1,721,022 research outputs found
Acque di miniera dell’Iglesiente: storia, analisi e caratterizzazione
No full textThe paper is concerned with the analysis of the groundwater resources contained in the deep carbonate aquifer
situated in the Iglesiente region in SW Sardinia. The study aimed to determine whether these resources could alleviate
the region's water scarcity problem. Based on considerations of a general nature and on recent monitoring data we
have studied the evolution of, as well as the current water situation, in both quantitative and qualitative terms. This has
made it possible to update knowledge and acquire new data for the Acquaresi area. A preliminary characterization and
classification of the groundwater in this area has been performed to determine environmental conditions in the aquifer
and to assess suitability of the groundwater for drinking, domestic, irrigation and industrial uses
Aquatic macrophytes Azolla and Salvinia as biofilters for surfactant decontamination
No full textThe wide range of domestic and industrial applications of surfactants can arise ecological problems when these molecules are present in the aquatic environment in relatively high concentration, exhibiting toxic effects and affecting at different levels the ecosystems. Conventional wastewater treatment plants are not always perfectly designed to remove these contaminants, thus many of them can occur at different concentrations in surface waters and soils. In previous works two species of floating macrophytes, Azolla filiculoides Lam. and Lemna minor L., have been exploited for phytoremediation of sodium dodecyl sulphate (SDS), a commercially important anionic surfactant , that is the core component of several detergent and cosmetic product formulations, contributing significantly to the pollution profile of sewage and wastewater of all kinds. The uptake rates of SDS by duckweed and water velvet showed a potential and remarkably efficient phytoremediation system (Forni et al., 2008). Besides the use of living plants, dried macrophyte biomasses can be used to biosorption of pollutants like a wide range of heavy metals, as demonstrated by Tel-Or and coworkers (Cohen-Shoel et al., 2002; Tel-Or and Forni, 2011 and references therein); this biosorption procedure offers a different approach for reclame of metals from mining waste and industrial discharges.
The aim of this work was to verify the applicability of this technology for SDS removal from polluted water in order to offer a possible alternative solution to the use of wetlands and to the burning problem of our industrial society, i.e. to reduce water consumption trying to recycle waste water.
For this purpose, biomasses of Azolla filiculoides Lam. and Salvinia natans (L.) All. were dried in oven (70-80° C for 48 hrs) or in the sun and stored at room temperatures until use. 100 grams of mildly crushed dried biomass were rewetted in 500 ml distilled water for 1 hr, and packed in the column (Biorad), according to the procedure of Cohen- Shoel et al. (2002). Solutions, containing 40 ppm SDS were passed through the dried biomass by idrostatic pressure at a flow rate of 5 to 10 mL min−1. The effluent was collected in 250 mL fractions. pH effect on SDS biosorption was tested at pH 2, 7 and 10. The pH of the solution was adjusted by addition of HCl or NaOH. Before starting the filtration, each biofilter was rinsed with double distilled water (DDW) at the same pH of the experiments. The amount of SDS in the eluates was determined according to Forni et al. (2008).
The different pH of SDS solution influenced the binding ability of the biofilters, which biosorption rates enhanced along with the increase in pH, being higher at pH 7 than at pH 2. The binding of SDS to insoluble constituents in the fern matrix most probably involves cell wall charged groups, therefore low pH influenced the binding of the anionic surfactant probably because of the negative charged groups of the cell walls. In fact, the dry biomass of both ferns contains very little cellulose and higher amount of pectins, a major component in Azolla (5-7%), and lignin (Cohen-Shoel et al., 2002). These molecules together with polyphenols and phytates may play a role in biosorption.
Good binding performances were obtained at pH 7 and 10. Azolla biofilter was better than Salvinia, in some cases 90 -100 % of SDS removal could be obtained. A good rate of the binding already occurred in the first fractions, suggesting that the initial rinsing with DDW at different pH was necessary to adjust the charges of binding groups and a progressive saturation of the binding sites.
References
Cohen-Shoel N., Ilzycer D., Gilath I. and Tel-Or E. (2002). The involvement of pectin in Sr2+ biosorption by Azolla. Water, Air, and Soil Pollution 135: 195–205
Forni C., Giordani F., Pintore M. and Campanella L. (2008). Effects of Sodium Dodecyl Sulphate on the aquatic macrophytes Azolla and Lemna. Plant Biosystems 142/3: 665-668.
Tel-Or E. and Forni C. (2011). Phytoremediation of hazardous toxic metals and organics by photosynthetic aquatic systems. Plant Biosystems 145 (1): 224-235
Effects of treated industrial wastewaters and temperatures on growth and enzymatic activities of duckweed (Lemna minor L.).
