Downstream composition changes of acidic volcanic waters discharged into the Banyupahit stream, Ijen caldera, Indonesia     

P. Delmelle  A. Bernard 《Journal of Volcanology and Geothermal Research》2000,97(1-4)

The crater lake of Kawah Ijen volcano contains extremely low pH (<0.4) waters with high SO₄ (70000 mg/kg), Cl (21000 mg/kg), F (1500 mg/kg), Al (5000 mg/kg), Fe (2000 mg/kg) and trace metal (Cu 0.5, Zn 4, Pb 3 mg/kg) contents. These brines seep outward through the western crater rim and reappear on the other side as streamlets, which form the headwaters of the Banyupahit stream. The Banyupahit first mixes with fresh rivers and thermal springs in the Ijen caldera and then irrigates a coastal agricultural plain which is 30 km from the summit crater.We discuss the downstream composition changes affecting the Banyupahit waters by using stable isotope, chemical and mineralogical data collected from sites along the stream length. The saturation of the stream waters with respect to minerals was evaluated with SOLVEQ and WATEQ4F and compared with the geochemical observations. An aluminous mineralogy (alunogen, pickeringite, tamarugite and kalinite) develops in the upper part of the Banyupahit due to concentration of the headwaters by evaporation. Downstream attenuation of dissolved element concentrations results principally from dilution and from mineral precipitation. The stream pH changes from 0 at the source to >4 close to the mouth. The δD and δ¹⁸O values and the relative SO₄–Cl–F contents of the Banyupahit waters indicate that the tributaries are mostly meteoric. Dissolved SO₄ in the acidic stream come only from the crater lake seepages and are not involved later in microbially mediated reactions, as shown by their δ³⁴S and δ¹⁸O values. Re-equilibration of the stream SO₄ oxygen-isotope composition with H₂O from tributaries does not occur.Calcium, SiO₂, Al, Fe, K and SO₄ behave non-conservatively in the stream waters. Gypsum, silica (amorphous or poorly ordered), a basic aluminum hydroxysulfate (basaluminite?), K-jarosite and amorphous ferric hydroxide may exert a solubility control on these elements along the entire stream length, or in certain stream sections, consistent with the thermochemical model results. Downstream concentration trends and mineral saturation levels suggest that precipitation of Sr-, Pb-rich barite and celestite consume Ba, Sr and Pb, whereas dissolved Cu, Pb and Zn may adsorb onto solid particles, especially after the junctions of the acidic stream with non-acidic rivers. We calculated that significant fluxes of SO₄, F, Cl, Al, SiO₂, Ti, Mn and Cu may reach the irrigation system, possibly causing serious environmental impacts such as soil acidification and induration.  相似文献   

Electrical conductivity and crustal structure beneath the central Hellenides around the Gulf of Corinth (Greece) and their relationship with the seismotectonics   总被引：4，自引：0，他引：4  

V. N. Pham  P. Bernard  D. Boyer  G. Chouliaras  J. L. Le Mouël  G. N. Stavrakakis 《Geophysical Journal International》2000,142(3):948-969

A deep magnetotelluric sounding (MTS) investigation in the western part of the Gulf of Corinth has revealed a complex electrical image of the crustal structure. The geotectonic structure of the Parnassos unit and the Transition zone in the central Hellenides, overthrusting the Pindos zone both towards the west and towards the south, has been clearly identified by its higher resistivity and its intrinsic anisotropy related to the N–S strike of the Hellenides range. Subsequent N–S extension of the Gulf introduced another heterogeneous anisotropy characteristic that corresponds to E–W-trending normal faults on both sides of the Gulf. The 2-D modelling of the MTS results reveals the existence of a relatively conductive layer about 4 km thick at a depth greater than 10 km in the middle crust. It corresponds to a ductile detachment zone suggested by microseismic and seismic studies ( King et al . 1985 ; Rigo et al . 1996 ; Bernard et al . 1997a ). It may be attributed to the phyllite series lying between the allochthonous Hellenic nappes and the autochthonous Plattenkalk basement. Towards the east, under the Pangalos peninsula, approaching the internal Hellenides, the detachment zone could root deeply into the lower crust.
Some strong local electrical anomalies are observed, reaching the conductive layer in the middle crust, such as that under the Mamousia fault and under the front of the overthrust of the Transition zone on the Pindos zone. Other anomalies affect only the shallower zones such as that beneath the Helike fault and in the Psaromita peninsula. These shallower anomalies provide complementary information to the study of spatial and temporal variations of the seismic anisotropy in relation to the short- and long-term tectonic activity of the Gulf ( Bouin et al . 1996 ; Gamar et al . 1999 ).  相似文献   

Potentially modified hydropower production under climate change in the Italian Alps     

Giovanni Martino Bombelli  Andrea Soncini  Alberto Bianchi  Daniele Bocchiola 《水文研究》2019,33(17):2355-2372

