1,721,072 research outputs found
Geochemical processes governing the chemistry of groundwater hosted within the Hyblean aquifers
No full textA raingauge network made of six stations was installed in the Hyblean region. Stations were located at different altitudes (from 5 m to 986 m a.s.l.) and along two directions (E-W and SW-NE). Rainwater samples were monthly collected for stable isotope measurements.
Spatial distribution of rainwater isotope composition has confirmed the wet air masses
move from South-East/South-West toward North. Water balance has highlighted that the annual volume of infiltrating waters is in the range of 1-1.5 *105 m3 Km-2.
82 well waters and 12 spring waters located within the Hyblean Plateau (South-Estern Sicily), were also collected from 1999 to 2001 during several surveys for chemical (major,minor and trace elements) analyses. Water chemistry allowed to identify two main aquifers: the first aquifer hosted within sedimentary rocks is characterized by earthalkaline bicarbonate waters, while the second aquifer, located within the volcanic deposits (mainly towards North- North-East) is characterized by groundwaters evolving from earthalkaline bicarbonate water-type towards a Na-HCO3-type.
A slightly anomaly in water temperature (24-28°C) have been identified along the northern margin, while the lower Eh values have been recorded along the M.Lauro-Scicli and the Hyblean Malta Escarpment fault systems. Isotope composition of groundwaters has suggested the occurrence of evaporative processes during soil infiltration having a dD/d18O slope close to 4.5.
Chemical and isotope composition of dissolved gases (d13CTDIC, d13CCH4, 3He/4He) have
revealed, as expected, that deeply-derived gases rise along the main tectonic discontinuities. Chemical and isotope analyses of dissolved carbon have revealed the existence of two sampling sites (NA and FE samples) attesting the interaction between groundwaters and a consistent amount of deep inorganic carbon dioxide.
He isotope ratios (from 0.81Ra to 6.19 Ra) have revealed the occurrence of mixing process,
in different proportions, between crustal and mantle components.
On the base of the obtained results, a clear picture of the groundwaters circulation within
the Hyblean aquifers has been drawn. In framework of projecting of a geochemical network for the continuous monitoring of the local seismic activity the most suitable geochemical parameters and the sites of great interest have been identified.- Unione Europea Fondo Sociale Europeo;
- Ministero dell’Università e della Ricerca Scientifica e Tecnologica;
- Università degli studi di PalermoPublishedope
Geochemical processes governing the chemistry of groundwater hosted within the Hyblean aquifers
No full textA raingauge network made of six stations was installed in the Hyblean region. Stations were located at different altitudes (from 5 m to 986 m a.s.l.) and along two directions (E-W and SW-NE). Rainwater samples were monthly collected for stable isotope measurements.
Spatial distribution of rainwater isotope composition has confirmed the wet air masses
move from South-East/South-West toward North. Water balance has highlighted that the annual volume of infiltrating waters is in the range of 1-1.5 *105 m3 Km-2.
82 well waters and 12 spring waters located within the Hyblean Plateau (South-Estern Sicily), were also collected from 1999 to 2001 during several surveys for chemical (major,minor and trace elements) analyses. Water chemistry allowed to identify two main aquifers: the first aquifer hosted within sedimentary rocks is characterized by earthalkaline bicarbonate waters, while the second aquifer, located within the volcanic deposits (mainly towards North- North-East) is characterized by groundwaters evolving from earthalkaline bicarbonate water-type towards a Na-HCO3-type.
A slightly anomaly in water temperature (24-28°C) have been identified along the northern margin, while the lower Eh values have been recorded along the M.Lauro-Scicli and the Hyblean Malta Escarpment fault systems. Isotope composition of groundwaters has suggested the occurrence of evaporative processes during soil infiltration having a dD/d18O slope close to 4.5.
Chemical and isotope composition of dissolved gases (d13CTDIC, d13CCH4, 3He/4He) have
revealed, as expected, that deeply-derived gases rise along the main tectonic discontinuities. Chemical and isotope analyses of dissolved carbon have revealed the existence of two sampling sites (NA and FE samples) attesting the interaction between groundwaters and a consistent amount of deep inorganic carbon dioxide.
He isotope ratios (from 0.81Ra to 6.19 Ra) have revealed the occurrence of mixing process,
in different proportions, between crustal and mantle components.
