Behavior of manganese in aqua-benthic environment in the Hiro Bay     

Shizuko Hirata  Osamu Takimura  Takayuki Shiozawa 《Journal of Oceanography》1978,34(6):237-241

The horizontal and vertical distributions of manganese in sea water, interstitial water and sediments in the Hiro Bay, Seto Inland Sea, Japan, have been investigated. The outflow from a pulp mill is the primary source of manganese in this bay. The industrial waste water contained 0.19 mg l^–1 of manganese, mostly in a dissolved form. This manganese diffused out both horizontally and vertically into the surrounding sea water. The content of manganese in the liquid and solid phases in the sediments, however, are inverse with that in the sea water; namely the lowest concentration of manganese in the sediments was observed at the station near the outfall and manganese concentration increased with the distance from the outfall.  相似文献   

Vertical distribution of heavy metals and its seasonal variations in Beppu Bay     

Takayuki Shiozawa  Kichiichiro Kawana  Akira Hoshika  Terumi Tanimoto  Osamu Takimura 《Journal of Oceanography》1977,33(6):350-356

From July to November, the thermocline which has strong temperature gradient (0.7C m^–1) is formed in the bottom water of Beppu Bay, and it prevents the downward mixing of surface water. This has caused the bottom water of the basin to become depleted in oxygen, and in November the bottom water below about 60 m depth becomes anoxic. Accordingly manganese and iron are reduced and more soluble under the anoxic condition, those concentrations are high relative to surface water, and the maximums are 1,240g l^–1 and 80g l^–1. Under the anoxic condition, the flux of dissolved manganese from the sediment is about 10g cm^–2 day^–1.  相似文献   

Deep sea circulation of particulate organic carbon in the Japan Sea     

Shigeyoshi Otosaka  Takayuki Tanaka  Orihiko Togawa  Hikaru Amano  Eugeny V. Karasev  Masayuki Minakawa  Shinichiro Noriki 《Journal of Oceanography》2008,64(6):911-923

Seasonal and spatial variations of particulate organic carbon (POC) flux were observed with sediment traps at three sites in the Japan Sea (western and eastern Japan Basin and Yamato Basin). In order to investigate the transport processes of POC, radiocarbon (¹⁴C) measurements were also carried out. Annual mean POC flux at 1 km depth was 30.7 mg m⁻²day⁻¹ in the western Japan Basin, 12.0 mg m⁻²day⁻¹ in the eastern Japan Basin and 23.8 mg m⁻²day⁻¹ in the Yamato Basin. At all stations, notably higher POC flux was observed in spring (March–May), indicating biological production and rapid sinking of POC in this season. Sinking POC in the high flux season showed modern Δ¹⁴C values (>0‰) and aged POC (Δ¹⁴C < −40‰) was observed in winter (December–January). The Δ¹⁴C values in sinking POC were negatively correlated with aluminum concentration, indicating that Δ¹⁴C is strongly related to the lateral supply of lithogenic materials. The Δ¹⁴C values also showed correlations with excess manganese (Mn_xs) concentrations in sinking particles. The Δ¹⁴C-Mn_xs relationship suggested that (1) the majority of the aged POC was advected by bottom currents and incorporated into sinking particles, and (2) some of the aged POC might be supplied from the sea surface at the trap site as part of terrestrial POC. From the difference in the Δ¹⁴C-Mn_xs relationships between the Japan Basin and the Yamato Basin, we consider that basin-scale transport processes of POC occur in the Japan Sea.  相似文献   

Migration of protoplanets: Effects on terrestrial planet formation     

Takayuki Tanigawa 《Planetary and Space Science》2008,56(13):1758-1763

I review the role of planetary migration on the formation process of terrestrial planets. I first show a simple estimation for growth timescale of solid proto-planets and review a linear theory of disk-planet gravitational interaction to estimate the migration rate of proto-planets in a gas disk, and then discuss the difficulty of the formation of terrestrial planets in terms of comparison between migration timescale and growth timescale. Next I show recent studies which suggest possible mechanisms to solve the problem. I briefly discuss the formation process of Mercury in the context of terrestrial-planet formation.  相似文献   

Constraining tephra dispersion and deposition from three subplinian explosions in 2011 at Shinmoedake volcano,Kyushu, Japan     

Fukashi Maeno  Masashi Nagai  Setsuya Nakada  Rose E. Burden  Samantha Engwell  Yuki Suzuki  Takayuki Kaneko 《Bulletin of Volcanology》2014,76(6):1-16

