1,720,964 research outputs found
Studio della composizione chimica del particolato atmosferico negli ambienti confinati e valutazione delle relazioni con la composizione del particolato negli ambienti esterni
No full textChemical characterization of indoor and outdoor fine particulate matter in an occupied apartment in Rome, Italy
No full textThe daily concentration and chemical composition of PM2.5 was determined in indoor and outdoor 24-h samples simultaneously collected for a total of 5 weeks during a winter and a summer period in an apartment sited in Rome, Italy. The use of a specifically developed very quiet sampler (<35 dB) allowed the execution of the study while the family living in the apartment led its normal life. The indoor concentration of PM2.5 showed a small seasonal variation, while outdoor values were much higher during the winter study. Outdoor sources were found to contribute significantly to indoor PM concentration especially during the summer, when the apartment was naturally ventilated by opening the windows. During the winter the infiltration of outdoor PM components was lower and mostly regulated by the particle dimensions. Organics displayed In/Out ratios higher than unity during both periods; their indoor production increased significantly during the weekends, where the family stayed mostly at home. PM components were grouped into macrosources (soil, sea, secondary inorganics, traffic, organics). During the summer the main contributions to outdoor PM2.5 came from soil (30%), secondary inorganics (29%) and organics (22%). Organics dominated both indoor PM2.5 during the summer (60%) and outdoor and indoor PM2.5 during the winter (51% and 66%, respectively)
Particulate matter concentration and chemical composition in the metro system of Rome, Italy
No full textAir quality at the main station of the metro system of Rome (Termini hub) has been characterized by the point of view of particulate matter (PM) concentration and chemical composition. Indoor air in different environments (underground train platform and shopping center, metro carriages with and without air conditioning system) has been studied and compared with outdoor air at a nearby urban site. Air quality at the railway station, located outdoor at surface level, has been also considered for comparison. PM chemical characterization included ions, elemental carbon, organic carbon, macro-elements, and the bio-accessible and residual fractions of micro- and trace elements. Train platform and carriages without air conditioning resulted to be the most polluted environments, with indoor/outdoor ratio up to two orders of magnitude for many components. PM mass concentration was determined on filter membranes by the gravimetric procedure as well as from the optical particle counter (OPC) number concentration measurements. The OPC results, taken with the original calibration factor, were below 40 % of the value obtained by the gravimetric measurements. Only a chemical and morphological characterization of the collected dust could lead to a reconciliation of the results yielded by the two methods. Macro-components were used to estimate the strength of the main macro-sources. The most significant contribution is confirmed to derive from wheels, rails, and brakes abrasion; from soil re-suspension (over 50 % at the subway platform); and from organics (about 25 %). The increase in the concentration of elements was mostly due to the residual fraction, but also the bio-accessible fraction showed a remarkable enrichment, particularly in the case of Ba, Zn, Cd, and Ni
Thermal stability of inorganic and organic compounds in atmospheric particulate matter
No full textThe thermal behaviour of atmospheric particulate matter (PM) has been investigated by using different analytical approaches to explore the added value offered by these technique in environmental studies. The thermogravimetric analysis (TGA), carried out on both certified material and real PM samples, has shown that several mass losses can be detected starting from 80 degrees C up to above 500 degrees C, when pyrolysis occur. Thermo-optical analysis of PM and ion chromatographic analysis of the residual have shown that the mass losses in the temperature range 80-180 degrees C are not justified by the release of either organic or inorganic compounds; it can be thus attributed to the release of weakly and strongly bound water. Release of water has also been evidenced in the temperature range 225-275 degrees C. The release of ammonium chloride and nitrate has been detected only above 80 degrees C. This indicates that the release of nitric acid, hydrochloric acid and ammonia, which is observed downstream of the filters during the sampling of atmospheric PM at ambient temperature, cannot be reproduced off-line, after the end of the sampling. We successfully explored one of the possible explanations, that is the desorption of HNO3, HCl and NH3 adsorbed on collected particles. NH4NO3 and NH4Cl which can be thermally released by the filter, exhibit a different thermal behaviour from NaNO3 and NaCl, which are thermally stable up to 370 degrees C. This different behaviour can be used to discriminate between natural and secondary sources of atmospheric inorganic salts, as the interconversion that is observed when heating mixtures of pure salts resulted to be not relevant when heating real PM samples. (C) 2012 Elsevier Ltd. All rights reserved
Influenza del riscaldamento domestico a legna sulle concentrazioni e sulla composizione di PM10 e PM2.5 in ambiente indoor
No full textIn questo lavoro vengono discussi i risultati di uno studio volto a valutare il contributo del riscaldamento domestico a biomasse all’inquinamento indoor. La campagna di misura, della durata di 15 gg, ha coinvolto 2 abitazioni poste in area periurbana (ca. 30 Km da Roma), riscaldate rispettivamente mediante un termo-camino a legna ed una stufa a pellet. Il PM10 e il PM2.5 sono stati campionati parallelamente all’interno ed all’esterno delle abitazioni e sono state effettuate analisi di macro-componenti (macro-elementi, EC, OC, ioni) e di elementi in traccia. Parallelamente sono state effettuate misure ad elevata risoluzione temporale mediante un contatore ottico (OPC) ed un campionatore PILS (Particle Into Liquid Sampler) appositamente modificato per permettere la misura delle concentrazioni elementari con risoluzione temporale di 10 minuti.
