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11.
Daniela Zeppilli Marianna Mea Cinzia Corinaldesi Roberto Danovaro 《Progress in Oceanography》2011,91(3):260-272
Mud volcanoes are cold seeps, in which the escape of gas and fluids associated with mud creates 3-D bottom structures that enhance the spatial heterogeneity and potentially alter the functioning of the benthic ecosystems. We investigated a complex system of mud volcanoes of the Mediterranean Sea characterised by the presence of different structures (i.e., isolated domes, domes surrounded by moats, clustered domes, and ridges) displaying different levels of seepage. We hypothesize that the combined effects of seafloor heterogeneity (i.e., different 3-D structures as revealed by detailed topographic analysis), fluid emissions and trophic characteristics of these systems can influence the structural and functional biodiversity of meiofauna (with special focus on the nematodes). We found that sediments affected by intensive seepage displayed the lowest faunal abundances and number of higher taxa. However, mud volcanoes without emissions, but characterized by a high structural complexity (such as the ridges), were associated with the highest meiofaunal abundances and number of higher taxa. Mud volcanoes hosted also a remarkable abundance of rare taxa specifically associated with these structures (e.g., acarians, cumaceans, tanaids, cladocerans and hydroids) and absent in slope sediments (used as a control). Each mud-volcano area displayed a different nematode species composition. Overall 76 nematode species (from a total of 235) were exclusively associated with mud-volcano structures, whilst 29 were exclusively encountered in slope sediments. We conclude that the presence of mud volcanoes, for their contribution to increase spatial heterogeneity and for the extreme conditions associated with gas emissions, promotes higher levels of beta diversity, thus enhancing the regional (gamma) benthic diversity. These findings provide new insights on the factors controlling meiobenthic biodiversity in mud volcanoes and clues for future action of conservation of the biodiversity specifically associated with these habitats. 相似文献
12.
The present work reports on the isotopic characterization of rainfall and groundwater at Mt. Vesuvius. Values of δ 18O, monthly measured on rain samples collected during the period 2002–2004 in a rain-gauge network composed of 10 stations, were compared with meteorological and DEM data. Air temperature, controlled by the local orographic structure, was identified as the main factor influencing rain isotopic composition. Another important role is played by orographic clouds, whose condensation over the top of Mt. Vesuvius is responsible for anomalously high δ 18O values recorded in rain samples from the summit area of the volcanic edifice. A spatial model of rain isotopic composition, based on a 3D distribution of temperature derived by a 1 × 1 km DEM, was implemented and used for calculating the theoretical isotopic signature of seepage, further compared with data measured in the groundwater monitoring network. The analysis evidenced the role of local meteoric recharge as the main source feeding Mt. Vesuvius aquifers. The unique exception is the Olivella drainage gallery, located on the north-eastern flank of the volcanic edifice, whose isotopic composition is slightly more positive than the one expected for its altitude, likely caused by both evaporation processes and mixing with condensed hydrothermal vapor. 相似文献
13.
Dominik Hennhoefer Aisha Al Suwaidi Cinzia Bottini Emina Helja Thomas Steuber 《Sedimentology》2019,66(2):536-555
The sedimentary record of the Arabian Shelf offers a unique opportunity to study the Cretaceous (Albian–Turonian) greenhouse climate from a palaeoequatorial perspective. In particular, hemipelagic to pelagic carbonate successions from the extensive Shilaif intra‐shelf basin have the potential to produce an excellent record of carbon cycle perturbations during this interval. This study presents a 269 m thick chemostratigraphic (carbonate δ13C and δ18O) record from the Middle Albian to Early Turonian of central Abu Dhabi (United Arab Emirates), representing over 14 Myr of uninterrupted carbonate sedimentation. The Mauddud to Shilaif formations represent outer ramp to basinal intra‐shelf carbonates with variations from laminated organic‐rich to clean bioturbated intervals. Isotopic evidence of the latest Albian Anoxic Event (Oceanic Anoxic Event 1d), Middle Cenomanian Event I and the Cenomanian–Turonian Anoxic Event (Oceanic Anoxic Event 2) are confirmed and biostratigraphically calibrated by means of calcareous nannofossils. The carbon isotope record allows correlation with other regional records and well‐calibrated records across the Tethyan Ocean and represents a significant improvement of the chronostratigraphic framework of the United Arab Emirates (Shilaif) and Oman (Natih) intra‐shelf basins. The study further confirms that low carbon isotope values corresponding to the two source rock intervals in the Shilaif Formation clearly precede the isotopic expressions of Oceanic Anoxic Event 1d and Oceanic Anoxic Event 2. 相似文献
14.
