Speciation of Chromium in Artificially Contaminated Soil Reference Material GSJ JSO-2 Using XANES and Chemical Extraction Methods     

Hiroshi Tsuno  Atsuyuki Ohta  Hiroyuki Kagi  Noboru Imai  Hiroaki Tao  Masaharu Nomura 《Geostandards and Geoanalytical Research》2006,30(1):55-62

The oxidation states of chromium in GSJ JSO-2 (artificially contaminated soil) and three other geochemical reference materials (GSJ JSO-1, JLS-1 and JMS-1) were observed using X-ray near edge structure (XANES). For comparison, other artificially contaminated soil materials (mimic-JSO-2) were prepared by adding Cr(VI) into JSO-1. Their oxidation states of chromium were determined using XANES. The chromium contents were 1118 μg g^-1 for JSO-2, 1352 μg g^-1 for mimic-JSO-2 and 69-113 μg g^-1 for the other reference materials. Most chromium was present as hexavalent in mimic-JSO-2. No hexavalent species were detected in other samples. These results for chromium oxidation state in JSO-2 and mimic-JSO-2 obtained with XANES resembled those obtained from a chemical extraction method. The present JSO-2 has no trace of Cr(VI), although Cr(VI) was added as a major species during preparation. On the other hand, the content of Cr(VI) obtained in mimic-JSO-2 agreed with the original Cr(VI) content. A time-elapse study showed that Cr(VI) contents in mimic-JSO-2 decreased gradually to 70% of the original abundance during 240-day preservation in dry conditions. Moreover, the abundance of Cr(VI) decreased markedly to 15% after 240 days in the wet mimic-JSO-2 containing 20% m/m of water. These experiments suggested that soil humidity enhanced the reduction of Cr(VI) and that Cr(VI) was reduced even in dry conditions. Consequently, it is reasonable to infer that Cr(VI) doped into JSO-2 was completely reduced to Cr(III) during the preservation period of 5 years. The certification of the long-term stability of the chemical form in reference materials will be much more important in future.  相似文献   

Effect of stirring on crystallization kinetics of basalt: texture and element partitioning     

Akira Kouchi  Akira Tsuchiyama  Ichiro Sunagawa 《Contributions to Mineralogy and Petrology》1986,93(4):429-438

Isothermal crystallization experiments on basalt have been carried out using an infrared heating furnace to investigate the effect of stirring. When stirring was not applied (static experiment), the results agreed well with previous experiments. But when stirring was applied and a flow of Reynolds number=10^–3–4 was present (dynamic experiment), considerably different results were obtained, especially in respect to the nucleation rate and the morphology of crystals. At T=25° C essentially similar results were obtained on the nucleation rates and morphologies of crystals in both static and dynamic experiments. However, at supercoolings larger than 45° C, nucleation density increased drastically in dynamic experiments reaching up to ten times as large as that in static experiments. Crystals of plagioclase and clinopyroxene were small and adapted acicular morphology regardless of T in dynamic experiments, and hyalopilitic textures were formed. A TTT-diagram shows that the nucleation incubation time is shorter in dynamic experiments than in static experiments. No compositional difference in major elements was found in plagioclase and clinopyroxene produced in both static and dynamic experiments. However, minor element concentrations, e.g., Mg in plagioclase and Ti, Al in clinopyroxene, were found to increase with both T and flow velocity. All these results imply that although chemical diffusion in the melts did not play an important role in the dynamic experiments, interface kinetics were important. It is suggested that hyalopilitic texture commonly seen in natural basalt is mainly due to flow in magma.  相似文献   

A model for mixing basaltic and dacitic magmas as deduced from experimental data     

Akira Kouchi  Ichiro Sunagawa 《Contributions to Mineralogy and Petrology》1985,89(1):17-23

