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91.
Morphological characteristics and medium-term evolution of the beaches between Ceuta and Cabo Negro (Morocco) 总被引:1,自引:0,他引:1
G. Anfuso J. A. Martínez del Pozo D. Nachite J. Benavente A. Macias 《Environmental Geology》2007,52(5):933-946
This work presents the results of a combined study on the beach morphology and the evolution at short- and medium-term of
the littoral between Ceuta and Cabo Negro (Morocco). It is an interesting sector showing a great increase of human occupation
and coastal structures. The monitoring program allowed for the reconstruction of the beach morphological behavior and the
seasonal changes. The studied beaches presented reflective profiles recording little seasonality, with the most notable morphological
changes being strictly related to storms. Surf Similarity and Surf Scaling parameters highlighted the existence of intermediate
and reflective beach states, characterized by plunging breakers. Aerial photographs and a satellite image have been geo-referenced
and elaborated with GIS tools to reconstruct the short- and medium-term evolution of the littoral and the sediment transport
pathways. The littoral showed important erosion at short- and medium-term related to a negative sedimentary budget because
of offshore transport. Sand accumulation was recorded close to the main ports, i.e., Marina Smir and Marina Kabila. These
port structures constituted impermeable, fixed limits, which divided the studied area into littoral cells. Other free, transit
limits were also observed. 相似文献
92.
The influence of streambed sediment clogging on macroinvertebrate communities was investigated in the Lemme creek (NW Italy). To assess how fine sediment accumulation can influence the colonisation process and community composition of macroinvertebrates, we placed 48 traps in the riverbed. The traps consisted of boxes built with metal net (mesh 1 cm, height 15 cm, sides 5 cm) covered with nylon net except for the apex, allowing access exclusively from the top. We created four trap types filled with 100% gravel, 30% sand and 70% gravel, 70% sand and 30% gravel and 100% sand. After 20 and 40 days, we removed 6 traps/type. Macroinvertebrates rapidly colonised the traps, as we found no significant community differences between the two removal dates. Among the four trap types, we found significant differences in taxa number and abundance, which both decreased with increasing clogging. Thus, our study supports the hypothesis that clogging and the accumulation of fine substratum elements strongly affects benthic stream communities. 相似文献
93.
An incentive mechanism for reducing emissions from conversion of intact and non-intact forests 总被引:1,自引:0,他引:1
Danilo Mollicone Frédéric Achard Sandro Federici Hugh D. Eva Giacomo Grassi Alan Belward Frank Raes Günther Seufert Hans-Jürgen Stibig Giorgio Matteucci Ernst-Detlef Schulze 《Climatic change》2007,83(4):477-493
This paper presents a new accounting mechanism in the context of the UNFCCC issue on reducing emissions from deforestation
in developing countries, including technical options for determining baselines of forest conversions. This proposal builds
on the recent scientific achievements related to the estimation of tropical deforestation rates and to the assessment of ‘intact’
forest areas. The distinction between ‘intact’ and ‘non intact’ forests used here arises from experience with satellite-based
deforestation measurements and allows accounting for carbon losses from forest degradation. The proposed accounting system
would use forest area conversion rates as input data. An optimal technical solution to set baselines would be to use historical
average figures during the time period from 1990 to 2005. The system introduces two different schemes to account for preserved
carbon: one for countries with high forest conversion rates where the desired outcome would be a reduction in their rates,
and another for countries with low rates. A ‘global’ baseline rate would be used to discriminate between these two country
categories (high and low rates). For the hypothetical accounting period 2013–2017 and considering 72% of the total tropical
forest domain for which data are available, the scenario of a 10% reduction of the high rates and of the preservation of low
rates would result in approximately 1.6 billion tCO2 of avoided emissions. The resulting benefits of this reduction would be shared between those high-rate countries which reduced
deforestation and those low-rate countries which did not increase their deforestation over an agreed threshold (e.g., half
of “global” baseline rate). 相似文献
94.
Giorgio E. O. Giacaglia 《Celestial Mechanics and Dynamical Astronomy》1975,12(4):519-520
Using Sylvester's theorem on matrices, an elegant expression is obtained for the solutions of the restricted problem of three bodies in the neighborhood of the equilibrium points. 相似文献
95.
