Orographic shaping of US West Coast wind profiles during the upwelling season     

Lionel Renault  Alex Hall  James C. McWilliams 《Climate Dynamics》2016,46(1-2):273-289

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Effects of industrial outfalls on tropical macrobenthic sediment communities in Reunion Island (Southwest Indian Ocean)     

Bigot L  Conand C  Amouroux JM  Frouin P  Bruggemann H  Grémare A 《Marine pollution bulletin》2006,52(8):865-880

Temporal changes in the composition of soft bottom macrobenthic assemblages at Reunion Island (Southwest Indian Ocean) were studied in the context of a long-term environmental monitoring programme studying the impacts of effluents of industrial sugar cane refineries that are transferred to shallow and deep coastal environments by different pathways: surface discharge and deep underground injection. Seven stations (between 20 and 160 m depth) were surveyed between 1994 and 2003 on the industrial zone. One additional station was surveyed on a reference site. Spatio-temporal changes in the composition of macrobenthic communities were assessed using several diversity indices, ABC curves, MDS and associated ANOSIM tests and biotic indices. Among the 171 taxa recorded, polychaetes were dominant (89 species), followed by crustaceans and molluscs. The analysis of spatial changes in the composition of macrobenthos showed the existence of distinct benthic communities along the depth gradient. Temporal changes in macrobenthos composition were most prominent at the shallowest station. They mainly corresponded to the decline of several initially dominant taxa and the increase of the Eunicid polychaete Diopatra cuprea. This station further showed increasing macrofaunal abundance, biomass and sediment organic content over time, concomitant with decreasing sediment grain sizes. In deeper environments, temporal changes were much smaller. Macrofaunal abundance and species richness increased progressively, suggesting a moderate impact on benthic ecosystems resulting from slight enrichments due to effluents rich in organic matter. Our results highlight an original response to disturbance pattern involving opportunistic Eunicidae species (D. cuprea) not previously described. Moreover, they allow for the comparison of the impact on macrofauna caused by industrial effluents exported by two distinct and different pathways in a tropical coastal high-energy marine environment.  相似文献   

Pyroclast loss or retention during explosive volcanism on asteroids: Influence of asteroid size and gas content of melt     

Lionel WILSON  Klaus KEIL  Timothy J. McCOY 《Meteoritics & planetary science》2010,45(8):1284-1301

Abstract– We review the conditions under which explosive volcanism took place on early‐forming differentiated asteroids. The pressure‐dependent solubility of typical asteroid volatiles in melts implies that the gas driving explosive volcanism on asteroids less than approximately 100 km in diameter was probably present mainly as a free phase capable of accumulating into large gas bodies and, thus, causing slug flow in melts approaching the surface. In contrast, in asteroids larger than approximately 100 km the gas was probably present largely as a dispersion of small bubbles. We show that these gas distributions have implications for the size distribution of the pyroclastic droplets produced in explosive eruptions at the surface. All pyroclastic melt droplets are accelerated by the expanding gases, but their speeds lag the gas speed by a finite amount that is a function of the droplet size and density and the asteroid size and, hence, acceleration due to gravity. We compute pyroclast speeds and, by comparing them with escape velocities, we identify the critical pyroclast diameter on a given‐size asteroid that distinguishes droplets lost to space from droplets that return to the surface. Identification of asteroidal pyroclasts and measurements of their sizes could throw light on the amounts of gas driving eruptions.  相似文献   

Which variables are essential for renewable energies?     

Thierry Ranchin  Mélodie Trolliet  Lionel Ménard  Lucien Wald 《International Journal of Digital Earth》2020,13(2):253-261

ABSTRACT

Essential Variables are defined as a minimal set of variables that explain the state of the system. They are crucial for predicting its developments, and support metrics that measure its evolution. The variables should be relevant to meet requirements of stakeholders and be technically and economically feasible for systematic observation. A definition of Essential Renewable Energies Variables is proposed linked with their identification in several domains in renewable energy using a bottom-up and user-driven approach, and spanning over several years of documented interaction with stakeholders. Lists of variables are proposed in hydropower, solar, wind, and marine energies. It does not comprise the variables relating to social and economic aspects supporting decision making in investment nor those relating to civil engineering that are needed to erect a plant or farm.  相似文献   

Igneous scapolite-bearing associations in the Chaîne des Puys,Massif Central (France) and Atakor (Hoggar,Algeria)     

