1,721,013 research outputs found
Advances in In Situ Biological and Chemical Groundwater Treatment
Full text linkGroundwater contamination generically refers to modifications in biological, physical, or
chemical characteristics; radioactivity; or the presence of undesirable solutes at significant
concentrations. In terms of undesirable solutes, inorganic or organic chemical mixtures frequently
occur, including metals and semi-metals, such as chromium and arsenic, and volatile chlorinated
hydrocarbons (e.g., tetrachloroethene, trichloroethene).
“Pump and treat” is a common method for cleaning up groundwater contaminated with
dissolved chemicals. Groundwater is pumped from wells to an above-ground treatment system that
removes the contaminants. Pump and treat may last from a few years to several decades, with the
actual cleanup time being long when the concentrations of the contaminants are high, the pollution
source has not been completely removed, or the groundwater flow is slow.
The increasing availability of scientific studies has progressively drawn attention to in
situ technologies for groundwater remediation. Most of them are innovative compared to the
pump-and-treat approach, allowing the remediation time to be reduced and the remediation
sustainability to be increased. In situ bioremediation of groundwater involves the encouragement
of indigenous bacterial populations to metabolize target contaminants through the addition of
various amendments, or the use of selected strains of bacteria in the subsurface to help treatment.
Bacteria perform coupled oxidation/reduction reactions to live, and bioremediation exploits all
these reactions to remove contaminants from groundwater. Aerobic bioremediation most commonly
takes place in the presence of oxygen, and it is most effective in treating non-halogenated organic
compounds. Anaerobic reductive bioremediation takes place in the absence of oxygen and promotes
the bioreduction of oxidized contaminants such as chlorinated solvents.
Microbes or their enzymes may also effectively remediate toxic heavy metal contamination via
their metal-resistance mechanisms, including the transformation of metals into less toxic species,
biosorption to the cell wall, entrapment in extracellular capsules, or precipitation.
Nanotechnology is a multidisciplinary field that has gained significant momentum in recent
years. The use of nanomaterials, such as zero-valent iron and carbon nanotubes, in the cleanup
of groundwater is relatively new and has a great potential for providing efficient, cost-effective,
and environmentally acceptable solutions to face the increasing requirements of stringent quality
standards. The large surface area of these nanoparticles results in high sorption capacity, along
with the ability to be functionalized for the enhancement of their affinity and selectivity. Nanoand
microplastics have received widespread attention in recent years as they can sorb various
organic contaminants
STUDIO DELLE EMISSIONI PRODOTTE DA COMBUSTIONE DI BIODIESEL E DI MISCELE BIODIESEL-GASOLIO
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In Water Markovnikov Hydration and One-Pot Reductive Hydroamination of Terminal Alkynes under Ruthenium Nanoparticle Catalysis
No full textIn the presence of Shvo's catalyst [2,3,4,5-tetraphenyl-1,3-cyclopentadien-1-ol, ruthenium(II) complex], a small quantity of aniline and TGPS-750-M surfactant, terminal alkynes were hydrated under microwave (MW) dielectric heating in water as solvent with high conversion and good yield. The reaction gives the Markovnikov product exclusively, unlike that commonly observed with ruthenium complexes. Under the influence of MWs, Ru nanoparticles embedded in the nanomicelle environment were formed, acting as the effective hydration catalyst. Introducing sodium formate in the aqueous phase and using a stoichiometric amount of amines, the Ru nanoparticle nanomicelle catalyst gave the first example of one-pot single-step hydroamination of alkynes with the formation of the corresponding secondary amines. The reaction is characterized by low environmental impact as TGPS-750-M is required in low amount, and organic solvents employed only for product separation or catalyst recycling
ERASE – ElectRode-Aided Soil rEmediation: prove a scala di laboratorio
No full textERASE - ElectRode-Aided Soil rEmediation è una tecnologia di bonifica basata sull’integrazione di meccanismi fisici, chimici e biologici indotti da una appropriata alimentazione di almeno una coppia di elettrodi installati in un mezzo poroso (terreno eterogeneo/materiali di riporto, in condizioni sature o insature) interessato da inquinamento chimico organico e/o inorganico. Nell’ambito dell’appalto del progetto POSIDON PCP sono state condotte numerose prove di laboratorio su terreni con differenti tessiture e in varie condizioni operative, utilizzando apparati 2D e 3D. Viene illustrata la prova di laboratorio conclusiva, condotta con l’apparato 3D, ove sono stati investigati i meccanismi elettrocinetici, di interesse per la rimozione dei metalli, contestualmente all'ossidazione chimica con persolfato attivato, di interesse per la degradazione in situ degli inquinanti organici. Il test ha mostrato che l’approccio è una valida opzione per il trattamento di terreni insaturi affetti da inquinanti organici e inorganici, estendendo le attuali esperienze di letteratura, focalizzate principalmente a terreni saturi a granulometria fine e contaminazione disciolta
Assessing the Risk of Wastewater Reuse in Agriculture: Is Irrigated Crops’ Food the main Exposure Route for Alkylphenols compared to Drinking Water?
Full text linkThe excessive exploitation and contamination of freshwater pose threats to public health, leading to cross-contamination among interconnected environmental compartments such as freshwater, soil and crops. In particular, contaminants of emerging concern (CECs) originating from human activities are not completely removed by wastewater treatments plants and the effluent discharged in surface waters as well as wastewater reuse determine their presence in drinking water (DW) sources, soil and crops intended for human consumption. Bisphenol A (BPA) and nonylphenol (NP) have been frequently detected in DW and food, namely the major exposure sources for humans, with adverse effect, respectively, on immune and renal systems. Currently, health risk assessments focus solely on individual exposure sources without considering the multiple exposure routes humans are exposed to. We propose an integrated approach to quantitatively assess health risk from CECs considering multiple exposure from both DW and food consumption across the relevant interconnected environmental compartments. This procedure was applied to BPA and NP to calculate their probabilistic Benchmark Quotient (BQ), demonstrating its ability to quantitatively apportion the risk between contaminants and exposure sources. Scenario analyses simulating BPA and NP reduction strategies were conducted, underscoring the quantitative risk assessment potential as a decision support tool for prioritizing mitigation actions. The estimated health risk from BPA was significantly higher compared to NP, with the consumption of food from edible crops posing a greater risk than tap water. Therefore, prioritizing mitigation actions for the prevention and removal of BPA from food would be more effective in minimizing the health risk
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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