Diversity of Epiphytic Lichens and Hg Contents of Xanthoria parietina Thalli as Monitors of Geothermal Air Pollution in the Mt. Amiata Area (Central Italy)     

Stefano Loppi  Luca Paoli  Carlo Gaggi 《Journal of Atmospheric Chemistry》2006,53(2):93-105

The diversity of epiphytic lichens and mercury concentrations in lichen samples were measured to monitor the release of airborne pollutants from the industrial exploitation of geothermal resources in the Mt. Amiata area (Italy). The lichen biodiversity showed a general condition of moderate environmental alteration around the geothermal power plants, contrasting with the low environmental alteration of the remaining sites investigated. According to the accumulated Hg in lichen thalli, it was possible to estimate mean Hg and H₂S concentrations in the air, which resulted in very good agreement with values measured instrumentally. Based on these data and the correlation between lichen diversity values and Hg concentrations in lichens, it was possible to calculate the threshold of 8 μg/m³ H₂S as responsible for the worsening from low to moderate environmental alteration according to the biodiversity of epiphytic lichens, and to infer that around geothermal power plants, although not toxic to humans, H₂S concentrations are such to alter the nasal quality of the air. Based on the growth rate of X. parietina, it was possible to convert Hg concentrations into estimates of average Hg deposition rates, which showed fluxes of the order of 65–100 mg/ha/y, indicating a dispersions factor of about 10⁴ for the Hg emitted from the geothermal power plants.  相似文献   

Effects of column axial force – bending moment interaction on inelastic seismic response of steel frames     

Marina Como  Mario De Stefano  Roberto Ramasco 《地震工程与结构动力学》2003,32(12):1833-1852

It is well known that axial force – bending moment interaction (N–M interaction) affects to a large extent the cyclic inelastic behaviour of structural elements, especially columns in framed structures, with reduction in bending capacity and loss of available ductility. A few studies have also shown that significant inelastic axial shortening affects the response of column elements subjected to medium–high levels of axial loads and cyclic bending. This paper is primarily aimed at evaluating the effects of column N–M interaction on the inelastic seismic response of steel frames. By considering the contemporaneous action of vertical loads, due to gravity, and of horizontal seismic excitation, it is shown that the progressive axial shortening of adjacent columns may differ substantially, thus inducing significant relative settlements at the ends of the connecting beams and, then, remarkable amplifications in beam plastic rotations. An evaluation of additional beam plastic rotations induced by column N–M interaction is carried out for real structures by investigating the inelastic response of steel frames designed according to European standards under horizontal and vertical earthquake excitations. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Geological and geomorphological evolution of the Etna volcano NE flank and relationships between lava flow invasions and erosional processes in the Alcantara Valley (Italy)     

Stefano Branca   《Geomorphology》2003,53(3-4):247-261

In this paper, the interrelationships between volcanic activity and fluvial events in the Alcantara Valley are investigated. Based on the correlation between the stratigraphy of the NE flank of Mt Etna and subsurface data, the geological and geomorphological evolutions of the valley are reconstructed. New 1:10 000 scale geological mapping shows that the bulk of this sector of the volcano is made up of the Ellittico volcano lava flows, though they are widely covered by the products of the eruptive activity of the last 15 ka. The present-day morphological setting of the Alcantara Valley is the result of two main evolutionary phases initiated during the activity of the Ellittico volcano. Only one lava flow invasion of the valley floor occurred in the first phase. This phenomenon was followed by a long period of erosional processes leading to the entrenchment of the drainage pattern and the erosion of the Ellittico lava flow. About 20–25 ka ago, an important change in the frequency of the lava flow invasions into the valley occurred associated with the final stage of the Ellittico volcano activity marking the beginning of the second phase. During this phase, volcanic processes became predominant with respect to other morphogenetic processes in the Alcantara Valley. Lava flows coming from the NE flank of the Ellittico volcano caused a radical modification of the morphological setting of this area, even though only one lava flow emitted by an eruptive fissure located within the valley partially filled the riverbed. During the eruptive activity of the last 15 ka, the complete filling of the Alcantara Valley floor occurred. In particular, between 15 and 7 ka, a lava flow originated from the Mt Moio scoria cone filled the valley floor for a distance of about 9 km. Following a short period of erosion, an eruptive fissure located within the valley generated a 20–21-km-long lava flow that was channelled along the full extent of the Alcantara Valley and stretches for about 3 km offshore in the Ionian sea. In the last 7 ka, lava flows originating from the NE-Rift zone produced only temporary damming of the riverbed without any important contribution to the filling of the Alcantara Valley.  相似文献   

