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BACKGROUND: Geographic distribution of essential metals on earth is largely uneven. Therefore, regional specific approaches to assess metal contents in freshwater ecosystems are mandatory. Cd, Cu, Cr, Pb, Ni, Mn and Zn concentrations were measured in water, sediments and fish tocharacterize the partitioning of these essential and non-essential metals in three river ecosystems of the Pampean Plain==. METHODS: Water, sediment and eight fish species were collected at three rivers from the Pampean Plain. After sample-specific pretreatments, Cd, Cr, Cu, Mn, Ni, Pb and Zn concentrations in water, sediment and muscle were determined in triplicate by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Contamination (Hakanson´s index) and bioconcentration factors were calculated to assess the degree of contamination and the relationship between the matrices, while the target hazard quotient was estimated to explore the risk to human health from fish consumption. RESULTS: Water metal concentration was below detection limit in all sampled rivers. Sediments were mostly enriched by Mn (186-474 mg kg-1) followed by Zn (36.8-40.3 mg kg-1), whereas in fish, the situation was the opposite, suggesting different biogeochemical pathways and uneven bioaccumulation of these elements. The largest concentrations for all explored metals were invariably recorded in fish from the Sauce Grande River, although only Cd, Cu and Ni in sediments were highest at this site. Indeed, the bioconcentration factor showed that Cd and Zn are actively accumulated by almost all species in all sampled rivers. The Targeted Hazard Quotient based on the muscle metal concentration tissue of the edible fish species (Odontesthes bonariensis) was less than 1. CONCLUSION: None metal seemed to pose a significant risk for humans. In some sites biota-sediment concentration factors of Cd and Zn and muscle Cd, Cr, Ni, Zn and Pb levels were highest in the silurid Pimelodella laticeps, suggesting that it may be used as a sentinel species for biomonitoring programs in Neotropical fish assemblages.

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The Chacopampean plain is one of the most arsenic affected areas in Argentina, especially in groundwater, used both for animal drinking and forage irrigation. The main objective of this study was to determine the effect of arsenic (As) present in irrigation water on the germination parameters of red clover (Trifolium pratense L.), white clover (Trifolium repens L.), and alfalfa (Medicago sativa L.) seeds exposed to different concentrations of As(V). The germination and viability parameters of seeds from the three species were not affected by elevated concentrations of As. However, As significantly reduced the radicle and hypocotyl lengths of the three forage specimens. The inhibition level of the plants increased with the increase in the  concentration of As. Regarding to hypocotyl length/radicle length ratio, the results evidenced that both the hypocotyl and radicle of clover species are affected in the same degree, while alfalfa radicles seemed more affected than hypocotyls at higher concentrations of As. Our results showed that irrigation with solutions containing As affect seedling growth parameters differently in the three species, and the effect of As is mostly evidenced when in high concentrations.

A planície de Chacopampeana é uma das áreas mais afetadas pelo arsênico na Argentina, principalmente em águas subterrâneas, usada tanto para água potável animal quanto para irrigação forrageira. O principal objetivo deste estudo é determinar o efeito do arsênio (As) presente na água de irrigação sobre os parâmetros de germinação de sementes forrageiras: trevo vermelho (Trifolium pratense L.), trevo branco (Trifolium repens L.) e alfafa (Medicago sativa L.) expostos a diferentes concentrações de As (V). Verificou-se que os parâmetros de germinação e viabilidade das sementes das três espécies não foram afetados pelas concentrações elevadas de As. No entanto, reduziu significativamente o comprimento da radícula e o comprimento do hipocótilo das três mudas de forragem, e seu nível de inibição é maior com o aumento da concentração de As. Quanto à relação comprimento de hipocótilo/comprimento da radícula, os resultados evidenciaram que nas espécies de trevo tanto o hipocótilo quanto a radícula são afetados no mesmo grau, enquanto as radículas de alfafa pareceram mais afetadas do que os hipocótilos em concentrações maiores de As. Nossos resultados mostraram que a irrigação com soluções contém Afetar os parâmetros de crescimento de plântulas de maneira diferente nas três espécies, e foi demonstrado que o efeito do As é principalmente evidenciado em altas concentrações.

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The Chacopampean plain is one of the most arsenic affected areas in Argentina, especially in groundwater, used both for animal drinking and forage irrigation. The main objective of this study was to determine the effect of arsenic (As) present in irrigation water on the germination parameters of red clover (Trifolium pratense L.), white clover (Trifolium repens L.), and alfalfa (Medicago sativa L.) seeds exposed to different concentrations of As(V). The germination and viability parameters of seeds from the three species were not affected by elevated concentrations of As. However, As significantly reduced the radicle and hypocotyl lengths of the three forage specimens. The inhibition level of the plants increased with the increase in the  concentration of As. Regarding to hypocotyl length/radicle length ratio, the results evidenced that both the hypocotyl and radicle of clover species are affected in the same degree, while alfalfa radicles seemed more affected than hypocotyls at higher concentrations of As. Our results showed that irrigation with solutions containing As affect seedling growth parameters differently in the three species, and the effect of As is mostly evidenced when in high concentrations.(AU)

