1,721,060 research outputs found
Historical sedimentary trends of mercury and other trace elements from two saltmarshes of the Marano and Grado lagoon (northern Adriatic Sea)
No full textPurpose: Previous research conducted in the Marano and Grado Lagoon (northern Adriatic Sea) has shown that this environment has been affected by trace metal contamination, especially by mercury (Hg), from both industrial (the chlor-alkali plant) and mining activities (Idrija mine, Slovenia). Sediment cores were collected from two different saltmarshes of this lagoon environment to evaluate the degree of the anthropogenic enrichments and the historical geochronology of Hg.
Materials and methods: Core subsampling was performed by cutting 1-cm-thick slices at discrete intervals. Mercury determination was done differently from the other parameters in that the two long cores were subsampled at 1-cm intervals to obtain continuous concentration profiles. Samples were completely decomposed, using a mixture of mineral acids in a closed microwave system before being analysed for trace metal content using ICP-OES. Total Hg content in the solid-phase was determined by DMA-80. 137Cs was measured via gamma spectrometry. 210Pb activity was measured via alpha-counting of its daughter, 210Po, assuming secular equilibrium between the two isotopes.
Results and discussion: In saltmarsh sediments, Fe, Co, Li, Sc and V show no enrichment at both sites thus suggesting that they are essentially lithogenic elements. Conversely, enrichments are minimal (EF= <2) for As, Cd, Cr, Ni, Pb and Zn and moderate (EF= 2-5) for Cu and Mn and also for Pb and Zn but only in some levels of the sedimentary sequences. An exception is Hg, as expected due to the long-term input proceeding from the historical mining activity which has especially affected the eastern sector of the lagoon.
Conclusions: The core collected from the saltmarsh in the eastern lagoon (Grado) displays a better time resolution during the last century although the Hg background level has not been reached. Conversely, the core collected in the western sector (Marano) has recorded a longer and more complete history of Hg contamination, from the beginning of the height of Hg extraction activity at the Idrija mine (1850). Both salt marshes still receive Hg inputs and the sediment accumulation rates in the upper section appear to have increased over the last 10-20 years (from 0.30 to 0.45 cm y-1 at Marano and from 0.30 to 0.74 cm y-1 at Grado). Many of these morphological structures suffer erosive processes thus representing a potential source of contaminants associated with sediments, in particular Hg. Conservation and monitoring of saltmarshes should be taken into consideration also from this environmental point of view
Temporal variability of particle fluxes in an Arctic fjord (Kongsfjorden, Svalbard): biogeochemical characterization of the trapped material
No full textThis study is part of ARCA (Arctic: present Climatic change and pAst extreme events) Project, an interdisciplinary project funded by the Italian Minister of Education and Research (MIUR), aiming to cross-different area and intervention to gain a wider overview on the climate change.
The thesis concerns the analysis of a 6-year time series of particle fluxes in a small Arctic fjord of Svalbard (Kongsfjorden). Such information will be processed, and the data observed to date back to the sources. The nature of the particle supply allows us to understand the physical and biogeochemical dynamics of the inner fjord through which it will be possible to detect a potential correlation with the global change.
To improve the knowledge about this extreme environment, a mooring array (Mooring Dirigibile Italia) and long-term sediment traps were installed in the inner bay, since 2010.
A brief description of the study area and the framework of the thesis in terms of related research projects will be reported in Chapter 1, 2, 3. The methodologies for the preliminary treatment of the sediment trap samples and the processing of the dataset will be discussed in Chapter 4. Chapter 5 will summarize the thesis structure, and the results will be showed and discussed in Chapters 6 and 7 in the form of two main topics: the major source of particles and the mesozooplankton abundance, respectively. Finally, chapter 8 will report a final discussion highlighting the concluding remarks emerged by this research.
Chapter 6.