Single-force point-source static fields: an exact solution for two elastic half-spaces   总被引：1，自引：0，他引：1  

Stefano Tinti  & Alberto Armigliato 《Geophysical Journal International》1998,135(2):607-626

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Observations of Atmospheric Solitary Waves in the Urban Boundary Layer     

M. P. Rao  Paolo Castracane  Stefano Casadio  Daniele Fuá  Giorgio Fiocco 《Boundary-Layer Meteorology》2004,111(1):85-108

The simultaneous operation of a three-axis Doppler sodar system in the centralurban area of Rome and two similar systems in the suburban area, forming atriangle about 20 km on each side, provided evidence of solitary-type wavesin the urban boundary layer. Three events, each lasting from a few minutes toabout 30 min, and ranging in depth from the minimum range of the sodar (39 m) to over 500 m, are reported here. Two events were recognizable onall three sodar records while the third event could be observed at the urbanlocation only. Time-height acoustic echo intensity records showed no-echoregions within the wave indicating transport of trapped recirculating air.This is typical of large amplitude solitary waves. The time series plots ofsodar-derived vertical wind velocity revealed a maximum peak-to-peakvariation of about 5 m s^-1 during periods of wave-associated disturbance.The vertical velocity is found to increase with height up to the top of the closedcirculation within the wave and decreases further above. The normalisedamplitude-wavelength relationship for the two events indicates that theobserved waves are close to a strongly nonlinear regime.  相似文献   

Statistical analysis of earthquake activity at Etna volcano (March 1981 eruption)     

Giuseppe De Natale  Stefano Gresta  Giuseppe Patané  Aldo Zollo 《Pure and Applied Geophysics》1985,123(5):697-705

Seismic activity that preceded, accompanied, and followed the 17–23 March 1981 Etnean eruption has been statistically analyzed.On the grounds of both time evolution of seismicity and catalogue completeness, three time intervals have been defined (12 February–2 March, 12–17 March, 19–31 March) and for each of these periods both the b coefficient of theGutenberg-Richter's (1956) relationship and the E parameter of the cluster size (Shlien andToksoz, 1970) have been calculated.No significant variations were observed between the first and third periods, while lower values of bothb andE coefficients were found in the second one. These findings might indicate that changes in the seismicity features occur just before the eruption start.Small but fast variations in the stress field acting on the volcano might originate this type of seismic activity, while the importance of the tectonic control on volcanic phenomena seems to be confirmed.  相似文献   

A statistical analysis of flank eruptions on Etna volcano     

Francesco Mulargia  Stefano Tinti  Enzo Boschi 《Journal of Volcanology and Geothermal Research》1985,23(3-4)

A singularly complete record exists for the eruptive activity of Etna volcano. The time series of occurrence of flank eruptions in the period 1600–1980, in which the record is presumably complete, is found to follow a stationary Poisson process. A revision of the available data shows that eruption durations are rather well correlated with the estimates of the volume of lava flows. This implies that the magnitude of an eruption can be defined directly by its duration. Extreme value statistics are then applied to the time series, using duration as a dependent variable. The probability of occurrence of a very long (300 days) eruption is greater than 50% only in time intervals of the order of 50 years. The correlation found between duration and total output also allows estimation of the probability of occurrence of a major event which exceeds a given duration and total flow of lava. The composite probabilities do not differ considerably from the pure ones. Paralleling a well established application to seismic events, extreme value theory can be profitably used in volcanic risk estimates, provided that appropriate account is also taken of all other variables.  相似文献   