A planície de Chacopampeana é uma das áreas mais afetadas pelo arsênico na Argentina, principalmente em águas subterrâneas, usada tanto para água potável animal quanto para irrigação forrageira. O principal objetivo deste estudo é determinar o efeito do arsênio (As) presente na água de irrigação sobre os parâmetros de germinação de sementes forrageiras: trevo vermelho (Trifolium pratense L.), trevo branco (Trifolium repens L.) e alfafa (Medicago sativa L.) expostos a diferentes concentrações de As (V). Verificou-se que os parâmetros de germinação e viabilidade das sementes das três espécies não foram afetados pelas concentrações elevadas de As. No entanto, reduziu significativamente o comprimento da radícula e o comprimento do hipocótilo das três mudas de forragem, e seu nível de inibição é maior com o aumento da concentração de As. Quanto à relação comprimento de hipocótilo/comprimento da radícula, os resultados evidenciaram que nas espécies de trevo tanto o hipocótilo quanto a radícula são afetados no mesmo grau, enquanto as radículas de alfafa pareceram mais afetadas do que os hipocótilos em concentrações maiores de As. Nossos resultados mostraram que a irrigação com soluções contém Afetar os parâmetros de crescimento de plântulas de maneira diferente nas três espécies, e foi demonstrado que o efeito do As é principalmente evidenciado em altas concentrações.(AU)

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The temporal variation of As, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in surface waters and sediments, and trace element accumulation and physiological changes in the macrophytes Stuckenia filiformis and Potamogeton pusillus, were estimated in the Ctalamochita River, Argentina, both upstream and downstream of Río Tercero. Chromium, Fe, Pb and Zn in surface water were higher at the downstream site, while Cu and Mn were higher upstream. Chromium, Mn and Zn in S. filiformis correlated with concentrations observed in sediments, whereas only Zn did in water. In P. pusillus, As, Co, Cr, Ni, Pb and Zn correlated with concentrations in sediments. P. pusillus revealed greater variations in the photosynthetic pigments and malondialdehyde content in the site downstream of the city than those observed in S. filiformis. Therefore, P. pusillus has a greater potential use in monitoring studies in aquatic environments with ecological risk than S. filiformis.

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Dichlorvos (DDVP) is an organophosphorus pesticide that has been classified as highly hazardous chemical by the World Health organization. In this study, the fate of the pesticide DDVP in natural water compartments was examined under simulated sunlight. Moreover, the effect of UV-254 irradiation on DDVP depletion was also studied. In deionized water, DDVP was photodegraded only in the presence of dissolved molecular oxygen. The photodegradation during the first 6 h of sunlight irradiation occurred with pseudo first-order kinetics, and the rate constants were 0.040 h-1 at pH 7 and 0.064 h-1 at pH 3. A reaction mechanism for the generation of reactive oxygen species (ROS) via DDVP photoabsorption was proposed. Humic acids (HA) played a double role as photosensitizer and inhibitor, observing an enhancement on DDVP photodegradation at low HA concentration (TOC = 2 mg L-1). The depletion of DDVP under 254 nm UV irradiation was ascribed to direct photodegradation and oxygen mediated photoinduced reactions. Direct photodegradation of DDVP decreased with 254 nm irradiation reduction, highlighting the importance of radical mediated mechanisms at low irradiation doses. Based on LC/MS data, the main photoproducts under simulated solar light and UV-C irradiation were identified and potential reaction pathways were postulated. The three main identified products were o-methyl 2,2-dichlorovinyl phosphate, dichloroacetaldehyde and dimethylphosphate. Moreover, the toxicity of samples was evaluated along the irradiation exposure time using Microtox® assays. This study brings new insights into the role of oxygen in the photodegradation of DDVP and the induced and inhibition mechanisms involved in the presence of the humic acids in natural waters.

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In order to study the bioaccumulation of Pb, Cr, Ni, and Zn and the stress response, the floating aquatic plant Limnobium laevigatum was exposed to increasing concentrations of a mixture of these metals for 28 days, and its potential use in the treatment of wastewater was evaluated. The metal concentrations of the treatment 1 (T1) were Pb 1 µg L-1, Cr 4 µg L-1, Ni 25 µg L-1, and Zn 30 µg L-1; of treatment 2 (T2) were Pb 70 µg L-1, Cr 70 µg L-1, Ni 70 µg L-1, and Zn 70 µg L-1; and of treatment 3 (T3) were Pb 1000 µg L-1, Cr 1000 µg L-1, Ni 500 µg L-1, and Zn 100 µg L-1, and there was also a control group (without added metal). The accumulation of Pb, Cr, Ni, and Zn in roots was higher than in leaves of L. laevigatum, and the bioconcentration factor revealed that the concentrations of Ni and Zn in the leaf and root exceeded by over a thousand times the concentrations of those in the culture medium (2000 in leaf and 6800 in root for Ni; 3300 in leaf and 11,500 in root for Zn). Thus, this species can be considered as a hyperaccumulator of these metals. In general, the changes observed in the morphological and physiological parameters and the formation of products of lipid peroxidation of membranes during the exposure to moderate concentrations (T2) of the mixture of metals did not cause harmful effects to the survival of the species within the first 14 days of exposure. Taking into account the accumulation capacity and tolerance to heavy metals, L. laevigatum is suitable for phytoremediation in aquatic environments contaminated with moderated concentrations of Cr, Ni, Pb, and Zn in the early stages of exposure.

