maintenance dredging data. It is shown that, keeping the present dredging elevations, the sedimentation volume would increase with the increment in discharge, and vice versa, with relative rates of change significantly larger than that of the discharge. If, on the contrary, the dredging elevations were adjusted to new reference levels, the trend would be the opposite, with relative rates of change only moderately larger than that of the discharge, in absolute value.

Dotro G.,Cranfield University | Castro S.,Instituto Nacional del Agua | Tujchneider O.,National University of Santa | Tujchneider O.,CONICET | And 7 more authors.
Journal of Hazardous Materials | Year: 2012

Tannery operations consist of converting raw animal skins into leather through a series of complex water- and chemically-intensive batch processes. Even when conventional primary treatment is supplemented with chemicals, the wastewater requires some form of biological treatment to enable the safe disposal to the natural environment. Thus, there is a need for the adoption of low cost, reliable, and easy-to-operate alternative secondary treatment processes. This paper reports the findings of two pilot-scale wetlands for the secondary treatment of primary effluents from a full tannery operation in terms of resilience (i.e., ability to produce consistent effluent quality in spite of variable influent loads) and reliability (i.e., ability to cope with sporadic shock loads) when treating this hazardous effluent. Areal mass removal rates of 77.1g COD/m2/d, 11g TSS/m2/d, and 53mg Cr/m2/d were achieved with a simple gravity-flow horizontal subsurface flow unit operating at hydraulic loading rates of as much as 10cm/d. Based on the findings, a full-scale wetland was sized to treat all the effluent from the tannery requiring 68% more land than would have been assumed based on literature values. Constructed wetlands can offer treatment plant resilience for minimum operational input and reliable effluent quality when biologically treating primary effluents from tannery operations. © 2012 Elsevier B.V.

Halac S.R.,Estacion de Fotobiologia Playa Union | Halac S.R.,Instituto Nacional del Agua | Guendulain-Garcia S.D.,National Autonomous University of Mexico | Villafane V.E.,Estacion de Fotobiologia Playa Union | And 4 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2013

The aim of this study was to evaluate the effects of UVR on growth and taxonomic composition of tropical plankton communities in a scenario of increased temperature and ultraviolet radiation. Water samples were collected from a reef lagoon in the Mexican Caribbean (20.5° N, 86.5° W) during July 2010 and grown for 16. days in microcosms under two natural radiation treatments: a) PAB (PAR + UV-A + UV-B, 280-700. nm) and, b) P, (PAR, 400-700. nm) and two temperature conditions: a) ambient (28 °C), and, b) increased (ambient + 3 °C). A differential factorial response of the studied variables among the main taxonomic groups and more frequent species was found. The biomass of dinoflagellates and colorless plankton was negatively affected by UVR while the increased temperature had negative effects on diatom biomass and cell abundance. During the experimental period there were changes in the contribution of each taxonomic group. At ambient temperature there was a shift from a flagellate- to a diatom-dominated community; whereas at increased temperature diatoms co-dominated with flagellates. UVR exposure decreased the contribution of naked dinoflagellates (> 20 μm) and cryptophytes. On the other hand, the most frequent diatom, Cylindrotheca closterium was negatively affected at increased temperature, while small chlorophytes (< 10 μm), which were one of the dominant groups of flagellates, contributed significantly to the biomass at increased temperature at the end of the experiment. Synergistic effects of UVR and temperature were only detected at the species level in large diatoms (> 20 μm; e.g. Leptocylindrus sp. and Amphora sp.) and in cryptophytes (> 10 μm). Our results suggest that planktonic assemblages from the Mexican Caribbean are generally well-adapted to the high UVR fluxes and temperature with some species being positively influenced by increased temperature. However there are exceptions with some species being negatively affected by UVR, increased temperature or the combination of both factors. Therefore, our results indicate that under the high radiation conditions of tropical oceans, changes in community structure in terms of taxonomic composition and size distribution would occur in a scenario of global climate change. © 2013 Elsevier B.V.

