Excess CO2 and pHexcess in the Intermediate Water Layer of the Northwestern Pacific     

Andrey Andreev  Makio Honda  Yuichiro Kumamoto  Masashi Kusakabe  Akihiko Murata 《Journal of Oceanography》2001,57(2):177-188

Excess CO₂ and pH_excess showing an increase in dissolved inorganic carbon and a decrease in pH from the beginning of the industrial epoch (middle of the 19th century) until the present time have been calculated in the intermediate water layer of the northwestern Pacific and the Okhotsk Sea. It is concluded that: (1) The Kuril Basin (Okhotsk Sea) and the Bussol' Strait areas are characterized by the greatest concentrations of excess CO₂ at isopycnal surfaces due to the processes of formation and transformation of intermediate water mass. (2) The largest difference in excess CO₂ concentration between the Okhotsk Sea and the western subarctic Pacific (about 8 µmol/kg) is found at the = 27.0. (3) The difference in excess CO₂ between the western subarctic Pacific and subtropical regions is significant only in the upper part of the intermediate water layer ( = 26.7–27.0). (4) About 10% of the excess CO₂ accumulation in the subtropical north Pacific is determined by water exchange with the subarctic Pacific and the Okhotsk Sea.  相似文献   

A numerical study of intermittent sediment concentration under breaking waves in the surf zone     

Takayuki Suzuki  Akio Okayasu  Tomoya Shibayama 《Coastal Engineering》2007

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X-ray observation of the Jovian impacts of comet Shoemaker - Levy 9     

Kentaro Terada  Hitoshi Negoro  Kiyoshi Hayashida  Shunji Kitamoto  Hiroshi Tsunemi  Hiroshi Oya  Takayuki Ono  Akira Morioka  Yuzuru Tawara  Toshifumi Mukai  Masahiro Hoshino  Toshio Terasawa 《Earth, Moon, and Planets》1994,66(1):75-81

An ASCA observation of the Jovian impact of the comet Shoemaker-Levy 9 is reported. Four impacts of H, L, Q1 and R were observed and four impacts of B, C, G, and Q2 were observed within 60 minutes after their impacts. No significant flaring of X-ray emission was observed. Upper limit X-ray fluxes of 90 % confidence level, averaged 5 minutes just after the impacts, were 2.4 × 10^–13 erg sec^–1 cm^–2, 3.5 × 10^–13 erg sec^–1 cm^–2, 1.6 × 10^–13 erg sec^–1 cm^–2 and 2.9 × 10^–13 erg sec^–1 cm^–2 for the impacts of H, L, Q1 and R, respectively, in the 0.5(0.7 for H and Q1)–10 keV energy range. However, a hint of X-ray enhancement around Jupiter from July 17 to July 19 was detected with about 2 6 × 10^–14 erg sec^–1 cm^–2 in the 0.5–10 keV energy range.  相似文献   

Estimation of the annual primary production of the lichen Cetrariella delisei in a glacier foreland in the High Arctic, Ny-Ålesund, Svalbard     

Masaki Uchida  Takayuki Nakatsubo  Hiroshi Kanda  Hiroshi Koizumi 《Polar research》2006,25(1):39-49

The fruticose lichen Cetrariella delisei is among the dominant lichen species in the deglaciated High Arctic areas of Svalbard. As part of a study of carbon cycling in the High Arctic, we aimed to estimate the primary production of lichen in a deglaciated area in Ny-Ålesund, Svalbard (79° N), by examining the effects of abiotic factors on the net photosynthesis ( Pn ) and dark respiration ( R ) rates of C. delisei . Experiments were conducted in the snow-free season of 2000 using an open-flow gas exchange system with an infrared gas analyser. Positive photosynthetic activities were observed on rainy days or soon after rainfall when the thallus water content was high, whereas photosynthetic activities dropped below the detectable limit on clear days because of the low thallus water content. Under a sufficiently high thallus water content and close to light saturation, Pn was nearly constant over a wide temperature range of 4–20 °C, while R increased with increasing temperature. We constructed a model for estimating the net primary production ( NPP ) of lichen based on the relationships between abiotic factors and the CO₂ exchange rate. The mean, minimum and maximum NPP values in the snow-free season, estimated using meteorological data obtained from 1995–2003, were 5.1, 1.0 and 8.4 g dry wt. m⁻² snow-free season⁻¹, respectively. These results suggest that NPP is highly variable and the contribution of lichen to carbon input is small compared with that of vascular plants and mosses in the study site.  相似文献   

