Germination and establishment of the invasive cordgrass Spartina densiflora in acidic and metal polluted sediments of the Tinto River     

Guillermo Curado  Alfredo E. Rubio-Casal  Enrique Figueroa  Jesús M. Castillo 《Marine pollution bulletin》2010,60(10):1842-1848

Heavy metal pollution is common in rivers in the vicinity of mining areas. In these polluted environments, the survival of alien species with a high tolerance to metals may be favored. The Tinto River (Southwest Iberian Peninsula) is an excellent natural laboratory for the study of plants’ responses to acidic and metal polluted sediments. This work analyzes the tolerance of the alien species Spartina densiflora to low pH and high metal loads in the Tinto River. The main aim of this study was to determine if this alien species can invade landward along the banks of the Tinto River. S. densiflora seeds were able to germinate in heavy metal polluted aerobic sediments even at pH 2. However, these conditions decreased S. densiflora final germination, altered germination dynamics, decreased aerial and subterranean growth rates, and prevented its establishment.  相似文献   

Evolution of earthquake losses in Portuguese residential building stock     

Maria Luísa Sousa  Alfredo Campos Costa 《Bulletin of Earthquake Engineering》2016,14(7):2009-2029

The evolution of the expected earthquake losses in different Portuguese regions was studied in order to determine whether the natural regeneration of buildings could contribute to the mitigation of seismic risk, although the building exposure has increased over time in most analysed regions. To achieve this goal, five inter-related risk indicators were estimated, based on the Portuguese censuses’ surveys of residential buildings and inhabitants obtained in two different moments in time: 2001 and 2011. The FEMA (2008) approach was used to estimate the risk indicators, i.e., the Annualized Economic and Human earthquake Losses, either in absolute terms or normalised by building and population exposure. This study offers a perspective of the seismic risk in the Portuguese mainland, provides a comparison of risk levels between different epochs, and analyses the obtained results in order to compare the risk among Portuguese regions. It is important to mention that the comparison of economic losses based on the building stocks surveyed in 2001 and in 2011 took into account the Portuguese inflation rate in that time interval. The main findings of the study show that the natural regeneration of the residential housing stock contributes to the reduction of the expected seismic economic losses in Portugal, at an average rate of 14 % per 10 years, and to the reduction of the expected annualized human losses to almost one half after 10 years. The results support the conclusion that the natural regeneration of the residential housing stock contributed to the mitigation of the seismic risk in mainland Portugal, in the 10 year period under analysis, even though there was an increase of the building exposure in the region.  相似文献   

Force reduction factors for steel buildings with welded and post-tensioned connections     

Alfredo Reyes-Salazar  Mario D. Llanes-Tizoc  Juan Bojorquez  Edén Bojórquez  Arturo López-Barraza  Achintya Haldar 《Bulletin of Earthquake Engineering》2016,14(10):2827-2858

The seismic responses of steel buildings with perimeter moment resisting frames (MRF) with welded connections (WC) are estimated and compared to those of similar buildings with semi-rigid post-tensioned connections (PC). The responses are estimated in terms of ductility reduction factors (R _µ,), ductility demands (µ _G ) and force reduction factors (R). Two steel model buildings, which were modeled as complex-3D-MDOF systems, were used in the study. Results indicate that the reduction magnitude of global response parameters is larger than that of local response parameters, contradicting the same reduction implicitly assumed in the static equivalent lateral force procedure, implying that non-conservative design may result. The value of 8 for R, suggested in many codes for ductile steel MRF, and the value of 1 suggested in the well known Newmark and Hall procedure for the ratio of R to µ _G , cannot be justified. The reason for this is that SDOF systems were used to model actual structures, where higher mode effects, energy dissipation and structural overstrength weren’t explicitly considered. The codes should be more transparent regarding the magnitude and the components involved in the force reduction factors. The seismic performance of steel buildings with PC may be superior to that of the buildings with WC, since their force reduction factors are larger and their ductility demands smaller, implying that PC buildings could be designed for smaller lateral seismic forces. The conclusions of this paper are for the particular structural systems and models considered. Much more research is needed to reach more general conclusions.  相似文献   

The 2006 Bahía Asunción Earthquake Swarm: Seismic Evidence of Active Deformation Along the Western Margin of Baja California Sur,Mexico     

