Seasonal cycle of manganese in seawater in Harima Sound     

Takayuki Shiozawa  Akira Hoshika  Osamu Takimura  Terumi Tanimoto 《Journal of Oceanography》1982,38(1):15-20

Vertical and horizontal distributions of manganese in Harima Sound (Harima Nada, Seto Inland Sea) were measured in August and December 1979. High concentrations of dissolved and particulate manganese were found in bottom waters in August, suggesting that the bottom enrichment is probably due to the diffusion of dissolved manganese out of the sediment. From measured distributions, we estimate the annual flux of manganese at the sediment-water interface to be more than 800 tons per year, if Harima Sound is a closed system for manganese.  相似文献   

Sedimentation rate and heavy metal pollution in sediments in Harima Nada (Harima Sound), Seto Inland Sea     

Akira Hoshika  Takayuki Shiozawa  Eiji Matsumoto 《Journal of Oceanography》1983,39(2):82-87

Sedimentation rates were determined with the²¹⁰Pb technique in six sediment cores from Harima Nada (Harima Sound), Seto Inland Sea. The rate of deposition varies from 0.11 g cm^–2y^–1 in the northern part to 0.33 g cm^–2 y^–1 in the southern part of the basin. A marked increase in copper and zinc content was observed above a depth in the core corresponding to about 1900 A.D. as a result of increasing human activities. Anthropogenic input of copper and zinc decreased slightly after 1970. Natural background levels of copper and zinc in the sediment in this sound are 11–16 ppm and 100–120 ppm, respectively. The total amounts of anthropogenic copper and zinc in the sediments were estimated to be 110–180g cm^–2 and 610–1,280g cm^–2, respectively. These values constitute 40–50% of the total sedimentary input of copper and zinc in the sediments since about 1900 A.D.  相似文献   

Vertical distribution of particulate manganese and iron in the Beppu Bay     

Akira Hoshika  Osamu Takimura  Takayuki Shiozawa 《Journal of Oceanography》1978,34(6):261-264

Around the thermocline, difference in the depth of the maximum concentration between particulate manganese and iron was observed above the basin located at the south-western corner of the Beppu Bay, along with the remarkable difference in pH and Eh.  相似文献   

A Numerical Study of Turbulence Statistics and the Structure of a Spatially-Developing Boundary Layer Over a Realistic Urban Geometry     

Atsushi Inagaki  Manabu Kanda  Nurul Huda Ahmad  Ayako Yagi  Naoyuki Onodera  Takayuki Aoki 《Boundary-Layer Meteorology》2017,163(2):161-177

Sonic anemometer measurements are analyzed from two primary field programs and 12 supplementary sites to examine the behaviour of the turbulent heat flux near the surface with high wind speeds in the nocturnal boundary layer. On average, large downward heat flux is found for high wind speeds for most of the sites where some stratification is maintained in spite of relatively intense vertical mixing. The stratification for high wind speeds is found to be dependent on wind direction, suggesting the importance of warm-air advection, even for locally homogenous sites. Warm-air advection is also inferred from a large imbalance of the heat budget of the air for strong winds. Shortcomings of our study are noted.  相似文献   

Mass balance of heavy metals in the seto inland sea, Japan     

Akira Hoshika  Takayuki Shiozawa  Yasushi Kitano 《Marine Chemistry》1988,24(3-4)

To discuss the geochemical and environmental behavior of heavy metals in the Seto Inland Sea, the largest semi-enclosed coastal sea in Japan, mass balances of Cu and Zn were studied by application of a simple box model using sedimentation rates and heavy metal contents of core sediments. In 1980, total sedimentary loads of Cu and Zn over the whole area of the Sea were estimated to be 630 and 3500 tons year⁻¹, respectively. Further, the sedimentary loads without (natural) and with human activities were estimated separately to be, respectively, 320 and 310 tons year⁻¹ for Cu and 1800 and 1700 tons year⁻¹ for Zn. Total inputs of Cu and Zn into the Sea, in 1980 were estimated to be 870 and 4250 tons year⁻¹ about one half of this being the result of human activities. 70% of the Cu input and 80% of the Zn input are taken into the sediments. Mean residence times of Cu and Zn in the Sea are calculated to be ≈0.3 and 0.2 years, respectively. Since these values are relatively small compared to the mean residence time of the seawater (0.9 years), Cu and Zn supplied to the Sea are considered to be accumulated rapidly in the sediments.  相似文献   

Fluid Inclusion Study of Skarns in the Maruyama Deposit, the Kamioka Mine, Central Japan   总被引：1，自引：0，他引：1  

Naoto TAKENO  Takayuki SAWAKI  Hiroyasu MURAKAMI  Kazuhiro MIYAKE 《Resource Geology》1999,49(4):233-242

