Heavy metal contamination in surface sediments from the Gulf of Venice, Italy     

Romano Donazzolo  Oplinia Hieke Merlin  Laura Menegazzo Vitturi  Angelo A. Orio  Bruno Pavoni  Guido Perin  Sandro Rabitti 《Marine pollution bulletin》1981,12(12):417-425

The authors studied surface sediments from 102 stations in four areas of the three port entrances to the Lagoon of Venice, examining the relationships between textural character, mineralogical composition, and Hg, Pb, Cd, Cu, Ni, Cr, Zn, Co and Fe content. Heavy metal distribution allowed boundaries to be fixed between polluted and nonpolluted zones. While the Cavallino area is not polluted, very high concentrations of Zn, Pb and Hg in the two central areas, facing the Lido and Malamocco port entrances, respectively, suggest that wastes mainly from industrial production of zinc are present. High concentrations of Cr in the southern part of the Chioggia area are probably due to tannery wastes reaching the sea from the Brenta river.  相似文献   

Seismic Vulnerability Assessment of Gravity Load Designed R/C Frames     

Angelo Masi 《Bulletin of Earthquake Engineering》2003,1(3):371-395

The seismic vulnerability of some frame structures, typical of existing Reinforced Concrete buildings designed only to vertical loads, has been evaluated. They are representative of building types widely present in the Italian building stock of the last 30 years. A simulated design of the structures has been made with reference to the codes in force, the available handbooks and the current practice at the time of construction. The seismic response is calculated through non linear dynamic analyses with artificial and natural accelerograms. Three main types have been examined: bare frames, regularly infilled frames and pilotis frames. The results show a high vulnerability for the pilotis buildings: they can be assigned to the class B of the European Macroseismic Scale of 1998 (EMS98). On the contrary, a low vulnerability (class D of EMS98) can be attributed to the regularly infilled buildings: in this case collapse can be considered unlikely also with strong earthquakes. An intermediate seismic behavior is shown by buildings without infills, whose vulnerability can be placed between the classes B and C of EMS98. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A probabilistic approach for estimating the seismic response of elasto‐plastic SDOF systems     

Angelo D'Ambrisi  Marco Mezzi 《地震工程与结构动力学》2005,34(14):1737-1753

The seismic response of elasto‐plastic structures to both recorded and generated accelerograms is characterized by a large scattering of the results, even for accelerograms with similar peak ground acceleration values and frequency content. According to current code recommendations a design value of the seismic response of an elasto‐plastic structure can be computed as the mean of the responses to a certain number of spectrum‐fitting generated accelerograms. A more effective probabilistic approach is presented herein. It allows the analyst to calculate a design value of the seismic response characterized by a predefined non‐exceedance probability using a limited number of generated accelerograms. The results of the performed analyses are presented in diagrams that can be used for structural design applications. The applicability of the proposed method is demonstrated in the case of an elasto‐plastic structural system and the results are compared with those obtained applying current code recommendations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Petrological significance of high-pressure ultramafic xenoliths from ultrapotassic rocks of Central Italy     

Sandro Conticelli  Angelo Peccerillo 《Lithos》1989,24(4):305-322

Two suites of ultramafic xenoliths have been found in ultrapotassic lavas from the 0.9 Ma old Torre Alfina volcano sited at the northern border of the Vulsinian district (Central Italy). One group of Xenoliths consists of spinel-bearing lherzolites, harzburgites, minor wherlites and dunites with a maximum size of 3–4 cm. Some samples contain discrete laths of phlogopite. A second class consists of phlogopite-rich, glass-bearing peridotites. The first suite displays textural characteristics such as triple points, deformed olivine with well developed kink banding and porphyroclastic textures indicating equilibration at high pressure. Pressure estimates give values in the range 1.3–2.5 GPa, corresponding to mantle depths in the area, where the present-day Moho is about 25 km deep. Equilibration temperatures have been estimated in the range between 950–1000°C. The chemical composition of some phases, such as the very high Fo contents of olivines (up to Fo₉₄ in harzburgites), Mg content of orthopyroxenes and Cr/Cr+Al ratios of clinopyroxenes and spinels, suggest that these xenoliths represent peridotites which suffered different degrees of partial melting before being incorporated into the Torre Alfina magma. On the other hand, the occurrence of phlogopite speaks for metasomatic events. The phlogopite-rich, glass-bearing xenoliths consist of phlogopite, olivine, clinopyroxene, rare orthopyroxene and glass. Apatite is the most common accessory. Olivine is present in both euhedral and strained crystals. A few relics of protogranular textures are also observed. Textural and chemical evidence suggests that these xenoliths represent mica-rich peridotites which have undergone phlogopite breakdown during rapid rise to the surface with the development of a K-rich liquid which reacted with mafic phases producing a rapid growth of olivine and, to a lower extent, pyroxene. Originally, these xenoliths may have represented intensively metasomatized upper mantle. However, a cumulitic origin from previous potassic magmatic events cannot be excluded. The host lavas have compositions intermediate between high-silica lamproite and Roman-type ultrapotassic rock. They have high abundances of incompatible elements and radiogenic Sr, coupled with high Mg content, MgO/CaO, Ni and Cr. These features support a genesis in a residual upper mantle which has suffered partial melting with the extraction of basaltic liquids, followed by metasomatic events which caused an enrichment in incompatible elements and radiogenic Sr. The presence of mantle-derived ultramafic xenoliths in the torre Alfina lavas testifies for a rapid uprise of the magma which reached the surface without suffering fractional crystallization and significant interaction with the upper crust. Accordingly, the Torre Alfina lavas represent an unique example of primitive potassic liquid in Central Italy.  相似文献   