Hubert J. Morel‐Seytoux Calvin D. Miller Cinzia Miracapillo Steffen Mehl 《Ground water》2017,55(3):399-407
Flow exchange between surface and groundwater is of great importance be it for beneficial allocation and use of water resources or for the proper exercise of water rights. In large‐scale regional studies, most numerical models use coarse grid sizes, which make it difficult to provide an accurate depiction of the phenomenon. In particular, a somewhat arbitrary leakance coefficient in a third type (i.e., Cauchy, General Head) boundary condition is used to calculate the seepage discharge as a function of the difference of head in the river and in the aquifer, whose value is often found by calibration. A different approach is presented to analytically estimate that leakance coefficient. It is shown that a simple equivalence can be deduced from the analytical solution for the empirical coefficient, so that it provides the accuracy of the analytical solution while the model maintains a very coarse grid, treating the water‐table aquifer as a single calculation layer. Relating the empirical leakance coefficient to the exact conductance, derived from physical principles, provides a physical basis for the leakance coefficient. Factors such as normalized wetted perimeter, degree of penetration of the river, presence of a clogging layer, and anisotropy can be included with little computational demand. In addition the river coefficient in models such as MODFLOW, for example, can be easily modified when grid size is changed without need for recalibration. 相似文献
15.
Cinzia Belmonte Dino Boccaletti Giuseppe Pucacco 《Celestial Mechanics and Dynamical Astronomy》2006,95(1-4):101-116
We investigate the dynamics in a galactic potential with two reflection symmetries. The phase-space structure of the real system is approximated with a resonant detuned normal form constructed with the method based on the Lie transform. Attention is focused on the stability properties of the axial periodic orbits that play an important role in galactic models. Using energy and ellipticity as parameters, we find analytical expressions of bifurcations and compare them with numerical results available in the literature. 相似文献
16.
Javier Blanco-Sacristán Cinzia Panigada Rodolfo Gentili Giulia Tagliabue Roberto Garzonio M. Pilar Martín Mónica Ladrón de Guevara Roberto Colombo Thomas P. F. Dowling Micol Rossini 《地球表面变化过程与地形》2021,46(12):2466-2484
Biocrusts (topsoil communities formed by mosses, lichens, bacteria, fungi, algae, and cyanobacteria) are a key biotic component of dryland ecosystems. Whilst climate patterns control the distribution of biocrusts in drylands worldwide, terrain and soil attributes can influence biocrust distribution at landscape scale. Multi-source unmanned aerial vehicle (UAV) imagery was used to map and study biocrust ecology in a typical dryland ecosystem in central Spain. Red, green and blue (RGB) imagery was processed using structure-from-motion techniques to map terrain attributes related to microclimate and terrain stability. Multispectral imagery was used to produce accurate maps (accuracy > 80%) of dryland ecosystem components (vegetation, bare soil and biocrust composition). Finally, thermal infrared (TIR) and multispectral imagery was used to calculate the apparent thermal inertia (ATI) of soil and to evaluate how ATI was related to soil moisture (r2 = 0.83). The relationship between soil properties and UAV-derived variables was first evaluated at the field plot level. Then, the maps obtained were used to explore the relationship between biocrusts and terrain attributes at ecosystem level through a redundancy analysis. The most significant variables that explain biocrust distribution are: ATI (34.4% of variance, F = 130.75; p < 0.001), Elevation (25.8%, F = 97.6; p < 0.001), and potential solar incoming radiation (PSIR) (52.9%, F = 200.1; p < 0.001). Differences were found between areas dominated by lichens and mosses. Lichen-dominated biocrusts were associated with areas with high slopes and low values of ATI, with soil characterized by a higher amount of soluble salts, and lower amount of organic carbon, total phosphorus (Ptot) and total nitrogen (Ntot). Biocrust-forming mosses dominated lower and moister areas, characterized by gentler slopes and higher values of ATI with soils with higher contents of organic carbon, Ptot and Ntot. This study shows the potential to use UAVs to improve our understanding of drylands and to evaluate the control that the terrain has on biocrust distribution. 相似文献
17.
Giuseppe Pucacco Dino Boccaletti Cinzia Belmonte 《Celestial Mechanics and Dynamical Astronomy》2008,102(1-3):163-176
The phase-space structure of two families of galactic potentials is approximated with a resonant detuned normal form. The normal form series is obtained by a Lie transform of the series expansion around the minimum of the original Hamiltonian. Attention is focused on the quantitative predictive ability of the normal form. We find analytical expressions for bifurcations of periodic orbits and compare them with other analytical approaches and with numerical results. The predictions are quite reliable even outside the convergence radius of the perturbation and we analyze this result using resummation techniques of asymptotic series. 相似文献
18.
