Wakefieldite‐(Nd), a New Neodymium Vanadate Mineral in the Arase Stratiform Ferromanganese Deposit,Kochi Prefecture,Japan     

Takeru Moriyama  Ritsuro Miyawaki  Kazumi Yokoyama  Satoshi Matsubara  Hideo Hirano  Hiroyasu Murakami  Yasushi Watanabe 《Resource Geology》2011,61(1):101-110

Wakefieldite‐(Nd), NdVO₄, is a new mineral found from the Arase stratiform ferromanganese deposit in Kochi Prefecture, Shikoku Island, Japan. It is the Nd‐dominant analogue of wakefieldite‐(Y) and wakefieldite‐(Ce). The ferromanganese ore specimen mainly consists of hematite and caryopilite, and wakefieldite‐(Nd) is typically enclosed in caryopilite. Wakefieldite‐(Nd) is tetragonal, I4₁/amd, a = 7.338(16) Å, c = 6.509(19) Å, V = 350.5(18) ų, Z = 4. The four strongest lines in the X‐ray diffraction pattern [d(Å), I/I₀, hkl] using a Gandolfi camera are (3.67, 100, 200); (2.74, 51, 112); (4.84, 27, 101) and (1.89, 25, 312). Chemical composition of wakefieldite‐(Nd) are V₂O₃ 35.25, As₂O₃ 0.93, SiO₂ 0.14, MnO 1.45, Fe₂O₃ 0.41, Y₂O₃ 2.87, La₂O₃ 7.61, Ce₂O₃ 7.37, Pr₂O₃ 6.04, Nd₂O₃ 26.79, Sm₂O₃ 4.41, Eu₂O₃ 1.36, Gd₂O₃ 3.41, Tb₂O₃ 0.22, Dy₂O₃ 1.41, Er₂O₃ 0.10, total 99.77 wt.%. The empirical formula is (Nd_0.403La_0.118Ce_0.114Pr_0.093Y_0.064Sm_0.064Mn_0.052Gd_0.048Eu_0.020Dy_0.019Fe_0.013Tb_0.003Er_0.001)_1.012(V_0.981As_0.020Si_0.006)_1.007O₄ on the basis of O = 4. The calculated density is 4.782 g/cm³. Microtexture and co‐existing relationship between wakefieldite‐(Nd) and caryopilite suggest that recrystallization and dehydration of Fe‐ and Mn‐oxyhydroxide led to the generation of hematite, caryopilite, rhodochrosite and wakefieldite‐(Nd) by the metamorphism during the accretion of the host unit of the Arase deposit. Chondrite‐normalized REE pattern of the host ferromanganese ore, which is regarded as oceanic metalliferous sediment in origin, shows negative Ce anomaly. Chemical composition of wakefieldite‐(Nd) reflects Ce‐depleted bulk composition of REE‐enriched ferromanganese ore.  相似文献   

Temporal variability in physicochemical properties,phytoplankton standing crop and primary production for 7 years (2002–2008) in the neritic area of Sagami Bay,Japan     

Koichi Ara  Koh Yamaki  Keisuke Wada  Satoshi Fukuyama  Takeshi Okutsu  Sadao Nagasaka  Akihiro Shiomoto  Juro Hiromi 《Journal of Oceanography》2011,67(1):87-111

Seasonal and interannual variations in physicochemical properties (i.e., temperature, salinity, dissolved oxygen and dissolved inorganic nutrients), chlorophyll a (Chl-a), particulate carbon and nitrogen (PC and PN, respectively), and primary production were investigated in the neritic area of Sagami Bay, Kanagawa, Japan, from January 2002 to December 2008. These abiotic/biotic variables, except for NH₄ ⁺–N, repeated similar seasonal variations for all 7 years. On the basis of the analysis of data obtained on 167 sampling dates, depth-integrated primary production in this water can be easily estimated from Chl-a at the surface using the regression equations obtained in the present study. Intermittently high values of dissolved inorganic nutrients, Chl-a, PC, PN and primary productivity at the surface during the summer stratified period were induced by high freshwater discharge from the rivers after rainfalls and by the expansion of nutrient-rich Tokyo Bay Water. Temperature, salinity and dissolved inorganic nutrients showed drastic variations within a scale of a few days and/or weeks, and these variations were related to sea levels that represent the intrusion of the Kuroshio Water, Intermediate Oyashio Water or deep water from the continental slope. However, there was no consistent trend in the variations in Chl-a, PC, PN and primary production due to the complex effects of these waters.  相似文献   

