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81.
Coastal processes and environmental hazards: the Buenos Aires (Argentina) and Venetian (Italy) littorals 总被引:1,自引:0,他引:1
Jorge Pousa Luigi Tosi Eduardo Kruse Dardo Guaraglia Maurizio Bonardi Andrea Mazzoldi Federica Rizzetto Enrique Schnack 《Environmental Geology》2007,51(8):1307-1316
The Buenos Aires (Argentina) and Venice (Italy) coastlands have experienced significant saltwater contamination of the phreatic
aquifer, coastal erosion, hydrodynamic changes and relative sea level rise processes due to natural and man-induced factors.
These factors expose coastal areas to morpho-hydro-geological hazards, such as soil desertification, frequency and degree
of flooding, littoral erosion, and the silting of river mouths and channels. Man-made interventions and actions, such as beach
mining, construction of coastal structures and exploitation of aquifers without an adequate knowledge of the hydrology setting
and an adequate management program, worsen these natural hazards. Uncontrolled human activity induces environmental damage
to the overall coastal plains. The coastal plains play an important role in the social/economic development of the two regions
based on land use, such as agriculture, horticulture, breeding, and tourism, as well as industry. Results of investigations
on saltwater contamination, sea level rise and morphological changes recently performed in these two coastal areas are presented
here. 相似文献
82.
83.
84.
Wolfram Wobrock Andrea I. Flossmann Marie Monier Jean-Marc Pichon Laurent Cortez Jean-Franois Fournol Alfons Schwarzenbck Stephan Mertes Jost Heintzenberg Paolo Laj Giordano Orsi Loretta Ricci Sandro Fuzzi Harry Ten Brink Piet Jongejan Ren Otjes 《Atmospheric Research》2001,58(4):7907
The second field campaign of the Cloud Ice Mountain Experiment (CIME) project took place in February 1998 on the mountain Puy de Dôme in the centre of France. The content of residual aerosol particles, of H2O2 and NH3 in cloud droplets was evaluated by evaporating the drops larger than 5 μm in a Counterflow Virtual Impactor (CVI) and by measuring the residual particle concentration and the released gas content. The same trace species were studied behind a round jet impactor for the complementary interstitial aerosol particles smaller than 5 μm diameter. In a second step of experiments, the ambient supercooled cloud was converted to a mixed phase cloud by seeding the cloud with ice particles by the gas release from pressurised gas bottles. A comparison between the physical and chemical characteristics of liquid drops and ice particles allows a study of the fate of the trace constituents during the presence of ice crystals in the cloud.In the present paper, an overview is given of the CIME 98 experiment and the instrumentation deployed. The meteorological situation during the experiment was analysed with the help of a cloud scale model. The microphysics processes and the behaviour of the scavenged aerosol particles before and during seeding are analysed with the detailed microphysical model ExMix. The simulation results agreed well with the observations and confirmed the assumption that the Bergeron–Findeisen process was dominating during seeding and was influencing the partitioning of aerosol particles between drops and ice crystals. The results of the CIME 98 experiment give an insight on microphysical changes, redistribution of aerosol particles and cloud chemistry during the Bergeron–Findeisen process when acting also in natural clouds. 相似文献
85.
Paolo Laj Andrea I. Flossmann Wolfram Wobrock Sandro Fuzzi Giordano Orsi Loretta Ricci Stephan Mertes Alfons Schwarzenbck Jost Heintzenberg Harry Ten Brink 《Atmospheric Research》2001,58(4):256
We investigated the partitioning of trace substances during the phase transition from supercooled to mixed-phase cloud induced by artificial seeding. Simultaneous determination of the concentrations of H2O2, NH3 and black carbon (BC) in both condensed and interstitial phases with high time resolution showed that the three species undergo different behaviour in the presence of a mixture of ice crystals and supercooled droplets. Both H2O2 and NH3 are efficiently scavenged by growing ice crystals, whereas BC stayed predominantly in the interstitial phase. In addition, the scavenging of H2O2 is driven by co-condensation with water vapour onto ice crystals while NH3 uptake into the ice phase is more efficient than co-condensation alone. The high solubility of NH4+ in the ice could explain this result. Finally, it appears that the H2O2–SO2 reaction is very slow in the ice phase with respect to the liquid phase. Our results are directly applicable for clouds undergoing limited riming. 相似文献
86.
