454 research outputs found
Carbon Dioxide Diffuse Emission from the Soil at Vesuvio and Campi Flegrei (Pozzuoli): Ten Years of Observations
Carbon dioxide flux from the soil is regularly monitored
in selected areas of Vesuvio and Solfatara (Campi Flegrei,
Pozzuoli) with the main aim of investigating if the
surface phenomena could provide information about
the processes occurring at depth. Surveyed areas include
15 fixed points around the rim of Vesuvio and 71
fixed points in the floor of Solfatara crater, where soil
CO2 flux is measured since 1998, at least once a month.
In addition, two automatic permanent stations, located
at Vesuvio and Solfatara, continually measure the CO2
flux and some environmental parameters that can potentially
influence the CO2 diffuse degassing.
We analysed, with statistical procedures, the feature
of the acquired signals, evaluating the spatial and temporal
variations of the CO2 degassing process.
Series acquired by continuous stations are characterized
by an annual periodicity that is related to the
typical periodicities of some meteorological parameters
(e.g., air temperature, air humidity, etc.). Such a kind of
signal permits to define the “reference” level of the CO2
degassing process that diffusely affects the flanks and
the base of the volcanoes.
Conversely, series of CO2 flux data arising from periodic
measurements over the arrays of Vesuvio and
Solfatara, are less dependent on external factors such
as meteorological parameters, local soil properties (porosity,
hydraulic conductivity) and topographic effects
(high or low ground). Therefore we argue that the longterm
trend of this signal contains the “best” possible
representation of the endogenous signal related to the
upflow of deep hydrothermal fluids. At Vesuvio and Solfatara,
the variations of these series have shown some correspondence with other physical changes of the volcanic systems
Temperature and pressure gas geoindicators at the Solfatara fumaroles (Campi Flegrei)
Long time series of fluid pressure and temperature within a hydrothermal
system feeding the Solfatara fumaroles are investigated here, on the basis
of the chemical equilibria within the CO2-H2O-H2-CO gas system. The
Pisciarelli fumarole external to Solfatara crater shows an annual cycle of
CO contents that indicates the occurrence of shallow secondary processes
that mask the deep signals. In contrast, the Bocca Grande and Bocca Nova
fumaroles located inside Solfatara crater do not show evidence of
secondary processes, and their compositional variations are linked to the
temperature–pressure changes within the hydrothermal system. The
agreement between geochemical signals and the ground movements of the
area (bradyseismic phenomena) suggests a direct relationship between the
pressurization process and the ground uplift. Since 2007, the gas
geoindicators have indicated pressurization of the system, which is most
probably caused by the arrival of deep gases with high CO2 contents in
the shallow parts of the hydrothermal system. This pressurization process
causes critical conditions in the hydrothermal system, as highlighted by
the increase in the fumarole temperature, the opening of new vents, and
the localized seismic activity. If the pressurization process continues with
time, it is not possible to rule out the occurrence of phreatic explosions
Geochemical monitoring integrated in a real time hydrological network
Hydrological data relative to springs and water wells collected by the Hydrografic National Service in Naples indicate that some anomalies can be correlated with the seismic activity in Southern Apennines. In this paper we report some hydrological anomalies for the November 23, 1980 earthquake and suggest that an improvement of the hydrometeorological network of the Hydrographic National
Service can reveal geochemical and hydrological anomalies before the earthquakes
Long time-series of chemical and isotopic compositions of Vesuvius fumaroles: evidence for deep and shallow processes
Long time-series of chemical and isotopic compositions of Vesuvius
fumaroles were acquired in the framework of the volcanic surveillance in
the 1998-2010 period. These allow the identification of processes that
occur at shallow levels in the hydrothermal system, and variations that are
induced by deep changes in volcanic activity. Partial condensation
processes of fumarolic water under near-discharge conditions can explain