The Arctic Kongsfjorden, as many Svalbard’s fjords, experienced the climate warming with the ice-free and the retreat of glacier front. These phenomena lead to an increase in sediment supply. Continuous investigations for a long time series data collection are fundamental to understand the meteorological, biogeochemical and thermohaline dynamics inside the fjord. In 2010, the National Research Council, Institute of Marine Sciences (CNR – ISMAR) installed Mooring Dirigibile Italia in the inner fjord. An automatic sediment trap at the bottom depth was set for continuous investigations, together with current meters and thermometers at different depths. Our results suggest that, as the Arctic temperature rises in a warming scenario, the flux of glacier-derived material will increase accordingly. In particular, our time-series points towards the subglacial runoff driven by air temperature will be the dominant process affecting the glacier-fjord exchange of lithogenic material. Despite the light availability will likely increase due to the reduced sea-ice coverage, water column stratification modulated by the inflow of warm Atlantic waters will progressively increase and it will hamper the exchange of nutrients from the bottom waters. This, in turn, will severely reduce the biological production and in particular the primary productivity in the fjord. Concluding, this study highlighted the influence of the glaciers stress in Kongsfjorden. This forcing resulted to be more influent than other sources, such as the coastal debris runoff and the biological activity. As the melt-water supply in Kongsfjorden allows to an increase of settling particles, most of which lithogenic, it is predictable to expect an always greater input of them in the future, due to the global change.
Chapter 7.
The prerogative of our study is to have a continuous 6-year data set (2010 – 2016), showing the trend of zooplankton abundance and downward particles inside the fjord. The Mooring Dirigibile Italia have been deployed since September 2010 to May 2016 at 100m of water depth in the inner part of Kongsfjorden, Svalbard. Samples are collected from an automatic sediment trap set on it. The intact swimmers apparently enter actively in the sediment trap, so they cannot be considered in the passive flux. They are picked and identified at the order level to estimate their abundance over time. During May and June of each year, the maximum content of organic matter is recorded, symptom of a consistency with the solar activity. The δ13C variation indicated high contribution of marine organic matter in concomitance with the peaks of %OC. The Margalef index exhibited high values, sometimes reaching 1. This means that a discrete number of species per area occurs in Kongsfjorden, nevertheless it is an extreme environment. The trend in the abundance of the organisms is very heterogeneous over the time. The most abundant zooplankton group is Calanoida. At least five different groups occur in the samples, Calanus, Metridia, Aetideidae, Euchaetidae and Pseudocalanus, together with some unidentified specimen. The seasonal trend according to the annual Polar days and nights, show a high occurrence of Calanus sp., Appendicularians (Copelats) and Limacina Haelicina (Thecosomats) in the darkness periods. Rather, Amphipods, Euphausiids, Anellids and Chaetognaths abound during the light months. Even though the number of zooplankton in terms of flux should not be representative of the real abundance in the water column, our results provide useful information on seasonal and inter-annual variations of the epi-pelagic fauna composition in Kongsfjorden, Svalbard. The results revealed that solar irradiance, sea ice cover, turbidity and hydrodynamics, affect directly and indirectly on the marine biosphere, above all in a vulnerable region like the Arctic. The great amount of freshwater in summer makes the biological pump hard to work, with shifted time of phytoplankton bloom and cascading consequences on the primary consumers, and the subsequent trophic chain. Hence, the affecting stressors on the fitness of the individuals in Kongsfjorden are different. Concluding, the results show a changing in the magnitude of the species, due to the alteration of the ecological equilibrium of their niches. This is a good point since pelagic communities are mostly consumed by Arctic cod, tern and seal
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Planktonic foraminifera response to the azores high and industrial-era global warming in the central-western Mediterranean Sea
Full text linkThe Mediterranean Sea is warming about 20 % more rapidly than global ocean and this phenomenon is
impacting ecosystems and biodiversity. Planktonic foraminifera are an important component of surface and
subsurface water ecosystems and food chains. Their species communities have been altering across the oceans
since the Industrial Era, in response to the ongoing climate change, especially in the western Mediterranean Sea,
where a significant productivity decrease has been recently reported.
Here we show planktonic foraminifera and multispecies stable isotopes from three short sediment cores,
recovered on the eastern flank of the Sicily Channel, central Mediterranean Sea. Results fully confirm the
planktonic foraminifera productivity decrease in the Industrial Era, which is especially relevant for the second
half of the 20th century. The planktonic foraminifera productivity decrease matches with a higher number of
Large Azores High events, i.e., the establishment of an exceptional and persistent winter atmospheric highpressure ridge over the western-central Mediterranean Sea. This is an unprecedented atmospheric phenomenon for the last millennia Mediterranean Sea history, as a direct response of the global warming. Surface productivity and DCM species are especially declining since ~1960 CE, at expenses of winter mixed layer taxa,
suggesting that the Azores High activity prevents a sustained water column vertical mixing and surface water
nutrient fuelling. Our results document and confirm that the climate change has already been affecting Mediterranean marine ecosystems and the basic level of the trophic chain, by extending the surface water stratification period
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