Luis Munguía  Sergio Mayer  Alfredo Aguirre  Ignacio Méndez  Mario González-Escobar  Manuel Luna 《Pure and Applied Geophysics》2016,173(10-11):3615-3629

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A restricted charged four-body problem     

J. Casasayas  A. Nunes 《Celestial Mechanics and Dynamical Astronomy》1989,47(3):245-266

We consider a restricted charged four body problem which reduces to a two degrees of freedom Hamiltonian system, and prove the existence of infinite symmetric periodic orbits with arbitrarily large extremal period. Also, it is shown that an appropriate restriction of a Poincaré map of the system is conjugate to the shift homeomorphism on a certain symbolic alphabet.Partially supported by a grant of the CGICT no. P1386-0351.On leave of absence from Departamento de Fisica, Universidade de Lisboa. Partially supported by a grant of Fundaçao Calouste Gulbenkian no. 32/85/13.  相似文献   

Geology and tectonics of the Boa Vista Basin (Paraíba, northeastern Brazil) and geochemistry of associated Cenozoic tholeiitic magmatism     

Zorano Srgio de Souza  Marcos Antonio Leite do Nascimento  Rogrio Vidal Nunes Barbosa  Luis Gustavo da Silveira Dias 《Journal of South American Earth Sciences》2005,18(3-4):391-405

The Boa Vista Basin (BVB) is located approximately 60 km southwest of Campina Grande, Paraíba, northeastern Brazil. It has a half-graben geometry controlled by dip-slip normal faults striking NE–SW. From the base to the top, the BVB is composed of (1) a lower volcanic unit of altered basalts and basaltic andesites overlying Precambrian basement rocks, (2) an intermediate unit of bentonitic shales that pass upward to medium- to coarse-grained sandstones and conglomerates and downward to sandstones and siltstones, and (3) an upper volcanic unit of massive to vesiculated basaltic flows grading to pillowed or autobrecciated basalts. These basalts show porphyritic (olivine and augite microphenocrysts), glomeroporphyritic, intersetal, pilotaxitic, and variolitic textures. They are medium-K, Fe-rich tholeiites with SiO₂ of 50.2–53.3 wt%, magnesium number of 50.54–60.21 wt%, total alkali of 2.15–3.92 wt%, and TiO₂ of 1.8–1.9 wt% and are related by low-pressure fractionation of olivine, plagioclase, magnetite, ilmenite, and apatite. They are LREE-enriched (La_N/Yb_N=8.54–44.14) with no significant europium anomaly. Trace element modeling suggests a garnet-bearing metasomatised lherzolite as their source. The geological context and geochemistry of the basalts suggest a close connection between reactivated deep-rooted Precambrian shear zones, which channeled mantle-derived Tertiary tholeiitic magmas, and continental rifting in northeastern Brazil.  相似文献   

Propagation of seismic slip from brittle to ductile crust: Evidence from pseudotachylyte of the Woodroffe thrust, central Australia     

Aiming Lin  Tadashi Maruyama  Stallard Aaron  Katsuyoshi Michibayashi  Alfredo Camacho  Ken-ichi Kano 《Tectonophysics》2005,402(1-4):21

The Woodroffe thrust, central Australia, is a > 1.5-km-wide mylonitized shear zone marked by large volumes of mm- to cm-scale pseudotachylyte veins. The pseudotachylytes display typical melt-origin features, including rounded and embayed clasts, spherulitic and dentritic microlites, and flow structures within a fine-grained matrix. Three types of pseudotachylyte are identified on the basis of deformation texture, vein morphology, and host-rock lithology: cataclasite-related (C-Pt), mylonite-related (M-Pt), and ultramylonite-related (Um-Pt). The M-Pt and Um-Pt veins intrude into mylonite and ultramylonite and are themselves overprinted by subsequent mylonitization. These pseudotachylytes contain an internal foliation defined by flattened porphyroclasts and layering of the fine-grained vein matrix, and the foliation is generally oriented parallel to foliation in the surrounding mylonite and ultramylonite. These observations constrain the timing and environment of M-Pt and Um-Pt pseudotachylyte formation to a protracted period of deformation and mylonitization within the ductile regime of the crust. The M-Pt and Um-Pt veins, as well as the host mylonite, are overprinted by cataclasis and multiple generations of late-stage C-Pt veins that were generated in the brittle-dominated regime of the upper crust during uplift and exhumation of the shear zone.The coexistence of multiple generations of voluminous C-Pt, M-Pt, and Um-Pt veins indicates that the pseudotachylyte veins represent a large number of large earthquakes and accompanying seismic slip over an extended period of seismicity on the Woodroffe thrust. The timing and distribution of pseudotachylyte indicate that the earthquakes nucleated at the base of the brittle-dominated seismogenic zone and propagated down through the brittle–ductile transition into the ductile-dominated regime of the crust.  相似文献   