Abstract: Fluid inclusions in skarn minerals in the Maruyama deposit, the Kamioka mine, central Japan were studied. Homogenization temperatures (Th) of fluid inclusions in 48 skarn minerals (hedenbergite, andradite, epidote and quartz) were measured, and gas composition of fluid inclusions in 12 skarn minerals was measured with a quadrupole mass spectrometer. The maximum Th value of primary inclusions in hedenbergite is 380C with peaks around 360C. Primary inclusions in hedenbergite near contact between skarn and limestone have slightly lower Th values and their distribution has a tendency of long trail skirt toward low temperature, which indicates ceasing of skarnization coincides with temperature decrease. Fluid inclusions in andradite and quartz in the hedenbergite skarn have lower Th values, in this order, than those in hedenbergite. CH4–detected fluid inclusions are localized around the Maruyama fault. Gas composition of the fluid inclusions indicates that fluid trapped in the hedenbergite has CO2 content less than 1 mole % and is not in equilibrium with graphite.  相似文献   

Primary productivity and solar radiation off Sanriku in May 1997     

Akihiro Shiomoto  Shinji Hashimoto  Takayuki Murakami 《Journal of Oceanography》1998,54(5):539-544

We measured the in situ primary production at four stations from the surface to 80 m off Sanriku in late May 1997. The depth-integrated daily primary production in the upper 80 m was estimated to be 391, 468, and 855 mgC m⁻²d⁻¹ in water from the Oyashio, and 336 mgC m⁻²d⁻¹ in the warm-core ring. The variation in the primary production was primarily due to the variation in phytoplankton activity (chlorophyll α-specific primary production). A combination of previous and present studies in water from the Oyashio and the warm-core ring suggested that phytoplankton activity is proportional to light intensity between 12 and 50 Ein m⁻²d⁻¹ which is close to the usual light condition (61–75 Ein m⁻²d⁻¹) off Sanriku in May and June. Light may be a limiting factor for phytoplankton off Sanriku in late spring and early summer.  相似文献   

Depositional ages and characteristics of Middle–Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia          下载免费PDF全文

Hitoshi Hasegawa  Hisao Ando  Noriko Hasebe  Niiden Ichinnorov  Tohru Ohta  Takashi Hasegawa  Masanobu Yamamoto  Gang Li  Bat‐Orshikh Erdenetsogt  Ulrich Heimhofer  Takayuki Murata  Hironori Shinya  G. Enerel  G. Oyunjargal  O. Munkhtsetseg  Noriyuki Suzuki  Tomohisa Irino  Koshi Yamamoto 《Island Arc》2018,27(3)

Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250 m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150 m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8 ±2.0 Ma and 118.5 ±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165–158 Ma of Callovian–Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7 ±2.6 cm/ky and 10.0 ±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer‐scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro‐laminae and calculated sedimentation rate, the micro‐lamination is most likely of varve origin. Both Middle–Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo‐Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian–Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.  相似文献   

Dynamic loading test and simulation analysis of full‐scale semi‐active hydraulic damper for structural control     

Naoki Niwa  Takuji Kobori  Motoichi Takahashi  Hiroshi Midorikawa  Narito Kurata  Takayuki Mizuno 《地震工程与结构动力学》2000,29(6):789-812

A semi‐active hydraulic damper (SHD) for a semi‐active damper system, which is useful for practical structural control especially for large earthquakes, has been developed. Its maximum damping force is set to 1 or 2 MN, and it is controlled by only 70 W of electric power. An SHD with a maximum damping force of 1 MN was applied to an actual building in 1998. This paper first presents the results of a dynamic loading test to confirm the control performance of the SHD. Next, an analytical model of SHDs (SHD model) is constructed with the same concept for two kinds of SHDs based on the test results. Through simulation analyses of the test results using the proposed SHD model, the dynamic characteristics of the SHD can be well represented within practical conditions. Simulation analyses are also carried out using a simple structure model with the SHD model. It is shown that this SHD model can be used to precisely evaluate the control effect of the semi‐active damper system and is useful in practical SHD design under the applied conditions. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

High precision oxygen three‐isotope analyses of anhydrous chondritic interplanetary dust particles     

Daisuke NAKASHIMA  Takayuki USHIKUBO  Michael E. ZOLENSKY  Noriko T. KITA 《Meteoritics & planetary science》2012,47(2):197-208

Abstract– Oxygen three‐isotope ratios of three anhydrous chondritic interplanetary dust particles (IDPs) were analyzed using an ion microprobe with a 2 μm small beam. The three anhydrous IDPs show Δ¹⁷O values ranging from ?5‰ to +1‰, which overlap with those of ferromagnesian silicate particles from comet Wild 2 and anhydrous porous IDPs. For the first time, internal oxygen isotope heterogeneity was resolved in two IDPs at the level of a few per mil in Δ¹⁷O values. Anhydrous IDPs are loose aggregates of fine‐grained silicates (≤3 μm in this study), with only a few coarse‐grained silicates (2–20 μm in this study). On the other hand, Wild 2 particles analyzed so far show relatively coarse‐grained (≥ few μm) igneous textures. If anhydrous IDPs represent fine‐grained particles from comets, the similar Δ¹⁷O values between anhydrous IDPs and Wild 2 particles may imply that oxygen isotope ratios in cometary crystalline silicates are similar, independent of crystal sizes and their textures. The range of Δ¹⁷O values of the three anhydrous IDPs overlaps also with that of chondrules in carbonaceous chondrites, suggesting a genetic link between cometary dust particles (Wild 2 particles and most anhydrous IDPs) and carbonaceous chondrite chondrules.  相似文献