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241.
Beatrice M.S. Giambastiani Nicolò Colombani Nicolas Greggio Marco Antonellini Micòl Mastrocicco 《水文研究》2017,31(8):1613-1621
With global warming and sea level rise, many coastal systems will experience increased levels of inundation and storm flooding, especially along sandy lowland coastal areas, such as the Northern Adriatic coast (Italy). Understanding how extreme events may directly affect groundwater hydrology in shallow unconfined coastal aquifers is important to assess coastal vulnerability and quantify freshwater resources. This study investigates shallow coastal aquifer response to storm events. The transitory and permanent effects of storm waves are evaluated through the real time monitoring of groundwater and soil parameters, in order to characterize both the saturated and unsaturated portions of the coastal aquifer of Ravenna and Ferrara (southern Po Delta, Italy). Results highlight a general increase in hydraulic head and soil moisture, along with a decrease in groundwater salinity and pore water salinity due to rainfall infiltration during the 2 days storm event. The only exceptions are represented by the observation wells in proximity to the coastline (within 100 m), which recorded a temporary increase in soil and water salinity caused by the exceptional high waves, which persist on top of the dune crest during the storm event. This generates a saline plume that infiltrates through the vadose zone down to the saturated portion of the aquifer causing a temporary disappearance of the freshwater lens generally present, although limited in size, below the coastal dunes. Despite the high hydraulic conductivity, the aquifer system does not quickly recover the pre‐storm equilibrium and the storm effects are evident in groundwater and soil parameters after 10 days past the storm overwash recess. 相似文献
242.
243.
Fluid‐induced breakdown of monazite in medium‐grade metasedimentary rocks of the Pontremoli basement (Northern Apennines,Italy)
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D. Lo Pò R. Braga H.‐J. Massonne G. Molli A. Montanini T. Theye 《Journal of Metamorphic Geology》2016,34(1):63-84
The last (decompression) stages of the metamorphic evolution can modify monazite microstructure and composition, making it difficult to link monazite dates with pressure and temperature conditions. Monazite and its breakdown products under fluid‐present conditions were studied in micaschist recovered from the cuttings of the Pontremoli1 well, Tuscany. Coronitic microstructures around monazite consist of concentric zones of apatite + Th‐silicate, allanite and epidote. The chemistry and microstructure of the monazite grains, which preserve a wide range of chemical dates ranging from Upper Carboniferous to Tertiary times, suggest that this mineral underwent a fluid‐mediated coupled dissolution–reprecipitation and crystallization processes. Consideration of the chemical zoning (major and selected trace elements) in garnet, its inclusion mineralogy (including xenotime), monazite breakdown products and phase diagram modelling allow the reaction history among accessory minerals to be linked with the reconstructed P–T evolution. The partial dissolution and replacement by rare earth element‐accessory minerals (apatite–allanite–epidote) occurred during a fluid‐present decompression at 510 ± 35 °C. These conditions represent the last stage of a metamorphic history consisting of a thermal metamorphic peak at 575 °C and 7 kbar, followed by the peak pressure stage occurring at 520 °C and 8 kbar. An anticlockwise P–T path or two clockwise P–T loops can fit the above P–T constraints. The former path may be related to a context of late Variscan strike‐slip‐dominated exhumation with minor Tertiary (Alpine‐related) reworking and fluid infiltration, while the latter requires an Oligocene–Miocene fluid‐present tectono‐metamorphic overprint on the Variscan paragenesis. 相似文献
244.
Flavio Justino A. S. de Mélo A. Setzer R. Sismanoglu G. C. Sediyama G. A. Ribeiro J. P. Machado A. Sterl 《Climatic change》2011,106(2):285-302
Vegetation fires are the second largest source of greenhouse gas emissions to the atmosphere. The reduction of the climatic
impact of these emissions is related to the vegetation susceptibility to fire (fire risk), as well as to the understanding
of possible implications of changes in atmospheric circulation on fire risk in the near-future. This study evaluates the environmental
susceptibility to fire occurrence based on a Potential Fire Index (PFI). Two climate simulations from the ECHAM5/MPI-OM climate
model have been used to calculate the PFI: present day (1980–2000) and an experiment for the end of the twenty-first century
(2080–2100). The results indicate that the proposed PFI methodology could properly reproduce the areas with the highest fire
incidence under present conditions. Moreover, it was found that under greenhouse warming conditions the PFI foresees an increase
in the fire risk area, particularly for the Amazon region. We concluded, furthermore, that changes of vegetation predicted
to occur in the future lead to substantial modifications in the magnitude of the PFI, and may potentially extend the length
of the fire season due to induced longer drought periods as compared to current conditions. 相似文献
245.
Autonomous underwater vehicle teams for adaptive ocean sampling: a data-driven approach 总被引:1,自引:1,他引:0
Andrea?MunafòEmail author Enrico?Simetti Alessio?Turetta Andrea?Caiti Giuseppe?Casalino 《Ocean Dynamics》2011,61(11):1981-1994
The current technological developments in autonomous underwater vehicles (AUVs) and underwater communication have nowadays
allowed to push the original idea of autonomous ocean sampling network even further, with the possibility of using each agent
of the network not only as an operative component driven by external commands (model-driven) but as a reactive element able
to act in response to changing conditions as measured during the exploration (data-driven). With this paper, we propose a
novel data-driven algorithm for AUVs team for adaptive sampling of oceanic regions, where each agent shares its knowledge
of the environment with its teammates and autonomously takes decision in order to reconstruct the desired oceanic field. In
particular, sampling point selection is made in order to minimize the uncertainty in the estimated field while keeping communication
contact with the rest of the team and avoiding to repeatedly sampling sub-regions already explored. The proposed approach
is based on the use of the emergent behaviour technique and on the use of artificial potential functions (interest functions)
to achieve the desired goal at the end of the mission. In this way, there is no explicit minimization of a cost functional
at each decision step. The oceanic field is reconstructed by the application of radial basis functions interpolation of irregularly
spaced data. A simulative example for the estimation of a salinity field with sea data obtained using the Mediterranean Sea
Forecasting System is shown in the paper, in order to investigate the effect of the different uncertainty sources, including
sea currents, on the behaviour of the exploration team and ultimately on the reconstruction of the salinity field. 相似文献
246.
