Continuous monitoring of distal gas emanations at Vulcano,southern Italy   总被引：1，自引：0，他引：1  

Jean-Paul Toutain  Jean-Claude Baubron  Joseph Le Bronec  Patrick Allard  Pierre Briole  Bernard Marty  Gerarda Miele  Dario Tedesco  Giuseppe Luongo 《Bulletin of Volcanology》1992,54(2):147-155

The increasing activity of Vulcano Island (Italy) since 1985 led to the initiation of continuous geochemical monitoring of the lateral soil gas emissions. On the basis both of their relative geochemical characteristics and of local considerations, three gaseous components were selected for monitoring, namely CO₂, He and ²²²Rn. Monitoring has been performed by means of specific analysers. Gases extracted from a water well located at the foot of the active cone were selected for monitoring, on the basis of their geochemical and isotopic characters that indicate their genetic link with central high temperature fumarolic gases emitted at the crater. Very strong variations of gas composition can be observed within one day (from 1 to about 94% for CO₂). Some variations display a daily character and can be correlated with that of atmospheric pressure. The three monitored gases are highly correlated, suggesting very high kinetics of gas transfer in the system. Because of these considerable variations of chemical composition, bulk concentrations obviously are not suitable for monitoring at Vulcano. However, the evolution with time of ratios such as ²²²Rn/CO₂ and He/CO₂ (the latter being corrected for atmospheric contamination) supplies numerical parameters that the expected to characterize the intensity of the degassing process. A new input of magmatic gases, that would lead to an increase in the ²²²Rn/CO₂ and He/CO₂ ratios, should therefore be detected by such a monitoring station.  相似文献   

Geological study of sedimentary basins using SPOT data     

Nathalie Pisot  Jean-Paul Xavier  Vronique Miegebielle  Dominique Coquelet  Pierre Leymarie 《ISPRS Journal of Photogrammetry and Remote Sensing》1993,48(6)

This paper illustrates the benefits of DTMs created from SPOT images for the exploration of sedimentary basins. We chose an example located in the Ebro sedimentary basin in Spain, characterized by good outcropping conditions and slight deformations. The data used consist of a pair of SPOT panchromatic images and a SPOT XS image. The work consists of making up a 3D database, followed by interpretation of stereo pairs computed from orthoimages and the DTM. This interpretation is made on a stereoscopic desk and results in a digital file containing in the form of vectors all the observed faults and lithology. These vectors are then used to make calculations on the geometry of the objects they represent: we demonstrate that we can accurately measure layer directions and dips, sediment thicknesses and fault throws. Synthesis of perspective views made at the same time provide a good understanding of the structures and help to test their geometric consistency. Thus knowledge about relief given by DTMs helps to interpret remote detection images in 3D space, and particularly to accurately quantify the results of this interpretation.  相似文献   

Impact of oil on the marine environment: Policy of the Paris commission on operational discharges from the offshore industry     

Claire Nihoul  Jean-Paul Ducrotoy   《Marine pollution bulletin》1994,29(6-12):323-329

Environmental impacts occur at all stages of oil and gas production. They are the result of prospecting activities, of the physical impact due to the installation of rigs, of the operational discharges when production starts and of accidental spills. The input of oil to the North Sea due to the offshore industry has been estimated at 29% of the total input of oil. The operational discharges consist of production water and drilling cuttings. An overview of statistics collected over the last 10 years shows that although the amount of oil discharged via production water is increasing as platforms are getting older, cuttings still account for 75% of the oil entering the sea as a result of normal operations. Spills represent a relatively small source of oil. The effects on the marine environment of discharges of production water and of discarded oily cuttings have been extensively studied, by national authorities as well as by the industry. Although it has not always been possible to reach consensus about the significance of the observed effects, a number of ‘agreed facts’ have led to establishment of regulations in the framework of the Paris Commission. The ‘decisions’ and ‘recommendations’ adopted by the Commission are regularly reviewed in the light of new developments.  相似文献   

Spatial–temporal variations of water vapor content over Ethiopia: a study using GPS observations and the ECMWF model     

Abraha  Kibrom Ebuy  Lewi  Elias  Masson  Frédéric  Boy  Jean-Paul  Doubre  Cécile 《GPS Solutions》2017,21(1):89-99

GPS Solutions - We characterize the spatial–temporal variability of integrated water vapor (IWV) in Ethiopia from a network of global positioning system (GPS) stations and the European Center...  相似文献   

Characterization of Mediterranean Magnetotactic Bacteria     

Lefèvre Christopher 《中国海洋大学学报(英文版)》2007,6(4):355-359

Magnetotactic bacteria are a diverse group of motile prokaryotes that are ubiquitous in aquatic habitats and cosmopolitan in distribution. In this study, we collected magnetotactic bacteria from the Mediterranean Sea. A remarkable diversity of morphotypes was observed, including multicellular types that seemed to differ from those previously found in North and South America. Another interesting organism was one with magnetosomes arranged in a six-stranded bundle which occupied one third of the cell width. The magnetosome bundle was evident even under optic microscopy. These cells were connected together and swam as a linear entire unit. Magnetosomes did not always align up to form a straight linear chain. A chain composed of rectangle magnetosomes bent at a posi- tion with an oval crystal. High resolution transmission electron microscopy analysis of the crystal at the pivotal position suggested uncompleted formation of the crystal. This is the first report of Mediterranean magnetotactic bacteria, which should be useful for studies of biogeochemical cycling and geohistory of the Mediterranean Sea.  相似文献   

