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51.
Kazue TAZAKI Hiroaki WATANABE Siti Khodijah CHAERUN Koichi SHIRAKI Ryuji ASADA 《《地质学报》英文版》2006,80(3):432-440
Pollution of petroleum hydrocarbons, in particular oil spills, has attracted much attention in the past and recent decades. Oil spills influence natural microbial community, and physical and chemical properties of the affected sites. The biodegradation of hydrocarbons by microorganisms is one of the primary ways by which oil spill is eliminated from contaminated sites. One such spill was that of the Russian tanker the Nakhodka that spilled heavy oil into the Sea of Japan on January 2, 1997. The impact of the Nakhodka oil spill resulted in a viscous sticky fluid fouling the shores and affected natural ecosystems. This paper describes the weathering of hydrocarbon-degrading bacteria （genus Pseudomonas） and crystallized organic compounds from the Nakhodka oil spill-polluted seashores after nine years. The Nakhodka oil has hardened and formed crust of crystalline paraffin wax as shown by XRD analysis （0.422, 0.377, and 0.250 nm d-spacing） in association with graphite and calcite after 9 years of bioremediation. Anaerobic reverse side of the oil crust contained numerous coccus typed bacteria associated with halite. The finding of hydrocarbon-degrading bacteria and paraffin wax in the oil crust may have a significant effect on the weathering processes of the Nakhodka oil spill during the 9- year bioremediation. 相似文献
52.
We present our new model for the thermal infrared emission of Saturn's rings based on a multilayer approximation. In our model, (1) the equation of classical radiative transfer is solved directly for both visible and infrared light, (2) the vertical heterogeneity of spin frequencies of ring particles is taken into account, and (3) the heat transport due to particles motion in the vertical and azimuthal directions is taken into account. We adopt a bimodal size distribution, in which rapidly spinning small particles (whose spin periods are shorter than the thermal relaxation time) with large orbital inclinations have spherically symmetric temperatures, whereas non-spinning large particles (conventionally called slow rotators) with small orbital inclinations are heated up only on their illuminated sides. The most important physical parameters, which control ring temperatures, are the albedo in visible light, the fraction of fast rotators (ffast) in the optical depth, and the thermal inertia. In the present paper, we apply the model to Earth-based observations. Our model can well reproduce the observed temperature for all the main rings (A, B, and C rings), although we cannot determine exact values of the physical parameters due to degeneracy among them. Nevertheless, the range of the estimated albedo is limited to 0-0.52±0.05, 0.55±0.07-0.74±0.03, and 0.51±0.07-0.74±0.06 for the C, B, and A rings, respectively. These lower and upper limits are obtained assuming all ring particles to be either fast and slow rotators, respectively. For the C ring, at least some fraction of slow rotators is necessary (ffast?0.9) in order for the fitted albedo to be positive. For the A and B rings, non-zero fraction of fast rotators (ffast?0.1-0.2) is favorable, since the increase of the brightness temperature with increasing solar elevation angle is enhanced with some fraction of fast rotators. 相似文献
53.
Though the Moon is considered to have been formed by the so-called giant impact, the mass of the Earth immediately after the impact is still controversial. If the Moon was formed during the Earth's accretion, a subsequent accretion of residual heliocentric planetesimals onto the protoearth and the protomoon must have occurred. In this co-accretion stage, a significant amount of lunar-impact-ejecta would be ejected to circumterrestrial orbits, since the mean impact velocity of the planetesimals with the protomoon is much larger than the escape velocity of the protomoon. Orbital calculations of test particles ejected from the protomoon, whose semimajor axis is smaller than that of the present Moon, reveal that most of the particles escaping from the protomoon also escape from the Hill sphere of the protoearth and reduce the planetocentric angular momentum of the primordial Earth-Moon system. Using the results of the ejecta simulations, we investigate the evolution of the mass ratio and the total angular momentum (Earth's spin angular momentum + Moon's orbital angular momentum) of the Earth-Moon system during the co-accretion. We find that the mass of the protomoon is almost constant or rather decreases and the total angular momentum decreases significantly, if the random velocity of planetesimals is as large as the escape velocity of the protoearth. On the other hand, if the random velocity is the half of the escape velocity of the protoearth, the mass ratio is kept to be almost as large as the present value and the decrease of the total angular momentum is not so significant. Comparing with the results of giant impact simulations, we find that the mass of the protoearth immediately after the Moon-forming impact was 0.7-0.8 times the present value if the impactor-to-target mass ratio was 3:7, whereas the giant impact occurred almost in the end of the Earth's accretion if the impactor-to-target mass ratio was 1:9. 相似文献
54.
