407 research outputs found
First test of a BAE transducing scheme on a Resonant Gravitational-Wave Antenna
We present the results obtained with a resonant capacitive transducer, suitable for Back Action Evasion (BAE) measurements, coupled for the first time to a
gravitational-wave antenna. This scheme was developed in collaboration with the
Group of the University of Rome La Sapienza. The antenna is a 270 kg aluminum 5056 alloy cylinder, with a resonant frequency of 1805 Hz, operating at 4.2K in the ALTAIR
cryostat, located in Frascati (Italy) at the IFSI-CNR laboratory. The apparatus was able to work continuously for periods as long as days, both in up-conversion and BAE
configurations, with good stability. The behaviour of the system is in reasonable Agreement with a proposed model of a double harmonic oscillator in a BAE readout scheme. The limits on the sensitivity of this set-up are discussed as well as the possible future improvements
Mineralogy and geochemical trapping of CO2 in an Italian carbonatic deep saline aquifer: preliminary results
CO2 Capture & Storage (CCS) is presently one of the most promising technologies
for reducing anthropogenic emissions of CO2 . Among the several potential geologi-
cal CO2 storage sites, e.g. depleted oil and gas field, unexploitable coal beds, saline
aquifers, the latter are estimated to have the highest potential capacity (350-1000 Gt
CO2 ) and, being relatively common worldwide, a higher probability to be located
close to major CO2 anthropogenic sources. In these sites CO2 can safely be retained
at depth for long times, as follows: a) physical trapping into geologic structures; b) hy-
drodynamic trapping where CO2(aq) slowly migrates in an aquifer, c) solubility trap-
ping after the dissolution of CO2(aq) and d) mineral trapping as secondary carbon-
ates precipitate. Despite the potential advantages of CO2 geo-sequestration, risks of
CO2 leakage from the reservoir have to be carefully evaluated by both monitoring
techniques and numerical modeling used in “CO2 analogues”, although seepage from
saline aquifers is unlikely to be occurring. The fate of CO2 once injected into a saline
aquifer can be predicted by means of numerical modelling procedures of geochemical
processes, these theoretical calculations being one of the few approaches for inves-
tigating the short-long-term consequences of CO2 storage. This study is focused on
some Italian deep-seated (>800 m) saline aquifers by assessing solubility and min-
eral trapping potentiality as strategic need for some feasibility studies that are about
to be started in Italy. Preliminary results obtained by numerical simulations of a geo-
chemical modeling applied to an off-shore Italian carbonatic saline aquifer potential
suitable to geological CO2 storage are here presented and discussed. Deep well data,
still covered by industrial confidentiality, show that the saline aquifer, includes six
Late Triassic-Early Jurassic carbonatic formations at the depth of 2500-3700 m b.s.l.
These formations, belonging to Tuscan Nappe, consist of porous limestones (mainly
calcite) and marly limestones sealed, on the top, by an effective and thick cap-rock
(around 2500 m) of clay flysch belonging to the Liguride Units. The evaluation of the
potential geochemical impact of CO2 storage and the quantification of water-gas-rock
reactions (solubility and mineral trapping) of injection reservoir have been performed
by the PRHEEQC (V2.11) Software Package via corrections to the code default ther-
modynamic database to obtain a more realistic modelling. The main modifications to
the Software Package are, as follows: i) addition of new solid phases, ii) variation
of the CO2 supercritical fugacity and solubility under reservoir conditions, iii) addi-
tion of kinetic rate equations of several minerals and iv) calculation of reaction sur-
face area. Available site-specific data include only basic physical parameters such as
temperature, pressure, and salinity of the formation waters. Rocks sampling of each
considered formation in the contiguous in-shore zones was carried out. Mineralogy
was determined by X-Ray diffraction analysis and Scanning Electronic Microscopy
on thin sections. As chemical composition of the aquifer pore water is unknown, this
has been inferred by batch modeling assuming thermodynamic equilibrium between
minerals and a NaCl equivalent brine at reservoir conditions (up to 135 ̊C and 251
atm). Kinetic modelling was carried out for isothermal conditions (135 ̊C), under a
CO2 injection constant pressure of 251 atm, between: a) bulk mineralogy of the six
formations constituting the aquifer, and b) pre-CO2 injection water. The kinetic evolu-
tion of the CO2 -rich brines interacting with the host-rock minerals performed over 100
years after injection suggests that solubility trapping is prevailing in this early stage
of CO2 injection. Further and detailed multidisciplinary studies on rock properties,
geochemical and micro seismic monitoring and 3D reservoir simulation are necessary
to better characterize the potential storage site and asses the CO2 storage capacity
The gas membrane sensor (GMS) method: a new analytical approach for real-time gas concentration measurements in volcanic lakes
Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage.