Volcanological and magmatological evolution of Stromboli volcano (Aeolian Islands): The roles of fractional crystallization,magma mixing,crustal contamination and source heterogeneity   总被引：1，自引：0，他引：1  

Lorella Francalanci  Piero Manetti  Angelo Peccerillo 《Bulletin of Volcanology》1989,51(5):355-378

The present paper reports the results of a detailed stratigraphical, petrological and geochemical investigation on the island of Stromboli, Aeolian arc, Southern Tyrrhenian sea. Major and trace element data determined on a large quantity of samples from well-established stratigraphic positions indicate that the magmatological evolution of the island through time was more complex than previously known. The activity of the exposed part of Stromboli, which occurred over a time span of about 100 000 years, started with the emission of high-K calc-alkaline (HKCA) volcanics, which were covered by calc-alkaline (CA), shoshonitic (SHO), high-K calc-alkaline (HKCA) and potassic (KS) products. The most recent activity consists of HKCA lavas and the present-day SHO-basaltic volcanics emitted by mildly explosive “strombolian” activity. Most of the products are lavas, with minor amounts of pyroclastic rocks emplaced mainly during the early stages of activity. The transition from the SHO to the KS cycle was associated with the collapse of the upper part of the volcanic apparatus; the transition from KS to the present-day SHO activity has been found to have occurred at the time of the sliding of the western portion of the volcano that generated the “Sciara del Fuoco” depression. The rock series cropping out at Stromboli show variable enrichment in potassium, incompatible trace elements and radiogenic Sr which increase from CA through HKCA, and SHO up to KS rocks. Major, trace element and Sr-isotopic data agree in indicating that the HKCA and SHO series evolved by crystal/liquid fractionation starting from different parental liquids, whereas crustal assimilation appears to have been the leading process during the evolution of KS volcanics. Mixing processes also played a role although they can be well documented only when they occurred between magmas with different isotopic and geochemical characteristics. Geochemical modelling based on trace element and isotopic data indicates that the mafic magmas of the different volcanic series may be generated by melting of an upper mantle heterogeneously enriched in incompatible elements and radiogenic Sr by addition, via subduction, of different amounts of crustal material. Geochemical data, however, are also in agreement with the alternative hypothesis that the most mafic magmas of the different series have been generated by combined processes of fractional crystallization, assimilation and mixing of a CA magma in a deep-sited magma chamber; the mafic magmas formed by these complex processes were successively emplaced in a shallow reservoir where they evolved by simple fractional crystallization (HKCA and SHO series) and by assimilation of crustal material (KS). The occurrence of changes in the geochemical signatures of the magmas at the time of the structural modification of the volcano is believed to favour the hypothesis that the variable composition observed in the volcanic rocks of Stromboli is the result of processes occurring within the volcanic system.  相似文献   

A boundary integral equation technique for visco-elastic stress analysis     

Angelo Carini  Giancarlo Gioda 《国际地质力学数值与分析法杂志》1986,10(6):585-608

On the basis of the correspondence principle of visco-elasticity, an application is discussed of the boundary integral equation method to the solution of time-dependent stress analysis problems. The adopted solution technique, in addition to the time-dependent stress and strain distributions, enables the determination of a measure of the error affecting the numerical results. The governing equations for the plane strain visco-elastic problem are derived with reference to a generalized Kelvin model consisting of the series of any number of simple kelvin elements, having both volumetric and deviatoric components. To get some insight into the overall performance of the technique, the results obtained in the solution of some test examples are discussed and compared with those dering from the available closed from solutions.  相似文献   

Seasonal variation of particulate organic compounds in atmospheric PM₁₀ in the biggest municipal waste landfill of Algeria   总被引：1，自引：0，他引：1  

Riad Ladji  Noureddine Yassaa  Angelo Cecinato  Brahim Youcef Meklati 《Atmospheric Research》2007,86(3-4):249-260