The local structure of Ca-Na pyroxenes. I. XANES study at the Na K-edge     

Annibale Mottana  Takatoshi Murata  Ziyu Wu  Augusto Marcelli  Eleonora Paris 《Physics and Chemistry of Minerals》1997,24(7):500-509

 X-ray absorption Na K-edge spectra have been recorded on synthetic endmember jadeite and on a series of natural Ca-Na pyroxenes compositionally straddling the Jd-Di join. The C2/c members of the series are systematically different from the P2/n members. Differences can be interpreted and explained by comparing the experimental spectra with theoretical spectra. These have been calculated by the multiple-scattering formalism from the atomic positional parameters determined by single-crystal X-ray diffraction structure refinement on the same samples. In the full multiple scattering region of the spectra (1075 to 1090 eV) C-pyroxenes exhibit three features which reflect the 6-2 configuration of the O back-scattering atoms around the Na absorber located at the center of the cluster (site M2 of the jadeite structure). P-pyroxenes show more complicated spectra in which at least four (possibly five) features can be recognized; they reflect the two types of configuration (6-2 and 4-2-2) of O around Na in the two independent M2 and M21 eight-fold coordinated sites of the omphacite structure. A weak, sometimes poorly resolved peak at 1079 eV is diagnostic and discriminates C- from P-pyroxenes. The Garnet Ridge C2/c impure jadeite exhibits a spectrum which is intermediate between those of jadeite and omphacite. The Hedin-Lundqvist potential proves best for these insulating materials and allows multiple-scattering calculations agreeing well with experiments. Received: July 11, 1996/Revised, accepted: October 21, 1996  相似文献   

Diagnosis of earth-fill dams by synthesised approach of sounding and surface wave method     

Shin-ichi Nishimura  Toshifumi Shibata  Takayuki Shuku 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(4):312-319

The spatial distribution of the strength inside the earth-fill is identified by the sounding tests. In this research, the Swedish weight sounding (SWS) is employed, and the spatial high-density test is performed to identify the spatial correlation structure. Furthermore, the synthesised approach of the SWS and surface wave method, which is one of the geophysical method, is proposed to compensate the shortage of each approach. Consequently, the correlation structure of an earth-fill could be identified accurately, and the high resolution of the spatial distribution could be visualised based on the survey results.  相似文献   

A spatio-temporal three-dimensional conceptualization and simulation of Dera Ismail Khan alluvial aquifer in visual MODFLOW: a case study from Pakistan   总被引：1，自引：0，他引：1  

Anwar Qadir  Zulfiqar Ahmad  Tahseenullah Khan  Mohammad Zafar  Atwar Qadir  Mamoru Murata 《Arabian Journal of Geosciences》2016,9(2):149

Dera Ismail Khan (DIK) is situated in the Lower Indus Basin of Pakistan. The land use has been changed in the canal command area due to irrigation activities near the Indus River. To check the current status and predict the groundwater levels in the area, the unconfined aquifer has been simulated in Visual MODFLOW for a period of 35 years, i.e., from 1985 to 2020. The 2900-km² area has been modeled with a grid of 500 by 500 m and the depth set to 100 m. The aquifer in the study area has been divided vertically and laterally into three and ten zones, respectively, for the characterization. Water wells and streams were used as the sinks and hydrologic boundaries, respectively. The model was successfully calibrated in steady and the non-steady state. The simulation revealed that the whole simulation can be divided into two phases, i.e., before and after the construction of the Chashma Right Bank Canal (CRBC), whereas the results were summarized in the form of water table depth maps and groundwater budget calculations. To determine the groundwater sustainability, a conjunctive use scenario has been employed to simulate the aquifer dynamics till 2020. The simulation revealed incremental drawdowns till the end.  相似文献   

