Comparison of reductive accumulation of Re and Os in seawater-sediment systems   总被引：2，自引：0，他引：2  

Yoshiro Yamashita  Hiromitsu Haba  Hiroshi Shimizu 《Geochimica et cosmochimica acta》2007,71(14):3458-3475

In order to understand the fractionation of Re and Os in marine environments, their removal from artificial seawater to Tokyo Bay sediments is studied using a multitracer technique. The chemical processes of the removal of Re and Os are also estimated based on their speciation analyses by X-ray absorption fine structure (XAFS) spectroscopy. The partitioning experiments, which use the multitracer technique, provide information on Re and Os regarding (i) their distributions between artificial seawater-sediment systems, (ii) their complexation with humic acid, and (iii) their carriers in sediments. In addition, XAFS spectroscopy provides direct information on the chemical states of Re and Os in the sediments.In an artificial seawater-sediment system containing a multitracer, Re is removed from the artificial seawater only under a reducing environment. The speciation of Re by X-ray absorption near-edge structure (XANES) suggests that the majority of Re remains as in the artificial seawater even under highly reducing conditions, during laboratory time scale (about 2 weeks). Moreover, XANES simulation shows that some Re exists at a lower oxidation state, such as ReO₂, in the reducing sediment. These results can be explained by the slow kinetics of the reaction which is similar to those suggested by previous geochemical studies.In contrast, Os is readily removed from the artificial seawater into sediments under various redox conditions. Even under oxic conditions, a large fraction of Os is removed from the artificial seawater to sediments without organic matter. Based on the Os XANES study, it is confirmed that the oxidation states of Os incorporated in the reducing sediment and oxic sediment are trivalent and tetravalent, respectively. Sequential extraction suggests that the main carrier of Os in the organic-rich sediment is either ferromanganese oxides or organic matter, and that the Os in these two fractions may correspond to hydrolyzed insoluble Os species and Os species interacting with organic matter, at lower valence, respectively. The results of distribution study of Os in the absence and presence of humic acid (HA) also imply that Os assumes more than one chemical species, and a small fraction of Os may interact with HA in the experimental system. Meanwhile, extended X-ray absorption fine structure (EXAFS) confirms that the first neighboring atom of Os in the reducing sediment is oxygen. If Os(VIII) is the main dissolved species in seawater, as is expected thermodynamically, reductive removal may control the enrichment of Os in the sediment. Osmium, which is removed as Os(IV), is reduced further to Os(III) by a diagenetic process and may be complexed with organic matter in the reducing sediment.The results of the removal behaviors of Re and Os obtained in the current study show that Re can be removed from the artificial seawater only under highly reducing conditions within 2 weeks, but Os removal from the artificial seawater can be found under various redox conditions. Thus, a high ¹⁸⁷Re/¹⁸⁸Os ratio can occur only in reducing sediments, such as black shales. The high¹⁸⁷Re/¹⁸⁸Os ratio, in turn, makes black shales suitable for Re-Os dating. In contrast, authigenic sediments (and minerals) under oxic environments can enrich Os, but since Re is not distributed to the sediments under oxic conditions, this will cause a much lower ¹⁸⁷Re/¹⁸⁸Os ratio than that of seawater. The Os isotope system of these materials can be used as a paleo-marine environmental tracer since the ¹⁸⁷Os/¹⁸⁸Os ratio cannot grow significantly due to its extremely low ¹⁸⁷Re/¹⁸⁸Os ratio.  相似文献   

Use of Thermal Image Velocimetry to Measure a Dust-Devil-Like Vortex Within a Sports Ground in a Residential Area     

Inagaki  Atsushi  Kanda  Manabu 《Boundary-Layer Meteorology》2022,183(1):125-141

Boundary-Layer Meteorology - We investigate the characteristics of a dust-devil-like vortex (DDLV) observed using thermal image velocimetry (TIV) at a sports ground in Tokyo. Thermal image...  相似文献   

Stable carbon isotope values in dissolved inorganic carbon of ambient waters and shell carbonate of the freshwater pearl mussel (Hyriopsis sp.)     

