1,721,066 research outputs found
Assessment of the risk of pollution from Arsenic on human health as a function of its speciation in intestinal fluids.
No full textABSTRACT
Investigating the risk on human health arising from exposure to As-polluted drinking water is a very important task since many area of the world has to face with this problem. Actually, chronic poisoning by arsenic carried by water has been well documented in many European and extra-European countries. Pollution of water with arsenic develops generalized symptoms of poisoning and carcinogenesis. It is well known that inorganic As is rapidly absorbed after oral exposure, but little information is still available about the fate of arsenic after oral ingestion. In particular, the mechanism which affects the speciation of this element in the gastrointestinal tract is not clear, especially when other trace elements are present. In this paper we present an estimate of the health risk due to the ingestion of water containing micro-pollutants, such as As and B, using two computational codes: PHREEQC, which allowed us to determine the effect of boron on arsenic speciation in equilibrium with the fluids of the gastrointestinal tract; SADA software for assessing the risk of exposure to contaminated matrices. The use of software in the present case study is mandatory since it is quite impossible to obtain experimental data. We focused on a sample area, the geothermal field of Larderello (Italy), where anomalous concentrations of arsenic and boron were found in the drinking water.
The results obtained in this study prove that the risk to human health depends on the speciation of As, which is strictly related to the pH values reached at equilibrium with intestinal fluids. The pH values change as a function of the concentration of boric acid in drinking water. In waters characterized by high contents of B, the risk factor is amplified by the increase of the species As3+ in intestinal fluids. Specifically, this study suggests that interactions between two elements in solution, such as boric acid and arsenic, both in solution in drinking water, can have a negative impact on human health when balanced with intestinal fluids, since the effects of one may magnify the toxicity of the other
A quantitative approach to trace element and Sr-isotope evolution in the Adamello batholith (northern Italy).
No full textThe alpine paleo-arcs in the Adriatic plate margin (Eastern Alps)
No full textThe North-eastern Italy (Adriatic paleo-margin) is a laboratory to study past orogenetic processes. The paleomargin was involved in the subduction of the Mesozoic Tethys lithosphere with development of (a) an early magmatic
belt, (b) a typical fore-arc crust, (c) a back-arc crust and (d) a collisional paleo-arc.
Early alpine magmatic belt. This is represented by the Re di Castello, Central Adamello, Mt. Marser and Corno Alto plutons of ultrabasic to intermediate composition, the Mt. Ospedale diorite dykes, and other ultrabasic to
andesitic dykes distributed in the Southern Alps basement and cover. The ages of these magmatic rocks span between Upper Cretaceous (Northern Calcareous Alps and Dolomites), Paleocene (Val Camonica and Valtellina)
and Middle Eocene (Adamello). Volcanics of Middle Eocene age are widespread in the Western Trentino and in the Southern Lombardy sedimentary sequences. In Trentino they crop out in a very restricted zone because of the transpressive deformation and shortening of the Giudicarie fault zone. Adriatic fore-arc crust. This is represented by the high-grade Austroalpine Tonale nappe and the Lombardian Edolo/Morbegno basements which show evidence of a pervasive crustal deformation. These basements show swarms of pseudotachylytes often associated to mylonites, testifying crustal deformation at a critical depth in the Adriatic paleo-margin during the alpine subduction/collision.Adriatic back-arc crust. This is testified by Paleocene to Oligocene ultrabasic to basic dykes and volcanics in the Venetian region. These volcanic rocks show HIMU-DM-OIB geochemical features, ascribed to deep mantle upwelling after a possible failure of the slab. Collisional paleo-arc. Subduction was followed by a collisional to post-collisional magmatism at Oligocene, characterized by intrusion of large tonalite to quartz-diorite plutons (e.g., Western Adamello, Presanella, Ries, Rensen), apophyses, dykes and volcanics, very common in the Southern Alps and in the Austroalpine basements mostly along the Periadriatic Lineament. This magmatism continued up to Miocene in the Southern Alps. A relevant seismotectonic activity of Oligocene age developed across the tonalite plutons of the Adamello.