Fission-track (FT) analysis using apatite and zircon was performed on samples from two fracture zones (FZ) at the depths of 1140 and 1310 m within the 1838 m borehole core penetrating the Ryoke Granitic Rocks in the Nojima Fault at Nojima-Hirabayashi, Awaji Island, Japan, drilled just after the 1995 Hyogo-ken Nanbu earthquake. Clear discordance in apatite and zircon FT age was found for two samples located at 2 m below the central part of each FZs where the presence of pseudotachylyte and/or fault gouge would predict the largest amount of slip. Asymmetric distribution was identified by discordant ages with respect to the central part of FZs. These very local discordant ages in the fault reflect thermal anomalies caused by secondary heating with an inferred maximum temperature in the region between apatite and zircon closure temperatures at a time post-48 Ma. As a source of the secondary heating, heat transfer or dispersion via geothermal fluids caused presumably the observed similarity in asymmetric distribution of discordant FT ages at two different FZs. Other samples yield concordant FT zircon and apatite ages and these indicate rapid cooling within the bounds of two closure temperatures of these minerals at 60 Ma of the Ryoke Granitic Rocks. 相似文献
55.
Tomoki Nakamura Aiko Nakato Hatsumi Ishida Shigeru Wakita Takaaki Noguchi Michael E. Zolensky Masahiko Tanaka Makoto Kimura Akira Tshuchiyama Toshihiro Ogami Takahito Hashimoto Mitsuru Konno Masayuki Uesugi Toru Yada Kei Shirai Akio Fujimura Ryuji Okazaki Scott. A. Sandford Yukihiro Ishibashi Masanao Abe Tatsuaki Okada Munetaka Ueno Junichiro Kawaguchi 《Meteoritics & planetary science》2014,49(2):215-227
The mineralogy and mineral chemistry of Itokawa dust particles captured during the first and second touchdowns on the MUSES‐C Regio were characterized by synchrotron‐radiation X‐ray diffraction and field‐emission electron microprobe analysis. Olivine and low‐ and high‐Ca pyroxene, plagioclase, and merrillite compositions of the first‐touchdown particles are similar to those of the second‐touchdown particles. The two touchdown sites are separated by approximately 100 meters and therefore the similarity suggests that MUSES‐C Regio is covered with dust particles of uniform mineral chemistry of LL chondrites. Quantitative compositional properties of 48 dust particles, including both first‐ and second‐touchdown samples, indicate that dust particles of MUSES‐C Regio have experienced prolonged thermal metamorphism, but they are not fully equilibrated in terms of chemical composition. This suggests that MUSES‐C particles were heated in a single asteroid at different temperatures. During slow cooling from a peak temperature of approximately 800 °C, chemical compositions of plagioclase and K‐feldspar seem to have been modified: Ab and Or contents changed during cooling, but An did not. This compositional modification is reproduced by a numerical simulation that modeled the cooling process of a 50 km sized Itokawa parent asteroid. After cooling, some particles have been heavily impacted and heated, which resulted in heterogeneous distributions of Na and K within plagioclase crystals. Impact‐induced chemical modification of plagioclase was verified by a comparison to a shock vein in the Kilabo LL6 ordinary chondrite where Na‐K distributions of plagioclase have been disturbed. 相似文献
56.