Tephrochronological study in the quaternary Val d’Agri intermontane basin (Southern Apennines,Italy)
Irene Zembo Pietro Vignola Sergio Andò Riccardo Bersezio Luigina Vezzoli 《International Journal of Earth Sciences》2011,100(1):173-187
In the south-eastern depocentre of the Val d’Agri basin (Southern Apennines), a volcanic ash layer crops out interbedded within
poorly structured alluvial fan deposits of Late Pleistocene age. Textural, depositional and pedological features of this weathered
layer suggest a primary deposition from a pyroclastic fall-out of volcanic ash. Chemical analyses of feldspars show an alkali
trachytic composition and accessory minerals association allow to correlate this tephra layer with the regionally dispersed
Y-7 marine tephra layer (Tufo Verde Epomeo eruption, Ischia volcano), dated at 56 ± 4 ka. The Val d’Agri tephra here described
for the first time was deposited during MIS Stage 3. Its recovery and characterization permit to contribute to regional correlation
of the Mediterranean climatic and volcanic events from marine to continental successions and to describe landscape evolution
of the Southern Apennines during glacial–interglacial cycles. 相似文献
247.
F. Sansò 《Journal of Geodesy》1990,64(4):313-330
To apply the least squares method for the interpolation of harmonic functions is a common practice in Geodesy. Since the method
of least squares can be applied only to overdetermined problem, the interpolation problem which is always under-determined,
is often reduced to an overdetermined form by truncating a series of spherical harmonics. When the data points are the knots
of a regular grid it is easy to see that the estimated harmonic coefficients converge to the correct theoretical values, but
when the observation density is not constant a significant bias is introduced. The result is obtained by assuming that the
number of observations tends to infinity with points sampled from a given distribution. Under the same conditions it is shown
that quadrature and “collocation-like” formulas displays a statistically consistent behaviour. 相似文献
248.
Mauro?BoccolariEmail authorView authors OrcID profile Flavio?Parmiggiani 《Theoretical and Applied Climatology》2018,132(3-4):739-749
Climatology, trends and variability of cloud fraction cover (CFC) data over the Arctic (north of 70°N), were analysed over the 1982–2009 period. Data, available from the Climate Monitoring Satellite Application Facility (CM SAF), are derived from satellite measurements by AVHRR. Climatological means confirm permanent high CFC values over the Atlantic sector during all the year and during summer over the eastern Arctic Ocean. Lower values are found in the rest of the analysed area especially over Greenland and the Canadian Archipelago, nearly continuously during all the months. These results are confirmed by CFC trends and variability. Statistically significant trends were found during all the months over the Greenland Sea, particularly during the winter season (negative, less than ?5?%?dec ?1) and over the Beaufort Sea in spring (positive, more than +5?%?dec ?1). CFC variability, investigated by the Empirical Orthogonal Functions, shows a substantial “non-variability” in the Northern Atlantic Ocean. Statistically significant correlations between CFC principal components elements and both the Pacific Decadal Oscillation index and Pacific North America patterns are found. 相似文献
249.
Stefania Bilardi Paolo S. Calabrò Sabine Caré Nicola Moraci Chicgoua Noubactep 《洁净——土壤、空气、水》2013,41(9):835-843
Current knowledge of the basic principles underlying the design of Fe0 beds is weak. The volumetric expansive nature of iron corrosion was identified as the major factor determining the sustainability of Fe0 beds. This work attempts to systematically verify developed concepts. Pumice and sand were admixed to 200 g of Fe0 in column studies (50:50 volumetric proportion). Reference systems containing 100% of each material have been also investigated. The mean grain size of the used materials (in mm) were 0.28 (sand), 0.30 (pumice), and 0.50 (Fe0). The five studied systems were characterized (i) by the time dependent evolution of their hydraulic conductivity (permeability) and (ii) for their efficiency for aqueous removal of CuII, NiII, and ZnII (about 0.3 mM of each). Results showed unequivocally that (i) quantitative contaminant removal was coupled to the presence of Fe0, (ii) additive admixture lengthened the service life of Fe0 beds, and (iii) pumice was the best admixing agent for sustaining permeability while the Fe0/sand column was the most efficient for contaminant removal. The evolution of the permeability was well‐fitted by the approach that the inflowing solution contained dissolved O2. The achieved results are regarded as starting point for a systematic research to optimize/support Fe0 filter design. 相似文献
250.
E. Calabrò 《Astrophysics and Space Science》1993,208(1):5-13
Photometric observations carried out from October to November 1991 of the symbiotic system EG Andromedae are here presented. The secondary minimum has been repeated with a period of about 480 days, as inferred from the orbital elements (P = 482 days, Skopalet al., 1991). The light curve shape led us to suggest a model in which two hot spots result through evaporation from a low mass red giant by a compact object. 相似文献