Subduction-related mafic to felsic magmatism in the Malayer–Boroujerd plutonic complex,western Iran     

Reza Deevsalar  Ryuichi Shinjo  Jean P. Liégeois  Mohammad V. Valizadeh  Jamshid Ahmadian  Hadi Yeganehfar  Mamoru Murata  Iain Neill 《Swiss Journal of Geoscience》2018,111(1-2):269-293

The Malayer–Boroujerd plutonic complex (MBPC) in western Iran, consists of a portion of a magmatic arc built by the northeast verging subduction of the Neo-Tethys plate beneath the Central Iranian Microcontinent (CIMC). Middle Jurassic-aged felsic magmatic activity in MBPC is manifested by I-type and S-type granites. The mafic rocks include gabbroic intrusions and dykes and intermediate rocks are dioritic dykes and minor intrusions, as well as mafic microgranular enclaves (MMEs). MBPC Jurassic-aged rocks exhibit arc-like geochemical signatures, as they are LILE- and LREE-enriched and HFSE- and HREE-depleted and display negative Nb–Ta anomalies. The gabbro dykes and intrusions originated from metasomatically enriched garnet-spinel lherzolite [Degree of melting (f_mel) ~ 15%] and exhibit negative Nd and positive to slightly negative ε_Hf(T) (+ 3.0 to ? 1.6). The data reveal that evolution of Middle Jurassic magmatism occurred in two stages: (1) deep mantle-crust interplay zone and (2) the shallow level upper crustal magma chamber. The geochemical and isotopic data, as well as trace element modeling, indicate the parent magma for the MBPC S-type granites are products of upper crustal greywacke (f_mel: 0.2), while I-type granites formed by partial melting of amphibolitic lower crust (f_mel: 0.25) and mixing with upper crustal greywacke melt in a shallow level magma chamber [Degree of mixing (f_mix): 0.3]. Mixing between andesitic melt leaving behind a refractory dense cumulates during partial crystallization of mantle-derived magma and lower crustal partial melt most likely produced MMEs (f_mix: 0.2). However, enriched and moderately variable ε_Nd(T) (? 3.21 to ? 4.33) and high (⁸⁷Sr/⁸⁶Sr)_i (0.7085–0.7092) in dioritic intrusions indicate that these magmas are likely experienced assimilation of upper crustal materials. The interpretations of magmatic activity in the MBPC is consistent with the role considered for mantle-derived magma as heat and mass supplier for initiation and evolution of magmatism in continental arc setting, elsewhere.  相似文献   

The Baiu in a historical period from the viewpoint of intraseasonal variations     

Akihiko M. Murata 《Climatic change》1993,23(2):169-189

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Relation between chemical composition and particle-size distribution of ores in the profile of nickeliferous laterite deposits of the Rio Tuba Mine, Philippines   总被引：1，自引：0，他引：1  

Yoshio Ogura  Katsuyuki Murata  Michio Iwai 《Chemical Geology》1987,60(1-4):259-271

Lateritic Ni ore mined in the Rio Tuba Mine, Philippines, derived from ultramafic rock by tropical intense weathering, is generally composed of two accumulated zones, an upper laterite zone and a lower saprolite zone. These two zones are very different in appearance, mineral assemblage, chemical composition, and in other ways. A transitional zone may be seen between the upper and lower zones, but it does not develop to any appreciable thickness. Although serpentine and goethite are still predominant in the constituent minerals, other clay minerals are increasing.

The transitional zone may be subdivided into three groups based on chemical composition. The behaviour of the chemical composition in this horizon indicates a complicated process of component transportation under the weathering process.

In the ore, chemical components are closely related in particle size of constituent minerals. In the laterite - transitional - saprolite sequence, a common variation range and tendency in chemical composition for each particle size can be seen. However, taking samples with the same particle size the chemical composition obviously differed, representing the characteristics of the components for each zone.

Concerning the correlation coefficient of the chemical components of each zone, a somewhat different inter-component relationship can be seen in these zones. These differences of correlation suggest the different complicated lateritized conditions under which they are formed.  相似文献