Double origin of hydrothermal convective flux variations in the Fossa of Vulcano (Italy)     

Maurice Aubert  Serena Diliberto  Anthony Finizola  Yashmin Chébli 《Bulletin of Volcanology》2008,70(6):743-751

Soil-temperature measurements can provide information on the distribution of degassing fissures, their relationship to the internal structure of the volcano, and the temporal evolution of the system. At Vulcano Island (Italy), heat flux from a <3 km-deep magma body drives a hydrothermal system which extends across the main Fossa crater. This heat flux is also associated with variable magmatic gas flow. A high-density map of soil-temperatures was made in 1996 at a constant depth of 30 cm on the central and southern inner flanks of the Fossa crater. These measurements extended over an area covering about 0.04 km², across which the heat flux is predominantly associated with a shallow boiling aquifer. The map shows that hot zones relate to structures of higher permeability, mainly associated with a fissure system dating from the last eruptive cycle (1888–1890). From 1996 to January 2005, we studied the evolution of the heat flux for the high temperature part of the map, both by repeating our measurements as part of 14 visits, during which temperatures were measured at a constant depth, and using data from permanent stations which allowed soil-temperatures to be continuously measured for selected vertical profiles. These data allowed us to calculate the heat flux, and its variation, with good precision for values lower than about 100 W m⁻², which is generally the case in the study area. Above 100 W m⁻², although the heat flux value is underestimated, its variations are recorded with an error less than 10%. During the period 1996–2004, two increases in the thermal flux were recorded. The first one was related to the seismic crisis of November 1998 which opened existing or new fissures. The second, in November 2004, was probably due to magma migration, and was associated with minor seismic activity.  相似文献   

Effects of offshore platforms on soft-bottom macro-benthic assemblages: a case study in a Mediterranean gas field     

Terlizzi A  Bevilacqua S  Scuderi D  Fiorentino D  Guarnieri G  Giangrande A  Licciano M  Felline S  Fraschetti S 《Marine pollution bulletin》2008,56(7):1303-1309

The exploitation of fossil fuels in the Mediterranean Sea will likely lead to an increase in the number of offshore platforms, a recognized threat for marine biodiversity. To date, in this basin, few attempts have been made to assess the impact of offshore gas and oil platforms on the biodiversity of benthic assemblages. Here, we adopted a structured experimental design coupled with high taxonomic resolution to outline putative effects of gas platforms on soft-bottom macrofauna assemblages in the North Ionian Sea. The analysis was based on a total of 20,295 specimens of 405 taxa, almost entirely identified at species level. Multivariate and univariate analyses showed idiosyncratic patterns of assemblage change with increasing distance from the platforms. Potential reasons underlying such inconsistency are analyzed and the view that structured experimental monitoring is a crucial tool to quantify the extent and magnitude of potential threats and to provide sound baseline information on biodiversity patterns is supported.  相似文献   

Diversity and functions of microscopic fungi: a missing component in pelagic food webs     

Marlène Jobard  Serena Rasconi  Télesphore Sime-Ngando 《Aquatic Sciences - Research Across Boundaries》2010,72(3):255-268

Fungi are a highly complex group of organisms of the kingdom Eumycota (i.e. the true-fungi) and other fungus-like organisms traditionally studied by mycologists, such as slime molds (Myxomycota) and oomycota (Straminopiles or Heterokonts). They constitute a significant proportion of the as yet undiscovered biota that is crucial in ecological processes and human well-being, through at least three main trophic modes: saprophytism, parasitism, or symbiosis. In addition to direct benefit (sources of antibiotics) or adverse effects (agents of disease), fungi can impact many environmental processes, particularly those associated with the decomposition of organic matter. They are present in almost all regions and climates, even under extreme conditions. However, studies have focussed mostly on economically interesting species, and knowledge of their diversity and functions is mainly restricted to soil, rhizosphere, mangrove, and lotic ecosystems. In this study, we review the diversity and potential functions of microscopic fungi in aquatic ecosystems, with focus on the pelagic environments where they often are regarded as allochthonous material, of low ecological significance for food-web processes. Recent environmental 18S rDNA surveys of microbial eukaryotes have (1) unveiled a large reservoir of unexpected fungal diversity in pelagic systems, (2) emphasized their ecological potentials for ecosystem functioning, and (3) opened new perspectives in the context of food-web dynamics. In spite of persisting methodological difficulties, we conclude that a better documentation of the diversity and quantitative and functional importance of fungi will improve our understanding of pelagic processes and biogeochemical cycling.  相似文献   

