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11.
Akihiro Hachikubo Oleg Khlystov Alexey Krylov Hirotoshi Sakagami Hirotsugu Minami Yutaka Nunokawa Satoshi Yamashita Nobuo Takahashi Hitoshi Shoji Shin’ya Nishio Masato Kida Takao Ebinuma Gennadiy Kalmychkov Jeffrey Poort 《Geo-Marine Letters》2010,30(3-4):321-329
We investigated the molecular composition (methane, ethane, and propane) and stable isotope composition (methane and ethane) of hydrate-bound gas in sediments of Lake Baikal. Hydrate-bearing sediment cores were retrieved from eight gas seep sites, located in the southern and central Baikal basins. Empirical classification of the methane stable isotopes (δ13C and δD) for all the seep sites indicated the dominant microbial origin of methane via methyl-type fermentation; however, a mixture of thermogenic and microbial gases resulted in relatively high methane δ13C signatures at two sites where ethane δ13C indicated a typical thermogenic origin. At one of the sites in the southern Baikal basin, we found gas hydrates of enclathrated microbial ethane in which 13C and deuterium were both highly depleted (mean δ13C and δD of –61.6‰ V-PDB and –285.4‰ V-SMOW, respectively). To the best of our knowledge, this is the first report of C2 δ13C–δD classification for hydrate-bound gas in either freshwater or marine environments. 相似文献
12.
Phyllosoma larvae were identified and their distribution was examined, based on the larvae in ichthyoplankton samples collected in the Japanese Eel Expedition to the spawning area of A. japonica in the western North Pacific from August 30 to September 13, 1986 (Leg. 1), and from September 22 to 25, 1986 (Leg. 2), on board the R/V Hakuho-maru. Phyllosoma larvae belonged to 3 families (Scyllaridae, Palinuridae and Synaxidae) representing 6 genera and 14 species. A total of 336 palinurid and synaxid phyllosoma larvae were collected, of which 233 larvae (about 70%) were identical with P. longipes s. l, while a total of 362 scyllarid phyllosoma larvae were collected, of which 274 larvae (about 76%) were identical with S. cultrifer. Phyllosoma larvae of P. longipes s. l and S. cultrifer showed a similar distribution to each other. The larvae were abundant in the water close to Mariana Islands, although late stage examples were abundant in waters of Luzon and eastern Taiwan. Distributions of these larvae may be related intimately with the North Equatorial Current existing along 15°N. The North Equatorial Current approaches the eastern coast of the Philippines and then separates into two branches of northward and southward flows. The northward flow contributes to generating the Kuroshio Current while the southward flow goes to generate the Mindanao Current. Judging from distributions of phyllosoma larvae in the present study, it is assumed that the larvae of the above two species may have been released in Mariana Islands and transported westward from there through the North Equatorial Current. These larvae may then be transported to eastern Taiwanese waters. 相似文献
13.
Kalmychkov G. V. Hachikubo A. Pokrovsky B. G. Minami H. Yamashita S. Khlystov O. M. 《Lithology and Mineral Resources》2020,55(6):439-444
Lithology and Mineral Resources - We studied the composition and isotopic characteristics (δ13C and δD) of hydrocarbon gases from the Kotelnikovsky, Zmeiny, and Goryachnisky hot springs... 相似文献
14.
15.
Abigail Parcasio Cid Syouhei Urushihara Tomoharu Minami Kazuhiro Norisuye Yoshiki Sohrin 《Journal of Oceanography》2011,67(6):747-764
The distribution of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater was investigated on the Bering Sea shelf (56–64°N,
165–169°W) in September 2000. The unfiltered and filtered seawater samples were used for determination of total dissolvable
(TD) and dissolved (D) metals (M), respectively. The TD-M concentrations were generally higher than in the Pacific Ocean.