Spatial variability of phytoplankton, nutrients and new production estimates in the waters around Svalbard 总被引:3,自引:0,他引:3
Georgina Owrid Giorgio Socal Giuseppe Civitarese Anna Luchetta Jozef Wiktor Eva-Maria Nöthig Inger Andreassen Ursula Schauer Volker Strass 《Polar research》2000,19(2):155-171
Phytoplankton dynamics and carbon input into Arctic and sub-Arctic ecosystems were investigated around Svalbard, in summer 1991. Phytoplankton biomass, species composition and dissolved nutrient concentrations were analysed from water samples collected along seven transects. Phytoplankton biomass was low especially to the north (Chlorophyll-a mean 0.3 pg 1- '), where flagellates dominated the communities and only ice-diatoms were present. To the west, the phytoplankton composition was representative of a summer Atlantic community, in a post-bloom state. Zooplankton grazing, mainly by copepods, appeared to be the main control on biomass to the west and north of Svalbard.
In the Barents Sea (east of Svalbard), an ice edge bloom was observed (Chlorophyll-a max. 6.8 pgl-') and the ice edge receded at a rate of approximately 1 1 km day-'. The phytoplankton community was represented by marginal ice species, especially Phaeocystis poucherii and Chaeroceros socialis. South of the ice edge, Deep Chlorophyll Maxima (DCM) were observed, as surface waters became progressively nutrient-depleted. In these surface waters, the phytoplankton were predominantly auto- and heterotrophic flagellates.
Carbon production measurements revealed high net production (new and regenerated) to the north of the Barents Sea Polar Front (BSPF); it was especially high at the receding ice edge (reaching 1.44gC m-'day-'). To the south, a low level of production was maintained, mainly through regenerative processes. 相似文献
In the Barents Sea (east of Svalbard), an ice edge bloom was observed (Chlorophyll-a max. 6.8 pgl-') and the ice edge receded at a rate of approximately 1 1 km day-'. The phytoplankton community was represented by marginal ice species, especially Phaeocystis poucherii and Chaeroceros socialis. South of the ice edge, Deep Chlorophyll Maxima (DCM) were observed, as surface waters became progressively nutrient-depleted. In these surface waters, the phytoplankton were predominantly auto- and heterotrophic flagellates.
Carbon production measurements revealed high net production (new and regenerated) to the north of the Barents Sea Polar Front (BSPF); it was especially high at the receding ice edge (reaching 1.44gC m-'day-'). To the south, a low level of production was maintained, mainly through regenerative processes. 相似文献
96.
Potential evidence for slab detachment from the flexural backstripping of a foredeep: Insight on the evolution of the Pescara basin (Italy)
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Paolo Mancinelli Cristina Pauselli Giorgio Minelli Massimiliano R. Barchi Guy Simpson 《地学学报》2018,30(3):222-232
The discrepancy between the size of the Apenninic chain and the depth of the Adriatic foredeep is investigated using 2D flexural backstripping on well‐constrained depth‐converted cross‐sections in the Pescara basin (Central Italy). The procedure consisted of removal, uplift, unfolding and unfaulting of the Pliocene–Pleistocene foreland deposits to produce a palaeogeographic map of the basin at the end of the Messinian and to constrain sedimentary rates since the Miocene. Results are found to support the contribution of an external load to the foreland evolution together with the Apenninic chain load. The interplay of the two types of loads resulted in spatial and temporal variations of the foredeep evolution that are quantified by palaeogeographic maps and sedimentation rates obtained through backstripping. Results are interpreted as representing the effects of a southward‐migrating wave linked to slab detachment beneath the Adriatic foredeep. This procedure can be useful to investigate similar problems on other chains worldwide. 相似文献
97.
Paula M. Carreira José M. Marques M. Rosário Carvalho Giorgio Capasso Fausto Grassa 《Journal of Volcanology and Geothermal Research》2010,189(1-2):49-56
Na–HCO3–CO2-rich thermomineral waters issue in the N of Portugal, within the Galicia-Trás-os-Montes region, linked to a major NNE-trending fault, the so-called Penacova-Régua-Verin megalineament. Along this tectonic structure different occurrences of CO2-rich thermomineral waters are found: Chaves hot waters (67 °C) and also several cold (16.1 °C) CO2-rich waters. The δ2H and δ18O values of the thermomineral waters are similar to those of the local meteoric waters. The chemical composition of both hot and cold mineral waters suggests that water–rock reactions are mainly controlled by the amount of dissolved CO2 (g) rather than by the water temperature. Stable carbon isotope data indicate an external CO2 inorganic origin for the gas. δ13CCO2 values ranging between ? 7.2‰ and ? 5.1‰ are consistent with a two-component mixture between crustal and mantle-derived CO2. Such an assumption is supported by the 3He/4He ratios measured in the gas phase, are between 0.89 and 2.68 times the atmospheric ratio (Ra). These ratios which are higher than that those expected for a pure crustal origin (≈ 0.02 Ra), indicating that 10 to 30% of the He has originated from the upper mantle. Release of deep-seated fluids having a mantle-derived component in a region without recent volcanic activity indicates that extensive neo-tectonic structures originating during the Alpine Orogeny are still active (i.e., the Chaves Depression). 相似文献
98.