Toshihiro Yoshimura  Hisato Izumida  Rei Nakashima  Toyoho Ishimura  Naotatsu Shikazono  Hodaka Kawahata  Atsushi Suzuki 《Journal of Paleolimnology》2015,54(1):37-51

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Spatial and Seasonal Variation in Surface Water pCO2 in the Ganges,Brahmaputra, and Meghna Rivers on the Indian Subcontinent     

Takuya Manaka  Hiroyuki Ushie  Daisuke Araoka  Souya Otani  Akihiko Inamura  Atsushi Suzuki  H. M. Zakir Hossain  Hodaka Kawahata 《Aquatic Geochemistry》2015,21(5):437-458

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Implications of36A excess on Venus     

Mikio Shimizu 《Earth, Moon, and Planets》1979,20(3):317-319

The finding of³⁶A excess on Venus by the mass-spectroscopic measurement of the Venus Pioneer appears to endorse the more rapid accretion theory of Venus than the Earth and the secondary origin of the terrestrial atmosphere.  相似文献   

ELEMENTAL CONCENTRATIONS IN NINE NEW JAPANESE ROCK REFERENCE SAMPLES     

Shigeru TERASHIMA  Atsushi ANDO 《Geostandards and Geoanalytical Research》1987,11(1):75-77

Twenty-eight major, minor and trace elements in nine new rock reference samples of Geological Survey of Japan (GSJ), JA-2, JA-3 JB-1a, JG-1a, JG-2, JG-3, JF-1, JF-2 and JP-1 have been determined using atomic absorption spectrometry, flame emission spectrometry and wet chemical techniques.  相似文献   

An ion microprobe study of the partitioning of trace elements between clinopyroxene and liquid in the system diopside-albite-anorthite     

G.L. Ray  N. Shimizu  S.R. Hart 《Geochimica et cosmochimica acta》1983,47(12):2131-2140

The partitioning of trace elements (Sc, Ti, Sr and Sm) between diopsidic clinopyroxene and liquid was studied experimentally in the system diopside-albite-anorthite at 1250°C, 1300°C and 1345°C at 1 atm. Twelve different bulk compositions were selected to study the effects of temperature and chemical composition. A Cameca ion microprobe was used to determine trace element concentrations in both clinopyroxene and liquid. Experiments of different run duration $\text{1}\text{4}\text{8}\text{?}$ days) showed that equilibrium was approached in less than 4 days at 1275°C. Equilibrium was also evaluated by a reversal run. A series of runs of constant bulk composition but with variable trace element contents showed that Henry's Law was obeyed over concentration ranges of the trace elements similar to those encountered in natural systems. The partition coefficients show significant ranges: Sc, 0.345~2.61; Ti, 0.084~0.214; Sr, 0.075~0.136; Sm, 0.054~0.328; the values are comparable with those obtained experimentally by other investigators. The partition coefficients vary as a function of both temperature and chemical composition. The experimental results are discussed in terms of exchange equilibria using the Bottinga-Weill silicate melt model. It is demonstrated that analytical uncertainties of both major and trace elements play an important role in understanding trace element exchange equilibria; propagation of analytical errors in the thermodynamic treatment is equally important.  相似文献   

Trace element concentrations in the isotopically unique Allende inclusion,EK 1-4-1     

Hiroshi Nagasawa  Douglas P. Blanchard  Hiroshi Shimizu  Akimasa Masuda 《Geochimica et cosmochimica acta》1982,46(9):1669-1673