It has been demonstrated experimentally that basaltic and dacitic magmas can be easily mixed to form both banded dacite and homogeneous andesite in less than a few hours. The presence of phenocrysts larger than 0.5 mm increased considerably the efficiency of mixing. Flow patterns in the experimental system were visualized using Pt spheres, which indicated that convection occurs in basalt melt, but not in dacite melt. The Reynolds numbers of the basaltic and dacitic melts in the experimental system were calculated to be about 10^–3 and 10^–6, respectively. Mixing proceeds initially by mechanical mixing of the two magmas in a large scale, but later by coupling interfacial convection and mutual diffusion. Thus, depending on the depth where vesiculation and following disruption of the magma occurs, banded pumice, homogeneous pumice and homogeneous andesite lava are erupted. The observed textures of mixed rocks of Plinian type eruption and the limiting occurrence of banded pumice are satisfactorily accounted for on this model.  相似文献   

The velocity field associated with the birth of sunspots     

Ichiro Kawaguchi  Reizaburo Kitai 《Solar physics》1976,46(1):125-135

A velocity field is found to occur prior to the birth of sunspots or during the rapidly developing phase of new spots. Fraunhofer lines are always shifted redwards in the observed active regions which are situated at various distances from the disk center. The velocity amplitude derived from Na i D1-line, 5895.940, amounts to, at maximum, 1.5 km s^–1 which is always a little larger than that derived from the weaker line, NI i 5892.883. The velocity field disappears when the spot ceases to grow. The lifetime of the velocity is, at least, 1 hr. The velocity field is interpreted in terms of the continuous downward flow in the process of formation of sunspots.Bray and Loughhead (1964) regard the disturbance in the granulation pattern accompanying the birth and growth of sunspot pores as an evidence of the existence of rising loops of magnetic flux. In view of the similarity of the phase of development of active regions and the lifetime in the observations by Bray and Loughhead and by us, we suggest that the velocity field may be a spectroscopic feature accompanying the rising magnetic loops in the photosphere and the chromosphere. We briefly discuss the observed mode of penetration of the magnetic flux to the solar surface before and after the appearance of AFS's.  相似文献   

Oxygen isotopic distribution in an amoeboid olivine aggregate from the Allende CV chondrite: Primary and secondary processes     

Hajime Imai  Hisayoshi Yurimoto 《Geochimica et cosmochimica acta》2003,67(4):765-772

The oxygen isotopic distribution in an amoeboid olivine aggregate (AOA), TTA1-02, from the Allende CV3 chondrite has been determined by secondary ion mass spectrometry. The irregular shaped TTA1- 02 (5×3mm) consists mostly of olivine grains of ca. 5μm in diameter. Olivine grains of Mg-rich (Fo₉₅) and Fe-rich (Fo₆₀) composition are in direct contact with each other, with a sharp compositional boundary. Oxygen isotopic compositions of Fe-rich olivine grains are ¹⁶O-poor (Δ¹⁷O ≅ −5‰), whereas Mg-rich olivine is ¹⁶O-rich (Δ¹⁷O ≅ −25‰). Several Al-rich inclusions (<ca. 500 μm in diameter) are enclosed by olivine grains in the AOA. Oxygen isotopic compositions of spinel and fassaite in Al-rich inclusions are ¹⁶O-rich (Δ¹⁷O ≅ −20‰), whereas those of anorthite, nepheline and phyllosilicate are ¹⁶O-poor (Δ¹⁷O ≅ −5‰). We propose the following sequence of events during the formation of AOAs in the Allende meteorite: 1) Formation of Al-rich inclusions with ¹⁶O-rich oxygen isotopic composition; 2) Accretion of Mg-rich olivine grains with ¹⁶O-rich oxygen isotopic composition around Al-rich inclusions; 3) Accretion into parent body; and 4) Aqueous alteration in the parent body, which led to crystallization of ¹⁶O-poor minerals, Fe-rich olivine, anorthite, nepheline, and phyllosilicate. This is reflecting reactions among primary ¹⁶O-rich AOA minerals and aqueous fluid having ¹⁶O-poor oxygen isotopic composition. Fe-rich olivine grains precipitated from aqueous fluids, which partially dissolved pre-existing Mg-rich olivine grains. Sintering and Mg-Fe diffusion occurred during thermal metamorphism. Anorthite, nepheline and phyllosilicate in Al-rich inclusions replaced primary anorthite or melilite during the aqueous alteration stage.  相似文献   