Seppure le concentrazioni di PM non mostrino variazioni particolarmente significative tra le due abitazioni, è stato osservato un aumento della concentrazione di PM (10-15%) in corrispondenza delle operazioni di pulizia e raccolta delle ceneri. Le analisi chimiche hanno mostrato che questo incremento è dovuto principalmente a materiale organico ed a particelle ricche di metalli. Questi eventi di breve durata sono stati ulteriormente caratterizzati mediante le misure ad elevata risoluzione temporale, che hanno evidenziato un forte incremento (più di un ordine di grandezza) delle concentrazioni di PM10 e PM2.5 durante le operazioni di manutenzione della stufa a pellet (aspirazione di ceneri e residui attraverso l’utilizzo di un aspiracenere provvisto di filtro di abbattimento). Le analisi elementali dei campioni PILS hanno mostrato picchi di concentrazione particolarmente significativi per Li, K, Ca, Ti, Mn, Cu, As, Rb, Sr, Mo, Cd, Sn, Sb e Te.
Un comportamento simile è stato osservato durante le operazioni di pulizia del termo-camino, effettuata rimuovendo manualmente la cenere, anche se, in questo caso, l’incremento di PM2.5 è risultato meno significativo. L’analisi elementare ha mostrato una differente composizione delle polveri, meno ricche di metalli pesanti; gli elementi che hanno avuto un incremento significativo sono stati in questo caso Mg, K, Ca, Mn, Rb, Sr e Pb. La diversa distribuzione dimensionale e la composizione elementale delle ceneri prodotte è probabilmente dovuta alla diversa qualità dei materiali combustivi e alle diverse condizioni di combustione, meno completa nel caso del termo- camino. I risultati ottenuti mostrano come l’utilizzo di legna per il riscaldamento domestico possa influenzare le concentrazioni indoor del PM, introducendo anche specie potenzialmente tossiche ad elevato contenuto di metalli pesant
Influence of advanced wood-fired appliances for residential heating on indoor air quality
No full textThis work was aimed at studying particulate matter (PM) in the indoor atmosphere of two flats where airtight biomass systems were used for domestic heating. PM10 and PM2.5 samples were collected by means of nine parallel sampling units, located in the outdoor and indoor areas of each flat. The samples were analyzed for PM macro-components (organic carbon, elemental carbon, macro-elements and inorganic ions) and for the soluble and residual fractions of micro-elements; the influence of the main PM sources on the indoor air quality was evaluated. The results confirm that infiltration from outdoor represents the main source of fine particles, while dust re-suspension, enhanced by the movements of the inhabitants, is one of the most important sources of coarse particles. Biomass-fueled heating systems are a significant source of indoor pollution, mainly due to the cleaning operations required for the removal of residual ash, which release particles in both the fine and the coarse size range. The impact of these operations resulted in indoor to outdoor ratios higher than one for most of the considered PM components. Very high amounts of copper and manganese, elements likely involved in the generation of oxidative stress, were released into the environment during ash removal from the pellet stove. Although this operation was very limited in time (about 15 min), the average concentration of Cu and Mn in PM10 and PM2.5 during the study period (18 days) was more than six times (Cu) and about twice (Mn) the concentration values measured outdoors. © 2018 Elsevier Lt
Thermal behaviour of water and inorganic ions in particulate matter
No full textThermal analysis have widely been used for the
characterization of various materials, but only few
studies concern its application to atmospheric particulate
matter (Matuschek et al., 2004; Duarte and Duarte,
2008). All these studies are focused on the identification
or quantification of desorbed organic species.