the annual 18O and deuterium variabilities that are observed at Vesuvius
fumaroles. Significant variations in the chemical compositions of
fumaroles occurred over the 1999-2002 period, which accompanied the
seismic crisis of autumn 1999, when Vesuvius was affected by the most
energetic earthquakes of its last quiescence period. A continuous increase
in the relative concentrations of CO2 and He and a general decrease in the
CH4 concentrations are interpreted as the consequence of an increment in
the relative amount of magmatic fluids in the hydrothermal system. Gas
equilibria support this hypothesis, showing a PCO2 peak that culminated in
2002, increasing from values of ~40 bar in 1998 to ~55-60 bar in 2001-
2002. We propose that the seismic crisis of 1999 marked the arrival of the
magmatic fluids into the hydrothermal system, which caused the observed
geochemical variations that started in 1999 and culminated in 2002
Long Time Series Of Fumarolic Compositions At Volcanoes: The Key To Understand The Activity Of Quiescent Volcanoes
Long time series of fumarolic chemical and isotopic
compositions at Campi Flegrei, Vulcano, Panarea,
Nisyros and Mammoth volcanoes highlight the occurrence
of mixing processes among magmatic and hydrothermal
fluids. At Campi Flegrei temperatures of
about 360°C of the hydrothermal system are inferred by
chemical and isotopic geoindicators. These high temperatures
are representative of a deep zone where magmatic
gases mix with hydrothermal liquids forming the gas plume feeding the fumaroles. Similar mixing processes
between magmatic fluids and a hydrothermal
component of marine origin have been recognized at
Vulcano high temperature fumaroles. In both the system
a typical ‘andesitic’ water type composition and high
CO2 contents characterizes the magmatic component.
Our hypothesis is that pulsing injections of these CO2-
rich magmatic fluids at the bottom of the hydrothermal
systems trigger the bradyseismic crises, periodically
affecting Campi Flegrei, and the periodical volcanic
unrest periods of Vulcano. At Campi Flegrei a strong
increase of the fraction of the magmatic component
marked the bradyseismic crisis (seismicity and ground
uplift) of 1982-84 and four minor episodes occurred in
1989, 1994 and 2000 and 2006. Increases of the magmatic
component in the fumaroles of Vulcano were recorded
in 1979-1981, 1985, 1988, 1996, 2004 and 2005
concurrently with anomalous seismic activity. Physicalnumerical
simulations of the injection of hot, CO2 rich
fluids at the base of a hydrothermal system, asses the
physical feasibility the process. Ground deformations,
gravitational anomalies and seismic crisis can be well
explained by the complex fluid dynamic processes
caused by magma degassing episodes. Sporadic data
on the fumaroles of other volcanoes, for example Panarea,
Nisyros (Greece), Mammoth (California), suggest
that magma degassing episodes frequently occur in
dormant volcanoes causing volcanic unrest processes
not necessarily linked to magma movement but rather
to pulsating degassing processes from deep pressurized,
possibly stationary, magma bodies
One year of geochemical monitoring of groundwater in the Abruzzi region after the 2009 earthquakes.
The presence of a deep and inorganic source of CO2 has been recently recognized in Italy on the basis of the
deeply derived carbon dissolved in the groundwater. In particular, the regional map of CO2 Earth degassing
shows that two large degassing structures (Tuscan Roman degassing structure, TRDS, and Campanian degassing
structure, CDS) affect the Tyrrhenian side of the Italian peninsula. The comparison between the map of CO2
Earth degassing and of the location of the Italian earthquakes highlights that the anomalous CO2 flux suddenly
disappears in the Apennine in correspondence of a narrow band where most of the seismicity concentrates. A
previous conceptual model proposed that in this area, at the eastern borders of TRDS and CDS, the CO2 from the
mantle wedge intrudes the crust and accumulate in structural traps generating over-pressurized reservoirs. These
CO2 over-pressurized levels can play a major role in triggering the Apennine earthquakes.
The 2009 Abruzzo earthquakes, like previous seismic crises in the Northern Apennine, occurred at the border of
the TRDS, suggesting also in this case a possible role played by deeply derived fluids in the earthquake generation.