The above mentioned magmatic, volcanic and seismotectonic data, evidences of the pre-collisional (subduction) and collisional stages, clearly indicate the position of the related paleo-arcs
The alpine paleoarc in the Adriatic plate margin (Eastern Alps)
No full textSui margini della placca Adriatica, nel Mediterraneo centrale e occidentale, sono presenti archi magmatici e bacini di retro-arco. I margini della placca Adriatica sono dunque un laboratorio ideale per lo studio dei processi di subduzione in atto e antichi, del magmatismo di arco e dei processi tettono-magmatici correlati.
Nel corso dell’orogenesi alpina il margine Adriatico è stato coinvolto nel processo di subduzione della litosfera dell’oceano Liguro-Piemontese che ha dato origine alle Alpi, con sviluppo di una fascia magmatica con plutoni e dicchi di composizione da ultrabasica a riolitica e vulcaniti situata soprattutto nel dominio Subalpino, formazione di una crosta di avan-arco, ed effusione di lave in un bacino di retro-arco. L’età del magmatismo di arco e delle effusioni laviche di retro-arco spazia dal Cretaceo superiore/Paleocene inferiore al Miocene inferiore.
L’area di avan-arco, intensamente perturbata da eventi sismo-tettonici, corrisponde attualmente al basamento Austroalpino e Sudalpino di medio-alto grado che formava il margine Adriatico, e ad alcune unità metamorfiche Austroalpine che formavano il prisma di accrezione alpino. Attualmente quest’area è esposta in superficie e mostra numerosi sciami di pseudotachiliti associate a miloniti e cataclasiti ed è attraversata da numerosi dicchi e apofisi.
Un magmatismo incipiente di retro-arco è testimoniato dall’attività magmatica di età Paleocene-Miocenica con prodotti da ultrabasici a trachitici nel Veneto occidentale (e.g., regione dei Lessini e Berici)
Slab detachment and mantle plume upwelling in subduction zones: An example from the Italian south-eastern Alps volcanism
No full textAbstract
The geochemical properties of the South-Eastern Alps volcanics (SEAV, Eocene age) call for a within-plate origin of the most primitive basalts,
in contrast to the widespread calc-alkaline magmatism which developed some million years later northwestwards along the Periadriatic Lineament.
The two contrasting magmatic suites that coexist in the Alpine area define binary mixing relationships in the Sr–Nd and Sr–Pb isotopic space, the
end members of which being a crustal component (e.g. lower continental crust) and a HIMU-DMM component (e.g. the SEAV). The occurrence
of a HIMU (high μ= high
238
U/
204
Pb) component, which normally traces mantle plumes of deep mantle origin, in a tectonic regime dominated
by collision tectonics (the tertiary convergence of European and Adriatic plates) can be explained by slab detachment and ensuing upwelling of
mantle material through the lithospheric gap. We combine geochemical data and geophysical modelling to unravel the evolution of the Alpine
slab after interaction with plume material and the genesis of the Alpine magmatism. The combination of changes in negative buoyancy caused by
continental subduction and softening of a part of the slab caused by slab–plume interaction may act as a regulator for the time of slab breakoff and,
consequently, for the variations of magmatism in the overriding lithosphere above a subduction zone. The thermal evolution of a subducting slab is
modified by contact with the plume material which decreases significantly the total strength of the slab and favours slab detachment. Interactions
between the HIMU component and the shallower depleted mantle can account for the geochemical characteristics of the SEAV. Counterflows of
plume material towards the top of the subducting slab may also increase heating and partial melting of the overriding mantle wedge, giving rise to
the calc-alkaline suite outcropping in the proximity of the Periadriatic Lineament.
© 2007 Elsevier Ltd. All rights reserved
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