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151.
Giorgio Socal Francesco Acri Mauro Bastianini Fabrizio Bernardi Aubry Franco Bianchi Daniele Cassin Joan Coppola Amelia De Lazzari Vinko Bandelj Gianpiero Cossarini Cosimo Solidoro 《Marine Ecology》2008,29(4):449-468
This paper reports on the main biogeochemical properties of the Northern Adriatic Sea in the period May 2003–November 2006 within the framework of the European program INTERREG III Italy‐Slovenia. Spatial and temporal distributions of water density, dissolved oxygen, nutrients (nitrogen, phosphorous and silicon) and chlorophyll a are presented. Multivariate methods such as fuzzy k‐means, self‐organising maps and cluster analysis were used to identify the different water masses and to characterise the temporal and spatial variability of the main biogeochemical features present in the area. The results confirm that the Po River outflows and the meteorological forcing factors are the main components triggering the alternation of stratification and mixing of the water column and that strongly affect the trophic state of the basin. In general, oligotrophic conditions dominate, and were more pronounced offshore, but mesotrophy occurred episodically in May 2004 and July 2005, when phytoplankton blooms were observed concomitant with vertical stability of the water column. A marked interannual variability was also observed, supporting the importance of maintaining long‐term observations of the basin. 相似文献
152.
Paola Del Negro Mauro Celussi Erica Crevatin Alessandro Paoli Fabrizio Bernardi Aubry Alessandra Pugnetti 《Marine Ecology》2008,29(3):375-386
The prokaryotic community, both in terms of abundance and activity (exoenzymatic hydrolysis of proteins, polysaccharides and phosphorylated molecules and leucine uptake), was investigated seasonally for a 3‐year period (2004–2006) in the Gulf of Venice (northern Adriatic Sea). By focusing on spatial and temporal variability, the prokaryote dynamics showed significant variations on a horizontal and seasonal scale, but no substantial differences were observed among years. The basin‐scale variability was mainly influenced by allochthonous inputs from the Po river and the Venice Lagoon, which were the main source of nutrients, acting as a ‘bottom up’ control on prokaryotes. On a seasonal scale, all the microbial parameters (except the polysaccharide degradation) showed significant variations following the temperature fluctuations. The annual rate of change was very low for all the chemical, physical and biological parameters and only the abundance and phosphatase activity of the prokaryotes differed significantly among years. 相似文献
153.
Giulia Zuecco Luca Carturan Fabrizio De Blasi Roberto Seppi Thomas Zanoner Daniele Penna Marco Borga Alberto Carton Giancarlo Dalla Fontana 《水文研究》2019,33(5):816-832
The spatial and temporal characterization of geochemical tracers over Alpine glacierized catchments is particularly difficult, but fundamental to quantify groundwater, glacier melt, and rain water contribution to stream runoff. In this study, we analysed the spatial and temporal variability of δ2H and electrical conductivity (EC) in various water sources during three ablation seasons in an 8.4‐km2 glacierized catchment in the Italian Alps, in relation to snow cover and hydro‐meteorological conditions. Variations in the daily streamflow range due to melt‐induced runoff events were controlled by maximum daily air temperature and snow covered area in the catchment. Maximum daily streamflow decreased with increasing snow cover, and a threshold relation was found between maximum daily temperature and daily streamflow range. During melt‐induced runoff events, stream water EC decreased due to the contribution of glacier melt water to stream runoff. In this catchment, EC could be used to distinguish the contribution of subglacial flow (identified as an end member, enriched in EC) from glacier melt water to stream runoff, whereas spring water in the study area could not be considered as an end member. The isotopic composition of snow, glacier ice, and melt water was not significantly correlated with the sampling point elevation, and the spatial variability was more likely affected by postdepositional processes. The high spatial and temporal variability in the tracer signature of the end members (subglacial flow, rain water, glacier melt water, and residual winter snow), together with small daily variability in stream water δ2H dynamics, are problematic for the quantification of the contribution of the identified end members to stream runoff, and call for further research, possibly integrated with other natural or artificial tracers. 相似文献
154.
