Atmospheric gravity waves identified by ground-based observations of the intensity and rotational temperature of OH airglow     

Hidehiko Suzuki  Kazuo Shiokawa  Masaki Tsutsumi  Takuji Nakamura  Makoto Taguchi 《Polar Science》2008,2(1):1-8

Spectroscopic observations of OH airglow undertaken on May 2, 2006 at Uji, Japan reveal variations in intensity and rotational temperature related to the passage of an atmospheric gravity wave. The variations exhibit a period of approximately 1 h and magnitudes of 2–6% in intensity and 0.5–2% in rotational temperature. The vertical wavelength and intrinsic frequency of the atmospheric gravity wave were determined from the horizontal wavelength derived by an OH airglow imager, the background horizontal wind velocity obtained by the middle and upper atmosphere (MU) radar, and the dispersion relationship. The observed variations are consistent with the values calculated using the model of Liu, A.Z., Swenson, G.R. [2003. A modeling study of O₂ and OH airglow perturbations induced by atmospheric gravity waves. J. Geophys. Res. 108 (No. D4), 4151. doi:10.1029/2002JD002474].  相似文献   

An ‘Effective’ Involvement of Indigenous People in Environmental Impact Assessment: the cultural impact assessment of the Saru River Region,Japan     

Naohiro Nakamura 《The Australian geographer》2008,39(4):427-444

The Cultural Impact Assessment of the Saru River Region represents the first time that a site investigation was implemented in Japan in order to preserve an ethnic culture in relation to the construction of a dam. One of the project's basic concepts was to get local residents, especially those of Ainu ethnicity, to participate in the investigation. Existing case studies of environmental impact assessment have argued that the assessment has failed to sufficiently involve Indigenous people in its process and has largely failed to incorporate Indigenous knowledge, cultural values, and voices into its processes and outcomes. Also, intangible aspects of Indigenous cultural heritage have not been protected. In the Cultural Impact Assessment of the Saru River Region, the Final Report was released in 2006 and significantly included the 3 year investigation of input by local residents. In this sense, this assessment succeeded in effectively involving Indigenous people in its process and in reflecting their cultural values in its results. The more important issue is, however, how these results were included in the final outcomes. If Indigenous people have no power over final decision making, their involvement is not effective. This paper analyses the significance and unresolved problems involved in this overall assessment process.  相似文献   

Two extraterrestrial dust horizons found in the Dome Fuji ice core,East Antarctica     

Keiji Misawa  Mika Kohno  Takayuki Tomiyama  Takaaki Noguchi  Tomoki Nakamura  Keisuke Nagao  Takashi Mikouchi  Kunihiko Nishiizumi 《Earth and Planetary Science Letters》2010,289(1-2):287-297

Two silicate-rich dust layers were found in the Dome Fuji ice core in East Antarctica, at Marine Isotope Stages 12 and 13. Morphologies, textures, and chemical compositions of constituent particles reveal that they are high-temperature melting products and are of extraterrestrial origin. Because similar layers were found ～ 2000 km east of Dome Fuji, at EPICA (European Project for Ice Coring in Antarctica)-Dome C, particles must have rained down over a wide area 434 and 481 ka. The strewn fields occurred over an area of at least 3 × 10⁶ km². Chemical compositions of constituent phases and oxygen isotopic composition of olivines suggest that the upper dust layer was produced by a high-temperature interaction between silicate-rich melt and water vapor due to an impact explosion or an aerial burst of a chondritic meteoroid on the inland East Antarctic ice sheet. An estimated total mass of the impactor, on the basis of particle flux and distribution area, is at least 3 × 10⁹ kg. A possible parent material of the lower dust layer is a fragment of friable primitive asteroid or comet. A hypervelocity impact of asteroidal/cometary material on the upper atmosphere and an explosion might have produced aggregates of sub-μm to μm-sized spherules. Total mass of the parent material of the lower layer must exceed 1 × 10⁹ kg. The two extraterrestrial horizons, each a few millimeters in thickness, represent regional or global meteoritic events not identified previously in the Southern Hemisphere.  相似文献   

Concentrations of 137Cs, 90Sr, 108m Ag, 239+240 Pu and atom ratio of 240Pu/239Pu in tanner crabs, Chionoecetes japonicus and Chionoecetes opilio collected around Japan     

Morita T  Ohtsuka Y  Fujimoto K  Minamisako Y  Iida R  Nakamura M  Kayama T 《Marine pollution bulletin》2010,60(12):2311-2322

The anthropogenic radionuclides, ¹³⁷Cs, ⁹⁰Sr, ^108mAg, ^239+240Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996–2007. There was no increase in the concentrations of these radionuclides and no large variation of the atom ratio of ²⁴⁰Pu/²³⁹Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher atom ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentration of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentration of radionuclides with sampling depth would depend on the concentration in the seawater and diet.  相似文献   