Development of a numerical model for nitrates in groundwater in the reservoir area of the Komesu subsurface dam, Okinawa, Japan   总被引：1，自引：0，他引：1  

Shuhei Yoshimoto  Takeo Tsuchihara  Satoshi Ishida  Masayuki Imaizumi 《Environmental Earth Sciences》2013,70(5):2061-2077

A numerical model consisting of simplified equations was developed to simulate nitrate concentrations in groundwater in a reservoir area of a subsurface dam in a Quaternary limestone region. The model was composed of a water balance sub-model and a nitrogen balance sub-model; the water balance sub-model was built from tank models which can express the quick dilution near caves and the effect of dam construction; and the nitrogen balance sub-model was made to represent changes in nitrogen forms and movement of nitrogen in the soil and aquifer zones. The model was calibrated and verified by observed data before and after the dam construction and then applied to a predictive simulation under a simple assumption that rainfall descends gradually. The model seemed applicable to long-term prediction of changes in NO₃-N in the reservoir area.  相似文献   

Experimental constraints on permeable gas transport in crystalline silicic magmas     

Satoshi Okumura  Michihiko Nakamura  Tsukasa Nakano  Kentaro Uesugi  Akira Tsuchiyama 《Contributions to Mineralogy and Petrology》2012,164(3):493-504

The gas and fluid transport in magmas via permeable flow through interconnected bubble networks controls the rate of outgassing from magmas ascending in volcanic conduits and the fluid transport in the mushy boundary layer of magma reservoirs. Hence, clarifying its mechanism and rate is crucial to understanding the explosivity of volcanic eruptions and the evolution and dynamics of a magma reservoir. Recent experimental studies have determined the gas permeabilities in crystal-free rhyolite and basalt. However, no experimental study has investigated the effect of the crystal contents on the permeable gas transport in magmas. In this study, we performed decompression experiments for hydrous rhyolitic melts having crystallinities of 30 and 50 vol% to examine the effect of crystals on the bubble microstructure and gas permeability during magma vesiculation. Size-controlled (100-meshed) corundum crystals were used as an analog of the phenocrysts in silicic magmas. Microstructural analyses using X-ray CT showed that bubbles coalesce and their connectivity increases with a decrease in the final pressure after the decompression, that is, an increase in the vesicularity. As long as the vesicularities of melt part in the crystal-free basis (melt vesicularity) were similar, no clear effect of the crystallinity on the degree of bubble coalescence and connectivity was observed at melt vesicularities <68 vol%. The corundum showed a large contact angle with aqueous fluid as well as plagioclase and alkaline feldspar; this failed to induce the efficient heterogeneous nucleation and coalescence of bubbles on its surface. The gas permeabilities of all the run products were lower than the detection limits of the present analysis (the order of 10⁻¹⁶ m²) at melt vesicularities <68 vol%. These results show that silicic magmas containing 30 and 50 vol% phenocrysts with a large contact angle have low gas permeabilities until the vesicularity becomes large (at least >68 vol%). This result indicates that the permeable fluid transport through a deep volcanic conduit, which has been proposed on the basis of the observations of volcanic gases and natural products, is so slow that other processes, like shear deformation or magma convection, may be needed to explain the observations.  相似文献   

Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets     

Satoshi Endo  Masaki Yuyama  Hideshige Takada 《Marine pollution bulletin》2013

This study investigated the desorption behavior of polychlorinated biphenyls (PCBs) from marine plastic pellets. Long-term desorption experiments were conducted using field-collected polyethylene (PE) pellets. The results indicate that the desorption kinetics highly depends on the PE-water partition coefficients of PCB congeners. After 128 d of the experiment, the smallest congener considered (CB 8) had desorbed nearly completely (98%), whereas major fractions (90–99%) of highly chlorinated congeners remained in the pellets. An intraparticle diffusion model mostly failed to reproduce the desorption kinetics, whereas an aqueous boundary layer (ABL) diffusion model well approximated the data. The desorption half-lives are estimated to 14 d to 210 years for CB 8 to CB 209 in an actively stirred solution (ABL thickness: 30 μm). Addition of methanol to water enhanced the desorption to a large extent. A need for further work to explore roles of organic matter in facilitating solute transfer is suggested.  相似文献   