Constraining physical parameters of tephra dispersion and deposition from explosive volcanic eruptions is a significant challenge, because of both the complexity of the relationship between tephra distribution and distance from the vent and the difficulties associated with direct and comprehensive real-time observations. Three andesitic subplinian explosions in January 2011 at Shinmoedake volcano, Japan, are used as a case study to validate selected empirical and theoretical models using observations and field data. Tephra volumes are estimated using relationships between dispersal area and tephra thickness or mass/area. A new cubic B-spline interpolation method is also examined. Magma discharge rate is estimated using theoretical plume models incorporating the effect of wind. Results are consistent with observed plume heights (6.4–7.3 km above the vent) and eruption durations. Estimated tephra volumes were 15–34?×?10⁶ m³ for explosions on the afternoon of 26 January and morning of 27 January, and 5.0–7.6?×?10⁶ m³ for the afternoon of 27 January; magma discharge rates were in the range 1–2?×?10⁶ kg/s for all three explosions. Clast dispersal models estimated plume height at 7.1?±?1 km above the vent for each explosion. The three subplinian explosions occurred with approximately 12-h reposes and had similar mass discharge rates and plume heights but decreasing erupted magma volumes and durations.  相似文献   

Tectonics of an Early Carboniferous forearc inferred from a high-P/T schist-bearing conglomerate in the Nedamo Terrane, Northeast Japan     

Takayuki  Uchino  Makoto  Kawamura 《Island Arc》2010,19(1):177-191

The Nedamo Terrane, an Early Carboniferous accretionary complex, is the oldest biostratigraphically dated accretionary complex in Japan. The purpose of this study is to describe and interpret a conglomerate from the Nedamo Terrane that contains clasts of high-pressure/low-temperature (high- P/T ) schist (mainly garnet-bearing phengite schist) and ultramafic rock, and to infer the tectonics of an Early Carboniferous arc–trench system at the eastern margin of the paleo-Asian continent. Clasts of high- P/T schist and ultramafic rock within the conglomerate make up 8.4 and 6.7% of the total clasts, respectively, based on modal counts. These clasts are subangular to subrounded, whereas volcanic clasts are well rounded. The source of the schist clasts, which yield a radiometric age of 347–317 Ma, is considered to be the Renge Metamorphic Rocks of Southwest Japan or equivalent rocks. Based on the chemical composition of chromian spinel, the source of ultramafic clasts is inferred to be the island-arc-type Ordovician Miyamori and Hayachine ultramafic complexes in the Kitakami Massif. The conglomerate records multiple provenance regions, including an island arc (South Kitakami Terrane) and a forearc ridge; the high P/T schist and ultramafic rocks were exhumed in the forearc region. The duration of the interval from the early stages of exhumation of the schist to its deposition in the trench as clasts is estimated to have been less than 30 my.  相似文献   

Observational Evidence of Dissipative Small Scale Processes: Geotail Spacecraft Observation and Simulation of Electrostatic Solitary Waves     

Y. Omura  H. Kojima  T. Umeda  H. Matsumoto 《Astrophysics and Space Science》2001,277(1-2):45-57

In recent spacecraft observations, coherent microscale structures such as electrostatic solitary waves are observed in various regions of the magnetosphere. The Geotail spacecraft observation has shown that these solitary waves are associated with high energy non-thermal electrons flowing along the magnetic field. The solitary structures are generated as a result of a long time evolution of coherent nonlinear trapping of electrons as found in bump-on-tail, bi-stream and Buneman instabilities. It is noted that these solitary waves can be generated at distant regions far away from the spacecraft locations, because these trapped electrons, or electron holes, are drifting much faster than the local thermal plasmas. Some of the solitary waves are accompanied by perpendicular electric fields indicating that two-or three-dimensional potential structures are passing by the spacecraft. Depending on the local plasma parameters, these multi-dimensional solitary structures couple with perpendicular modes such as electrostatic whistler modes and lower-hybrid modes. In a long time evolution, these perpendicular modes are dissipated via self-organization of small solitary potentials, leading to formation of one-dimensional potential troughs as observed in the deep magnetotail. The above dissipative small-scale processes are reproduced in particle simulations, and they can be used for diagnostics of electron dynamics from spacecraft observation of multi-dimensional solitary waves in various regions of the magnetosphere. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Upper Silurian–Middle Devonian radiolarian zones of the Yokokurayama and Konomori areas in the Kurosegawa Belt, Southwest Japan: Reply     

Masaki Umeda 《Island Arc》1999,8(4):538-538

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