1,720,959 research outputs found
Impact of a European directive on ship emissions on air quality in Mediterranean harbours
No full textShips have been found to be major sources of air pollution in harbours. However, from January 1, 2010, a
European Union directive requires that all ships at berth or anchorage in European harbours use fuels with
a sulphur content of less than 0.1% by weight while previously, outside of Sulphur Emission Control Areas,
up to 4.5% were allowed. The impact of this directive on air quality in some Mediterranean harbours was
investigated based on observations made from August to October 2009 and 2010 at a monitoring station
placed on a cruise ship, Costa Pacifica, following a fixed weekly route in the Western Mediterranean. The
concentrations of SO2 were found to decrease significantly from 2009 to 2010 in three out of the four EU
harbours; the average decrease of the daily mean concentrations in the different harbours was 66%. The
decrease of SO2 was not statistically significant in the harbour of Barcelona because of large day-to-day
variations, however measurements from monitoring stations in the harbour zone of Barcelona as well as
downwind of the harbour of Palma de Mallorca confirm a strong decrease in the SO2 concentrations from
2009 to 2010. No decrease was observed in the non-EU harbour of Tunis. Neither NOx nor BC
concentrations showed significant changes in any of the harbours
An integrated PM2.5 source apportionment study: Positive Matrix Factorisation vs. the Chemical Transport Model CAMx
No full textReceptor and Chemical Transport Models are commonly used tools in source apportionment studies, even if different expertise is required. We describe an experiment using both approaches to apportion the PM2.5 (i.e., particulate matter with aerodynamic diameters below 2.5 m) sources in the city of Genoa (Italy). A sampling campaign was carried out to collect PM2.5 samples daily for approximately six month during 2011 in three sites. The subsequent compositional analyses included the speciation of elements, major ions and both organic and elemental carbon; these data produced a large database for receptor modelling through Positive Matrix Factorisation (PMF). In the same period, a meteorological and air quality modelling system was implemented based on the mesoscale numerical weather prediction model WRF and the chemical transport model CAMx to obtain meteorological and pollutant concentrations up to a resolution of 1.1 km. The source apportionment was evaluated by CAMx over the same period that was used for the monitoring campaign using the Particulate Source Apportionment Technology tool. Even if the source categorisations were changed (i.e., groups of time-correlated compounds in PMF vs. activity categories in CAMx), the PM2.5 source apportionment by PMF and CAMx produced comparable results. The different information provided by the two approaches (e.g., real-world factor profile by PMF and apportionment of a secondary aerosol by CAMx) was used jointly to elucidate the composition and origin of PM2.5 and to develop a more general methodology. When studying the primary and secondary components of PM, the main anthropogenic sources in the area were road transportation, energy production/industry and maritime emissions, accounting for 40% - 50%, 20% - 30% and 10% - 15%, of PM2.5, respectively
Source apportionment of PM10 in the Western Mediterranean based on observations from a cruise ship
No full textCosta Pacifica during cruises in theWestern Mediterranean. Samples, mainly collected on an hourly basis,
were analysed with different techniques (Particle Induced X-Ray Emission, PIXE; Energy Dispersive - X
Ray Fluorescence, ED-XRF; Ion Chromatography, IC; Thermo-optical analysis) to retrieve the PM10
composition and its time pattern. The data were used for obtaining information about the sources of
aerosol, with a focus on ship emissions, through apportionment using chemical marker compounds,
correlation analysis and Positive Matrix Factorization (PMF) receptor modelling. For the campaign in
2010, 66% of the aerosol sulphate was found to be anthropogenic, only minor contributions of dust and
sea salt sulphate were observed while the biogenic contribution, estimated based on the measurements
of MSA, was found to be more important (26%), but influenced by large uncertainties. V and Ni were
found to be suitable tracers of ship emissions during the campaigns. Four sources of aerosol were
resolved by the PMF analysis; the source having the largest impact on PM10, BC and sulphate was
identified as a mixed source, comprising emissions from ships. The correlations between sulphate and V
and Ni showed the influence of ship emissions on sulphate in marine air masses. For the leg Palma
eTunis crossing a main ship route, the correlations between aerosol sulphate and V and Ni were
particularly strong (r2 1⁄4 0.9 for both elements
Size-resolved comprehensive characterization of airborne particulate matter
No full textAn update of a methodology to extract both the size-segregated source apportionment of atmospheric aerosol and the size distribution of each detected element or compound, is presented. The approach is based on the parallel use of standard low-volume samplers to collect particulate matter (PM) and of an Optical Particle Counter (OPC). The methodology was introduced and validated in previous works for the average size distribution of elemental components of PM: it has now been extended to PM compounds such as ions and carbonaceous aerosol (namely, organic end elemental carbon, OC and EC). Furthermore, the methodology has been now adopted in the frame of a field campaign, proving that it is able to provide not only an average size distribution but also information on the time evolution of the size distribution of specific PM species. Samples were collected in the urban area of Genoa (Italy) and their composition was measured by Energy Dispersive X-ray Fluorescence (ED-XRF), Ion Chromatography (IC) and Thermo-optical analysis. Positive Matrix Factorization (PMF) was applied to time series of daily concentration values in PM10 and PM2.5 (i.e. fraction of PM mass with aerodynamic diameter lower that 10 mu m and 2.5 mu m, respectively) to identify major PM sources, and both PM mass concentration and size-segregated particle number concentration were apportioned. Seven and six sources were respectively resolved in PM10 and PM2.5, with processes related to secondary aerosol formation accounting for about 53% and 57% of PM levels in the two fractions. The new methodology is complementary to size-segregated PM sampling, and it was actually tested against a 13-stage nanoMOUDI cascade impactor. Size distributions obtained with the new methodology and directly measured by the nanoMOUDI turned out to be in good agreement (R-2 > 0.60) with discrepancies observed for SO42- only
A multi-wavelength optical set-up for the characterization of carbonaceous particulate matter
No full textWe introduce a simple, fully automatic, multi-wavelength and non-destructive optical system, namely a Multi-Wavelength Absorbance Analyzer (MWAA), to measure off-line the light absorption in Particulate Matter (PM) collected on filters and hence to derive the black and brown carbon content in the PM. This gives the opportunity to measure in the same sample the concentration of PM mass by gravimetric analysis, black and brown carbon, elements by, for instance, X Ray Fluorescence, and finally ions by Ion Chromatography. Furthermore, the multi-wavelength analysis gives the possibility to apportion black and brown/organic carbon sources through the direct determination of the Angstrom exponent and a revised version of the so-called “the aethalometer method”. Up to 16 samples can be analyzed in sequence and in an automatic and controlled way within a few hours. The filter absorbance measured by MWAA was successfully validated both against a MAAP and a polar photometer. Our MWAA was used in several field campaigns with PM2.5 (PM with aerodynamic diameter less than 2.5 μm) samples collected on quartz fiber filters, and the mass absorption cross section at λ=405, 635 and 850 nm was obtained measuring at the same time the EC in particulate matter samples by thermal-optical analysis using the EUSAAR_2 protocol. First results on the MWAA application to the analysis of size-segregated samples collected by multi-stage impactor are also shown
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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