P. Boivin  G. Camus 《Contributions to Mineralogy and Petrology》1981,77(4):365-375

A scapolite+amphibole+clinopyroxene+Fe-Ti oxide+apatite association has been found as megacrysts in tephra from the Enval-Volvic volcanic line, east of the Chaîne des Puys (Massif Central, France) and in the cinder cone of the Segueïka volcano (Atakor, Algeria). In both kinds, lavahosts are basanites. Although never seen together in a single xenolith, a study of their inclusions indicates close genetic relationship between all 5 phases. This association must be considered as a paragenesis that crystallized within a narrow PT range. Volcanological, petrological and geochemical data suggest that these megacrysts are high-pressure phenocrysts rather than mechanically desintegrated fragments derived from coarse rocks. The composition of the amphibole suggests a pressure between 5 and 15 kb; Fe-Ti oxides imply a temperature close to 1,100° C.Crystallization of sulfur-rich scapolite involves a high fSO₃, and therefore a high fO₂, remarkable for such relatively undifferenciated alkalic magmas. Coexisting Fe-Ti oxides indicate a fO₂ close to 10^–6 bar. Such conditions imply that H₂O was a major component of the gaseous phase. This high water content can be explained in terms of derivation from an hydrated upper mantle source. This is in agreement with other petrological evidences indicating that the basic magmas of the Massif Central crystallized under high fSO₃ conditions.  相似文献   

Relationships between pressure, volatile content and ejecta velocity in three types of volcanic explosion   总被引：1，自引：0，他引：1  

Lionel Wilson 《Journal of Volcanology and Geothermal Research》1980,8(2-4)

Consideration of the energy equation for a flowing compressible fluid shows that the so-called modified Bernoulli equation, commonly used to relate ejects velocity to pre-explosion pressure in vulcanian-style volcanic explosions, is inadequate in almost all circumstances because of its neglect of the detailed role of volatiles in explosive eruptions.The physical differences between three common types of explosive volcanic activity, typified by plinian, strombolian and vulcanian events, are reviewed and simple mathematical models are proposed for them. The models relate velocities of ejects to initial pressures at the start of an explosive phase and to mass fractions of volatiles (generally taken to be water) in the explosion products. When fitted to observed ejects velocities (or velocities deduced from the dispersal of debris) up to 500 m/s the models predict pressures up to 300 bars — almost always much lower than those deduced in earlier treatments.  相似文献   

Chronological and geochemical study of lavas from the Chaîne des Puys,Massif Central,France: Evidence for crustal contamination     

M. Condomines  P. Morand  G. Camus  L. Duthou 《Contributions to Mineralogy and Petrology》1982,81(4):296-303

Datations of ancient lavas from the Chaîne des Puys through the ²³⁰Th-²³⁸U radioactive disequilibrium method confirm the eruption of several basaltic or slightly differentiated lavas around 40,000 years ago. The study of (²³⁰Th/²³²Th)₀ initial ratios of these lava flows clearly demonstrates the influence of a crustal contamination of magmas superimposed to crystal fractionation. This contamination probably affects many trace elements, in particular, U, Th and Sr. A model based on the (²³⁰Th/²³²Th)₀ initial ratio variations of non-contaminated lavas permits to consider that the first eruptions in the Chaîne des Puys could have occurred about 100,000 years ago.  相似文献   

Total oxyradical scavenging capacity responses in Mytilus galloprovincialis transplanted into the Venice lagoon (Italy) to measure the biological impact of anthropogenic activities     

Camus L  Pampanin DM  Volpato E  Delaney E  Sanni S  Nasci C 《Marine pollution bulletin》2004,49(9-10):801-808

