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Piacentini Daniela Devoto Stefano Mantovani Matteo Pasuto Alessandro Prampolini Mariacristina Soldati Mauro 《Natural Hazards》2015,78(1):681-697
Natural Hazards - Persistent Scatterers Interferometry (PSI) techniques are widely employed in geosciences to detect and monitor landslides with high accuracy over large areas, but they also suffer... 相似文献
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Jacopo Cabassi Franco Tassi Orlando Vaselli Jens Fiebig Matteo Nocentini Francesco Capecchiacci Dmitri Rouwet Gabriele Bicocchi 《Bulletin of Volcanology》2013,75(1):1-19
This paper focuses on the chemical and isotopic features of dissolved gases (CH4 and CO2) from four meromictic lakes hosted in volcanic systems of Central–Southern Italy: Lake Albano (Alban Hills), Lake Averno (Phlegrean Fields), and Monticchio Grande and Piccolo lakes (Mt. Vulture). Deep waters in these lakes are characterized by the presence of a significant reservoir of extra-atmospheric dissolved gases mainly consisting of CH4 and CO2. The δ13C-CH4 and δD-CH4 values of dissolved gas samples from the maximum depths of the investigated lakes (from ?66.8 to ?55.6?‰ V-PDB and from ?279 to ?195?‰ V-SMOW, respectively) suggest that CH4 is mainly produced by microbial activity. The δ13C-CO2 values of Lake Grande, Lake Piccolo, and Lake Albano (ranging from ?5.8 to ?0.4?‰ V-PDB) indicate a significant CO2 contribution from sublacustrine vents originating from (1) mantle degassing and (2) thermometamorphic reactions involving limestone, i.e., the same CO2 source feeding the regional thermal and cold CO2-rich fluid emissions. In contrast, the relatively low δ13C-CO2 values (from ?13.4 to ?8.2?‰ V-PDB) of Lake Averno indicate a prevalent organic CO2. Chemical and isotopic compositions of dissolved CO2 and CH4 at different depths are mainly depending on (1) CO2 inputs from external sources (hydrothermal and/or anthropogenic); (2) CO2–CH4 isotopic exchange; and (3) methanogenic and methanotrophic activity. In the epilimnion, vertical water mixing, free oxygen availability, and photosynthesis cause the dramatic decrease of both CO2 and CH4 concentrations. In the hypolimnion, where the δ13C-CO2 values progressively increase with depth and the δ13C-CH4 values show an opposite trend, biogenic CO2 production from CH4 using different electron donor species, such as sulfate, tend to counteract the methanogenesis process whose efficiency achieves its climax at the water–bottom sediment interface. Theoretical values, calculated on the basis of δ13C-CO2 values, and measured δ13CTDIC values are not consistent, indicating that CO2 and the main carbon-bearing ion species (HCO3 ?) are not in isotopic equilibrium, likely due to the fast kinetics of biochemical processes involving both CO2 and CH4. This study demonstrates that the vertical patterns of the CO2/CH4 ratio and of δ13C-CO2 and δ13C-CH4 are to be regarded as promising tools to detect perturbations, related to different causes, such as changes in the CO2 input from sublacustrine springs, that may affect aerobic and anaerobic layers of meromictic volcanic lakes. 相似文献
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A new hydrostratigraphic model of Venice area (Italy) 总被引:3,自引:3,他引:0
Matteo Cultrera Renzo Antonelli Giordano Teza Silvia Castellaro 《Environmental Earth Sciences》2012,66(4):1021-1030
Two environmental problems affect the Venice area: subsidence, which has been increasing due to the intensive water abstraction after the Second World War, and contamination of the soil and shallow aquifers. In order to address these problems, which are decisive factors in the entire Venetian ecosystem, the aquifer structure must be known in detail. The lithologic data are abundant and of good quality up to a depth of 50 m, whereas boreholes beyond this depth are much rarer and more dispersed, making their associated lithological data unreliable. This work, which uses the available data together with fast and low cost passive seismic measurements, provides an improved understanding of the deeper hydrogeologic domain. For this purpose, a MATLAB package (Modalstrata) has been developed to improve the correlation of the stratigraphic succession for each selected homogeneous sub-area and applied to obtain a new, upgraded hydrostratigraphic model. The horizontal to vertical spectral ratio passive seismic surveys have confirmed the lateral correlations among the sample areas at least for the two main aquifer horizons. Analysis and comparisons of several previous studies performed on the data related to the only drilling continuous coring 951 m deep in the Tronchetto Island (Venice), have allowed a satisfactory validation of the proposed hydrogeological model. 相似文献
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Matteo Masotta Carmela Freda Mario Gaeta 《Contributions to Mineralogy and Petrology》2012,163(1):49-65
Crystal-poor, differentiated magmas are commonly erupted from shallow, thermally zoned magma chambers. In order to constrain
the origin of these magmas, we have experimentally investigated crystallization, differentiation and crystal-melt separation
in presence of a thermal gradient. Experiments have been designed taking advantage of the innate temperature gradient of the
piston cylinder apparatus and carried out on a phonolitic system at 0.3 GPa and temperature ranging from 1,050 to 800°C. Crystallization
degree and melt composition in experimental products vary as a function of the temperature gradient. In particular, melt composition
differentiates from tephri-phonolite (starting material) to phonolite moving from the hotter, glassy zone (T ≤ 1,050°C) towards the cooler, heterogeneously crystallized zone (T ≤ 900°C) of the charge. The heterogeneously crystallized zone is made up of: (1) a crystal-rich, mushy region (crystallinity
>30 vol%), (2) a rigid crystal framework (crystallinity ≤80 vol%) and (3) glassy belts of phonolitic glass at the top. Thermal
gradient experiments picture crystallization, differentiation and crystal-melt separation processes occurring in a thermally
zoned environment and reveal that relatively large volumes of crystal-poor melt (glassy belts) can originate as a consequence
of the instability and collapse of the rigid crystal framework. Analogously, in thermally zoned magma chambers, the development
and collapse of a solidification front may represent the controlling mechanism originating large volumes of crystal-poor,
differentiated magmas. 相似文献