A framework for economic loss estimation due to seismic transportation network disruption: a spatial computable general equilibrium approach   总被引：4，自引：4，他引：0  

Hirokazu Tatano  Satoshi Tsuchiya 《Natural Hazards》2008,44(2):253-265

This paper presents a framework for assessing the economic impact of disruption in transportation that can relate the physical damage to transportation networks to economic losses. A spatial computable general equilibrium (SCGE) model is formulated and then integrated with a transportation model that can estimate the traffic volumes of freight and passengers. Economic equilibrium under a disruption in the transportation network is computed subject to the condition that the adjustment of labor and capital inputs is restricted; the model reflects slow adjustment of these linked to the state of recovery. As a case study, the model reviews the large Niigata-Chuetsu earthquake of 2004. Considering the damage to the transportation infrastructure, the model indicates the extent of the economic losses arising from the earthquake distributed over regions as a consequence of the intra- and interregional trade in a regional economy. The results show that 20% of the indirect losses occur in the Niigata region directly affected by the earthquake, whereas 40% of the total losses are experienced in the Kanto region and non-negligible losses reach rather remote zones of the country such as Okinawa.  相似文献   

Seasonal Changes in Submarine Groundwater Discharge and Associated Nutrient Transport into a Tideless Semi-enclosed Embayment (Obama Bay,Japan)     

Ryo Sugimoto  Hisami Honda  Shiho Kobayashi  Yoshitake Takao  Daisuke Tahara  Osamu Tominaga  Makoto Taniguchi 《Estuaries and Coasts》2016,39(1):13-26

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Mechanism and future risk of slope instability induced by extreme rainfall event in Izu Oshima Island,Japan     

Towhata  Ikuo  Goto  Satoshi  Goto  Shigeru  Akima  Takeshi  Tanaka  Junya  Uchimura  Taro  Wang  Gonghui  Yamaguchi  Hiroshi  Aoyama  Shogo 《Natural Hazards》2021,105(1):501-530

Natural Hazards - A volcanic slope in Izu Oshima Island in Japan experienced a profound rain-induced disaster in October 2013. Since this slope had been stable for centuries except for minor...  相似文献   

Controlling factors of seasonal variation in the nitrogen isotope ratio of nitrate in a eutrophic coastal environment     

Ryo Sugimoto  Akihide Kasai  Toshihiro Miyajima  Kouichi Fujita 《Estuarine, Coastal and Shelf Science》2009,85(2):231-240

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Planetary growth with collisional fragmentation and gas drag     

Hiroshi Kobayashi  Hidekazu Tanaka  Satoshi Inaba 《Icarus》2010,209(2):836-492

As planetary embryos grow, gravitational stirring of planetesimals by embryos strongly enhances random velocities of planetesimals and makes collisions between planetesimals destructive. The resulting fragments are ground down by successive collisions. Eventually the smallest fragments are removed by the inward drift due to gas drag. Therefore, the collisional disruption depletes the planetesimal disk and inhibits embryo growth. We provide analytical formulae for the final masses of planetary embryos, taking into account planetesimal depletion due to collisional disruption. Furthermore, we perform the statistical simulations for embryo growth (which excellently reproduce results of direct N-body simulations if disruption is neglected). These analytical formulae are consistent with the outcome of our statistical simulations. Our results indicate that the final embryo mass at several AU in the minimum-mass solar nebula can reach about ∼0.1 Earth mass within 10⁷ years. This brings another difficulty in formation of gas giant planets, which requires cores with ∼10 Earth masses for gas accretion. However, if the nebular disk is 10 times more massive than the minimum-mass solar nebula and the initial planetesimal size is larger than 100 km, as suggested by some models of planetesimal formation, the final embryo mass reaches about 10 Earth masses at 3-4 AU. The enhancement of embryos’ collisional cross sections by their atmosphere could further increase their final mass to form gas giant planets at 5-10 AU in the Solar System.  相似文献