Among inorganics, the species that are expected to
thermally desorb from PM are ammonium salts and
water. Ammonium salts are subjected to solid/vapour
equilibria that are responsible for one of the main
artefacts in PM determination. The extent of these
artefacts has been proved to be influenced by water
vapour, which may be absorbed on particles. In the
scientific literature, however, only a few and contrasting
results have been reported about the analytical
determination of water in PM samples, and they have
been mostly obtained by the Karl Fischer method (Otha
et al., 1998; Tsai and Kuo, 2005).
In this work, the thermal behaviour of water and
ammonium salts has been examined under controlled
conditions, with the purpose of exploring the potential of
thermogravimetry and thermal desorbtion techniques
with respect to both the analytical determination of water
and the study of sampling artifacts mechanisms.
The themogravimetric curves of reference materials
NIST 1648 and NIST 1649a (figure 1) show, as
expected, different steps of mass loss. In the range from
25°C to 180°C a loss of ca. 6% (6.3% for NIST 1648
and 4.9 % for NIST 1649a) in two steps has been
evidenced. These losses have been assigned,
respectively, to weakly and strongly bounded water by
using hyphenated TG-MS and TG-FTIR and by carrying
out the chemical analysis of the residual obtained after
heating at different temperatures. Although the method
needs further validation, the thermo-gravimetric
determination of PM water content seems to be a
convenient alternative to the use of Karl Fischer method.Despite the evidence of ammonium salts evolution
during the sampling at ambient temperature, the loss of
ammonium salts from reference materials starts above
180°C and the residual concentrations of nitrate, chloride
and ammonium become negligible at about 310°C. Mass
loss registered by the TG analysis in the 180-310 °C
range is 7.2% for NIST 1648 and 7.9 % for NIST 1649a.
This loss is partially due to inorganic salts (i.e. for NIST
1648: ammonium 1.8%, nitrate ca. 1,1%, chloride 0.3%
and sulfate, that partially decomposes to SO2, ca. 1.1%)
and partially to organic matter. The latter has been
estimated to be about 2.5% by EC/OC thermoanalysis
carried out in the same temperature range.
Similar results have been obtained also on real PM10
samples collected on Teflon membranes at an urban site
in Rome, Italy. Even though the presence of the filter
causes a worsening of signal to background ratio, also in
this case water loss at T<120 °C may be measured with
sufficient repeatability (about 10% on pairs of equivalent
samples).
In the case of real PM samples, all the other release
processes occur at lower temperatures than in the case of
NIST (about 60°C less). The reasons for this behavior
are not clear, but it is reasonable to hypothesize that the
aging of dust plays a significant role. Anyway, no
significant losses of inorganic ions and OC can be
detected below 120°C, in contrast with the usual
behaviour observed during the sampling phase (negative
artifact due to the release of ammonium salts).
About 80% of the mass losses in the range 120-
250°C were due to inorganic ions and OC. After heating
up to 250°C ammonium concentration was always below
15% of the initial value, while nitrate and chloride
residual amounts strongly depended on the nature of
collected PM and were much higher in case of high
contribution of natural dust (sea-salt and soil
contributions). This residual nitrate and chloride
concentrations remain constant also after further heating
and are probably associated with sodium salts.
This work was supported by private fundings
Duarte, R.M.B.O. and Duarte A.C. (2008) Atmos.
Environ. 42, 6670–6678.
Matuschek, G., Saritas, Y., Karg, E., Schroeppel, A.
(2004) J. Therm. Anal. Cal. 78, 575–586.
Ohta, S., Hori, M., Yamagata, S., Murao, N. (1998)
Atmos. Environ. 32, 1021-1025.
Tsai, Y.I., Kuo, S.C. (2005) Atmos. Environ. 39, 4827–
4839
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
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