Concentrations of rare-earth elements (REE), Sc, Fe, Co, Cr, Na and Ir in the bulk sample and mineral separates of the isotopically unique Allende inclusion, EK 1-4-1, were determined by instrumental neutron activation analysis. REE concentrations were also determined by mass-spectrometric isotope dilution for two density separates.The inclusion showed enrichment of light REE over heavy REE with a positive Yb anomaly, thus showing a tendency to resemble group II fine-grained inclusions in REE abundances, although EK 1-4-1 is a coarse-grained inclusion. High Cr concentrations also indicate group II affinity. However, high Ir (6 ppm) and Sc (105 ppm), and low FeO (1.80%), and Co (13.8 ppm) concentrations in the bulk sample and low Na concentrations in mineral separates show group I affinity.Between melilite and pyroxene fractions, the same samples in which mass-fractionated O isotope ratios were observed (Clayton and Mayeda, 1977), REE, Sc, Co and Fe showed distributions which are substantially different from those observed for “ordinary” Allende type B inclusions. These two minerals do not appear to be in equilibrium with respect to trace element distributions.The results indicate that the isotopically unique EK 1-4-1 is also unusual in its elemental abundances and distributions.  相似文献   

Multicomponent observation of crustal activity in the DPRI 800 m borehole close to the Nojima Fault   总被引：1，自引：0，他引：1  

Hiroshi Ishii  Atsushi Mukai  Kunio Fujimori  Shigeru Nakao  Shigeo Matsumoto  Yasuhiro Hirata 《Island Arc》2001,10(3-4):282-287

Abstract An 800 m borehole was drilled near the Nojima Fault, on which a strike–slip larger then 1 m occurred during the 1995 Hyogo-ken Nanbu earthquake ( M = 7.2). Crustal activity near the fault has been observed since May 1996 using a multicomponent instrument installed at the bottom of the borehole. Data of three components of strain, two components of tilt and temperature observed from May 1996 to December 1998 were analyzed. Long-term changes of strain and tilt show a north-east–south-west extension and southwards subsidence. As for the Earth tides and atmospheric effect, orientation of the principal axis of strain was mainly east-west and orientation of the maximum subsidence was mainly north-south. The observational data of strain had variations corresponding to a change in temperature at a depth of 800 m. The thermal expansion coefficient of the crust was calculated to be approximately 2.0 × 10⁻⁶/°K.  相似文献   

Effects of CO<Subscript>2</Subscript> on Marine Fish: Larvae and Adults     

Atsushi Ishimatsu  Takashi Kikkawa  Masahiro Hayashi  Kyoung-Seon Lee  Jun Kita 《Journal of Oceanography》2004,60(4):731-741

CO₂-enriched seawater was far more toxic to eggs and larvae of a marine fish, silver seabream, Pagrus major, than HCl-acidified seawater when tested at the same seawater pH. Data on the effects of acidified seawater can therefore not be used to estimate the toxicity of CO₂, as has been done in earlier studies. Ontogenetic changes in CO₂ tolerance of two marine bony fishes (Pag. major and Japanese sillago, Sillago japonica) showed a similar, characteristic pattern: the cleavage and juvenile stages were most susceptible, whereas the preflexion and flexion stages were much more tolerant to CO₂. Adult Japanese amberjack, Seriola quinqueradiata, and bastard halibut, Paralichthys olivaceus, died within 8 and 48 h, respectively, during exposure to seawater equilibrated with 5% CO₂. Only 20% of a cartilaginous fish, starspotted smooth-hound, Mustelus manazo, died at 7% CO₂ within 72 h. Arterial pH initially decreased but completely recovered within 1-24 h for Ser. quinqueradiata and Par. olivaceus at 1 and 3% CO₂, but the recovery was slower and complete only at 1% for M. manazo. During exposure to 5% CO₂, Par. olivaceus died after arterial pH had been completely restored. Exposure to 5% CO₂ rapidly depressed the cardiac output of Ser. quinqueradiata, while 1% CO₂ had no effect. Both levels of ambient CO₂ had no effect on blood O₂ levels. We tentatively conclude that cardiac failure is important in the mechanisms by which CO₂ kills fish. High CO₂ levels near injection points during CO₂ ocean sequestration are likely to have acute deleterious effects on both larvae and adults of marine fishes. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献