Metal Complexation with Different types of Soluble and Adsorbed Freshwater Ligands Followed by DPASV     

Cidália Maria Sousa Botelho  Rui Alfredo Rocha Boaventura  Maria de Lurdes Sadler Simões Gonçalves 《Aquatic Geochemistry》2007,13(2):173-186

In order to understand metal speciation in a polluted river (Este River, Northern Portugal) filtrate, freeze dried particles and organics desorbed from surfaces were titrated with Cd(II) and Zn(II), followed by differential pulse anodic stripping voltammetry (DPASV). The obtained results are compared with those previously published for Pb(II) and Cu(II). Due to the heterogeneity of the system, a continuous and a discrete ligand model were used to interpret the titration data. Two types of ligands could be detected and quantified by the discrete ligand model: small molecules with high affinities for cations such as Cd(II), Cu(I), and Zn(II) and macromolecules with higher affinities for Pb(II) and Cu(II). Small ligands were strongly adsorbed onto the particles, as inferred from the desorption of Zn(II) during titration with Pb(II) and Cd(II). The total concentrations of the different ligands and the complex formation constants with the different metals are reported.  相似文献   

The Indian Ocean tsunami of December 26, 2004: observations in Sri Lanka and Thailand     

T. Rossetto  N. Peiris  A. Pomonis  S. M. Wilkinson  D. Del Re  R. Koo  S. Gallocher 《Natural Hazards》2007,42(1):105-124

On December 26, 2004 a great earthquake (M _W 9.3) occurred off the western coast of Sumatra triggering a series of tsunami waves that propagated across the Indian Ocean causing damage and life loss in 12 countries. This paper summarizes the observations of lifeline performance, building damage and its distribution, and the social and economic impact of the tsunami made by the Earthquake Engineering Field Investigation Team (EEFIT) in Thailand and Sri Lanka. EEFIT operates under the umbrella of the UK’s Institution of Structural Engineers. It is observed that good engineering practice can reduce economic losses, but additional measures are required to reduce risk to life.  相似文献   

Analysis of the mobilization of solid loads and heavy metals in runoff waters from granite quarries     

Enrique Peña González  Joaquín Suárez López  Jordi Delgado Martín  Alfredo Jácome Burgos  Jerónimo Puertas Agudo 《Environmental Geology》2006,50(6):823-834

The cutting operations of dimension stone at quarries produce a large amount of fines that, in turn, cause a negative environmental impact over local surface waters. This article presents a detailed analysis of the mobilized contamination associated with runoff waters in a large granite quarry (～200 ha) which is located in Porriño (Galicia, NW Spain), the most important production centre of dimension stone in Spain. There, an intensive monitoring survey was developed in order to characterize the hydrology of the system as well as the release and transport of pollutants. This was accomplished by means of different control sections for the flow and by the collection of 52 random water samples. Automatic samplers were also used to collect 192 water samples associated with runoff generated by significant rain events. For each of the samples collected, a wide battery of analytic determinations was performed, including solid loads, turbidity, organic pollution, nutrient and selected metals. Upon careful examination it has been possible to obtain different parameters related to the contamination control, like the “event mean concentration” (EMC), maximum concentrations and specific sediment loads. Moreover, a comprehensive statistical study including parameter correlation and cumulative probability analyses helped to understand the pollutant mobilization behaviour within the quarry system. It can be concluded that mobilized contamination shows the anomalous presence of some metals, whose concentrations are in excess when compared to the natural rock. This excess metal amount must be attributed to an anthropogenic source associated to mining and cutting operations.  相似文献