Oxidative stress related investigations to monitor the impact of the pollutant discharges into the Venice lagoon (Italy) originating from anthropogenic activities (raw sewage water, agricultural and industrial effluents, oil tanker traffic), on marine organisms have classically been carried out by analyzing specific, single antioxidants (i.e. catalase, superoxide dismutase). In this paper, two studies are reported where the total oxyradical scavenging capacity assay (TOSC) was selected and measured toward peroxyl, and hydroxyl free radicals, and peroxynitrite in mussels (Mytilus galloprovincialis) transplanted into the Venice city and throughout the lagoon to measure the biological effects of anthropogenic activities. In the first experiment, mussels from a clean site (farm) were transplanted to the urban area of Venice for 0, 1, 2 and 4 weeks; cytosolic TOSC toward peroxyl and hydroxyl free radicals, and peroxynitrite revealed that the transplantation process caused a stress (handling stress, anoxia, oxidative burst) resulting in a reduction of TOSC in both control and urban sites, therefore, preventing clear interpretation of the data after one week. At week 2, a significant TOSC reduction (P < 0.05) toward peroxyl and hydroxyl radicals in the urban site revealed that mussels experienced oxidative pressure exerted by pollutants. Most TOSC values returned to initial levels at week 4; however, TOSC induction was noticed in the control group toward peroxyl and hydroxyl radicals while in the exposed group it was not indicating an inhibition of the oxidative metabolism. In the second experiment, mussels were deployed at seven different sites throughout the lagoon. After five weeks of exposure, significant TOSC reduction was measured (P < 0.05) toward peroxyl for Palude della Rosa, Chioggia and Valle Millecampi, toward hydroxyl radicals for Valle Millecampi and Campalto and toward peroxynitrite for Valle Millecampi. Although these data indicate a depletion of the low molecular weight scavengers, additional biomarkers are needed to draw a conclusion on the health of the mussels. TOSC was proved to be an interesting health index parameter to measure pollution impact in a transplantation study provided that the mussels are exposed for two weeks and a control is run in parallel.  相似文献   

Temperature-dependent physiological response of Carcinus maenas exposed to copper   总被引：1，自引：0，他引：1  

Camus L  Davies PE  Spicer JI  Jones MB 《Marine environmental research》2004,58(2-5):781-785

The effect of temperature on the heart rate (fH) of Carcinus maenas exposed to a sublethal nominal concentration (0.5 mg l(-1)) of copper is reported. Adult, intermoult males (4 cm carapace width) were collected from Stavanger Fjord (Norway) in August (seawater TEMPERATURE=17 degrees C) and maintained in the laboratory (fed ad libitum) at 5, 15 and 25 degrees C for 7 days. Following this holding period, crabs were exposed to waterborne copper at the same temperature. After 3 days of exposure, individual fH was measured using the non-invasive Computer Aided Physiological MONitoring system (CAPMON) method. Copper-exposed individuals demonstrated significantly increased fH compared with controls at 5 and 25 degrees C (P<0.01). It is inferred that physiological function in C. maenas may be more vulnerable to copper contamination at seasonal temperature extremes (5 and 25 degrees C) than at the 'standard' test temperature (15 degrees C). Additionally, cardiac arrest observed at 5 degrees C is interpreted as a physiological response to limit copper uptake while the erratic fH in the 25 degrees C group reflected enhanced copper toxicity.  相似文献   

Clast sizes of ejecta from explosive eruptions on asteroids: implications for the fate of the basaltic products of differentiation     

Lionel Wilson  Klaus Keil   《Earth and Planetary Science Letters》1996,140(1-4):191-200

We use a simple model of the formation, growth, coalescence and migration of veins of basaltic melt generated by partial melting in chondritic asteroids to deduce the sizes of, and pressures within, the fluid-filled dikes reaching the surfaces of such bodies. The gas contents ( 1000 ppm of mainly CO and N₂) of the asteroids were high enough that bubbles of free gas trapped in the melt veins gave the basaltic melts significant buoyancy; expansion of these gases as a dike opened to the vacuum at the surface led to fragmentation of the melts into liquid droplets which were transported upwards by the accelerating gases to the surface. The sizes of these droplets and, hence, of the pyroclastic glass beads into which they cooled, are calculated to lie in the range 30 μm to 4 mm; this range is essentially independent of the size or gas content of the asteroid parent and only weakly dependent on the internal pressure of the erupting fluid. The fate of the pyroclasts, however, does depend on all of these factors. At very low internal pressures, significant separation of the gas and liquid in a rising dike may take place and not all of the liquid will be expelled from the dike when it opens to the surface. For relatively large ( 100 km radius) asteroids with relatively low ( 300 ppm) gas contents, the larger clasts are too heavy to be lifted from the level at which magma fragmentation takes place by the gas flow and so would also remain behind to form basaltic veins. The apparent absence of basaltic veins in meteorites then implies both that internal pressures in near-surface dikes were generally greater than 0.3 MPa and that low gas contents were not common. Finally, as long as pyroclasts are lofted from the magma fragmentation level, they will be accelerated to at least 90% of the final gas speed. If this speed exceeds the escape speed from the asteroid (as happens readily for high gas contents and small asteroids), the pyroclasts will be expelled into space and lost from the meteorite record. Otherwise (low gas contents or large asteroids), they will eventually fall back to be incorporated into the surface regolith, modifying the chemical and physical properties of meteorites subsequently derived from it.  相似文献