On the base of the obtained results, a clear picture of the groundwaters circulation within
the Hyblean aquifers has been drawn. In framework of projecting of a geochemical network for the continuous monitoring of the local seismic activity the most suitable geochemical parameters and the sites of great interest have been identified.- Unione Europea Fondo Sociale Europeo;
- Ministero dell’Università e della Ricerca Scientifica e Tecnologica;
- Università degli studi di PalermoPublishedope
Moisture source in the Hyblean mountains region (south-eastern Sicily,Italy):Evidence from stable isotopes signature
No full textHere the authors present results of an isotope study on precipitation collected during a 2-a period from a rain-gauge network consisting of 6 stations located at different elevations in the Hyblean Mountains (HM) region, in south-eastern Sicily. The slope of the local meteoric water line (δD = 6.50 δ18O + 9.87) obtained for the region suggests that precipitation is affected by evaporation during rainfall events. The main variations in rainwater isotope composition are due to seasonal effects and elevation. An average 2H excess value of +21.2‰ was found for precipitation events less affected by evaporation (i.e. when the rainfall was >65 mm/month). The spatial distribution of O isotope composition of precipitation shows a negative gradient from east and south to the inner areas. The depositional rate of Cl, used as a tracer of the origin of air masses, is highest at the coastal rain-gauges (SR and MRG stations) and lowest on the northern flank of the HM region (SC station). Based on these findings, a model is proposed for the origin of precipitation in the HM region, which assumes that a Mediterranean-derived component is the main source of moisture in the studied area. D/H and 18O/16O ratios of inferred meteoric recharge waters were also compared with the isotope composition of waters collected from the main local springs and wells. The best linear fit of the δ18O vs δD relationship for Hyblean groundwater is δD = 4.85 δ18O–2.01. The enrichment of heavy isotopes in Hyblean groundwater is probably due to evaporation occurring after precipitation events or to a recharging contribution from surface waters (lakes or rivers) enriched in heavy isotopes
Mantle-derived fluids in Central Mediterranean: Geochemical and geophysical constrains on sources of fluids and migration
No full textThe geodynamics of the central Mediterranean is
characterized by the interaction between the European plate
and the African’s. In this setting Sicily is a sector of the
Appenine-Maghrebide accretionary prism, which is located
between two areas affected by extensional tectonics (Sicily
Channel to the south and the Thyrrenian back arc basin to the
north).
Significant mantle-derived helium (0.4<R/Ra<2.8;
R=3He/4He in the sample, Ra in atmosphere) is found in the
CH4 and N2-CO2 rich fluids released in central western Sicily,
a region without evidence of recent magmatism. CH4-
dominated gases are released from mud volcanoes localized in
an area of both low heat flow and seismicity. On the contrary
CO2 is mainly associated to the thermal groundwater
circulating mainly in Mesozoic limestone over an area
characterized by high seismicity and heat flow anomaly. Total
carbon dissolved in thermal water is a mixture of mantlederived
and crustal inorganic CO2, while CH4-dominated
fluids show a mixing between a 3He rich and CH4-poor term
and a CH4-rich and 3He-poor one typical of crustal reservoir of
gases. The computed mantle derived He, much higher than
stable continental areas, indicates that the transfer of fluids is
controlled by tectonic mechanism through the crust. Finally,
recent geophysical investigations discovered the occurrence of
active lithospheric faults that could control the transfer of
mantle derived fluids from the sources to the crust and
throughout this towards the surface
VOLCANIC CO2 FLUX MEASUREMENTS BY TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY
Full text linkIntroduction
In the last decades, the use of near-infrared room-temperature diode lasers for gas sensing has grown significantly. The use of these devices, for instance in combination with optical fibers, is particularly convenient for volcanic monitoring applications [1,2]. Here, we report on the first results of the application of an open-path infrared tunable laser-based at Campi Flegrei (Southern Italy). Such Diode-laser-based measurements were performed, during two field campaigns (october 2012, and january 2013), in the attempt to obtain novel information on the current degassing unrest of Solfatara and Pisciarelli fumarolic fields.
Results and Discussion
At each site, we used an ad-hoc designed measurement geometry, using a TDLS (a Gas Finder unit) and several differently positioned retroreflectors (mirrors), to scan the fumaroles’ plume from different angles and distances. From post-processing of the data (acquired at 1 hz), we derived tomographic maps of CO2 concentrations in the plume and, by integration and combination with plume transport speed (from video cameras), we inferred the CO2 flux directly. The so-calculated fluxes, the first ever obtained at Campi Flegrei, average of 500 tons/day, and support a significant contribution of fumaroles to the total CO2 budget. The cumulative (fumarole [this study] +soil [3]) CO2 output from Campi Flegrei is finally evaluated at 1600 tons/day.