Takaaki Noguchi Makoto Kimura Takahito Hashimoto Mitsuru Konno Tomoki Nakamura Michael E. Zolensky Ryuji Okazaki Masahiko Tanaka Akira Tsuchiyama Aiko Nakato Toshinori Ogami Hatsumi Ishida Ryosuke Sagae Shinichi Tsujimoto Toru Matsumoto Junya Matsuno Akio Fujimura Masanao Abe Toru Yada Toshifumi Mukai Munetaka Ueno Tatsuaki Okada Kei Shirai Yukihiro Ishibashi 《Meteoritics & planetary science》2014,49(2):188-214
On the basis of observations using Cs‐corrected STEM, we identified three types of surface modification probably formed by space weathering on the surfaces of Itokawa particles. They are (1) redeposition rims (2–3 nm), (2) composite rims (30–60 nm), and (3) composite vesicular rims (60–80 nm). These rims are characterized by a combination of three zones. Zone I occupies the outermost part of the surface modification, which contains elements that are not included in the unchanged substrate minerals, suggesting that this zone is composed of sputter deposits and/or impact vapor deposits originating from the surrounding minerals. Redeposition rims are composed only of Zone I and directly attaches to the unchanged minerals (Zone III). Zone I of composite and composite vesicular rims often contains nanophase (Fe,Mg)S. The composite rims and the composite vesicular rims have a two‐layered structure: a combination of Zone I and Zone II, below which Zone III exists. Zone II is the partially amorphized zone. Zone II of ferromagnesian silicates contains abundant nanophase Fe. Radiation‐induced segregation and in situ reduction are the most plausible mechanisms to form nanophase Fe in Zone II. Their lattice fringes indicate that they contain metallic iron, which probably causes the reddening of the reflectance spectra of Itokawa. Zone II of the composite vesicular rims contains vesicles. The vesicles in Zone II were probably formed by segregation of solar wind He implanted in this zone. The textures strongly suggest that solar wind irradiation damage and implantation are the major causes of surface modification and space weathering on Itokawa. 相似文献
57.
Toru Kobari Hiroyasu Akamatsu Masato Minowa Toshihiro Ichikawa Kazuo Iseki Ryuji Fukuda Masataka Higashi 《Journal of Oceanography》2010,66(5):673-684
Seasonal changes in the shape and size composition of fecal pellets were investigated with sediment trap samples from 50 and
150 m in Kagoshima Bay to evaluate how the mesozooplankton community affects fecal pellet flux. Deep vertical mixing was evident
in March, and thermal stratification was developed above 50 m in June, August and November. Chlorophyll a, suspended particulate organic carbon (POC) and copepod abundance were uniform throughout the water column during the seasonal
mixing and concentrated above 50 m in the stratified seasons. Calanoids were the most predominant copepods in March and poecilostomatoids
composed more than 45% of the copepod community in June, August and November. Fecal pellet fluxes at 50 and 150 m were the
highest in March, nearly half of POC flux. The relative contribution declined considerably in the other months, especially
for less than 4% of POC flux in August. The decline was corresponded to the predominance of cyclopoids and poecilostomatoids.
Cylindrical pellets dominated the fecal matters at both depths throughout the study period, while larger cylindrical pellets
nearly disappeared at 150 m in June, August and November. Copepod incubation revealed that cylindrical and oval pellets were
egested by calanoids and the other copepods, respectively. We suggest that cylindrical fecal pellets produced by calanoid
copepods contribute to feces flux but the predominance of poecilostomatoids and/or cyclopoids decreases feces flux via the
increase of oval pellets and fragmentation of larger cylindrical pellets. 相似文献
58.