Towards a knowledge base to support global change policy goals     

Stefano Nativi  Mattia Santoro  Gregory Giuliani  Paolo Mazzetti 《International Journal of Digital Earth》2020,13(2):188-216

ABSTRACT

In 2015, it was adopted the 2030 Agenda for Sustainable Development to end poverty, protect the planet and ensure that all people enjoy peace and prosperity. The year after, 17 Sustainable Development Goals (SDGs) officially came into force. In 2015, GEO (Group on Earth Observation) declared to support the implementation of SDGs. The GEO Global Earth Observation System of Systems (GEOSS) required a change of paradigm, moving from a data-centric approach to a more knowledge-driven one. To this end, the GEO System-of-Systems (SoS) framework may refer to the well-known Data-Information-Knowledge-Wisdom (DIKW) paradigm. In the context of an Earth Observation (EO) SoS, a set of main elements are recognized as connecting links for generating knowledge from EO and non-EO data – e.g. social and economic datasets. These elements are: Essential Variables (EVs), Indicators and Indexes, Goals and Targets. Their generation and use requires the development of a SoS KB whose management process has evolved the GEOSS Software Ecosystem into a GEOSS Social Ecosystem. This includes: collect, formalize, publish, access, use, and update knowledge. ConnectinGEO project analysed the knowledge necessary to recognize, formalize, access, and use EVs. The analysis recognized GEOSS gaps providing recommendations on supporting global decision-making within and across different domains.  相似文献   

Towards integrated essential variables for sustainability     

Anthony Lehmann  Joan Masò  Stefano Nativi  Gregory Giuliani 《International Journal of Digital Earth》2020,13(2):158-165

ABSTRACT

Measuring the achievement of a sustainable development requires the integration of various data sets and disciplines describing bio-physical and socio-economic conditions. These data allow characterizing any location on Earth, assessing the status of the environment at various scales (e.g. national, regional, global), understanding interactions between different systems (e.g. atmosphere, hydrosphere, biosphere, geosphere), and modeling future changes. The Group on Earth Observations (GEO) was established in 2005 in response to the need for coordinated, comprehensive, and sustained observations related to the state of the Earth. GEO’s global engagement priorities include supporting the UN 2030 Agenda for Sustainable Development, the Paris Agreement on Climate, and the Sendai Framework for Disaster Risk Reduction. A proposition is made for generalizing and integrating the concept of EVs across the Societal Benefit Areas of GEO and across the border between Socio-Economic and Earth systems EVs. The contributions of the European Union projects ConnectinGEO and GEOEssential in the evaluation of existing EV classes are introduced. Finally, the main aim of the 10 papers of the special issue is shortly presented and mapped according to the proposed typology of SBA-related EV classes.  相似文献   

Inelastic response and design criteria of plan-wise asymmetric systems     

Mario De Stefano  Giuseppe Faella  Roberto Ramasco 《地震工程与结构动力学》1993,22(3):245-259

The study of the torsional response of buildings in the inelastic range of behaviour is of great interest since the ability of structures to resist strong earthquakes mainly relies on their ductility and capacity for energy dissipation. Furthermore, an examination of the performance of structures during past earthquakes demonstrates that plan-asymmetric buildings suffered greater damage due to torsional response. The paper deals with this subject by analysing a model which idealizes a one-storey building with resisting elements oriented along two perpendicular directions. In addition to the parameters of the elastic behaviour, the inelastic system response depends on full yield capacity and plan-wise strength distribution. The influence of the criterion adopted for the design of resisting elements on local ductility demand and damage has been evaluated by parametric analysis. In particular, a comparison has been carried out between systems with equal design levels for all elements and systems with design levels dependent on the element location. For a given elastic behaviour and total capacity, the strength distributions in plan have been defined which minimize ductility demand and structural damage. Finally, based on these findings, responses from models designed according to several seismic codes have been compared.  相似文献