Carbon monoxide in low-mass dwarf stars     

Hugh R. A. Jones  Yakiv Pavlenko  Serena Viti  R. J. Barber  Larisa A. Yakovina  David Pinfield  Jonathan Tennyson 《Monthly notices of the Royal Astronomical Society》2005,358(1):105-112

We compare high-resolution infrared observations of the CO 2–0 bands in the 2.297–2.310 μm region of M dwarfs and one L dwarf with theoretical expectations. We find a good match between the observational and synthetic spectra throughout the 2000–3500 K temperature regime investigated. None the less, for the 2500–3500 K temperature range, the temperatures that we derive from synthetic spectral fits are higher than expected from more empirical methods by several hundred kelvin. In order to reconcile our findings with the empirical temperature scale, it is necessary to invoke warming of the model atmosphere used to construct the synthetic spectra. We consider that the most likely reason for the back-warming is missing high-temperature opacity due to water vapour. We compare the water vapour opacity of the Partridge–Schwenke line list used for the model atmosphere with the output from a preliminary calculation by Barber & Tennyson. While the Partridge–Schwenke line list is a reasonable spectroscopic match for the new line list at 2000 K, by 4000 K it is missing around 25 per cent of the water vapour opacity. We thus consider that the offset between empirical and synthetic temperature scales is explained by the lack of hot water vapour used for computation of the synthetic spectra. For our coolest objects with temperatures below 2500 K, we find best fits when using synthetic spectra which include dust emission. Our spectra also allow us to constrain the rotational velocities of our sources, and these velocities are consistent with the broad trend of rotational velocities increasing from M to L.  相似文献   

Temporal Variation in the Trophic Levels of Secondary Consumers in a Mediterranean Coastal Lagoon (Cabras Lagoon,Italy)     

Serena Como  Gerard van der Velde  Paolo Magni 《Estuaries and Coasts》2018,41(1):218-232

Trophic levels (TLs) of fish were estimated on three sampling dates (March, May, and August 2006) for different fish sizes in the Cabras Lagoon (Sardinia, Italy). A temporal TL variation for Atherina boyeri, Gobius niger, and Engraulis encrasicolus was observed. In March and May, the TL ranged from 3.3 to 3.4, characterizing these species as secondary consumers, while in August, this range moved to between 3.7 and 3.8, indicating a TL shift towards tertiary consumers. For Liza ramada, TL was consistently lower in small individuals (mean TL 2.5) than in larger individuals (mean TL 3.0). Increased TL of the fish species A. boyeri, G. niger, and E. encrasicolus in August was consistent with the seasonal changes in the macrobenthic assemblage in this system, with a dominance of primary consumers (benthic deposit feeders) in winter–spring and a dominance of secondary consumers (the nereidids Alitta succinea and Hediste diversicolor) in summer. These fish species took advantage of the high availability of nereidids leading to a rise in their TL values. Furthermore, the increase of TL with size of L. ramada, the most economically valuable fish species in the Cabras Lagoon, indicated an ontogenetic diet shift, the juveniles being omnivorous, while the adults being secondary consumers. We conclude that variability in the trophic levels of fish due to species traits, ontogenetic diet shifts, and variation in prey availability should be taken into account to further understand the food web structure of coastal lagoons.  相似文献   

Bowing of marble slabs: can the phenomenon be arrested and prevented by inorganic treatments?     

Enrico Sassoni  Serena Andreotti  George W. Scherer  Elisa Franzoni  Siegfried Siegesmund 《Environmental Earth Sciences》2018,77(10):387

Bowing of thin marble slabs is a phenomenon affecting both historic monuments and modern buildings. In spite of the ubiquity and destructiveness of this phenomenon, no fully satisfactory treatment is currently available to arrest and/or prevent bowing. In this study, a treatment based on formation of hydroxyapatite (HAP) was investigated as a possible route to arrest and possibly prevent bowing of Carrara marble slabs. Four different formulations of the HAP treatment were tested and compared to ammonium oxalate and ethyl silicate (widely used in the practice of marble conservation). The treatments were applied onto pre-weathered and unweathered specimens to investigate their ability to arrest and prevent bowing, respectively. Marble behavior was studied in terms of residual strain and bowing after thermal cycles up to 90 °C in dry and wet conditions. Marble cohesion was assessed before and after the thermal cycles by ultrasound. The HAP treatments exhibited promising results, as the residual strain and the bowing after the cycles were always lower or equal to the untreated references, while marble cohesion was always higher. Surprisingly, ammonium oxalate caused marked worsening of marble thermal behavior. In the case of ethyl silicate, most of the initial benefit after consolidation was lost after the thermal cycles. In general, the results of the study point out the importance of evaluating marble thermal behavior to assess the suitability of any conservation treatment and suggest that treatments able to strengthen marble without causing excessive pore occlusion and stiffening are preferable to enhance durability to thermal cycles.  相似文献   