Abstract The 1995 Hyogo-ken Nanbu (Kobe) earthquake, M 7.2, occurred along the north-east–south-west trending Rokko–Awaji Fault system. Three boreholes of 1001 m, 1313 m and 1838 m deep were drilled in the vicinity of the epicenter of the earthquake. Each borehole is located at characteristic sites in relation to active faults and the aftershock distribution. In particular, the Nojima–Hirabayashi borehole [Hirabayashi National Research Institute for Earth Science and Disaster Prevention (NIED) drilling] in Awaji Island was drilled to a depth of 1838 m, approximately 320 m southeast from the surface rupture of the Nojima Fault, and it crosses fracture zones below a depth of 1140 m. In situ stress measurements by the hydraulic fracturing method were conducted in these boreholes within 1.5 years after the earthquake. Measurement results suggest the following: (i) Differential stress values are very small, approximately 10 MPa at a depth of 1000 m at each site; (ii) the orientation of maximum horizontal compression is almost the same in the boreholes, perpendicular to the surface trace of the faults, north-west–south-east; (iii) fault types estimated from the state of stress differ among these sites; and (iv) the differential stress value just beneath the fault fracture zone decreases abruptly to one-half of that above the fault zone in the Hirabayashi NIED drilling. These features support the idea that the shear stress along the Rokko–Awaji Fault system decreased to a low level just after the earthquake. 相似文献
59.
Laboratory experiments were made to examine some characteristics of a radiation thermometer (PRT 14–313, Barnes Engineering
Company). Effect of nonblackness of the water surface and a large temperature difference between the water and the air above
it were investigated.
Sea surface temperatures were then measured by the radiation thermometer, thermistor thermometers and a mercury thermometer
from a marine tower. The result showed that the temperature at the air-sea interface was not always cooler than the subsurface
temperature. The standard deviation of difference of temperatures measured by the radiation thermometer and the thermistor
thermometer was 0.44°C. The dependence of the temperature difference on various factors was investigated with the result that
current velocity had a good correlation with the temperature difference. 相似文献
60.
Tatsuo Matsuda Kentaro Omura Ryuji Ikeda Takashi Arai Kenta Kobayashi Koji Shimada Hidemi Tanaka Tomoaki Tomita Satoshi Hirano 《Tectonophysics》2004,378(3-4):143
An 1800-m-deep borehole into the Nojima fault zone was drilled at Nojima-Hirabayashi, Japan, after the 1995 Hyogo-ken Nanbu (Kobe) earthquake. Three possible fracture zones were detected at depths of about 1140, 1300, and 1800 m. To assess these fracture zones in this recently active fault, we analyzed the distributions of fault rocks, minerals, and chemical elements in these zones. The central fault plane in the shallowest fracture zone was identified by foliated blue-gray gouge at a depth of 1140 m. The degree of fracturing was evidently greater in the hanging wall than in the footwall. Minerals detected in this zone were quartz, orthoclase, plagioclase, and biotite, as in the parent rock (granodiorite), and also kaolinite, smectite, laumontite, stilbite, calcite, ankerite, and siderite, which are related to hydrothermal alteration. Biotite was absent in both the hanging wall and footwall across the central fault plane, but it was absent over a greater distance from the central fault plane in the hanging wall than in the footwall. Major element compositions across this zone suggested that hydrothermal alteration minerals such as kaolinite and smectite occurred across the central fault plane for a greater distance in the hanging wall than in the footwall. Similarly, H2O+ and CO2 had higher concentrations in the hanging wall than in the footwall. This asymmetrical distribution pattern is probably due to the greater degree of wall–rock fracturing and associated alteration in the hanging wall. We attributed the characteristics of this zone to fault activity and fluid–rock interactions. We analyzed the other fracture zones along this fault in the same way. In the fracture zone at about 1300 m depth, we detected the same kinds of hydrothermal alteration minerals as in the shallower zone, but they were in fewer samples. We detected relatively little H2O+ and CO2, and little evidence for movement of the major chemical elements, indicating little past fluid–rock interaction. In the fracture zone at about 1800 m depth, H2O+ and CO2 were very enriched throughout the interval, as in the fracture zone at about 1140 m depth. However, smectite was absent and chlorite was present, indicating the occurrence of chloritization, which requires a temperature of more than 200 °C. Only smectite can form under the present conditions in these fracture zones. The chloritization probably occurred in the past when the fracture zone was deeper than it is now. These observations suggest that among the three fracture zones, that at about 1140 m depth was the most activated at the time of the 1995 Hyogo-ken Nanbu (Kobe) earthquake. 相似文献