215 research outputs found
Dissolved CO2 in natural waters: development of an automated monitoring system and first application to Stromboli volcano (Italy)
The study of geochemical parameters applied to natural systems has
provided improved knowledge of geochemical mechanisms of gas/rock
dissolution in natural waters that are linked to gasâwater and/or waterâ
rock interaction processes. Here we present the results of our studies focused
on the development of an automated monitoring system for measuring
the amount of dissolved CO2 in natural waters. The system is based on the
principle of a dynamic equilibrium between water and the air as the host
gas. The PCO2 measurements were carried out every four hours, and the
equilibration time was around 20 minutes. Moreover, application to the
thermal aquifer of Stromboli volcano during the 2009-2010 period is shown
and analyzed. The data highlight a clear correlation between the changes
in the PCO2 in the thermal aquifer and the changes in volcanic activity
Total CO2 output from Vulcano island (Aeolian Islands, Italy)
Total CO2 output from fumaroles, soil gas, bubbling gas discharges and water dissolved gases discharged
from the island, was estimated for Vulcano island, Italy. The CO2 emission from fumaroles from the La
Fossa summit crater was estimated from the SO2 crater output, while CO2 discharged through diffuse soil
emission was quantified on the basis of 730 measurements of CO2 fluxes from the soil of the island, performed
by using the accumulation chamber method. The results indicate an overall output of â
500 t day 1
of CO2 from the island. The main contribution to the total CO2 output comes from the summit area of
the La Fossa cone (453 t day 1), with 362 t day 1 from crater fumaroles and 91 t day 1 from crater soil
degassing. The release of CO2 from peripheral areas is â
20 t day 1 by soil degassing (Palizzi and Istmo areas
mainly), an amount comparable to both the contribution of water dissolved CO2 (6 t day 1), as well as to
seawater bubbling CO2 (4 t day 1 measured in the Istmo area). Presented data (September 2007) refer to a
period of moderate solphataric activity, when the fumaroles temperature were 450°C and gas/water
molar ratio of fumaroles was up to 0.16. The calculated total CO2 emission allows the estimation of the mass release and related thermal energy from the volcanic-hydrothermal system
Possible Micrometeorological Anomalies Induced by Volcanic Activity Recorded at Stromboli Island (Aeolian Archipelago, Italy)
Hourly values of atmospheric pressure and air temperature have been acquired at the top of two volcanic islands, Stromboli and
Salina in the Aeolian Archipelago (Italy), very similar in height and morphology but completely different with regard to their
volcanic activity state: the former is permanently active, whereas the latter is extinguished. During the last four years Stromboli
experienced normal activity, volcanic unrests, and an effusive eruption (AugustâNovember 2014).The comparative analysis of the
recorded data, both in the time and frequency domains, evidenced a peculiar micrometeorological regime at Stromboli, more
turbulent during unrests with respect to the quieter periods, but showing an apparent paradox during eruptions, characterized
by a lower atmospheric turbulence. These observations suggest that the studied volcanic-micrometeorological system is chaotic,
due to contemporary opposite transients generated in the atmosphere by volcanic activity changes, and that micrometeorological
conditions in volcanic areas are controlled both by exogenous processes and volcanic activity
CO2 output discharged from Stromboli Island (Italy)
Total CO2 output from soil gas and plume, discharged from the Stromboli Island, was estimated. The CO2
emission of the plume emitted from the active crater was estimated on the basis of the SO2 crater output
and C/S ratio, while CO2 discharged through diffuse soil emission was quantified on the basis of 419 measurements
of CO2 fluxes from the soil of the whole island, performed by using the accumulation chamber method.
