1,720,979 research outputs found
Chemical and isotopic (B, Sr) composition of alluvial sediments as archive of a past hydrothermal outflow
No full textThe geochemical and isotopic signature of Quaternary alluvial sediments filling a post-orogenic basin along the Tyrrhenian coasts of Italy (Cornia Plain, Tuscany) was investigated to unravel possible interactions with geothermal fluids from the Larderello geothermal field. Two cores located in the upper (UCP) and lower (LCP) sector of the plain were sampled to depths of up to 80 m. A third core in a neighbouring area not affected by geothermal activity was also sampled (Arno plain at Pisa), and its sediment composition was used as reference. The Cornia sediments (fraction < 65 μm) show high B, Cs and Sb concentrations related to a peculiar chemical enrichment of the clay fraction. They also show remarkable enrichments in As (up to 1000 μg g- 1) reflecting a contribution from local ore deposits. 87Sr/86Sr ratios, ranging from 0.71022 to 0.71698, reveal the nature of the weathered mother rocks of the alluvial sediments, whereas the boron isotopic composition, varying from - 20‰ to - 10‰,..
Geochemical investigation of fine sediments from the Cornia alluvial plain (Tuscany, Italy).
No full textBehaviour of boron and strontium isotopes in groundwater-aquifer interactions in the Cornia Plain (Tuscany, Italy)
No full textThe Cornia Plain alluvial aquifer, in Tuscany, is exploited intensely to meet the demand for domestic, irrigation and industrial water supplies. The B concentration of groundwater, however, is often above the European limit of 1 mg L−1, with the result that exploitation of these water resources requires careful management. Boron and Sr isotopes have been used as part of a study on the origin and distribution of B dissolved in groundwater, and indirectly as a contribution to the development of appropriate water management strategies.
The geochemistry of the Cornia Plain groundwater changes from a HCO3 facies in the inland areas to a Cl facies along the coastal belt, where seawater intrusion takes place. The B concentration of groundwater increases towards the coastal areas, while the 11B/10B ratio decreases. This indicates that there is an increasing interaction between dissolved B and the sediments forming the aquifer matrix, whose B content is in the order of 100 mg kg−1. Adsorption–desorption exchanges take place between water and the sediment fine fraction rich in clay minerals, with a net release of B from the matrix into the groundwater, and a consequent δ11B shift from positive to negative values. The aquifer matrix sediments therefore seem to be the major source of B dissolved in the groundwater.
The groundwater–matrix interactions triggered by the ionic strength increase caused by seawater intrusion can also be detected in the Ca–Na ion exchanges. Dissolved Sr follows a trend similar to that of Ca, while the 87Sr/86Sr ratio is equal to that of the exchangeable Sr of the aquifer matrix and therefore does not change significantly.
These results have helped to define a new strategy for groundwater exploitation, with the final objective of reducing B concentration in the water extracted from the aquifer
GIS Technologies supporting the monitoring of water resource in the Cornia river basin (Tuscany, Italy).
No full textHydrochemistry of the high-boron groundwaters of the Cornia aquifer (Tuscany, Italy)
No full textThe groundwaters of the Cornia River alluvial aquifer (southern Tuscany) were studied to determine the origin of their characteristic high-boron content. The interpretation is based on concentrations of major ions and selected minor and trace elements (B, Br, F, and Li). Mass balance calculations confirm that the main processes in the entire system are mixing of three water types and cation exchange between waters and sediments. The observed geochemical patterns indicate that the Ca-HCO3 waters recharging the aquifer interact with the alluvial sediments, increasing the TDS contents of the groundwaters without changing their chemical facies. High SO4 (up to 1840 mg/l) and F (up to 2.6 mg/l) thermal (hot) waters are discharged at several points in the Cornia basin. These Ca-SO4 waters mix with the Ca-HCO3 waters in the upstream part of the basin. Near the coastline, seawater intrusion occurs as a result of over-pumping, giving rise to Na-Cl-dominated waters near the shore. Further inland, within the transition zone between fresh and salty waters, cation exchange on the clay fraction of the aquifer leads to a loss of Na and a gain of Ca, shifting the composition towards Ca-Cl and mixed-anion waters. Interaction with clay minerals explains the higher contents of B and Li in the Cornia groundwaters than in the seawater.
The geochemical data, presented in the form of GIS-based geochemical maps, provide a baseline that can be used as a useful diagnostic tool to monitor the hydrochemical evolution of the Cornia groundwaters in view of possible future degradation of their quality in response to natural causes and human activities, including geothermal developments in the general Larderello area
Sediment control of chemical and isotopic characteristics (boron, strontium) of groundwater in the cornia alluvial aquifer (Tuscany, Italy).
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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
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