Detailed hydro-geochemical campaigns, with a monthly frequency, started immediately after the main shock of
the 6th of April 2009. The new campaigns include the main springs of the area which were previously studied in
detail, during a campaign performed ten years ago, constituting a pre-crisis reference case. Almost one year of
geochemical data of the main dissolved ions, of dissolved gases (CO2, CH4, N2, Ar, He) and of the stable isotopes
of the water (H, O), CO2 (13C) and He (3He/4He), highlight both that the epicentral area of L’Aquila earthquakes
is affected by an important process of CO2 Earth degassing and that that the gases dissolved in the groundwater
reflects the input in to the aquifers of a deep gas phase, CO2- rich, with an high He content and with low 3He/4He
ratios, similar to the gases emitted by natural manifestations located in the northern Apennines which are fed by
deep pressurized reservoirs. Furthermore a systematic increase in the content of the deeply derived CO2 dissolved
in the aquifers occurred respect to the July 1997 samples. This increase, followed by a gentle decline of the
anomaly, can be compatible with the occurrence of an episode of deep CO2 degassing concurrently with the earthquakes.
The origin of this regional variation is under investigation and, at the present moment, an unambiguous
interpretation of the data is not possible because the lack of a systematic monitoring of the springs before the
seismic events and because eventual seasonal effects on observed variation in CO2 flux are still under investigatio
A shallow-layer model for heavy gas dispersion from natural sources: Application and hazard assessment at Caldara di Manziana, Italy
Several nonvolcanic sources in central Italy emit a large amount of carbon dioxide (CO2). Under stable
atmospheric conditions and/or in the presence of topographic depressions, the concentration of CO2, which
has a molecular mass greater than that of air, can reach high values that are lethal to humans or animals.
Several episodes of this phenomenon were recorded in central Italy and elsewhere. In order to validate a
model for the dispersion of a heavy gas and to assess the consequent hazard, we applied and tested the code
TWODEE-2, an improved version of the established TWODEE model, which is based on a shallow-layer
approach that uses depth-averaged variables to describe the flow behavior of dense gas over complex
topography. We present results for a vented CO2 release at Caldara di Manziana in central Italy. We find
that the model gives reliable results when the input quantity can be properly defined. Moreover, we show
that the model can be a useful tool for gas hazard assessment by evaluating where and when lethal
concentrations for humans and animals are reached
A GIS-Based Hydrogeological Approach to the Assessment of the Groundwater Circulation in the Ischia Volcanic Island (Italy)
Assessing the variations in space and time of groundwater circulation in volcanic islands is of paramount importance to the description of the hydro-geo-thermal system and implementation of hydrogeological, geochemical, and volcanic monitoring systems. In fact, the reliable reconstruction of the groundwater potentiometric surface in such composite volcanic aquifer systems can enable the identification of the most advantageous strategies for both the sustainable use of groundwater resources and the management of volcanic risk. Geographical Information System (GIS) platforms can support the integration and analysis of many spatial and temporal variables derived from monitoring of active volcanoes and the elaboration of spatially continuous data. However, open issues still affect the reliability and general applicability of common spatial interpolation methods in the case of groundwater potentiometric surfaces. This is related to the assessment of the main stratigraphic and volcano-tectonic features affecting the hydraulic head changes. With regard to the dynamically very active Ischia Island (Italy), this study illustrates a GIS-based hydrogeological approach to identify the most accurate interpolation method for mapping the potentiometric surface in complex hydrogeological terrains. The proposed approach has been applied to the existing dataset (1977–2003) stored by Istituto Nazionale di Geofisica e Vulcanologia. Based on a careful geological and hydrogeological survey, a total of 267 wells, from 5 to 250 m in depth, were processed. The data pre-processing involved four meteorological time-series data (1922–1997) and six long records of piezometric water levels (1930–1994). As a result, knowledge of the delineation of rather homogeneous stratigraphic and volcano-tectonic structures at the basin-scale has improved. Thus, new, more reliable potentiometric surfaces of the four main geothermal areas closest to the coast were produced during both dry and wet seasons. The reliability of the processed potentiometric surface was then validated by comparing the spatially continuous data with complementary field data. These findings point toward an optimal interpolation approach for representing the seasonal and areal distribution of main hydrogeological parameters in complex aquifer systems. Finally, insights into variations of hydrological behavior at an active volcanic area will foster an understanding of possible involvement of fresh and thermal waters in triggering phreatic explosions
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