The average composition and seasonal variations of atmospheric organic particulates with respect to n-alkanes, n-alkanoic acid, polycyclic aromatic hydrocarbon (PAHs), and nitrated polycyclic aromatic hydrocarbons (N-PAHs) were determined at the biggest municipal waste landfill in Algeria located in Oued Smar, 13 km east of downtown Algiers. Samplings were carried out from August 2002 to February 2003, and organic compounds adsorbed in air particles having an aerodynamic diameter lower than 10 μm (PM₁₀) were characterized using gas chromatography coupled with mass spectrometric detection (GC/MSD). Total concentrations ranged from 828 to 11,068 ng per cubic meter of air for n-alkanes, from 1714 to 21,710 ng per cubic meter of air for n-alkanoic acids, from 13 to 212 ng per cubic meter of air for PAHs and from 93 to 205 pg per cubic meter of air for N-PAHs. n-Alkanoic acids accounted for 85 and 56% of the total organic composition of the aerosol measured in summer and winter, respectively, were the biggest fraction. The distribution profiles and the diagnostic ratios of some marker compounds allowed to identify the combustion and microbial activity as the major sources of particulate organic pollutants associated with direct emission. The year-time dependence of organic fraction content of aerosol in Oued Smar appeared to be related to average meteorological conditions as well as variability of rate and nature of materials wasted into the landfill.  相似文献   

Tonian to early Cryogenian synorogenic basin of the São Gabriel Terrane,Dom Feliciano Belt,southernmost Brazil     

Luiz Alberto Vedana  Ruy Paulo Philipp  Miguel Angelo Stipp Basei 《International Geology Review》2018,60(1):109-133

A provenance and stratigraphic study of the Neoproterozoic Pontas do Salso Complex (PSC), western portion of the Dom Feliciano Belt (DFB), was conducted with U–Pb zircon geochronological analysis of the metasediments and the host rocks. The U–Pb isotopic data from detrital zircon of the metasediments indicate the source from the latest Middle Tonian to Late Cryogenian (between 897 and 684 Ma) and maximum depositional age of 685 ± 18 Ma in an arc-related basin setting adjacent in the Sao Gabriel Arc. The metasediments of the PSC form an elongated body in the N35°E direction and occur in the central portion of the São Gabriel Terrane (SGT), which is constituted by ophiolitic complexes and arc-related rocks, generated probably during the final consolidation of Rodinia supercontinent, although this question is still open. Low- to medium-K calc-alkaline, metaluminous affinity, and trace-element geochemistry suggest that the chemical composition of the protoliths was generated from metasomatized mantle sources in subduction zones. The PSC is composed of meta-arkoses, with subordinate metaconglomerates and metapelites. The meta-arkoses are disposed in plane-parallel layers, which also internally feature small-scale cross-bedding structures. The matrix has a blastopsammitic, poorly selected, fine to coarse texture, and hexagonal quartz and plagioclase porphyroclasts with superimposed thermal metamorphism. The polymict metaconglomerates are matrix-supported, with 15–55% of clasts of metavolcanic rocks, metasediments, undeformed granites, and quartz veins. The metapelites comprise mainly muscovite phyllites with syn-tectonic garnet and chloritoid porphyroblasts. The PSC represents a sedimentary succession deposited on an arc-related basin formed during the collapse and uplift of the SGT.  相似文献   

Lahar simulation at active volcanoes of the Southern Andes: implications for hazard assessment   总被引：1，自引：1，他引：0  

Angelo Castruccio  Jorge Clavero 《Natural Hazards》2015,77(2):693-716

  相似文献   

Nursery areas of red mullet (Mullus barbatus), hake (Merluccius merluccius) and deep-water rose shrimp (Parapenaeus longirostris) in the Eastern-Central Mediterranean Sea     

Roberto Carlucci  Lembo Giuseppe  Maiorano Porzia  Capezzuto Francesca  Marano Chiara Alessandra  Sion Letizia  Spedicato Maria Teresa  Ungaro Nicola  Tursi Angelo  Gianfranco D'Onghia 《Estuarine, Coastal and Shelf Science》2009,83(4):529-538

The spatial pattern of the nursery areas of red mullet (Mullus barbatus), hake (Merluccius merluccius) (Linnaeus, 1758) and deep-water rose shrimp (Parapenaeus longirostris) (Lucas, 1846) was studied in the South Adriatic and North Ionian Seas (Eastern-Central Mediterranean) applying geostatistical techniques and data from time series trawl surveys conducted in the area. The analysed variables were: R (number of recruits/km²) and R/Tot (fraction of recruits on the total sampled population). The structural analysis showed a spatial pattern of both variables characterized by continuity on a small scale. Predictions of nursery area localization with probability of finding recruits at different threshold values were obtained through median indicator kriging. For the red mullet the nurseries were mainly identified in the South Adriatic Sea off the Gargano peninsula and between Molfetta and Monopoli within 50 m in depth. The main concentration of hake juveniles was found to be between 100 and 200 m in depth along the Gargano peninsula and between Otranto and Santa Maria di Leuca, where a nursery of deep-water rose shrimp was also detected. An overlapping depth, between 100 and 200 m, was identified for hake and deep-water rose shrimp nurseries. Protection of these areas through limitations of fishing pressure is discussed.  相似文献