Emanuela Ceccaroni Gabriele Ameri Antonio Augusto Gómez Capera Fabrizio Galadini 《Natural Hazards》2009,50(2):335-359
The 2nd century AD earthquake in central Italy is only known by an epigraph that mentions restorations to a damaged weighing-house
at the ancient locality of Pagus Interpromium. The available seismic catalogues report this event with the conventional date of 101 AD, a magnitude M
aw of 6.3, and an epicentral location at the village of San Valentino in Abruzzo Citeriore, in the province of Pescara. In order
to improve the knowledge of the damage pattern, we gathered all the archaeological data collected during modern excavations
at sites located in the area, which were presumably struck by the earthquake. This information is mainly represented by (1)
stratigraphic units due to the sudden collapse of buildings over still frequented floors; (2) stratigraphic units demonstrating
restoration or re-building of edifices; (3) stratigraphic units formed as the result of the abandonment of sites or of their
lack of frequentation for decades or centuries. Only stratigraphic evidence consistent with an earthquake occurrence during
the 2nd century AD has been considered. The most recent archaeological material found in a collapsed unit is a coin of Antoninus
Pius, dated at 147–148 AD. This may represent a post quem date very close to the occurrence of the earthquake. The gathered information, plus the stratigraphic data that excluded
the earthquake occurrence at some sites, has allowed us to roughly delineate an area of possible damage, including the Sulmona
Plain and surrounding areas. Comparisons between the possible 2nd century damage distribution and (i) the damage patterns
of more recent historical events that have struck the investigated area, (ii) the distribution of virtual intensities obtained
by simulating an earthquake having an epicenter in the Sulmona Plain and applying an intensity attenuation relationship and
(iii) a shaking scenario obtained by modelling the activation of the major active fault of the Sulmona Plain area (the Mt.
Morrone fault) have revealed consistency between the ancient earthquake and the activation of this fault. Since no other historical
events can be attributed to this active fault, we conclude that the time that has elapsed since the last fault activation
should be in the order of 1,850 years, i.e. a time span that is very close to the recurrence interval of Apennine seismogenic
sources. Moreover, considering the fault length, the causative source may be responsible for earthquakes with M up to 6.6–6.7. The comparison between the presumed 2nd century damage and the shaking scenario suggests that the magnitude
mentioned is consistent with the presumed effects of the ancient earthquake. Finally, considering that Sulmona (the most important
town in the region investigated) is located in the middle of the Mt. Morrone fault hanging wall, we consider it as the probable
epicentral area. Therefore, to summarise the information on the 2nd century AD earthquake, we can conclude that (i) it occurred
shortly after 147–148 AD; (ii) a magnitude M
w 6.6–6.7 can be attributed to it and (iii) the probable macroseismic epicentral area was Sulmona. 相似文献
155.
Real-time flood forecasting of the Tiber river in Rome 总被引:3,自引:2,他引:1
An adaptive, conceptual model for real-time flood forecasting of the Tiber river in Rome is proposed. This model simulates
both rainfall-runoff transformations, to reproduce the contributions of 37 ungauged sub-basins that covered about 30% of the
catchment area, and flood routing processes in the hydrographic network. The adaptive component of the model concerns the
rainfall-runoff analysis: at any time step the whole set of the model parameters is recalibrated by minimizing the objective
function constituted by the sum of the squares of the differences between observed and computed water surface elevations (or
discharges). The proposed model was tested through application under real-time forecasting conditions for three historical
flood events. To assess the forecasting accuracy, to support the decision maker and to reduce the possibility of false or
missed warnings, confidence intervals of the forecasted water surface elevations (or discharges), computed according to a
Monte Carlo procedure, are provided. The evaluation of errors in the prediction of peak values, of coefficients of persistence
and of the amplitude of confidence intervals of prediction shows the possibility to develop a flood forecast model with a
lead time of 12 h, which is useful for civil protection actions. 相似文献
156.
Fabrizio Nestola Joseph R. Smyth Luciano Secco Marco Bruno Alberto Dal Negro 《Geochimica et cosmochimica acta》2009,73(2):489-3427
A non-stoichiometric sample of spinel with composition T(Mg0.4Al0.6)M(Al1.8□0.2)O4 was investigated by single-crystal X-ray diffraction in situ up to about 8.7 GPa using a diamond anvil cell. The P(V) data were fitted using a third-order Birch-Murnaghan equation of state and the unit-cell volume V0, the bulk modulus KT0 and its first pressure derivative K′ were refined simultaneously providing the following coefficients: V0 = 510.34(6) Å3, KT0 = 171(2) GPa, K′ = 7.3(6). This KT0 value represents the lowest ever found for spinel crystal structures. Comparing our data with a stoichiometric and natural MgAl2O4 (pure composition) we observe a decrease in KT0 by about 11.5% and a strong increase in K′ by about 33%. These results demonstrate how an excess of Al accompanied by the formation of significant cation vacancies at octahedral site strongly affects the thermodynamic properties of spinel structure. If we consider that the estimated mantle composition is characterized by 3-5% of Al2O3 this could imply an Mg/Al substitution with possible formation of cation vacancies. The results of our study indicate that geodynamic models should take into account the potential effect of Mg/Al substitution on the incompressibility of the main mantle-forming minerals (olivine, wadsleyite, ringwoodite, Mg-perovskite). 相似文献
157.