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Mastitis affects the health and welfare of dairy cows worldwide. Coagulase-negative staphylococci (CNS) are known to form biofilms and are increasingly recognized as a cause of persistent bovine intramammary infections. A total of 90 CNS isolated from cows with clinical and subclinical mastitis in Argentina from 2008 to 2014 were identified by PCR-RFLP using the gap gene. Standard microtiter plate assays were used to assess CNS biofilm formation, and Staphylococcus haemolyticus species formed the strongest biofilms. The presence of biofilm-associated genes icaA, bap and aap was detected in a few isolates, while embP, fbe, atlE and eno were present in the majority of isolates. Genes encoding resistance to ß-lactams were detected among the isolates; blaZ, mecA and mecC were detected in 21, 4 and 1 isolate, respectively. Resistance to macrolides and lincosamides (n = 6) was attributable to ermB, ermC, mphC or mrsA or a combination of those genes. In this study, we identified CNS species involved in mastitis and provide information about pathogenicity and antimicrobial resistance, which is essential to design efficient strategies to control mastitis caused by CNS.

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The Chaco Pampean Plain of central Argentina represents one of the largest regions with high levels of arsenic (As) in groundwater. The aim of this study was the assessment of a biotransference factor (BTF) as a tool for the estimation of As concentration in cow's milk from As drinking water concentration. Total As content in livestock drinking water, soil, forage, and milk was determined in farms located in an area of high As groundwater, in order to analyze the relation between As uptake and its transfer to milk. The concentrations of As in milk ranged from 0.5 to 8.0 µg/L. From the results obtained, drinking water may be considered the main source of exposure to As, and the biotransference factor for milk ranges from 1.5 × 10(-5) to 4.3 × 10(-4). Therefore, BTF provides a simple tool for the estimation of arsenic levels in milk through the As livestock drinking water content.

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The concentrations of As, Ag, B, Ba, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hg, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Rb, Sb, Se, Sn, Sr, Te, Ti, U, V and Zn were determined in water and silverside (Odontesthes bonariensis) muscle samples from four important commercial fishing sites (Argentina) by ICPMS. Trace element concentrations in water with well-documented human health effects were above the recommended maximum levels established by Argentinean and international guidelines for the aquatic biota protection in three sampling sites (e.g. As: 28.4-367 µg L(-1); Cd: 0.17-1.05 µg L(-1); Hg: 0.07-0.63 µg L(-1); Zn: 71.3-90.0 µg L(-1)). High concentrations of As, Hg and Pb (0.03-0.76; 0.03-0.42 and 0.04-0.19 mg kg(-1) wet weight, respectively) were found in silverside muscle. Fishing communities associated with contaminated environments are likely to have higher consumption rates and are thus more likely to be exposed to higher concentrations of the toxic elements (As, Hg and Pb).

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Arsenic pollution of groundwater is a serious problem in many regions of Latin America that causes severe risks to human health. As a consequence, non-destructive monitoring methodologies, sensitive to arsenic presence in the environment and able to perform a rapid screening of large polluted areas, are highly sought-after. Both chlorophyll - a fluorescence and reflectance of aquatic plants may be potential indicators to sense toxicity in water media. In this work, the effects of arsenic on the optical and photophysical properties of leaves of different aquatic plants (Vallisneria gigantea, Azolla filiculoides and Lemna minor) were evaluated. Reflectance spectra were recorded for the plant leaves from 300 to 2400 nm. The spectral distribution of the fluorescence was also studied and corrected for light re-absorption processes. Photosynthetic parameters (Fv/Fm and ΦPSII) were additionally calculated from the variable chlorophyll fluorescence recorded with a pulse amplitude modulated fluorometer. Fluorescence and reflectance properties for V. gigantea and A. filiculoides were sensitive to arsenic presence in contrast to the behaviour of L. minor. Observed changes in fluorescence spectra could be interpreted in terms of preferential damage in photosystem II. The quantum efficiency of photosystem II for the first two species was also affected, decreasing upon arsenic treatment. As a result of this research, V. gigantea and A. filiculoides were proposed as bioindicators of arsenic occurrence in aquatic media.

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