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71.
Sotillo MG Fanjul EA Castanedo S Abascal AJ Menendez J Emelianov M Olivella R García-Ladona E Ruiz-Villarreal M Conde J Gómez M Conde P Gutierrez AD Medina R 《Marine pollution bulletin》2008,56(4):686-703
The ESEOO Project, launched after the Prestige crisis, has boosted operational oceanography capacities in Spain, creating new operational oceanographic services and increasing synergies between these new operational tools and already existing systems. In consequence, the present preparedness to face an oil-spill crisis is enhanced, significantly improving the operational response regarding ocean, meteorological and oil-spill monitoring and forecasting. A key aspect of this progress has been the agreement between the scientific community and the Spanish Search and Rescue Institution (SASEMAR), significantly favoured within the ESEOO framework. Important achievements of this collaboration are: (1) the design of protocols that at the crisis time provide operational state-of-the-art information, derived from both forecasting and observing systems; (2) the establishment, in case of oil-spill crisis, of a new specialized unit, named USyP, to monitor and forecast the marine oceanographic situation, providing the required met-ocean and oil-spill information for the crisis managers. The oil-spill crisis scenario simulated during the international search and rescue Exercise "Gijón-2006", organized by SASEMAR, represented an excellent opportunity to test the capabilities and the effectiveness of this USyP unit, as well as the protocols established to analyze and transfer information. The results presented in this work illustrate the effectiveness of the operational approach, and constitute an encouraging and improved base to face oil-spill crisis. 相似文献
72.
Hans-Ulrich Schmincke Steffen Kutterolf Wendy Perez Juanita Rausch Armin Freundt Wilfried Strauch 《Bulletin of Volcanology》2009,71(5):479-493
We present the stratigraphy, lithology, volcanology, and age of the Acahualinca section in Managua, including a famous footprint
layer exposed in two museum pits. The ca. 4-m-high walls of the main northern pit (Pit I) expose excellent cross sections
of Late Holocene volcaniclastic deposits in northern Managua. We have subdivided the section into six lithostratigraphic units,
some of which we correlate to Late Holocene eruptions. Unit I (1.2 m thick), chiefly of hydroclastic origin, begins with the
footprint layer. The bulk is dominated by mostly massive basaltic-andesitic tephra layers, interpreted to represent separate
pulses of a basically phreatomagmatic eruptive episode. We correlate these deposits based on compositional and stratigraphic
evidence to the Masaya Triple Layer erupted at Masaya volcano ca. 2,120 ± 120 a B.P.. The eruption occurred during the dry
season. A major erosional channel unconformity up to 1 m deep in the western half of Pit I separates Units II and I. Unit
II begins with basal dacitic pumice lapilli up to 10 cm thick overlain by a massive to bedded fine-grained dacitic tuff including
a layer of accretionary lapilli and pockets of well-rounded pumice lapilli. Angular nonvesicular glass shards are interpreted
to represent hydroclastic fragmentation. The dacitic tephra is correlated unequivocally with the ca. 1.9-ka-Plinian dacitic
Chiltepe eruption. Unit III, a lithified basaltic-andesitic deposit up to 50 cm thick and extremely rich in branch molds and
excellent leaf impressions, is correlated with the Masaya Tuff erupted ca. 1.8 ka ago. Unit IV, a reworked massive basaltic-andesitic
deposit, rich in brown tuff clasts and well bedded and cross bedded in the northwestern corner of Pit I, cuts erosionally
down as far as Unit I. A poorly defined, pale brown mass flow deposit up to 1 m thick (Unit V) is overlain by 1–1.5 m of dominantly
reworked, chiefly basaltic tephra topped by soil (Unit VI). A major erosional channel carved chiefly between deposition of
Units II and I may have existed as a shallow drainage channel even prior to deposition of the footprint layer. The swath of
the footprints is oriented NNW, roughly parallel to, and just east of, the axis of the channel. The interpretation of the
footprint layer as the initial product of a powerful eruption at Masaya volcano followed without erosional breaks by additional
layers of the same eruptive phase is strong evidence that the group of 15 or 16 people tried to escape from an eruption. 相似文献
73.