The results indicate an overall output of â
416 t dayâ1 of CO2 from the island. The main contribution to the
total CO2 output comes from the summit area (396 t dayâ1), with 370 t/day from the active crater and
26 t dayâ1 from the Pizzo sopra La Fossa soil degassing area. The release of CO2 from peripheral areas is
â
20 t dayâ1 by soil degassing (Scari area mainly). The result of the soil degassing survey confirms the persistence
of the highest CO2 degassing areas located on the North-East crater side and Scari area
Fluids Geochemistry of Stromboli
An accurate description of the geochemical system is presented here based on a review of scientific work performed during the past decade. The surface manifestations of the volcanic system of Stromboli have been investigated using several measuring techniques. Studying the chemical composition of the volcanic plume and of fumarolic emissions has provided information on magma degassing processes. The total fluxes of the emitted gases from both the plume and the soil were found to vary with changes in volcanic activity (from normal Strombolian activity to effusive and/or paroxysmal activity). Thermal water results from the interaction between volcanic gases, host rock, seawater and meteoric water and temporal changes observed in the chemical and the isotopic composition of the gases dissolved into thermal waters highlighted the rising of new magma batches.
Combining modelling of gas-water-rock interactions with an understanding of the volcanic system allowed to identify preferential sampling sites and parameters for the geochemical monitoring of volcanic activity at Stromboli Island
Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements
Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool
for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and powerinefficient,
making their application to remote environments extremely challenging. Recent developments in
fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have
now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote
locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used
to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up
to 1.2 1018 molec cm 2 ( 500 ppmm) were detected along open paths of up to 400m in total length. The
instrumentâs SO2 detection limit was determined to be 2 1016 molec cm 2 ( 8 ppmm), thereby making quantitative
detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic
volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide
(ClO) and carbon disulfide (CS2/ were both below the instrumentâs detection limits during the experiment, the
upper limits for the X/ SO2 ratio (XDClO, CS2/ could be derived, and yielded 2 10 3 and 0.1, respectively.
The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing
and understanding processes in a range of volcanic systems
Geochemistry of H2- and CH4-enriched hydrothermal fluids of Socorro Island, Revillagigedo Archipelago, Mexico. Evidence for serpentinization and abiogenic methane
Socorro Island is the exposed part of an approx. 4000-m-high volcanic edifice rising from the oceanic floor to
approx. 1000 m asl at the northern part of the Mathematician Ridge, Western Pacific. The volcano is active, with
the most recent basaltic eruption in 1993. Moderate fumarolic activity and diffuse degassing with a total CO2
flux of approx. 20 total day)1 are concentrated in the summit region of the volcano composed of a group of rhy-
olite domes. Low-temperature, boiling point, fumaroles discharge gas with high H2 (up to 20 mol% in dry gas)
and CH4 (up to 4 mol%). Both carbon and He isotopic ratios and abundances correspond to those in MORB flu-
ids (d13CCO2 )5&; 3He â 4He = 7.6 Ra, CO2 â 3He = (2â3) ¡ 109, where Ra is the atmospheric ratio 3He â 4He of
1.4 ¡ 10)6. Light hydrocarbons (CH4, C2H6, C3H8, and C4H10) are characterized by a high C1 âC2+ ratio of
approx. 1000. Methane is enriched in 13C (d13CCH4 from )15 to )20&) and 2H (d2H from )80 to )120&), and
hydrocarbons show an inverse isotopic trend in both d13C and d2H (ethane is isotopically lighter than methane).
These isotopic and concentration features of light hydrocarbons are similar to those recently discovered in fluids
from ultramafic-hosted spreading ridge vents and may be related to the serpentinization processes: H2 generation
and reduction of CO2 to CH4 within high-temperature zone of volcano-seawater hydrothermal system hosted in
basaltic and ultramafic rocks beneath a volcano edifice. The thermodynamic analysis of this unusual composition
of the Socorro fluids and the assessment of endmember compositions are complicated by the near-surface cool-
ing, condensation and mixing with meteoric water
Monitoring active volcanoes: The geochemical approach
Shallow magmas located beneath active volcanoes release volatiles both
during eruptive activity and during inter-eruptive periods (passive degassing). The fluids in
active volcanic areas rise directly from magma, and their composition is characterized mainly
by H2O, CO2, SO2, H2S, HF and HCl (condensable gases), and by some non-condensable gases
(e.g. He, H2, N2, CO, CH4).
