1,720,969 research outputs found
Searching nanoplastics: From sampling to sample processing
No full textNanoplastics (NPs) are considered emerging pollutants, namely unregulated contaminants whose toxic effect on humans and the environment has been demonstrated or suspected. They are the result of the physical fragmentation of the plastics that over time reach smaller dimensions (<100 nm). The issues related to the characterization and quantification of NPs in the environmental matrices are mainly related to the infinitesimal size, to the fact that they are found in bulk, and to the different physico-chemical forms in which the same polymer can evolve over time by degradation. To deal with the study of a new class of pollutants it is necessary to assess the entire analytical method, carefully considering every single step (sampling, cleanup, qualitative, and quantitative analysis) starting from the validation method in the laboratory. This paper reviews the analytical method steps, focusing on the first ones, which the current literature often underestimates: laboratory tests, sampling, and sample processing; in fact, most errors and the quality of the analyses often depend on them. In addition, all newly introduced sample processing methods were examined
Inquinanti organici nel particolato aerodisperso e nelle dust raccolte in parallelo in un appartamento
No full textParticolato aerodisperso e polveri di deposizione (dust) forniscono un importante contributo ai
livelli di esposizione agli inquinanti negli ambienti interni. Campioni di PM2.5 e dust sono stati
raccolti contemporaneamente in due ambienti di un appartamento in primavera ed inverno e la
frazione organica è stata caratterizzata quali/quantitativamente per accrescere le informazioni sulla
presenza di microinquinanti convenzionali e sviluppare conoscenza riguardo ai contaminanti
emergenti. Allo scopo, si è utilizzata la gascromatografia accoppiata alla spettrometria di massa ad
alta risoluzione e massa accurata (GC-HRAM-MS). Ancora, sono state studiate le relazioni esistenti
tra le composizioni delle polveri sospese e del dust.
Relativamente agli alcani e agli IPA, i dati indicano che le sorgenti individuate, sebbene situate in
uno solo dei locali esaminati, propagano i loro effetti anche al resto della casa e gli ambienti adiacenti
possono risultare più inquinati del sito ospitante la sorgente se scarsamente ventilati e soggetti a
fenomeni di accumulo. Riguardo gli ftalati, si sono notate ampie variazioni di concentrazione nel
tempo e nello spazio, probabilmente riconducibili alla marcata localizzazione della ricaduta delle
emissioni dovute all’utilizzo di prodotti o oggetti di uso quotidiano, che sembrano impattare più che
le sorgenti diffuse quali l’intrusione dall’esterno. Il confronto tra campioni di dust prelevati
simultaneamente da superfici diverse conferma l’importanza della normalizzazione della superficie
di raccolta per eliminare la variabilità associata all’assorbimento o emissione degli inquinanti dai
materiali nel punto di prelievo, quantunque di questo aspetto occorre tenere conto quando si vogliano
valutare i reali livelli di esposizione degli abitanti. L’analisi GC-HRAM-MS ha evidenziato con un
ampio margine di probabilità la presenza di interferenti endocrini e contaminanti emergenti,
confermandone l’importante diffusione in ambiente indoo
Determination of fragrances in interiors
No full textFragrances and essences (F&Es) have nowadays ascertained as contaminants of interiors, due to the
wide presence of these chemicals in personal care and house product formulas [1, 2]. Indeed, their
occurrence has been demonstrated in the air of homes and cars as well as of public premises like
schools, universities and hospitals. Despite their worldwide use, fragrances belong to the class of
emerging organic contaminants, also known as endocrine disruptors. In fact, though F&Es do not
seem to display carcinogenic properties, however they can give raise to long- and short-term health
problems, e.g. inflammation of skin, eyes and throat, allergies, and even heart, metabolism and brain
difficulties as well as gene damaging [3, 4]. Most F&Es are semi-volatile and exist overall as vapours,
nonetheless they have been observed also in airborne particulates (PM10, PM2.5) and in deposition
dusts of interiors; that worsens the exposure of humans to these chemicals, because it is not restricted
to inhalation but depends also on ingestion and contact paths. On the other hand, that makes necessary
to collect both gas and particle fractions to draw information about the impact of F&E in indoor
environment; that can be achieved by using filter-cartridge trains able to retain quantitatively the
targeted compounds. As for analytical procedures, usually they consist of solvent extraction/thermosdesorption coupled with GC-MS detection.
A dedicated procedure was optimized to determine the concentrations of F&Es in the interiors.
Airborne particles (PM2.5) were collected on PTFE membranes, while the gas fraction was retained
on XAD-2 cartridges. The analytes were recovered from XAD-2 through elution with acetone, and
from filters through extraction in ultrasonic bath; after solvent reduction, F&Es were determined
through GC-MSD operated in SIM mode. The recovery efficiency, LoD and LoQ values were
evaluated. The procedure was applied to a set of samples collected in two locations, which confirmed
the occurrence of F&Es in the interiors as well as outdoors.
[1] J. P. Lamas, L. Sanchez-Prado, C. Garcia-Jares, M. Llompart, J. Chromatog. A, 2010, 1217,
1882–1890.
[2] M. Fontal, B. L. van Drooge, J. O. Grimalt, J. Chromatog. A, 2016, 1447, 135–140
[3] E. Uhde, N. Schulz, Atmos. Environ., 2015, 106, 492-502
[4] P. Wolkoff, G. D. Nielsen, Environ. Int., 2017, 101, 96–107
Performance evaluation of a very-low-volume sampler for atmospheric particulate matter
Full text linkA cheap and small device for sampling atmospheric particulate matter (PM) has been recently developed. It works at a very low flow rate (0.5 L min–1) and is able to collect the atmospheric aerosol on filters, allowing subsequent chemical analyses. The samplings have a long duration (1–2 months), and the devices can be used to make cheap networks over a territory. These very-low-volume samplers (VLVS) can be used to trace long-term concentration variations and to draw up concentration maps of PM and its chemical components. The performance of the VLVS was evaluated in terms of measurement repeatability and of agreement with the results obtained when using a 2.3 m3 h–1 reference sampler (REF). The study period was 1 year. The considered PM components were ions, polycyclic aromatic hydrocarbons (PAHs), levoglucosan and elements. The repeatability of the measurements was very good for all the examined PM components: the standard deviation of 3 replicates (co-located samplers) over 9 measurement periods was in the range 2.0–5.5% for ions, 10–17% for PAH, 5.2% for levoglucosan and 5.6–16% for elements. It was 8.2% for the PM mass concentration. This satisfactory performance indicates that the VLVSs can be reliably used to evaluate the spatial variability and to draw concentration maps of PM and PM components. A very good agreement with the reference sampler was obtained for ions, with the only exception of ammonium nitrate and ammonium chloride (VLVS values were up to 10–20% lower than the reference values), levoglucosan and elements. In the case of PAH, instead, the ratio VLVS/REF was in the range 1.2–1.6 for 4-ring congeners and 0.4–0.8 for 5-and 6-ring congeners. For all the congeners, anyway, these typical ratios were kept, with small variations, during the whole study period
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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