Brent P. Stafford Natalie L. Cápiro Pedro J.J. Alvarez William G. Rixey 《Ground Water Monitoring & Remediation》2009,29(3):93-104
Neat ethanol (75.7 L) was released into the upper capillary zone in a continuous-flow, sand-packed aquifer tank (8.2 m3 ) with an average seepage velocity of 0.75 m/day. This model aquifer system contained a residual nonaqueous phase liquid (NAPL) that extended from the capillary zone to 10 cm below the water table. Maximum aqueous concentrations of ethanol were 20% v/v in the capillary zone and 0.08% in the saturated zone at 25 and 30 cm downgradient from the emplaced NAPL source, respectively. A bench-scale release experiment was also conducted for a similar size spill (scaled to the plan area). The concentrations of ethanol in ground water for both the bench- and pilot-scale experiments were consistent with advective–dispersive limited mass transfer from the capillary to the saturated zone. Concentrations of monoaromatic hydrocarbons and isooctane increased in the pore water of the capillary zone as a result of both redistribution of residual NAPL (confirmed by visualization) and enhanced hydrocarbon dissolution due to the cosolvent effect exerted by ethanol. In the tank experiment, higher hydrocarbon concentrations in ground water were also attributed to decreased hydrocarbon biodegradation activity caused by preferential microbial utilization of ethanol and the resulting depletion of oxygen. These results infer that spills of highly concentrated ethanol will be largely confined to the capillary zone due to its buoyancy, and ethanol concentrations in near-source zone ground water will be controlled by mass transfer limitations and hydrologic conditions. Furthermore, highly concentrated ethanol releases onto pre-existing NAPL will likely exacerbate impacts to ground water, due to NAPL mobilization and dissolution, and decreased bioattenuation of hydrocarbons. 相似文献
74.
Beatriz Vaz de Melo Mendes Luis Raúl Pericchi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(3):399-410
We model multivariate hydrological risks in the case that at least one of the variables is extreme. Recently, Heffernan JE,
Tawn JA (2004) A conditional approach for multivariate extremes. J R Stat Soc B 66(3):497–546 (thereafter called HT04) proposed a conditional multivariate extreme value model which applies to regions where
not all variables are extreme and simultaneously identifies the type of extremal dependence, including negative dependence.
In this paper we apply this modeling strategy and provide an application to multivariate observations of five rivers in two
clearly distinct regions of Puerto Rico Island and for two different seasons each. This effective dimensionality of ten-dimensions
cannot be handled by the traditional models of multivariate extremes. The resulting fitted model, following HT04 model and
strategies of estimation, is able to make long term estimation of extremes, conditional than other rivers are extreme or not.
The model shows considerable flexibility to address the natural questions that arise in multivariate extreme value assessments.
In the Puerto Rico 5 rivers application, the model clearly puts together two regions one of two rivers and another of three
rivers, which show strong relationships in the rainy season. This corresponds with the geographical distribution of the rivers.
相似文献
Beatriz Vaz de Melo MendesEmail: |
75.
J. Quereda Sala A. Gil Olcina A. Perez Cuevas J. Olcina Cantos A. Rico Amoros E. Montón Chiva 《Climatic change》2000,46(4):473-483
The evolution of the mean annual temperatures recordedin the major historical network of SpanishMediterranean observatories(36°N–45°/60°W–4°E)exhibits a significant warming trend. Analysis of thetrend is difficult and could be biased by non-climaticprocesses such as the urban effect and weather stationrelocation, which also need to be taken intoaccount.The present work examines the effects of non-climaticprocesses and shows that most of the temperature risecould be due to an urban effect. On correcting for theurban effect, the actual rise was found to be zero ornegligible. The assumption of temperature stability inthe Spanish Mediterranean should thereforenot be rejected. 相似文献
76.
R. González Felipe H. J. Mosquera Cuesta A. Pérez Martínez H. Pérez Rojas 《中国天文和天体物理学报》2005,5(4):399-411
The equations of state for degenerate electron and neutron gases are studied in the presence of magnetic fields. After including quantum effects in the investigation of the structural properties of these systems, it is found that some hypermagnetized stars can be unstable according to the criterion of stability of pressures. Highly magnetized white dwarfs should collapse producing a supernova type Ia, while superstrong magnetized neutron stars cannot stand their own magnetic field and must implode, too. A comparison of our results with a set of the available observational data of some compact stars is also presented, and the agreement between this theory and observations is verified. 相似文献
77.