[1] Gianfrani L. et al. (2000). Appl. Phys. B-Rapid Common. 70, 467-470. [2] Richter D. et al (2002), Optics and Lasers in Engineering, Volume 37, Issues 2–3, Pages 171-186. [3] Chiodini G. et al. (2010), Journal of Geophysical Research, Volume 115, B03205, doi:10.1029/2008JB006258
Mantle-derived helium in sedimentary basins of Central Mediterranean:Geologic and tectonic constrains on fluids accumulation and migration.
No full textThe geodynamics of the central Mediterranean is characterized by the interaction between the European plate and
the African one. In this setting Sicily is a sector of the Appenine-Maghrebide accretionary prism, which is located
between two areas affected by extensional tectonics (Sicily Channel to the south and the Thyrrenian back arc basin
to the north).
In the present study we present the first dataset of helium isotopic composition measured in fluids released from
the central-western Sicily.With the aim to constrain the transfer system of fluids in this area we relate the results of
geochemical investigations with the stratigraphy and structural setting, derived from field geology, deep boreholes
and new seismic reflection, gravimetry and magnetometry data.
Significant mantle-derived helium (0.4<R/Ra<2.8; R=3He/4He in the sample, Ra in atmosphere) is found in the
CH4 and N2-CO2 rich fluids released in central western Sicily. CH4-dominated gases are released from mud
volcanoes and feed everlasting fires mainly located in the central region, where upper Oligocene-Miocene terrigenous
cover Mesozoic carbonatic units. The abundance of CH4, usually linked to the presence of hydrocarbonsand/
or organic matter-rich layers, is almost exclusively linked to the Messinian evaporitic and pre-evaporitic levels
(containing diatomites).
On the other hand, CO2 is mainly associated to the thermal groundwaters circulating mainly in Mesozoic
limestone and dolomite, which here constitute the bulk of the deformed wedge of the Sicilian chain (up to 15 km
thick). In thermal waters, we found a positive correlation between water temperature, ranging between 22.1 C
and 59 C, and helium isotopic ratio. Taking into consideration that helium rises from the mantle coupled to
CO2 and others components, we discussed CO2 and CH4 coupled to helium. Our samples did no show any
correlation between C/3He vs. R/Ra and only samples of the Sciacca thermal basin show C/3He in the typical
ranges of the mantle fluids. CH4-dominated fluids shows a CH4/3He vs. R/Ra correlation that underlies a mixing
between a 3He rich and CH4-poor term and a CH4-rich and 3He-poor one typical of crustal reservoir of gases.
Our previous investigations showed up an heat excess coupled to the presence of mantle-derived helium in
western Sicily, which was linked to the occurrence of melts rising from the mantle below the continental crust
or intruding through lithospheric faults. This study shows that degassing of mantle derived fluids cover entirely
the central-western Sicily and the transfer of mantle helium rich fluids through the crust is mainly regulated
by fault-controlled advective flux. In particular: a) in the central-northern Sicily recent data from deep seismic
reflection investigations (SiRiPro project), evidenced a dense network of faults that develops between the area of
Caltanissetta and the central portion of the Madonie, involving both the deformed sedimentary units of the fold
and thrust belt and the underlying crust and upper mantle; b) in the Sciacca area multichannel seismic profiles
highlighted the occurrence of deep-seated faults (correlated with the N-S lineaments well known offshore in the
Sicily Straits), also characterized by strike-slip component (as evidenced by the seismicity of the Belice valley),
which involves the deeper portions of the chain; in addition gravimetry and magnetic data displayed a shallow
crustal basement, whose involvement in the deformation suggests a link with the fault systems recognized in the
overlying tectonic wedge
Large Isotopic Shift in Volcanic Plume CO2 Prior to a Basaltic Paroxysmal Explosion
Full text linkCarbon dioxide is a key gas to monitor at volcanoes because its concentration and isotopic signature can indicate changes to magma supply and degassing behavior prior to eruptions, yet carbon isotopic fluctuations at volcanic summits are not well constrained. Here we present δ13C results measured from plume samples collected at Stromboli volcano, Italy, by Uncrewed Aerial Systems (UAS). We found contrasting volcanic δ13C signatures in 2018 during quiescence (−0.36 ± 0.59‰) versus 10 days before the 3 July 2019 paroxysm (−5.01 ± 0.56‰). Prior to the eruption, an influx of CO2-rich magma began degassing at deep levels (∼100 MPa) in an open-system fashion, causing strong isotopic fractionation and maintaining high CO2/St ratios in the gas. This influx occurred between 10 days and several months prior to the event, meaning that isotopic changes in the gas could be detected weeks to months before unrest
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
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