TD-Cd was highest in deep water of the outer shelf domain and dominated by dissolved species. The other TD-M were highest
at stations close to the Yukon River delta and had higher fractions of labile particulate (LP) species that were obtained
as the difference between TD-M and D-M. Dissolved Al, Ni, and Cu were characterized by input from the Yukon River. Dissolved
Mn and Co showed maximums on the bottom of the coastal domain, suggesting influence of sedimentary Mn reduction. The correlations
of D-Zn, D-Cd, and macronutrients indicated their distributions were largely controlled through uptake by microorganisms and
remineralization from settling particles. All these three processes (river input, sedimentary reduction, and biogeochemical
cycle) had an influence on the distribution of D-Fe. D-Pb was fairly uniformly distributed in the study area. The stoichiometry
of D-M in the Bering Sea shelf showed enrichment of Co and Pb and depletion of Ni, Cu, Zn, and Cd compared with that in the
North Pacific. The LP-M/LP-Al ratio revealed significant enrichment of the other eight metals relative to their crustal abundance,
suggesting importance of formation of Fe–Mn oxides and adsorption of trace metals on the oxides. 相似文献
16.
Effects of structural walls on the elastic–plastic earthquake response of short- to medium-height reinforced concrete buildings were investigated. The analytical model consists of independent lumped mass systems representing walls and frames connected at each floor. The wall structure undergoes flexural as well as shear deformation and fails in shear at relatively small story drifts, the frames deforming only in shear. As a measure of structural damage, the ductility factor responses of frame structures were calculated for different combinations of base shear coefficients for the frames and walls. In buildings with relatively weak frames, the installation of structural walls did not improve the large plastic response of the frames up to the point where the walls were unfailed in shear and the ductility factors of the frame structure were suddenly reduced to a very small number. For relatively strong frames, however, the response displacements decreased gradually as the number of walls increased, whether or not the walls failed. Empirical formulas for the required base shear coefficients of the walls and frames which gave a target ductility factor response also were derived for two particular groups of accelerograms. These equations should be of practical use in designing frame-wall type buildings and in retrofitting damaged buildings. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
17.
Hirotsugu Minami Kazuya Tatsumi Akihiro Hachikubo Satoshi Yamashita Hirotoshi Sakagami Nobuo Takahashi Hitoshi Shoji Young Keun Jin Anatoly Obzhirov Nataliya Nikolaeva Alexander Derkachev 《Geo-Marine Letters》2012,32(5-6):525-534
The Sakhalin Slope Gas Hydrate Project (SSGH) is an international collaborative effort by scientists from Japan, Korea, and Russia to investigate natural gas hydrates (GHs) that have accumulated on the continental slope off Sakhalin Island, Okhotsk Sea. From 2009 to 2011, field operations of the SSGH-09, -10, and -11 projects were conducted. GH-bearing and -free sediment cores were retrieved using steel hydro- and gravity corers. The concentrations of sulfate ions in sediment pore waters were measured to investigate sulfate concentration–depth profiles. Seventeen cores showed linear depth profiles of sulfate concentrations. In contrast, eight cores and two cores showed concave-up and -down profiles plausibly explained by sudden increase and decrease in methane flux from below, respectively, presumably caused by the formation of gas hydrate adjacent to the core sampling sites. 相似文献
18.
Minami?Abe Takahiro?Nagai Michiko?Kurihara Shinya?HashimotoEmail author 《Journal of Atmospheric Chemistry》2017,74(2):157-169
Methyl halides such as methyl chloride (CH3Cl) are known to be important carriers of halogen from the ocean to the atmosphere, and the halogens they release into the stratosphere by photolysis catalyze ozone depletion. Marine phytoplankton have been reported as a source of CH3Cl, but the effects of environmental temperature on the CH3Cl production by phytoplankton have not been investigated. In this study, we investigated the effects of temperature on the production of CH3Cl in the culture of a marine diatom, Phaeodactylum tricornutum CCMP 630, incubated at 10, 15, 20, 25, and 30 °C. CH3Cl concentrations in cultured samples were determined using purge and trap gas chromatograph–mass spectrometry. Phytoplankton growth was monitored by measuring the chlorophyll a concentrations. CH3Cl production was observed for several weeks at four different temperatures ranging from 10 to 25 °C. The CH3Cl production from P. tricornutum was increased with increasing temperature from 10 to 25 °C, and the maximum production rate for CH3Cl was 0.21~0.26 μmol (g chlorophyll a)?1 d?1 at 25 °C, which was several times higher than that at 10 °C (~0.03 μmol (g chlorophyll a)?1 d?1). The Arrhenius equation was successfully used to characterize the effects of temperature on the production rates of CH3Cl in the culture of P. tricornutum. Our results suggest that water temperature directly affects CH3Cl production derived from P. tricornutum and that water temperature would be a significant factor for estimating the emissions of CH3Cl from marine environments. 相似文献
19.