Water-weakened lower crust and its role in the concentrated deformation in the Japanese Islands     

Yoshihisa Iio  Takeshi SagiyaYoji Kobayashi  Ichiro Shiozaki 《Earth and Planetary Science Letters》2002,203(1):245-253

The nature and origin of the concentrated deformation zone along the Japan Sea coast (NKTZ: Niigata-Kobe tectonic zone) was investigated by carefully analyzing the GPS data and qualitatively modeling the lower crust in NKTZ. It was concluded that this deformation zone is not a plate boundary between the Amurian plate (AMU) and the North America plate but is rather an internal deformation zone near the eastern margin of AMU. The data previously obtained on the conductivity anomalies in the lower crust and the ³He/⁴He ratios suggest that the concentrated deformation in NKTZ results from the lower crust in NKTZ being weakened by a high water content. The high water content is thought to result from the dehydration of subducting slabs. NKTZ has a higher water content in the lower crust than other regions do because there is no Philippine Sea plate (PHS) seismic slab beneath NKTZ. In other regions, it is estimated that the mantle wedge above the seismic Philippine Sea slab prevents the water dehydrated from the slab from rising to the lower crust, and that the lithosphere within PHS itself prevents the water dehydrated from the Pacific plate from rising up through it.  相似文献   

ESR dating of fault movement using various defect centres in quartz; the case in the western South Fossa Magna, Japan   总被引：1，自引：0，他引：1  

Tatsuro Fukuchi  Noboru Imai  Koichi Shimokawa 《Earth and Planetary Science Letters》1986,78(1)

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Photospheric velocity field associated with moustaches     

Reizaburo Kitai  Ichiro Kawaguchi 《Solar physics》1975,44(2):403-408

The photospheric velocity field was observed in an active region which was prolific in moustaches. It is shown that the moustaches occur at the locations where the sign of the line-of-sight velocity changes, and that the extension of the velocity field is large (≈10⁴ km) compared with the dimension of moustaches.  相似文献   

The brightening of sunspot umbra observed on 29 October, 1972     

Jun Kubota  Tatsuo Tamenaga  Ichiro Kawaguchi  Reizaburo Kitai 《Solar physics》1974,38(2):389-398

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Status of butyltin pollution along the coasts of western Japan in 2001, 11 years after partial restrictions on the usage of tributyltin     

Murai R  Takahashi S  Tanabe S  Takeuchi I 《Marine pollution bulletin》2005,51(8-12):940-949

Restrictions on the use of tributyltin (TBT) in aquaculture and on boats in coastal regions, except for ocean-going vessels, have been in place in Japan since 1990 due to the strong toxic effects of TBT on marine organisms. However, TBT pollution along the Japanese coasts has been reported after this legislation was enacted. In order to elucidate the present status of contamination by butyltin (BT) compounds, we measured the levels of BTs [monobutyltin (MBT), dibutyltin (DBT) and TBT] in seawater and Caprella spp. samples obtained from the western part of Seto Inland Sea, Uwa Sea and Uranouchi Bay in western Japan during March to September, 2001. Butyltins were detected in more than 90% of the seawater samples (n = 59), with average concentrations of 8.2 ± 9.2 (SD) ng MBT L⁻¹, 3.3 ± 3.0 ng DBT L⁻¹ and 9.0 ± 7.0 ng TBT L⁻¹. Among 41 stations situated on coastal lines, a sufficient number of Caprella organisms for chemical analysis could be collected from only 16 stations. The butyltin concentrations in seawater and Caprella samples from Uwa Sea and Uranouchi Bay, in which the dominant industry in both waters is aquaculture, showed significantly higher than or no significant differences from those samples from the western part of Seto Inland Sea, a major heavy-industry area in Japan. As the TBT concentration in seawater increased, the number of Caprella organisms collected decreased. The mean TBT concentration among the seawater samples was above the estimated lowest observable effect concentration (LOEC) that reduces the survival rate of Caprella danilevskii. Thus, the present study indicates that TBT is still a potential ecological hazard to the survival of marine invertebrates inhabiting coasts along western Japan, even 11 years after the partial ban on TBT usage was implemented.  相似文献