We present an assessment of the potential impacts of climate change on hydropower production within a paradigmatic, very highly exploited cryospheric area of upper Valtellina valley in the Italian Alps. Based on dependable and unique hydrological measures from our high‐altitude hydrometric network Idrostelvio during 2006–2015, we set up the Poly‐Hydro model to mimic the cryospheric processes driving hydrological flow formation in this high‐altitude area. We then set up an optimization tool, which we call Poly‐Power, to maximize the revenue of the plant manager under given hydrological regimes, namely, by proper operation of the hydroelectric production scheme (reservoirs, pipelines, and power plants) of the area. We then pursue hydrological projections until 2100, feeding Poly‐Hydro with the downscaled outputs of three general circulation models from the Intergovernmental Panel on Climate Change Fifth Assessment Report, under the scenarios Representative Concentration Pathway (RCP) 2.6, RCP 4.5, and RCP 8.5. We assess hydrological flows in two reference decades, that is, at half century (2040–2049), and end of century (2090–2099). We then feed the so obtained hydrological scenarios as inputs to Poly‐Power, and we project future production of hydroelectric power, with and without reoperation of the system. The average annual stream flows for hydropower production decreases along the century under our scenarios (?21 to +7%, on average ? 5% at half century; ?17 to ?2%, average ? 8%, end of century), with ice cover melting unable to offset such decrease. Reduction in snowfall and increase in liquid rainfall are the main factors affecting the modified hydrological regime. Energy production (and revenues) at half century may increase under our scenarios (?9 to +15%, +3% on average). At the end of century in spite of a projected increase on average (?7 to +6%, +1% on average), under the warmest scenario RCP 8.5 decrease of energy production is consistently projected (?4% on average). Our results provide an array of potential scenarios of modified hydropower production under future climate change and may be used for brain storming of adaptation strategies.  相似文献   

Petrology of pumices of April 1993 eruption of Lascar (Atacama, Chile)     

Bernard Déruelle  Oscar Figueroa A.  Eduardo Medina T.  Jose Viramonte G.  Mario Maragaño C. 《地学学报》1996,8(2):191-199

Lascar Volcano (Atacama, Chile) erupted on 18–20 April 1993. Several sub-Plinian explosions occurred, and some were mushroom-shaped. The highest column rose up to 23 km. Ash clouds crossed South America eastwards. Dacite pumice falls made of blocks and ashes were deposited on the flanks of the volcano as a result of collapsed columns. The pumice contains phenocrysts of plagioclase, enstatite, augite, biotite, magnetite and ilmenite and small crystals of apatite. The 1992 previous andesite dome inside the crater was destroyed. Banded blocks resulting from mingling of the dacitic pumice and andesite from the dome are found in the pumice flow. Both the lava dome and the pumice are representative of the Lascar high-K magma unit. Dacitic pumice is a product of crystal fractionation of the andesitic magma.  相似文献   

Gaseous drag and planetary formation by accretion     

Dominique Spaute  Bernard Lago  Anny Cazenave 《Icarus》1985,64(1):139-152

We have made numerical experiments of the collisional and gravitational interaction of a planetesimal swarm in the early Solar System. In particular we study the dynamical evolution of an initial population of kilometer-size planetesimals subject to collisions (accretion, rebound, cratering, and catastrophic fragmentation). This study is based on a Monte-Carlo statistical method and provides the mass and velocity distributions of the planetesimal swarm as a function of time as well as their distribution in heliocentric distance. Several experiments have been performed and three of them are presented here. They simulate the accretional growth of numerous planetesimals in the absence (or presence) of gaseous drag, with (or without) one larger embryo among them, and with (or without) a size gradient. The results show that (i) for a population of planetesimals submitted to a negative gradient in size as the heliocentric distance increases, the outer planetesimals spiral toward the Sun faster than inner ones, leading after some time to an accumulation of bodies inside the cloud which allows the formation of an embryo; (ii) the growth of one embryo among a population of planetesimals is accelerated by the presence of gas and is warranted as long as its feeding zone is fed by the inward flow of planetesimals due to gas drag. These results offer some complementary new insights in the understanding of the accretional formation of 4–5 terrestrial planets instead of the numerous Moon-size planets generally found in numerical experiments.  相似文献   

Physical study of asteroids: Ligthcurves and rotational periods of six asteroids     

M. Di Martino 《Icarus》1984,60(3):541-546

V band photoelectric lightcurves and rotational periods are presented for six asteroids: 150 Nuwa, 203 Pompeja, 336 Lacaderia, 545 Messalina, 984 Gretia, and 1240 Fantasia. Except for 984 Gretia, none of these asteroids has been previously observed. The observations were obtained during September 1983 at the Astrophysical Observatory of Catania and are part of a program devoted to increase the present data set of asteroids' rotational properties. For 336 Lacaderia and 984 Gretia the magnitude-phase relations, in terms ofQ_v and β_v, were also obtained.  相似文献   