Free cupric ion concentrations and Cu complexation in selected Swiss lakes and rivers 总被引:1,自引:0,他引:1
Hanbin Xue Andrea Oestreich David Kistler Laura Sigg 《Aquatic Sciences - Research Across Boundaries》1996,58(1):69-87
[Cu2+] and Cu complexation parameters in some selected freshwater systems in Switzerland were determined by the technique of ligand-exchange and DPCSV. Results from the water columns of some eutrophic and oligotrophic lakes are presented and compared to small acid lakes. Cu is strongly complexed by organic ligands which with very high stability constants at low concentrations are probably biologically produced, as indicated by the seasonal variations in the eutrophic lakes and by the relationship between Cu complexation and algal activity in the eutrophic (pCu=15–16), oligotrophic (pCu=13–14) and acidic (pCu=9–10) lakes. The extent of Cu complexation in river waters was generally lower than in the eutrophic lakes, at similar DOC levels. No obvious correlation between Cu complexation and DOC was observed, indicating that Cu complexing ligands are specific organic compounds. 相似文献
87.
88.
A model is proposed describing the mechanical evolution of a shear zone along compressional and extensional plate boundaries, subject to constant strain rate. The shear zones are assumed as viscoelastic with Maxwell rheology and with elastic and rheological parameters depending on temperature and petrology. Stress and strain are computed as functions of time and depth. For both kinds of boundaries the model reproduces the existence of a shallow seismogenic zone, characterized by a stress concentration. The thickness of the seismogenic layer is evaluated considering the variations of shear stress and frictional strength on faults embedded in the shear zone. Assuming that a fault dislocation takes place, the brittle-ductile transition is assumed to occur at the depth at which the time derivative of total shear stress changes from positive to negative values. The effects of different strain rates and geothermal gradients on the depth of the brittle-ductile transition are studied. The model predictions are consistent with values inferred from seismicity data of different boundary zones. 相似文献
89.
Carlo Bernasconi 《Pure and Applied Geophysics》1958,39(1):26-34
Riassunto L'Autore dimostra che, nel sistema di coordinate polari , , , si possono determinare un numeros di funzioni della sola variabile :Q
1,Q
3, ....Q
2s–1 tali che la sommatoria delleQ
2i–1/2i–1 rappresenti il potenzialeV di un geoide di rotazione. La condizione di armonicità determina ciascunaQ (che si riduce a un polinomio nelle potenze di sen ) a meno di una costante arbitraria; si dispone pertanto dis costanti che servono per soddisfare la natura dellaV sulla superficie del geoide. Come esempio l'Autore ha determinato la gravità sul geoide sferico, confermando i risultati delSomigliana, e su uno sferoide generico dove ha ritrovato la relazione diClairaut.
Summary The Author proofs that, in the system of polar coordinates , , , it is possible to determine a numbers of functions only of the variable :Q 1,Q 3 ....Q 2s–1 in such a way as to make the summatory of theQ 2i–1/2i–1 represent the potential function of a rotational geoid. The condition of harmonicity determines, saving an arbitrary constant, each of theQ which is reduced to a polynom developed by the sin powers; therefore one disposes of a number of constants to make use for satisfing theV on the geoid. To illustrate his theory the Author determines the gravity on the spherical geoid, thus confirmingSomigliana's formulas and on a spheroidal on which he pointed outClairaut's relations.相似文献
90.
Dr. Carlo Bernasconi 《Pure and Applied Geophysics》1955,32(1):1-6
Riassunto L'Autore presenta un procedimento per la ricerca dell'azimut di una geodetica ellissoidica passante per due punti molto lontani fra loro. Istituisce dapprima una corrispondenza fra la geodetica ed un arco di cerchio massimo, corrispondenza definita con l'imporre uguali coordinate agli estremi dei due archi e la latitudine sferica normale uguale a quella ellissoidica. Sviluppa poi la longitudine ellissoidicaw in funzione di quella sferical, e poichè l fra gli estremi dell'arco di cerchio deve essere uguale a w, ne deduce una equazione per ricavare l'azimut.
Summary The Author outlines a procedure to research the azimuth of an ellipsoidal geodesic, which passes through two points far distant from another. A corrispondence is first instituted between the geodesic and a bow of maximum circle; this correspondence may be defined by imposing the same coordinates to the extreme parts of the two bows and the spherical normal latitude equal to the ellipsoidal one. The ellipsoidal longitudew is next developed as a function of the spherical onel and, as l between the extreme parts of the circle bow must equal w, an equation is hereby deduced to find out the azimuth.相似文献