Marco Bertolino Barbara Calcinai Riccardo Cattaneo‐Vietti Carlo Cerrano Anna Lafratta Maurizio Pansini Daniela Pica Giorgio Bavestrello 《Marine Ecology》2014,35(2):149-158
The Mediterranean coralligenous substratum is a hard bottom of biogenic origin, mainly composed of calcareous algae, growing in dim light conditions. Sponges are among of the most representative taxa of the coralligenous assemblages, with more than 300 recorded species of different habits: massive, erect, boring and insinuating. When sponges die, their siliceous spicules remain trapped in the biogenic concretion, offering the opportunity to describe the coralligenous spongofauna over a very long span of time, virtually dating back to a large part of the Holocene period. The data reported here were obtained from core samples collected from four coralligenous concretions. Each block was collected in a different locality of the Ligurian Sea: Santo Stefano Shoals, Bogliasco, Punta del Faro (Portofino Promontory) and Punta Manara. Radiocarbon age determinations indicate for these conglomerates a maximal age between 1600 and 3100 years. The spicules trapped in the cores show deep dissolution marks in the form of circular holes on their surface or present an enlargement of the axial canal. However, their original shape, generally intact, suggests the absence of mechanical injuries and allows a tentative identification at the species level. The analysis of these old spicules reveals an ancient sponge assemblage composed of 30 recognisable species. This indicates that almost one half of the sponge community today settled on coralligenous substrata has been present in the conglomerates for their entire existence. 相似文献
99.
Luana Valentini Maria Antonia Brovelli Giorgio Zamboni 《International Journal of Digital Earth》2014,7(4):336-350
In this article, we present the realisation of a multi-frame and multi-dimensional WebGIS that allows users to simultaneously analyse a specific portion of the Earth taking into account the historical information, too. Two graphical panels have been realised: one for the usual 2D view and one for a more realistic 3D view. Both panels display historical maps of the city, the current orthophoto and the digital topographical map. The 3D frame is based on NASA World Wind, an open source virtual globe from where 3D buildings are shown extruding the 2D shapes using their mean height. Thanks to a specifically designed graphical user interface, it is also possible to dynamically thematise the buildings on the globe according to different criteria (e.g. the construction time span) so that only the geometries fulfilling the request are turned on. Within the proposed application, a synchronisation between the two panels has been implemented, in order to maintain a constant alignment of the two viewers. The application is also open to the time dimension. In fact, assigning to each geometry two dates (e.g. ‘year of construction’ and ‘year of demolition’), it is possible to dynamically view how buildings have changed over time, both in their shape and height. Future developments of this work will concern the possibility of implementing a city model with a higher level of detail. 相似文献
100.
Andrea Cattaneo Andrea Rossotti Giorgio Pasquarè Anna Somigliana Domenico M. Cavallo 《Environmental Earth Sciences》2011,63(4):861-871
Since Etrurian age, the Viterbo Province (Central Italy) is famous for its ancient towns carved out of local ignimbrite deposits
which geologically represent the sedimentation of pumice-rich, volcano-related pyroclastic flows. Almost the entire study
area is geologically characterized by a thick succession of ignimbrites, tephra fallouts and lava flow deposits locally subjected
to zeolitization. Among zeolites, fibrous erionite represents a well-known health hazard and so this work aims at locating
and quantifying the presence of fibrous zeolites in volcanic deposits of the Viterbo area, suggesting at the same time a standard
operational procedure useful in other areas showing the same possible hazard. 41 samples collected in the Viterbo area were
analyzed by X-ray powder diffraction, optical and electron microscopy. Fibrous zeolites were detected in five samples and
quantified in amounts ranging from 0.35 to 1.66% vol. They generally occur in tetragonal or orthorhombic prismatic habit and
showed chemical composition mainly consistent with K-phillipsite. Fibrous zeolites occurred with aspect ratios (mean = 6.3),
comparable or lower than those of erionite fibers reported in previous studies and mean diameters >3 μm. 相似文献