Alexey A. Krylov Oleg M. Khlystov Akihiro Hachikubo Hirotsugu Minami Yutaka Nunokawa Hitoshi Shoji Tamara I. Zemskaya Lieven Naudts Tatyana V. Pogodaeva Masato Kida Gennady V. Kalmychkov Jeffrey Poort 《Geo-Marine Letters》2010,30(3-4):427-437
We report on the isotopic composition of dissolved inorganic carbon (DIC) in pore-water samples recovered by gravity coring from near-bottom sediments at gas hydrate-bearing mud volcanoes/gas flares (Malenky, Peschanka, Peschanka 2, Goloustnoe, and Irkutsk) in the Southern Basin of Lake Baikal. The δ13C values of DIC become heavier with increasing subbottom depth, and vary between ?9.5 and +21.4‰ PDB. Enrichment of DIC in 13C indicates active methane generation in anaerobic environments near the lake bottom. These data confirm our previous assumption that crystallization of carbonates (siderites) in subsurface sediments is a result of methane generation. Types of methanogenesis (microbial methyl-type fermentation versus CO2-reduction) were revealed by determining the offset of δ13C between dissolved CH4 and CO2, and also by using δ13C and δD values of dissolved methane present in the pore waters. Results show that both mechanisms are most likely responsible for methane generation at the investigated locations. 相似文献
20.
Xiaodong Lai Kazuhiro Norisuye Michi Mikata Tomoharu Minami Andrew R. Bowie Yoshiki Sohrin 《Marine Chemistry》2008,111(3-4):171-183
The distribution of dissolved (D) and acid-dissolvable (AD) Fe, Ni, Cu and Pb in the upper water column (0–300 m depth) was determined in the Australian sector of the Southern Ocean (140°E meridian) during three cruises conducted between November 2001 and March 2002. For Ni and Cu, there was no significant difference in concentration between dissolved and acid-dissolvable species. DNi and DCu showed significant (P = 0.01) positive correlations with silicate, phosphate and nitrate, reflecting their strong nutrient-type behaviour. For Fe and Pb, the acid-dissolvable concentration mostly exceeded the dissolved concentration, reflecting the importance of labile particulate species for these elements. DPb decreased between January and February in the Polar Frontal Zone and in Antarctic continental shelf water. ADPb maxima occurred in the Antarctic Zone, resulting in a maximum AD/D ratio of 7. The mean DFe concentration in the surface mixed layer was 0.3 nM in the sub-Antarctic zone, 0.4 nM in the Polar Frontal Zone, 0.5 nM in the Antarctic Zone and increased southward beyond the Antarctic Divergence and towards the continent. DFe did not show a clear temporal change in its horizontal distribution, which was in contrast to the other nutrients and trace metals. ADFe substantially increased in Antarctic continental shelf water where the AD/D ratio reached 11. The following conclusions can be drawn from these data. (1) Ni and Cu exist exclusively as dissolved species and their distributions are mainly controlled by their biogeochemical cycling, similar to those of the major nutrients. (2) Pb is dominated by particulate species. The distribution of DPb is temporally and spatially variable due to a sporadic source and strong scavenging. (3) DFe is rather a minor fraction of total Fe in Antarctic continental shelf water where shelf sediments and Antarctic sea-ice appear to be strong sources for Fe. There is substantial temporal variation in the supply of Fe to the upper water column. DFe in the mixed layer of the open Southern Ocean is maintained at low concentrations throughout summer due to uptake by phytoplankton and scavenging. 相似文献