The chemical composition of fumarolic gases can reflect the pressure, temperature and
oxygen fugacity conditions of the deep magmatic source, provided that during their rise
towards the surface, the gases do not undergo re-equilibration processes [Giggenbach 1980,
Giggenbach 1996, Nuccio and Paonita 2001, Paonita et al. 2002]. As the equilibrium kinetics of
several chemical reactions is much slower than the rising velocities of the gases, the gas
molecular compositions often undergo quenching phenomena, so that the gases show
temperature and pressure equilibria higher than their outlet values.
The concentration of magmatic species or their molecular ratios can be determined by
means of direct sampling of fumarole gases or by using telemetric methods of observation.
The extensive parameters (mass output) of volcanic fluids, coupled with the intensive
parameters described before, provide basic and useful information for the formulation of
volcanic fluid degassing models [Italiano et al. 1997, Brusca et al. 2004, Inguaggiato et al. 2011].
The first step in the framework of the geochemical investigation of a volcanic system
aimed at surveillance is the chemical and isotopic characterization of the fluids, and the putting
forward of a geochemical model [Inguaggiato et al. 2011]; within this geochemical model, it is
possible to interpret the observed changes in any single investigated parameter. The
geochemical approach is to identify the following topics:
⢠The main end-members involved in the studied system;
⢠The possible type and degree of interaction processes: e.g. water-rock and gas-water interactions;
⢠The mixing among the individual end-members;
⢠The chemical and isotopic characterization of a possible hydrothermal system;
⢠The formulation of a geochemical model
Decoupling of ground level pressures observed in Italian volcanoes: are they driven by space weather geo-effectiveness?
Investigations on correlation drops between near-ground atmospheric
pressures measured at sea level and at higher altitudes on Italian volcanoes
have been carried out. We looked for perturbations of the atmospheric
pressure field driven by volcanic activity, but not excluding possible
external triggers for the observed anomalies. Decorrelations between atmospheric
pressures measured at Stromboli Island in stations located at
different altitudes (years 2002-10) have been analysed and compared with
data from other volcanic (Vesuvius) and non volcanic (Mt. Soro) orographic
structures. We investigated as their possible triggers volcanic, meteorological
and space weather parameters, with particular attention to
Total Solar Irradiance (TSI), Kp index and Forbush decreases. Pressure
decorrelations seems to be driven by astronomic cycles, with maxima in
summer and minima in winter. A further contribution was found, seemingly
assignable to TSI anomalies, with correlation minima occurring 12
hours after these but only during phases of high Sun activity. Moreover,
during the same phases a main periodicity of about 27 days in pressure
decorrelations was revealed by FFT analysis. This period is the same of
the Sun Carrington rotation, expressing the periodic reappearance of
sunspot groups on Sunâs surface. The strong similarity between recurrences
of sunspot number and atmospheric pressure anomalies further
supports the role of the former as a possible trigger for the latter
Transcranial direct current stimulation (tDCS) in unilateral cerebral palsy: A pilot study of motor effect
Transcranial Direct Current Stimulation (tDCS) is an emerging tool to improve upper limb motor functions after stroke acquired in adulthood; however, there is a paucity of reports on its efficacy for upper limb motor rehabilitation in congenital or early-acquired stroke. In this pilot study we have explored, for the first time, the immediate effects, and their short-term persistence, of a single application of anodal tDCS on chronic upper limb motor disorders in children and young individuals with Unilateral Cerebral Palsy (UCP). To this aim, in a crossover sham-controlled study, eight subjects aged 10-28 years with UCP underwent two sessions of active and sham tDCS. Anodal tDCS (1.5 mA, 20 min) was delivered over the primary motor cortex (M1) of the ipsilesional hemisphere. Results showed, only following the active stimulation, an immediate improvement in unimanual gross motor dexterity of hemiplegic, but not of nonhemiplegic, hand in Box and Block test (BBT). Such improvement remained stable for at least 90 minutes. Performance of both hands in Hand Grip Strength test was not modified by anodal tDCS. Improvement in BBT was unrelated to participantsâ age or lesion size, as revealed by MRI data analysis. No serious adverse effects occurred after tDCS; some mild and transient side effects (e.g., headache, tingling, and itchiness) were reported in a limited number of cases. This study provides an innovative contribution to scientific literature on the efficacy and safety of anodal tDCS in UCP
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