SCUBA's first-born: SMM J02399-0136     

Rob Ivison  Ian Smail  Andrew Blain  Jean-Paul Kneib  David Frayer 《Astrophysics and Space Science》1999,266(1-2):285-290

We discuss observations of the submm-selected galaxy,SMM J02399-0136, and what has been learnt about it during the yearfollowing its discovery. SMM J02399-0136 was the first distantgalaxy detected in surveys with the Submm Common-User Bolometer Array(SCUBA). Its association with a massive, gas-rich starburst/AGN atz = 2.8 has lead to suggestions that the prevalence of AGN in theearly Universe may be high (Ivison et al. 1998) and that these AGNmay account for a significant fraction of the far-IR background (e.g.Fixsen et al. 1998).  相似文献   

Star Formation in Accretion Disks Around Massive Black Holes and Pregalactic Enrichment     

Suzy Collin  Jean-Paul Zahn 《Astrophysics and Space Science》1999,265(1-4):501-505

Broad Absorption Lines (BALs) prove the existence of a high velocity outflowing gas with metallicities larger than solar in the central few parsecs of high redshift quasars. At the same distance from the black hole, accretion disks in quasars and Active Galactic Nuclei (AGN) are locally gravitationally unstable, and clumps must form with a size of the order of the scale height of the disk. This is hardly a coincidence, and we have tried to link these two facts. We have assumed that the unstable clumps give rise to protostars, which become massive stars after a rapid stage of accretion, and explode as supernovae, producing strong outflows perpendicular to the disk and inducing outward transfer of angular momentum in the plane of the disk. As a consequence a self-regulated disk made of gas and stars where supernovae sustain the inflow mass rate required by the AGN is a viable solution in this region of the disk. This model could explain the BALs, and could also account for a pregalactic enrichment of the intergalactic medium and of the Galaxy, if massive black holes formed early in the Universe. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Seasonal variations in dissolved organic carbon concentrations and characteristics in a shallow coastal bay   总被引：8，自引：0，他引：8  

Elizabeth C. Minor  Jean-Paul Simjouw  Margaret R. Mulholland 《Marine Chemistry》2006,101(3-4):166-179

Dissolved organic matter (DOM) composition and dynamics in temperate shallow coastal bays are not well described although these bays may be important as local sources of organic carbon to ocean waters and are often sites of economically-important fisheries and aquaculture. In this study surface water samples were collected on a monthly to bi-monthly basis over two years from a mid-Atlantic coastal bay (Chincoteague Bay, Virginia and Maryland, USA). Dissolved organic carbon (DOC) concentrations and light absorbance characteristics were measured on sterile-filtered water, and high-molecular weight (> 1 kDa) dissolved OM (DOM) was isolated to determine stable isotope composition and molecular-level characteristics. Our time series encompassed both a drought year (2002) and a year of above-average rainfall (2003). During the dry year, one of our sites developed a very intense bloom of the brown tide organism Aureococcus anophagefferens while during the wet year there were brown tide bloom events at both of our sampling sites. During early spring of the wet year, there were higher concentrations of > 1 kDa DOC; this fraction represented a larger proportion of overall DOC and appeared considerably more allochthonous. Based upon colored dissolved organic matter (CDOM) and high-molecular weight DOM analyses, the development of extensive phytoplankton blooms during our sampling period significantly altered the quality of the DOM. Throughout both years Chincoteague Bay had high DOC concentrations relative to values reported for the coastal ocean. This observation, in conjunction with the observed effects of phytoplankton blooms on DOM composition, indicates that Chincoteague Bay may be a significant local source of “recently-fixed” organic carbon to shelf waters. Estimating inputs of DOC from Chincoteague Bay to the Mid-Atlantic Bight suggests that shallow productive bays should be considered in studies of organic carbon on continental shelves.  相似文献   

La lune mange-t-elle les couleurs?     

Jean-Paul Parisot 《Earth, Moon, and Planets》1986,34(3):273-279

The hydrogen radicals play an important role in the photochemistry of the troposphere of the Earth. The chemistry of OH, HO₂ and H₂O₂ is linked directly to the photodissociation of O₃ through the production of O(¹D). Gaseous H₂O₂ (hydrogen peroxide may be removed by heterogeneous reactions involving aerosols and liquid water. During the day and the night the solubility of ambient H₂O₂ in water is estimated and the oxidant capacity of H₂O₂ may explain the bleaching properties of the dew used in the past. This phenomenon may also explain some old maxims concerning the properties of the Moon's light to corrupt colors.  相似文献   

Temperature effect on the photodissociation rates in the atmospheres of Mars and Venus     

Jean-Paul Parisot  Jean-Marc Zucconi 《Icarus》1984,60(2):327-331

The available solar flux at a given altitude in the atmospheres of Mars and Venus is attenuated mainly by CO₂ (molecular absorption and Rayleigh scattering) with an extra contribution due to SO₂ on Venus. The dissociation cross section of CO₂ depends on temperature. At temperatures appropriate for these atmospheres (～250°K), the cross sections are about 15% lower than those at room conditions (Y.L. Yung and W.B. De More, 1982, Icarus, 51, 199). It is shown that this temperature effect cannot be neglected in the evaluation of photolysis rates. Calculations of the photodissociation coefficients of CO₂, SO₂, HCl, and H₂O are presented. For example, at the surface of Mars, the coefficient of H₂O is nearly multiplied by a factor of 10!  相似文献