Ferric iron in mantle-derived garnets   总被引：4，自引：0，他引：4  

Robert W. Luth  David Virgo  Francis R. Boyd  Bernard J. Wood 《Contributions to Mineralogy and Petrology》1990,104(1):56-72

The oxidation state of a mantle assemblage may be defined by heterogeneous reactions between oxygen and iron-bearing minerals. In spinel lherzolites, the presence of Fe³⁺ in spinel allows use of the assemblage olivine-orthopyroxene-spinel to define f _{O 2} at fixed T and P. As a first step towards establishing an analogous reaction for garnet lherzolites, garnets from mantle-derived xenoliths from South Africa and the USSR have been analyzed with ⁵⁷Fe Mössbauer spectroscopy at 298 and 77K to determine Fe³⁺/Fe²⁺ and the coordination state of iron. Garnets from South African alkremites (pyrope+Mg-spinel) and eclogites, as well as garnet-spinel and low-temperature garnet lherzolites from both South Afica and the USSR, have Fe³⁺/Fe<0.07. In contrast, garnets from high-temperature garnet lherzolites from within the Kaapvaal craton of South Africa have Fe³⁺/Fe>0.10. Ferric iron is octahedrally coordinated, and ferrous iron is present in the dodecahedral site in all samples. The occurrence of significant Fe³⁺ in these garnets necessitates caution in the use of geothermometers and geobarometers that are applied to mantle samples. For example, the presence of 12% of the Fe as Fe³⁺ in garnets can increase temperatures calculated from existing Fe/Mg geothermometers by>200°C. The concomitant increase in pressures calculated from geobarometers that use the Al content in orthopyroxene coexisting with garnet are 10–15 kbar. Results of calculations based on heterogeneous equilibria between garnet, olivine, and pyroxene are consistent with the derivation of the peridotite samples from source regions that are relatively oxidized, between the f _{O 2} of the FMQ (quartz-fayalite-magnetite) buffer and that of the WM buffer. No samples yield values of f _{O 2} as reduced as IW (iron-wüstite buffer).  相似文献   

Solar and interplanetary observations of the mass ejection on 7 May, 1979     

Bernard V. Jackson  Bogdan Rompolt  Zdeněk Švestka 《Solar physics》1988,115(2):327-343

We present observations of a mass ejection that was observed by five different instruments along its way from the solar surface to more than 100 solar radii. The instruments involved are the ground-based H coronagraph at Wrocaw, the white-light SOLWIND coronagraph on board the P78-1 satellite, zodiacal light photometers of the HELIOS B spacecraft, in situ plasma detectors and magnetometers on board the HELIOS B spacecraft, and interplanetary scintillation measurements on the ground. By using a CAT-scan analysis of the images obtained by the SOLWIND coronagraph near the Earth and HELIOS B photometers placed at 0.3 AU perpendicular to the Earth-Sun line, we have been able to get a three-dimensional density reconstruction of the mass ejection and fit the best velocity curve for its propagation. Although problems exist in smoothly joining the height-time curves (for instance, we had to reduce the brightness of the SOLWIND data by more than a factor of two to make the data sets agree photometrically), both this analysis and direct measurements by the other experiments clearly indicate higher speeds at greater distances from the Sun. The plasma acceleration in this case was obviously not limited only to distances within 3 R ₀ , as is usually the case, but continued beyond the outer limit of the coronagraph view at 8 R ₀ .The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

    

Cristian Dascalu  Bernard Cambou 《Acta Geotechnica》2008,3(1):1

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Influence of surface heterogeneities of building granite on its thermal response and its potential for the generation of thermoclasty     

Miguel Gómez-Heras  Bernard J. Smith  Rafael Fort 《Environmental Geology》2008,56(3-4):547-560

Surface properties, especially albedo, and aspect are widely accepted as strong influences on the surface thermal response of building stone to insolation. However, the influence that adjacent areas of stone with very different surface properties may have on the thermal response of a patch of stonework, and the ways in which spatial variation in thermal characteristics might enhance stone decay has received relatively little attention. This paper examines the differential thermal response of granite used in construction that results from the presence of dark coloured micro-granular enclaves within a leucocratic host. Surface temperatures and temperature differences between enclaves exhibiting mico-spalling, enclaves with no spalling and the surrounding stone were measured for different aspects and seasons on a 20th century building in Madrid. These data were used to calculate a number of “indices” related to short-term temperature cycling and temperature gradients that have the theoretical capability of generating irreversible deformation of the stone. These indices suggest that micro-spalling of enclaves, compared to a lack of similar decay on the host-rock, is related to their differential thermal response to insolation, most importantly the lower albedo and thermal conductivity values of the enclaves. However, these factors are not sufficient on their own to trigger spalling, and breakdown was only observed where enclaves also experienced repeated, short-term surface temperature cycling caused by, for example, temporary shading by adjacent vegetation. These rapid temperature reversals are identified as a key contributory factor to the thermally driven decay observed on some of the enclaves.  相似文献