Luciano Morselli Elena Bernardi Ivano Vassura Fabrizio Passarini Enrico Tesini 《Journal of Atmospheric Chemistry》2008,59(3):151-170
The results of a 8 year survey of wet and dry depositions collected in Bologna (Northern Italy) are presented and discussed:
monthly fluxes of the main ions (hydrogen, sodium, potassium, calcium, magnesium, ammoniacal and nitrate nitrogen, sulphate
and chloride) have been registered and statistically discussed. The trend of hydrogen ion, whose largest correlation in the
global deposition was found with sulphate, is clearly downwards, with peaks mainly in winter months. By means of a data factor
analysis, three main sources to explain the variability of the deposition chemistry were recognized: an anthropogenic contribution
(particularly represented by NO3
−, SO4
2−, H+), the sea spray (Na+, Cl− and, to a lesser extent, K+ and Mg2+) and a terrigenous fraction, particularly characterized by higher Ca2+ concentration; however, some concentration peaks of this ion have been found in association with some episodes of Saharan
dust transportation. 相似文献
158.
159.
Philip D. Nicholson Matthew M. Hedman Mark R. Showalter Jeffrey N. Cuzzi Fabrizio Capaccioni Gary B. Hansen Pierre Drossart Bonnie J. Buratti Angioletta Coradini 《Icarus》2008,193(1):182-212
Soon after the Cassini-Huygens spacecraft entered orbit about Saturn on 1 July 2004, its Visual and Infrared Mapping Spectrometer obtained two continuous spectral scans across the rings, covering the wavelength range 0.35-5.1 μm, at a spatial resolution of 15-25 km. The first scan covers the outer C and inner B rings, while the second covers the Cassini Division and the entire A ring. Comparisons of the VIMS radial reflectance profile at 1.08 μm with similar profiles at a wavelength of 0.45 μm assembled from Voyager images show very little change in ring structure over the intervening 24 years, with the exception of a few features already known to be noncircular. A model for single-scattering by a classical, many-particle-thick slab of material with normal optical depths derived from the Voyager photopolarimeter stellar occultation is found to provide an excellent fit to the observed VIMS reflectance profiles for the C ring and Cassini Division, and an acceptable fit for the inner B ring. The A ring deviates significantly from such a model, consistent with previous suggestions that this region may be closer to a monolayer. An additional complication here is the azimuthally-variable average optical depth associated with “self-gravity wakes” in this region and the fact that much of the A ring may be a mixture of almost opaque wakes and relatively transparent interwake zones. Consistently with previous studies, we find that the near-infrared spectra of all main ring regions are dominated by water ice, with a typical regolith grain radius of 5-20 μm, while the steep decrease in visual reflectance shortward of 0.6 μm is suggestive of an organic contaminant, perhaps tholin-like. Although no materials other than H2O ice have been identified with any certainty in the VIMS spectra of the rings, significant radial variations are seen in the strength of the water-ice absorption bands. Across the boundary between the C and B rings, over a radial range of ∼7000 km, the near-IR band depths strengthen considerably. A very similar pattern is seen across the outer half of the Cassini Division and into the inner A ring, accompanied by a steepening of the red slope in the visible spectrum shortward of 0.55 μm. We attribute these trends—as well as smaller-scale variations associated with strong density waves in the A ring—to differing grain sizes in the tholin-contaminated icy regolith that covers the surfaces of the decimeter-to-meter sized ring particles. On the largest scale, the spectral variations seen by VIMS suggest that the rings may be divided into two larger ‘ring complexes,’ with similar internal variations in structure, optical depth, particle size, regolith texture and composition. The inner complex comprises the C and B rings, while the outer comprises the Cassini Division and A ring. 相似文献