1,721,026 research outputs found
Gas-particle concentration and distribution of n-alkanes and polycyclic aromatic hydrocarbons in the atmosphere of Prato (Italy)
No full textAir samples were collected in an urban and industrialised area of Prato (Italy) during 2002, as part of a study to identify and measure
aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). Total concentrations of aliphatic hydrocarbons ranged between 170 and 282 ng m3 in the gas phase and from 48.9 to 276 ng m3 in the particulate phase. The average total PAH oncentrations
(gas + particulate) were 59.4 ± 26.5 ng m3, and both gas and particulate phase PAH concentrations decreased with increasing temperature. Source identification using diagnostic ratios and principal component analysis identified automobile traffic, in particular, the strong influence of diesel fuel burning, as the major PAH source. Gas-particle partition coefficients (Kp’s) of n-alkane and PAHs were well correlated with the sub-cooled liquid vapour pressure P0L and indicate stronger sorption of PAHs to aerosol particles compared with -alkanes
Enrichment of organic pollutants in the sea surface microlayer (SML) at Terra Nova Bay, Antarctica: influence of SML on superficial snow composition.
Full text linkConcentrations of dissolved and particle-associated n-alkanes, phthalates and polycyclic aromatic
hydrocarbons (PAHs) were measured in sea surface microlayer (SML) and sub-surface water (SSL) samples
collected in the coastal area of Terra Nova Bay, Antarctica, during the Austral spring 1998/1999. SML
concentrations of the selected organic compounds were higher than SSL values and the enrichment factors
were greater in the particulate phase than in the dissolved phase. During the same campaign, ‘‘fresh’’ snow
samples, collected at different altitudes (from sea level up to 2670 m) near the coast on Mt Melbourne,
immediately after a snowy event, were analysed in order to provide more information on air/sea exchange
processes. The same classes of organic compounds found in sea water were also present in ‘‘fresh’’ snow
samples. The surfactant fluorescent organic matter (SFOM), adsorbed on the microdrop aerosol surface,
could be considered the main constituent of the enrichment and the carrier at higher altitudes of organic
compounds. In fact, hydrocarbons (n-alkanes and PAHs), which are not surfactants like phthalates, could
interact with SFOM and follow the same fate
Occurence of legacy and emerging persistent organic pollutants at the Ross Sea and circumpolar deep water convergence (Antarctica)
Full text linkPersistent organic pollutants (POPs) have attracted the attention of scientists and policy makers in recent decades due to their extreme persistence, semi-volatility, capacity to bio-accumulate in the food chain, and toxic
properties. Despite its geographical isolation, extreme meteorological conditions and an almost total absence of local point sources, the Antarctic continent is vulnerable to contamination by POPs, due to the ability of these
chemicals to undergo long range atmospheric transport (LRAT) and deposition in the open sea. In a few cases and for limited areas, POPs may be also introduced into the Antarctic ecosystem by human activities (scientific
stations, fishing, tourism, accidental oil pills, waste incineration and sewage).
Even if various studiesi.e.1,2,3,4,5 have revealed the presence of POPs in air, seawater, sediments and biota in Antarctica, more investigations are needed to implement the number of observations, integrate the data series
and meet the indications of the Stockholm Convention and the UNECE protocol in terms of improving knowledge of the temporal and spatial trends of POPs in biotic and abiotic environmental compartments.
In this study we present POP concentrations in water samples collected along vertical water columns from seven oceanographic stations located in the Ross Sea and close to the Circumpolar Convergence (see Figure 1).
Moreover, the occurrence of emerging and legacy POPs, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated naphthalenes (PCNs), organochlorine pesticides (OCPs) and
polybrominated diphenylethers (PBDEs) were investigated in order to evaluate their possible sources and relationship with physical and biological processes taking place in the water column.
The Ross sea is the formation site of two shelf waters which constitute an important part of the Antarctic Bottom Water (AABWs): the High Salinity Shelf Water (HSSW), which is relatively cold and generated inside the Ross
Sea basin and the Ice Shelf Water (ISW). The Ross sea is influenced by only one water mass of external origin,
the Circumpolar Deep Water (CDW), which is the largest circulation feature of the Southern Ocean, manly responsible for possible exchange processes between the Antarctic seas and the outer oceans, and thus a possible
source of persistent organic pollutants (POPs)2
.
The CDW is a relatively warm, salty and nutrient rich water mass carried around Antarctica by the Antarctic Circumpolar Current (ACC)6. Associated with the ACC is the Antarctic Convergence where the cold Antarctic
waters meet the warmer waters of the subantarctic creating a zone of upwelling nutrients. Moreover, the Drygalski Glacie Tongue plays an important role in the Polynya development in the Terra Nova Bay, in the Ross
sea. An important environmental concern is the accelerated glacier and snow melting that represent a massive release of both naturally occurring chemical substances and organic/inorganic pollutants of anthropogenic origin, which are stored in the deeper layers of the ice and may be delivered to surrounding ecosystems
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
The use of levoglucosan for tracing biomass burning in PM2.5 samples in Tuscany (Italy)
No full textLevoglucosan was present in all samples and its concentrations showed a pronounced annual cycle with maximum levels in the cold season. The annual percentage of ratios of levoglucosan to OC ranged from 0.04 to 9.75% evidencing a major contribution of biomass burning to the aerosol OC during the winter. In the urban-background site, OC was strongly correlated with EC in winter, suggesting that the major fraction of OC was generated as primary particles along with EC. A background levoglucosan component
showed that biomass burning was continuously taking place in all the investigated sites. The biomass burning contribution to the Tuscany aerosol was made up of a background component and an additional component during winter probably due to wood burning for domestic heating
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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