78.
Claudia Sayo Valladares Nuno Machado Monica Heilbron Beatriz Paschoal Duarte Gilles Gauthier 《Gondwana Research》2008,13(4):516-526
207Pb/206Pb ages from 420 zircons from 9 upper amphibolite and granulite facies quartzites of the post-1.8 Ga metasedimentary cover from the Occidental and Oriental terranes from the Neoproterozoic central Ribeira belt, in eastern Brazil, are discussed. Ages from the Occidental terrane show that Proterozoic ages predominate with a modal class at 2.1–2.2 Ga and that Archean ages are less common and lie within the 2.5–3.6 Ga range. A wider dispersion on Proterozoic ages down to 1.1 Ga and youngest Neoproterozoic ages (550–700 Ma) were also observed and could be related to the Brasiliano/PanAfrican metamorphic events. The data show that detrital sediments of the Occidental terrane were derived predominantly from erosion of a 1.8–2.2 Ga Paleoproterozoic terrane with a small proportion of a 2.6–3.6 Ga Archean crust. Ages from the Oriental terrane are greatly dispersed, but show a significant proportion of ages between 1.7 and 2.1 Ga, although the great majority are between 0.5 and 1.6 Ga. Only 3 out of 144 grains yield Archean ages, between 2.5 and 2.9 Ga. Based on the greatest errors observed on the data from the Oriental Terrane (100–300 Ma), and a continuum of obtained ages between 2072 Ma (Paleoproterozoic) and 517 Ma (Cambrian), the more plausible interpretation is that the dispersion of ages results from partial resetting of the U–Pb system by Brasiliano metamorphism in Proterozoic–Archean zircons, although a Mesoproterozoic source could not be discarded. 相似文献
79.
Experimental studies on the retention of metals (Cu, Co, Ni, and Zn) in bentonite samples from the Grau Region (Northern Peru)
have been accomplished using monometallic, bimetallic, trimetallic, and tetrametallic solutions. Parameters such as pH and
concentration of dissolved metals and organic compounds have been evaluated by means of batch adsorption experiments. Adsorption
rates indicate the suitability of these bentonites in the environmental industry for heavy metals retention purposes. In addition
to its quality as physical barrier to avoid the dispersion through the environment of polluted leachates, bentonite, due to
its high cation exchange capacity, can act also as a chemical barrier, protecting the quality of surface and groundwater systems,
while limiting the migration of heavy metals in solid residues or sludge stocked in security landfills. Adsorption rates of
tested bentonites were proved to decrease when concentrations of both metal and organic compounds, as well as the number of
ionic species, increase in solution; additionally, lower metal removal rates from solution were obtained when extremely acidic
conditions were achieved. 相似文献
80.
Rosario Iturbe Alejandrina Castro Guillermina Perez Carlos Flores Luis G. Torres 《Environmental Geology》2008,55(8):1785-1795
For the year 1996, 366 incidents related with clandestine poaching of oil-products were reported in Mexico, 159 in 1997, and
240 in 1998. For the year 2003 (the most recently reported figure), there were 136 events. Petroleos Mexicanos (PEMEX), very
concerned with the environmental agenda, has developed programs oriented to diminish contamination levels in all of its oil
facilities. This work was aimed at characterizing zones around polyduct segments, pipelines, pumping stations, and right-of-way
pipelines located in the center of Mexico. The TPH contaminated sites were, in decreasing order, polyduct km 39 + 150 > polyduct
km 25 + 020 > Zoquital > Tepetitlan > Catalina > Venta Prieta > Ceiba. Most of the sampled points showed the presence of more than one of the 16 PAHs considered by USEPA as priority pollutants.
Except point TEPE 2A, where no PAHs were detected, all the sampled points showed values from low to medium concentrations;
however, values found at the sites did not exceed the limits according to the Mexican or the American legislation. The place
with the largest contaminated area corresponded to the polyduct km 39 + 150, with 130 m2 and 260 m3 to be treated. The least contaminated area was that around the JUAN 4 point at Juandho station, with 20 m2 and 22 m3 of contaminated soil. The total area to be treated is about 230 m2 and 497 m3. 相似文献