1,720,959 research outputs found
Geochemistry and isotope geochemistry of the Monfalcone thermal waters (northern Italy): inference on the deep geothermal reservoir
No full textGeochemical investigations were carried out to define the origin of the low- to moderate-temperature thermal waters feeding the Monfalcone springs in northern Italy. Chemical data indicate that waters approach the
composition of seawater. Mixing processes with cold low salinity waters are highlighted. The δ18O and δD values
are in the range −5.0 to −6.4 ‰, and −33 to −40 ‰, respectively, suggesting the dilution of the saline reservoir
by karst-type freshwaters. A surplus of Ca2+ and Sr2+ ions with respect to a conservative mixing is ascribed to
diagenetic reactions of the thermal waters with Cretaceous carbonates at depth. The measured Sr isotopic
composition (87Sr/86Sr ratio) ranges between 0.70803 and 0.70814; after correction for the surplus Sr, a 87Sr/86Sr
ratio indicating Miocene paleo-seawater is obtained. The dissolved gases indicate long-lasting gas–water interactions with a deep-originated gas phase of crustal origin, dominated by CO2 and marked by a water TDIC isotopic composition in the range −5.9 to−8.8 and helium signature with 0.08<R/ Ra<0.27, which is a typical range for the crust. A possible scenario for the Monfalcone thermal reservoir consists of Miocene marine paleowaters which infiltrated through the karstic voids formed within the prevalently Cretaceous carbonates during the upper Eocene emersion of the platform, and which were entrapped by the progressive burial by terrigenous sediments
Geochemistry and stable isotope composition of surface waters from the Ravenna plain (Italy): implications for the management of water resources in agricultural lands
No full textThis paper examines the issues related to salinization
and water quality in the complex drainage system
of the historical land reclamation of Lamone basin (Ravenna
coastal plain, northern Italy), with the aim of guiding
ongoing agricultural-related decisions. Major and trace
element concentration and O–H–B–Sr isotope-ratios were
measured on surface water from a network of canals and
ditches. Sampling was carried out during the winter period
and in summer, to assess the effects of agricultural water
management on the aquatic system. Results show widespread
salinization of waters over the entire crop, due to
both the direct saltwater inland flushing through the canals
in proximity of the mouths, and sea salt leaching from
soils. During winter, salinization is partly mitigated by
rainfalls, while in summer dilution processes are due to
freshwater input from outside the watershed, planned to
assist the agricultural water demand. In the winter season,
the concentration of some elements such as Fe, Mn, Al, and
Cu in waters exceeds the maximum permissible limits
imposed by the Italian regulations, while during summer
the concentration of these elements is significantly reduced.
A seasonal cycling is established, where the bottom sediments
of canals and ditches act as sinks of harmful elements,
mostly through adsorption by Fe–Mn–Al oxyhydroxide
solid phases. The irrigation practice, although
improving the water quality, increases water turbidity by
re-mobilization of sediments which act as transport agents
of contaminants, with detrimental effects that may become
significant over the years
The fate of iron in waters from a coastal environment impacted by metallurgical industry in Northern Italy: hydrochemistry and Fe-isotopes
No full textThe source and cycling of Fe in groundwaters from the phreatic aquifer which characterizes a site impacted by metallurgical activity in a coastal area of northern Italy (Adriatic Sea) have been investigated by Fe-isotope analyses, H-O-Sr stable-isotope systematics and major and trace element chemistry. Waters are characterized by circum-neutral to alkaline pH and dissolved O-2 zoning, and range from a low-salinity Ca-Mg-HCO3 type to a brackish Na-Cl type resulting from seawater intrusion. The O-H isotopic data indicate that the Ca-Mg-HCO3 waters originate from meteoric precipitation that infiltrated at elevated altitudes, and that a variable seawater fraction, in some cases exceeding 90%, characterizes the Na-Cl type waters. The Fe content ranges from 0.48 to 9.99 mg/L and from 2.50 to 43.8 mg/L in low-salinity and brackish waters, respectively. The delta Fe-56 value varies over the wide range from +0.87 parts per thousand to -5.29 parts per thousand in low-salinity waters and between +2.15 parts per thousand and -2.34 parts per thousand in brackish waters. The isotopically lighter compositions are interpreted as reflecting isotopic fractionation during repeated cycling of Fe precipitation. Positive delta Fe-56 values might indicate either a higher solubility of oxyhydroxides, which during diagenesis preferentially incorporated the isotopically heavier fraction of Fe, or the leaching of the foundry landfill disposal which characterizes the site. (c) 2013 Elsevier Ltd. All rights reserved
OUTLINES OF BIOGEOCHEMICAL CYCLING IN THE SAN VITALE PINEWOOD
No full textThis paper is focused on the multicomponent exchange processes and elemental cycling in the subsurface and superficial environments which constitute the area of the Pineta di San Vitale and nearby farmlands. The coastal aquifers in the area of the Pineta underwent severe seawater intrusion due to subsidence and over-pumping, yielding a decline in the water quality and driving a number of processes in aquifers and soils. These include cation-exchange reactions by clay minerals, even if the cation exchange capacity of the aquifer is probably low; iron oxy-hydroxides extensive precipitation due to oxic seawater recirculation; adsorption processes of both essential micronutrient and potentially toxic elements on the sur-face of Fe and Al hydroxides. The development of local anoxic conditions due to respiration and decomposition of organic matter allows the reductive dissolution of the iron oxy-hydroxides, which liberate the sorbed elements to porewaters. This re-dox cycling appears to be important in the bioavailability and geochemical cycling of a number of trace metals in the subterranean environment of the Pineta. CO2 charged waters in soils account for the high alkalinity observed in most water sam-ples, through the role of carbonates and the control of pH and the Ca2+ content.
The active processes in the surface ecosystem of the plain bordering the Pineta di San Vitale, exploited for agricultural uses, include dry and wet atmospheric deposi-tion from marine and anthropogenic sources, leaching processes during runoff and retention and transport of trace elements by Fe and Mn oxides colloidal particles, through the network of canals and ditches towards the coastland. These processes are sensitive to flow fluctuations, and are deeply influenced by the management of water resources during summer, when a high water supply in irrigated crops is re-quired. Using geochemical simulation codes it is highlighted that the reverse phe-nomenon to salinization, leading to groundwater freshening, is a long process, also depending on the low cation exchange capacity of the site. Even if a detailed study concerning the recharge rate of the aquifers would be necessary, these preliminary observation indicate that attenuation planning for salinization is urgent
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
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