No full textThe efficacy of the removal of contaminants from wastewater depends on physico-chemical properties of pollutants and the efficiency of treatment plant. Sometimes, low amounts of toxic compounds can be still present in the treated sewage. In this work we considered the effects of contaminant residues in treated wastewaters and of temperatures on Lemna minor L. Treated effluent waters were collected, analyzed and used as duckweed growth medium. In order to better understand the effects of micropollutants and seasonal variation, the plants were grown under ambient conditions for seven days in summer and winter. Relative growth rate, pigments and phenolic compounds concentrations were determined, as well as the activities of catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (G-POD) and polyphenol oxidase (PPO).
The pollutant concentrations varied in the two seasons, depending on the industrial and municipal activities
and efficiency of treatments. Treated waters contained heavy metals, nitrogenous and phosphorus compounds, surfactants and hydrocarbons. Compared to the control, duckweed growth of treated plants decreased by 25% in summer, while in the winter due to the lower temperatures and the presence of pollutants was completely impeded. The amounts of photosynthetic pigments of treated plants were not significantly affected in the summer, while they were higher than the control in the winter when the effluent had a high nitrogen amount. High CAT activity was registered in both seasons. Treated plants had significantly lower APX activity in the summer (53%) and winter (59%) respect to the controls. The observed inhibition of the peroxidase activities in the exposed plants, confirms the controversy existing in the literature about the variability of enzymatic response in stress condition
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Interaction of Ca2+ and Na+ ions with polygalacturonate chains: a molecular dynamics study
No full textPartially esterified polygalacturonic acid is the main component of pectin in higher plants. The carboxylic groups and their methyl esters markedly affect the ability of the pectin molecules to bind oppositely charged ions and to form gels. In order to make a contribution to the understanding of the mechanisms which regulate the ionic transfer at the soil root interface and in the apoplast, we report the results of a set of molecular dynamics experiments in which the interactions of four fully deprotonated fragments of polygalacturonic acid, each counting 12 units, 300 water molecules and 48 or 24 Na+ and Ca2+ ions were studied. We observed the formation of Ca2+ bridges between the polygalacturonate chains. The forces driving the aggregation processes are characterized by the formation of strong coulombic interactions between the metal ions and the carboxylate groups. The results are consistent with experiment evidence of the formation of Ca polygalacturonate organized gels. The Ca polygalacturonate complex exhibits a lower energy compared to that of Na polygalacturonate. The ratio of the Na+ and Ca2+ diffusion coefficients agree well with experimental reports
Interaction of Ca2+ and Na+ ions with polygalacturonic chains: a molecular dinamics study
No full textPartially esterified polygalacturonic acid is the main component of pectin in higher plants. The carboxylic groups and their methyl esters markedly affect the ability of the pectin molecules to bind oppositely charged ions and to form gels. In order to make a contribution to the understanding of the mechanisms which regulate the ionic transfer at the soil root interface and in the apoplast, we report the results of a set of molecular dynamics experiments in which the interactions of four fully deprotonated fragments of polygalacturonic acid, each counting 12 units, 300 water molecules and 48 or 24 Na+ and Ca2+ ions were studied.
We observed the formation of Ca2+ bridges between the polygalacturonate chains. The forces driving the aggregation processes are characterized by the formation of strong coulombic interactions between the metal ions and the carboxylate groups. The results are consistent with experiment evidence of the formation of Ca polygalacturonate organized gels. The Ca polygalacturonate complex exhibits a lower energy compared to that of Na polygalacturonate. The ratio of the Na+ and Ca2+ diffusion coefficients agree well with experimental reports
Molecular dynamics study of polygalacturonic acid chains in aqueous solution
No full textMolecular dynamics (MD) simulations were performed on a system consisting of polygalacturonic acid (PGA) chains. MD experiments were conducted both in vacuo and in the presence of water. The PGA chains were formed by 12 GalA units and each chain had a molecular weight of 2132. Three chains were enclosed in the simulation cells. NPT runs, carried out either in the absence and in the presence of water molecules, evidenced the collapse of the chains which aggregate due to the formation of hydrogen bonds. NVT trajectories performed in the presence of water molecules show that the solvent moves in channels which separate the PGA aggregates, These findings well agree with experimental results about gel formation by PGA and other pectins in strong acid media. (C) 1997 Elsevier Science Ltd.Molecular dynamics (MD) simulations were performed on a system consisting of polygalacturonic acid (PGA) chains. MD experiments were conducted both in vacuo and in the presence of water. The PGA chains were formed by 12 GalA units and each chain had a molecular weight of 2132. Three chains were enclosed in the simulation cells. NPT runs, carried out either in the absence and in the presence of water molecules, evidenced the collapse of the chains which aggregate due to the formation of hydrogen bonds. NVT trajectories performed in the presence of water molecules show that the solvent moves in channels which separate the PGA aggregates, These findings well agree with experimental results about gel formation by PGA and other pectins in strong acid media
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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