1,721,053 research outputs found
Platform-Basins relationships in the Norian of the Carnia Region (NE Italy)
No full textCarulli G.B., Longo Salvador G., Podda F., Ponton M. Platform-Basins relationships in the Norian of the Carnia Region (NE Italy). In: Géologie Méditerranéenne. Tome 21, numéro 3-4, 1994. Perimediterranean carbonate platforms. First International Meeting. Marseille – France (5-8 septembre 1994) sous la direction de Jean-Pierre Masse. pp. 27-30
Environmental mineralogy in the mining area of Montevecchio Ponente (SW Sardinia)
No full textThe Montevecchio mining area (Arbus – Guspini, Sardinia SW) has been exploited for centuries, for the
extraction of lead and zinc minerals.
The following work focuses on the study and characterization of the sources and contaminants present in
the “Cantieri Sanna” from the area of Montevecchio Ponente.
There is a large amount of mining residues in the area downstream of the washing plants, affected by
important erosion phenomena, which involve a solid transport of contaminants in solution.
These mineral residues were characterized by diffractometric (XRD) and chemical analysis (ICP-MS), after
their solubilization. The whitish biomineral patinas present along the Rio Roia Cani were also analyzed by
means of diffractometric analysis and a scanning electron microscope (SEM).
From the analysis carried out, the presence of secondary phases emerged, such as: epsomite, glaucocerinite,
goethite, hydroxyapatite, minium, nantokite, plumbojarosite and zincite, indicating a remarkable reactivity
of the tailings with atmospheric agents; these results made it possible to identify tailings as a source of
contamination. Furthermore, the presence of sub-economic contents of rare earths elements (REE), more
particularly of light rare earths elements (LREE), and of Al, Fe, Pb and Zn emerged.
Biomineralization occurs in the area was found in the streambed of rio Roja Cani; it appears like that which
forms in the bed of the rio Naracauli, described in detail in Medas et al. (2014).
SEM-EDS analysis confirm that biomineralization is mediated by bacterial activity, due to the filamentous
and tubular structures present in biofilms; furthermore, the presence of zinc and oxygen emerges from the
compositional maps, confirming that the biomineralization is composed of hydrozincite, as revealed by the
XRD analysis.
We argued that this biomineralization rules natural attenuation of zinc as already found in rio Naracauli
(Wanty et al., 2013; De Giudici et al., 2014)
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
Geochemistry of rare earth elements in water and solid materials at abandoned mines in SW Sardinia (Italy)
No full textThis study investigates the behavior of rare earth elements (REE) in near-neutral waters that drain abandoned mines in SW Sardinia (Italy). The REE, together with other major and minor components, were determined in waters (146 samples) and solid materials (13 samples). Research was performed to evaluate the main factors that control the geochemical behavior of REE in non-acidic mining environments. Zinc, cadmium and lead are the main contaminants in the study area, either in the processing residues or in the waters that drain the mine site. Contamination of stream waters extends several km downstream of the mine, till the Mediterranean Sea.
The mine tailing (MT) materials are the main REE source, with peak concentrations of 300 mg/kg ΣREE. PAAS-normalized patterns of MT are characterized by light REE (LREE) enrichment with respect to heavy REE (HREE). The waters flowing out of the MT heaps are near-neutral (6.2 to 7.0 pH), with Zn-sulfate dominant composition, and a mean concentration of 53 μg/l ΣREE. Drainages from MT and an adit flow in the Naracauli stream headwaters (mean 1.4 μg/l ΣREE). Concentrations of REE in the Naracauli stream decrease dramatically about 400 m downstream of source. The REE decrease matches Fe and Zn decrease in waters, probably because the REE are sorbed on freshly precipitated solid phases.
Sorption processes, and/or co-precipitation with secondary phases, appear to control the REE geochemistry in the studied waters under near-neutral conditions. Also, despite the non-acidic environment, it is worth to observe that small changes in pH seem to affect the mobility of REE at Naracauli.
The PAAS-normalized REE patterns in the waters generally reflect the PAAS-normalized REE patterns in the solid materials with which the water interacts, either MT or secondary phases such as Fe-hydroxide and bio-hydrozincite. As it is expected in waters under oxidizing conditions, patterns with negative Ce anomalies are developed due to the poor solubility of Ce+ 4 species, and its consequent scavenging in solid phases. However, there is an exception: Ce shows a poor affinity for the bio-hydrozincite mineral, probably reflecting the role of bacteria in the precipitation of the Naracauli hydrozincite
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
Geomorphological surveys to assess propagation of rock falls in the village of Cimolais (Western Friuli Venezia Giulia, Italy)
No full textAppropriate 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
Stream water chemistry in the arsenic-contaminated Baccu Locci mine watershed (Sardinia, Italy) after remediation
No full textThe abandoned Pb-As Baccu Locci mine represents the first and only case of mine site remediation in Sardinia, Italy. Arsenic is the most relevant environmental concern in the Baccu Locci stream watershed, with concentrations in surface waters up to and sometimes over 1 mg/L. The main remediation action consisted in creation of a "storage site", for the collection of contaminated materials from different waste-rock dumps and most of tailings piles occurring along the Baccu Locci stream. This paper reports preliminary results on the level of contamination in the Baccu Locci stream after the completion of remediation measures. Post-remediation stream water chemistry has not substantially changed compared to the pre-remediation situation. In particular, dissolved As maintains an increasing trend along the Baccu Locci stream, with a concentration of about 400 μg/L measured at a distance of 7 km from the storage site. Future monitoring will provide fundamental information on the effectiveness of remediation actions conducted and their applicability to other mine sites in Sardinia. At the stage of mine site characterisation of future remediation plans, it is recommended to pay more attention to the understanding of mineralogical and geochemical processes responsible for pollution. Moreover, mixing of materials with different composition and reactivity in a storage site should require careful consideration and long-term leaching tests
Uptake of Pb by hydrozincite, Zn5(CO3)2(OH)6—Implications for remediation
No full textHydrozincite, Zn5(CO3)2(OH)6, periodically precipitates from heavy metal contaminated waters of the Rio
Naracauli stream, Sardinia, in association with a biological photosynthetic community. The precipitation
removes not only zinc from the waters, but also other toxic “heavy metals”, such as Cd, Cu, Pb. The
phenomenon is therefore of potential interest for “soft” remediation of contaminated waters. Previous
cation exchange experiments suggested that binding of Pb to hydrozincite is fairly strong. This suggestion
is in agreement with new release tests in deionized water and X-ray absorption spectroscopy (XAS)
spectra collected at the Pb LIII edge for natural hydrozincites from Naracauli, and synthetic Pb-doped
hydrozincites. The results suggest that, up to bulk concentration of 1.5 wt.% Pb, uptake of this metal
occurs in two distinct ways: (1) as a substitution for Zn in the tetrahedral site of the hydrozincite structure,
possibly via formation of a surface mononuclear tridentate inner sphere complex; (2) as an ill-defined,
presumably amorphous, phase with a local atomic structure similar to cerussite. These data support the
concept that Pb binding to hydrozincite is strong enough to make this mineral a potential sink for the
metal
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