Holocene paleolimnological changes in Lake Skallen Oike in the Syowa Station area of Antarctica inferred from organic components in a sediment core (Sk4C-02)     

Genki I. Matsumoto  Yukinori Tani  Koji Seto  Tomoko Tazawa  Masumi Yamamuro  Takahiro Watanabe  Toshio Nakamura  Tetsuo Takemura  Satoshi Imura  Hiroshi Kanda 《Journal of Paleolimnology》2010,44(2):677-693

Antarctic climate changes influence environmental changes at both regional and local scales. Here we report Holocene paleolimnological changes in lake sediment core Sk4C-02 (length 378.0 cm) from Lake Skallen Oike in the Soya Kaigan region of East Antarctica inferred from analyses of sedimentary facies, a range of organic components, isotope ratios of organic carbon and nitrogen, and carbon-14 dating by Tandetron accelerator mass spectrometry. The sediment core was composed of clayish mud (378.0–152.5 cm) overlain by organic sediments (152.5 cm-surface). The age of the surface and the core bottom were 150 (AD1950-1640) and ca. 7,030 ± 73 calibrated years before present (cal BP), respectively, and the mean sedimentation rate was estimated to be 0.55 mm/year. Multi-proxy analyses revealed that the principal environmental change in the core is a transition from marine to lacustrine environments which occurred at a depth of 152.5 cm (ca. 3,590 cal BP). This was caused by relative sea level change brought about by ongoing retreat of glaciers during the mid-Holocene warming of Antarctica, and ongoing isostatic uplift which outpaced changes in global (eustatic) sea level. The mean isostatic uplift rate was calculated to be 2.8 mm/year. The coastal marine period (378.0–152.5 cm, ca. 7,030–3,590 cal BP) was characterized by low biological production with the predominance of diatoms. During the transition period from marine to freshwater conditions (152.5-approximately 135 cm, ca. 3,590–3,290 cal BP) the lake was stratified with marine water overlain by freshwater, with a chemocline and an anoxic (sulfidic) layer in the bottom of the photic zone. Green sulfur bacteria and Cryptophyta were the major photosynthetic organisms. The Cryptophyta appeared to be tolerant of the moderate salinity and stratified water conditions. The lacustrine period (approximately 135 cm-surface, ca. 3,290 cal BP-present) was characterized by high biological production by green algae (e.g. Comarium clepsydra and Oedegonium spp.) with some contributions from cyanobacteria and diatoms. Biological production during this period was 8.7 times higher than during the coastal marine period.  相似文献   

Large-amplitude internal waves observed in the Kruzenshtern Strait of the Kuril Island Chain and possible water transport and mixing     

Tomohiro Nakamura  Yasuhiro Kawasaki  Tokihiro Kono  Toshiyuki Awaji 《Continental Shelf Research》2010

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Determination of Ge, As, Se and Te in Silicate Samples Using Isotope Dilution-Internal Standardisation Octopole Reaction Cell ICP-QMS by Normal Sample Nebulisation     

Akio Makishima  Eizo Nakamura 《Geostandards and Geoanalytical Research》2009,33(3):369-384

A method for the determination of Ge, As, Se and Te in silicate samples using isotope dilution-internal standardisation (ID-IS) octopole reaction cell (ORC) ICP-QMS by normal sample nebulisation was developed. The method does not involve either hydride generation or ion exchange. Germanium, Se and Te were determined by isotope dilution (ID), and As was determined by ID-IS. A silicate sample with an added Ge-Se-Te spike was digested with an HF-HNO₃-HBr mixture, dried, re-dissolved with HF and the supernatant liquid was directly aspirated into an ORC-ICP-QMS instrument with He or H₂ gas. No matrix effects were observed down to a dilution factor (DF) of ∼ 70 for Ge, Se and Te and DF of ∼ 1000 for As, which resulted in 3s detection limits in silicates of 2, 1, 0.1 and 4 ng g⁻¹, respectively. Advantages of the method are the simple sample introduction as well as a capability of determining S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by ID-IS-ICP-QMS/SFMS from the same solution. Furthermore, the total sample solution consumption was only 0.253 ml with DF = 2000. Therefore, only a 0.13 mg test portion was required. To demonstrate the applicability of this technique, Ge, As, Se and Te in eight silicate reference materials were determined, as well as S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta in four carbonaceous chondrites.  相似文献   

Late Pleistocene and Holocene vegetation and climate records from Lake Kotokel, central Baikal region     

Koji Shichi  Hikaru Takahara  Sergey K. Krivonogov  Elena V. Bezrukova  Kenji Kashiwaya  Akihide Takehara  Toshio Nakamura 《Quaternary International》2009,205(1-2):98