Heavy metals in surface waters and suspended solids from the Usciana River (Tuscany, central Italy)
Sedimentological, mineralogical and geochemical features of late quaternary sediment profiles from the Southern Tuscany Hg Mercury District (Italy): Evidence for the presence of pre-industrial mercury and arsenic concentrations
Southern Tuscany (Italy) is an important metallogenic district that hosts relevant S-polymetallic deposits that have intensely been exploited for centuries. Consequently, potential toxic elements, such as Hg and As, are widely distributed in the surrounding environment. In this paper, an extensive sedimentological, mineralogical and geochemical study of two Late Quaternary sediment profiles, partially outcropping along the coast of southern Tuscany (Ansedonia area), was carried out to evaluate the contents and mobility of Hg and As with the aims to contribute to the definition of the geochemical baseline of southern Tuscany before the human intervention and evaluate the potential dispersion of these harmful elements. The sedimentological, mineralogical and geochemical (major elements) features revealed that the studied profiles are mostly related to the local geological characteristics and the Quaternary geological history of the area. The concentrations and the normalized patterns of trace and rare earth elements highlighted the absence of any anthropogenic activity. This implies that the studied samples are to be regarded as good proxies for evaluating the geochemical baseline of southern Tuscany before the intense mining activity. The enrichment factors (EF) of most trace elements were indeed lower or close to 2, indicating a variability close to the average concentration of the Upper Continental Crust (UCC), while other elements slightly enriched, such as Pb, were in agreement with the natural baseline reported for southern Tuscany. Mercury and As displayed EF values >40 when compared to the average contents of UCC, although they decrease down to 4 when compared to the suggested baseline for southern Tuscany. The higher Hg and As contents detected in this study, inferred to natural sources, evidenced (i) the great natural variability occurring in largely mineralized areas and (ii) the importance of estimating reference environmental parameters in order to avoid misleading interpretations of the detected anomalies. Moreover, the results of leaching test on sediment samples denoted a relatively low mobility of Hg and As, suggesting that these elements are preferentially mobilized by transport of clastic sediments and such anomalies may be preserved for relatively long times in Quaternary sediments. However, leachable Hg (0.6-9.7 μg/L) and As (2.1-42.2 μg/L) concentrations are significantly high when compared to those of the Italian limit for groundwater (1 μg/L for Hg and 10 μg/L for As). Quaternary sediments from southern Tuscany could then be a potential, though natural, source of Hg and As to groundwater systems
Overview of the geochemical modeling on CO2 capture & storage in Italian feasibility studies
CO2 Capture & Storage in saline aquifers is presently one
of the most promising technologies for reducing
anthropogenic emissions of CO2. In these sites the short-longterm
consequences of CO2 storage into a deep reservoir can be
predicted by numerical modelling of geochemical processes.
Unfortunately a common problem working with off-shore
closed wells, where only the well-log information are
available, is to obtain physico-chemical data (e.g.
petrophysical and mineralogical) needed to reliable numerical
simulations. Available site-specific data generally include only
basic physical parameters such as temperature, pressure, and
salinity of the formation waters.
In this study we present a methodological procedure that
allows to estimate and integrate lacking information to
geochemical modelling of deep reservoirs such as: i) bulk and
modal mineralogical composition, ii) porosity and
permeability of the rock obtained from heat flow
measurements and temperature, iii) chemical composition of
formation waters (at reservoir conditions) prior of CO2
injection starting from sampling of analogue outcropping rock
formations.
The data sets in this way reconstructed constitute the base
of geochemical simulations applied on some deep-seated
Italian carbonatic and sandy saline aquifers potentially suitable
for geological CO2 storage.
Numerical simulations of reactive transport has been
performed by using the reactive transport code
TOUGHREACT via pressure corrections to the default
thermodynamic database to obtain a more realistic modelling.
Preliminary results of geochemical trapping (solubility and
mineral trapping) potentiality and cap-rock stability as
strategic need for some feasibility studies near to be started in
Italy are here presented and discussed
Morphological and geochemical features of crater lakes in Costa Rica: an overview.
This paper describes the compositional and morphological features of the crater lakes found in the volcanoes of Rincón de La Vieja, Poás, Irazú, Congo and Tenorio volcanoes (Costa Rica). As evidenced by the distribution of the water and dissolved gas chemistry along vertical profiles, the different fluid sources feeding the lakes reflect the present status of each of the volcanic systems. The chemical features of the Caliente (Poás volcano) and Rincón crater (Rincón de la Vieja volcano) lakes are mainly dependent on i) inputs of magmatic fluids from sub-lacustrine fumaroles and ii) water-rock interaction processes. Conversely, the Irazú lake is mainly affected by the presence of CO2(H2S)-rich fluids discharged from a hydrothermal system, which masked possible magmatic fluid contributions. Rainfall and organic activity are the main factors responsible for the chemical composition of Hule, Botos, Congo and Tenorio lakes. The chemical and isotopic water composition of Botos, Irazú and Hule lakes have displayed no significant variations along the vertical profiles. In contrast, Caliente lake shows a distinctive chemical stratification, mainly involving F-, Cl- and SO4 2-. The behaviour of these compounds seems to be governed by both dissolution of highly acidic species, i.e. HF, HCl and SO2 released from the magmatic environment, and microbial activity. Despite the significant increases with depth of dissolved CO2 at Caliente and Irazú lakes, the hazard for Nyos-type gas eruptions can be considered negligible, since i) the water volumes are too small and ii) the convective heat transfer limits the CO2 recharge rate. The relatively high concentrations of dissolved CO2 measured at the maximum depth of the Hule lake are likely produced by both degradation of organic material and degassing from a deep source. The sporadic episodes of fish deaths recently observed in this lake can be associated with lake overturn processes that have favoured the rise up to the lake surface of deep, oxygen-depleted waters.Journal of limnolog
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