Sericitic alteration at the La Crocetta deposit (Elba Island,Italy): interplay between magmatism,tectonics and hydrothermal activity 总被引：2，自引：0，他引：2
Cinzia?MaineriEmail author Marco?Benvenuti Pilar?Costagliola Andrea?Dini Pierfranco?Lattanzi Giovanni?Ruggieri Igor?M.?Villa 《Mineralium Deposita》2003,38(1):67-86
The La Crocetta mine near Porto Azzurro (Elba Island, Tuscany, Italy) is an important producer of raw material for the ceramic industry. Exploitation focuses on a pervasively sericitized porphyritic aplite of the Tuscan Magmatic Province, locally known as "eurite", which underwent significant potassium enrichment during sericitic alteration. Eurites are located along the hanging wall of the Elba Centrale Fault, a low-angle extensional lineament of regional significance. A later carbonatization stage, apparently associated with high-angle extensional tectonics, locally overprinted the sericitized facies. It is expressed by carbonate ± pyrite ± quartz veins, with adverse effects on ore quality. Sericitization was accompanied by addition of potassium, and loss of Na (± Ca, Fe). Rubidium was not enriched along with potassium during sericitization, contrary to what would be expected for interaction with late-magmatic fluids. New 40Ar–39Ar data from eurites provide an isochron age of about 6.7 Ma for the sericitization, whereas the age of the unaltered protolith is ca. 8.8 Ma. Field evidence indicates the Elba Centrale Fault to be the main channel for the hydrothermal fluids. On the other hand, the involvement of heat and/or fluids contributed by the Porto Azzurro pluton, which crops out in the La Crocetta area, is ruled out by field, geochemical and geochronological data (40Ar–39Ar age of Porto Azzurro =5.9 Ma, i.e. significantly younger than the sericitization event). Fluid inclusion studies suggest that sericitization was associated with a low-temperature (<250 °C) hydrothermal system. Fluids were locally boiling, of variable salinity (4–17 wt% NaCl equiv.), and contained some CO2 (XCO2≤0.027). Their ultimate source is not unequivocally constrained; meteoric and/or magmatic contributions may be possible. Low-salinity (≤2.6 wt% NaCl equiv.), low-temperature (<250 °C) fluids are associated with the late carbonate veining. They are considered to be of dominantly meteoric nature because of their low salinity. In summary, sericitization at La Crocetta is regarded as the product of a detachment fault-related, low temperature hydrothermal system, resulting from the structurally controlled focusing of meteoric and possibly magmatic fluids. Hence, potential targets for exploration for similar resources are represented by aplitic bodies located in the hanging wall of Elba Centrale Fault. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00126-002-0279-2. 相似文献
19.
Cinzia Bettiol Lorenzo Stievano Mariangela Bertelle Francesca Delfino Emanuele Argese 《Applied Geochemistry》2008
Acid extractions represent a simple and effective tool for the assessment of metal contamination, origin and bioavailability in the aquatic environment. Optimized microwave-assisted procedures utilizing two extractions (8 M HNO3 and 1 M HCl) were developed. Particular attention was given to the evaluation of efficiency and selectivity of the developed procedures. This involved an examination of the sediment and the extraction residues by Mössbauer spectroscopy and X-ray diffractometry. These instrumental approaches were used to identify the geochemical phases associated with acid decomposition. Microwave digestion with 8 M HNO3 produced an efficient solubilization of the most important metal-bearing phases and left unaffected only the minerals (quartz, feldspars, muscovite) with a negligible metal content, thus providing a good estimate of the total metal concentrations. The 1 M HCl extraction, despite the limitation due to the incomplete solubilization of pyrite and to the partial dissolution of sheet silicates, represents a simple and effective technique for providing an estimate of the bioavailable metal fraction in sediments. The combined use of the two microwave-assisted acid extractions can provide a rapid and simple approach for the risk assessment of metal-polluted sediments. 相似文献
20.
Fluid-present anatexis of metapelites at El Joyazo (SE Spain): constraints from Raman spectroscopy of graphite 总被引：2，自引：0，他引：2
The garnet-biotite-sillimanite anatectic xenoliths in the Neogene dacite dome of El Joyazo (also called Cerro de Hoyazo,
SE Spain) contain four types of graphite (I to IV), distinguished on the basis of grain size and texture. Structural characterization
of graphite by Laser Raman spectroscopy (LRS) shows systematic differences in the degree of ordering among the four types:
only type III is fully consistent with the granulite-facies conditions reached by the xenoliths during partial melting, the
others indicate metamorphic temperatures covering amphibolite-facies conditions, with only a few examples of granulite-grade
crystallinity. All graphite crystallized before or during the anatectic event, indicating that a large fraction of the graphite
did not equilibrate at peak temperatures. The mm-scale coexistence of different types and degrees of ordering in the graphite
suggests different origins, i.e. of biogenic derivation and “fluid-deposited”, and is explained in terms of fluid-melt-graphite
interaction during the anatectic event. Disequilibrium behaviour during high-temperature metamorphism and anatexis is typical
of types I, II and particularly of IV, and is attributed to sluggish kinetics of solid-state graphitization, mainly owing
to the limited time of the process and carbon saturation of the intergranular fluid. The coexisting, well-ordered type III
graphite is the product of melting in the presence of a graphite-saturated fluid, a process that would account for the deposition
of new graphite. The LRS results, together with petrologic observations, suggest that it is possible that high melt fractions
can be generated by fluid-present melting of a metasedimentary protolith also in a closed system. Although this contradicts
the commonly accepted hypothesis that, due to limited rock porosities, extensive fluid-present melting is precluded unless
infiltration occurs, it is a possible end-member model in anatectic settings characterized by rapid heating rates and low-grade
source rocks.
Received: 14 July 1998 / Accepted: 16 November 1998 相似文献