Climatically driven Late Pleistocene and Holocene vegetation changes were reconstructed based on pollen records from the sediments of Lake Kotokel and Cheremushka Bog, located on the eastern shore of Lake Baikal. The described paleoenvironmental record has higher resolution than records collected from Lake Baikal and unites individual events identified in prior studies of bottom and onshore cores. Remarkable shifts in landscapes and expansions of index plants are as follows. Forest tundra and/or forest steppe landscape with birch, spruce, Artemisia, and Poaceae prevailed at ca. 50–25 ¹⁴C kyr BP. Tundra and/or steppe vegetation dominated by Artemisia and Poaceae was typical for the Last Glacial Maximum. The expansion of shrub birch and willow occurred at ca. 15.5 ¹⁴C kyr BP. Two peaks of spruce expansion at ca. 47.5–42.4 ¹⁴C kyr BP (Karginian time) and at ca. 14.5–13 ka (Bølling-Allerød warm intervals) suggest that the condition were more humid than today. A slight increase in Artemisia at ca. 11–10.5 ¹⁴C kyr BP (13–12 ka) was indicative of the Younger Dryas event. An expansion of birch forests with fir at ca. 12–6.4 ka suggests higher humidity. The currently dominant Scots and Siberian pine forests with birch expanded since 6.4 ka.  相似文献   

Stable carbon isotope behaviour of natural seepage of deep underground C-rich methane detected along a fault zone and adsorbed in mudstone: Tokyo Bay area,Japan     

E. Nakata  S. Tanaka  H. Suenaga  Y. Mahara  T. Nakamura  K. Nakagawa  T. Ohta 《Applied Geochemistry》2012

Gas was sampled regionally, including by drilling into faults, in the South Kanto gas-field around Tokyo Bay, Japan. Gas samples were collected from cores in a gas sampling container immediately after drilling. A value of δ¹³C₁ = −44.3‰ was obtained for gas in the container and δ¹³C₁ = −36.3‰ for seeping gas in a fault zone. However, typical CH₄ in this dissolved-in-water gas-field is mainly depleted in ¹³C, and δ¹³C₁ values range from −66‰ to −68‰ owing to microbial degradation of organic material. ¹³C-rich CH₄ is so far uncommon in the South Kanto gas-field. Seepages were observed from the surface along the north–south fault zone. The natural gas is stored below the sandstone layer by impermeable mudstone underlying the boundary at a depth of 30 m. Gas seepages were not observed below a depth of 40 m. Gas rises along the fault zone dissolved-in-groundwater up to the shallow region and then separates from the groundwater. ¹³C-rich CH₄ (adsorbed CH₄) was found to have desorbed from drilled mudstone core samples taken at depths of 1400–1900 m in the main gas-production strata. Similarly, ¹³C-rich CH₄ was found in black shale overlying the oceanic crust forming part of a sedimentary accretionary prism underling the Tokyo region. It also appears in the spring-water of spa wells, originating at a depth of 1200–1500 m along a tectonic line. Methane generated by microbial degradation of organic material through CO₂ reduction in the South Kanto gas-field mainly originates as biogenic gas mixed with a small amount of ¹³C-rich CH₄, derived from thermogenic gas without oil components in strata. It is assumed that ¹²C-rich CH₄ is easily detached from core or pore water through gas production, whereas ¹³C-rich CH₄ is strongly adsorbed on the surfaces of particles. The ¹³C-rich CH₄ rises along the major tectonic line or up the 50 m wide normal fault zone from relatively deep sources in the Kanto region.  相似文献   

Correlation of large displacement drained shear strength of landslide soils measured by direct shear and ring shear devices   总被引：2，自引：0，他引：2  

Shriwantha Buddhi Vithana  Shinya Nakamura  Seiichi Gibo  Anshun Yoshinaga  Sho Kimura 《Landslides》2012,9(3):305-314

Based on a laboratory study of drained direct shear tests of remoulded, pre-cut and polished specimens and drained ring shear tests of uncut and remoulded specimens of slip surface materials of five landslide soils, significant correlations of the mobilized shear strength parameters, cohesion (c, c _r) and internal friction angle (Φ, Φ_r), are proposed. The investigated soils consisted of the slip surface material belonging to tuffaceous clay, mudstone, loess and siltstone. Most of the previous studies on residual shear strength measured by reversal direct shear and ring shear devices have obtained significantly different results using the two devices, even when pre-cut and polished specimens were used in the direct shear device. In this study, the residual shear strength values of remoulded specimens measured by a ring shear device are shown to significantly correlate with the drained large displacement shear strength values of remoulded specimens, which were measured using pre-cut and polished specimens in a direct shear device. The correlation between the cohesion measured in the two shear devices is expressed by the linear relationship, $ {c_{\text{r}}} = 0.{7394}c - {6}.{6857} $ , while the correlation between the friction angle measured in the two devices is expressed by the linear relationship, $ {\Phi_{\text{r}}} = {1}.0{852}\Phi - {6}.0{247} $ . The proposed linear correlations for effective cohesion (c′) and effective friction angle (Φ′) have yielded significant coefficients of determination within an effective normal stress range of 30–150?kN/m².  相似文献