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Ezeiza, Argentina

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. Source

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. Source

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. Source

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. Source

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. Source

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