Venencio M.D.V.,National University of Santa | Venencio M.D.V.,Instituto Nacional del Agua | Garcia N.O.,National University of Santa
Journal of Hydrology | Year: 2011

In recent times, significant areas of the Northeastern Argentine (NEA) have been affected by climatic fluctuations which have caused serious damages in ecosystems and people's livehoods, both by floods and droughts. This has mainly occurred in the Santa Fe Province, having a great impact on the underlying unconfined aquifer. This paper analyzes the relationships between meteorological variability and water table levels in the context of climate variability and climatic change in the lower Carcarañá river experimental basin (about 4700km2), located in the Santa Fe Province. The goal of the study is to obtain long-term (interannual) predictions of water table levels in the region. The methodology used responds to a hypothetical conception of the temporal series having a signal formed by random components with characteristics of white noise. Singular Spectral Analysis (SSA), among other non-parametric techniques were used to identify fluctuations and trend changes in climatic time-series. These characteristics provide valuable information for the evaluation of climatic evolution and for the detection of variations in this evolution, suggesting a climatic change either by natural mechanisms or by anthropogenic impacts. A positive trend in precipitation is found throughout the studied region with water table levels showing a similar spatial-temporal behavior. The SSA gives significant periodicities between 3 and 8years showing a possible link between El Niño-Southern Oscillation (ENSO) phenomenon and precipitation and water table levels. The periodicities linked with ENSO are always present and the structures of the series are similar for the different studied periods. The results obtained, even if they are experimental constitute a first approximation. In general, they are promising, since the generated basis will enable to face further and more complex stages. © 2011 Elsevier B.V.

Lopardo R.A.,Instituto Nacional del Agua
Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2014 | Year: 2014

This paper aims to present a new methodology to estimate the sizes of rockfill protection downstream of a hydraulic jump stilling basin. The classic length allows the transformation of kinetic energy into potential energy; however, is far from fully dissipate the turbulent energy of the flow, that moves downstream threatening to cause riverbed erosion. As a consequence, instant maximum velocities widely exceed the usual calculated values, putting at risk the protection of rocks determined with mean values of velocity. From laboratory experiences developed to determine fluctuating pressure and instantaneous velocities downstream of free and submerged hydraulic jumps it was possible to get extreme values of positive fluctuation closer to the bottom. This is taken at having amplitude 0.1% chance of being exceeded. That condition was considered for different incidents Froude Numbers and various submergence factors conditions. By those instant extreme values of velocity will come of the diameters of rockfill necessary to protect the riverbed substantially larger than those obtained from design conventional manuals. © 2014 Taylor & Francis Group, London.

Halac S.R.,Estacion de Fotobiologia Playa Union | Halac S.R.,Instituto Nacional del Agua | Villafane V.E.,Estacion de Fotobiologia Playa Union | Villafane V.E.,CONICET | And 2 more authors.
Journal of Photochemistry and Photobiology B: Biology | Year: 2010

The aim of this study was to assess the combined effects of temperature and UVR on the photosynthesis performance of two diatoms - Chaetoceros gracilis and Thalassiosira weissflogii. In particular, we evaluated the role of UVR in inducing photoinhibition and the potential mitigation of this negative effect by an increase in temperature. Cultures were pre-acclimated at two temperatures - 18 °C and 23 °C - and exposed to different radiation treatments - UVR. +. PAR (280-700 nm); UV-A. +. PAR (315-700 nm) and PAR only (400-700 nm) under two temperatures: 18 °C (local surface summer water temperature) and 23 °C (simulating a potential increase estimated by the year 2100). Exposure to natural solar radiation resulted in UVR-induced photoinhibition that was significantly higher in T. weissflogii than in C. gracilis. Both species benefited from the higher temperature (23 °C) resulting in a lower photoinhibition as compared to samples exposed at 18 °C. Inter-specific differences were determined in regard to the heat dissipation processes (NPQ) which were higher at high temperatures, and much more evident in C. gracilis than in T. weissflogii. The analyses of inhibition and recovery rates under different irradiances indicate that the balance between negative (inhibition) and positive (repair-dissipation) effects shifted towards a more positive balance with increasing temperature. Our results highlight for a beneficial effect of temperature on photosynthesis performance during exposure to UVR, although important inter-specific differences are found, probably due to differences in cell size as well as in their distribution within the oceanic realm (i.e., coastal versus oceanic species). © 2010 Elsevier B.V.

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