Presence of plastic debris in loggerhead turtle stranded along the Tuscany coasts of the Pelagos Sanctuary for Mediterranean Marine Mammals (Italy)     

Tommaso Campani  Matteo Baini  Matteo Giannetti  Fabrizio Cancelli  Cecilia Mancusi  Fabrizio Serena  Letizia Marsili  Silvia Casini  Maria Cristina Fossi 《Marine pollution bulletin》2013

This work evaluated the presence and the frequency of occurrence of marine litter in the gastrointestinal tract of 31 Caretta caretta found stranded or accidentally bycaught in the North Tyrrhenian Sea. Marine debris were present in 71% of specimens and were subdivided in different categories according to Fulmar Protocol (OSPAR 2008). The main type of marine debris found was user plastic, with the main occurrence of sheetlike user plastic. The small juveniles showed a mean ± SD of marine debris items of 19.00 ± 23.84, while the adult specimens showed higher values of marine litter if compared with the juveniles (26.87 ± 35.85). The occurrence of marine debris observed in this work confirms the high impact of marine debris in the Mediterranean Sea in respect to other seas and oceans, and highlights the importance of Caretta caretta as good indicator for marine litter in the Marine Strategy Framework Directive (MSFD) of European Union.  相似文献   

Regional landslide susceptibility zoning with considering the aggregation of landslide points and the weights of factors   总被引：4，自引：0，他引：4  

Xueliang Wang  Luqing Zhang  Sijing Wang  Serena Lari 《Landslides》2014,11(3):399-409

In this paper, we propose a methodology for landslide susceptibility assessment at a regional scale in Yunnan, southwestern province of China. A landslide inventory map including 3,242 landslide points was prepared for the study area. Five factors recognized as correlated to landslide (namely, lithology, relative relief, tectonic fault density, rainfall, and road density) were analyzed and mapped in geographic information system. An index expressing the correlation between each factor and landslides [called class landslide susceptibility index (CLSI)] was proposed in the study. While analyzing landslide distribution in a large area, point aggregation might be expected. To quantify the uncertainty caused by aggregation, class landslide aggregation index was proposed. To account for the importance of each of the factors in the landslide susceptibility assessment, some weights were calculated by means of analytic hierarchy process. We propose a weighted class landslide susceptibility model (WCLSM), obtained by the combination of CLSI values of each factor with the correspondent weight. WCLSM performance in the study area was evaluated comparing the results obtained by first modeling all landslides and then by performing a time partition. The model was run including only landslides that occurred before 2009 and then validated with respect to landslides that occurred after 2009. The prediction–rate curve shows that the WCLSM model provides a good prediction for the study area. Of the study area, 21.4 % shows very high and high susceptibility and includes the 87.7 % of the number of landslides that occurred after 2009.  相似文献   

Crystal structure of columbite under high pressure     

Serena C. Tarantino  Michele Zema  Tiziana Boffa Ballaran 《Physics and Chemistry of Minerals》2010,37(10):769-778

The structural evolution of two columbites under pressure, one ferrocolumbite from Raode (Africa) and one manganocolumbite from Kragero (Norway), has been determined by single-crystal X-ray diffraction. Structural investigations at high pressure have been carried out on samples which were preliminarily annealed to attain the complete cation-ordered state. For each crystal, five complete datasets have been collected from room pressure up to ca. 7 GPa. Structure refinements converged to final discrepancy factors R ranging between 5.2 and 5.8% for both the crystals. Structure refinements of X-ray diffraction data at different pressures allowed characterisation of the mechanisms by which the columbite structure accommodates variations in pressure. A and B octahedral volumes in both samples decrease linearly as pressure increases, with a larger compression of the larger A site. The difference in polyhedral bulk moduli of the A sites for the two samples does not appear to relate directly to the octahedral sizes, the A site being more compressible in the Fe-rich sample than in the Mn-rich one. By far the most compressible direction in both the analysed samples is along b. The cations are in fact free to move along this direction, thus allowing the octahedral chains to slide over each other; this effect is particularly evident in the manganocolumbite sample which shows a steep shortening of interchain A–B distances along b.  相似文献   

Stochastic sediment transport: anomalous diffusions and random movement     

Tsai  Christina W.  Hung  Serena Y.  Wu  Tsung-Han 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(2):397-413

Stochastic Environmental Research and Risk Assessment - A sediment particle in a flow not only follows the flow direction but also randomly diffuses through the surrounding fluid, because of the...  相似文献