研究者詳細 - 角皆　潤

論文 - 角皆　潤

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Polar and neutral isopranyl glycerol ether lipids as biomarkers of archaea in near-surface sediments from the Nankai Trough 査読有り

Oba, Masahiro, Sakata, Susumu, Tsunogai, Urumu

ORGANIC GEOCHEMISTRY 37 巻 ( 12 ) 頁： 1643-1654 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

The molecular and carbon isotopic compositions of polar isopranyl glycerol ether lipids, which are direct indicators of viable archaea, and neutral isopranyl glycerol ether lipids, which are derived from polar lipids via hydrolysis, in near-surface sediments from a methane seep in the Nankai Trough (off central Japan) were investigated. Procedures for extracting, separatine and derivatizing polar and neutral ether lipids for detection using gas chromatography were first examined with one sediment sample and a cultivated methanogen. For all sediment samples, archaeol and hydroxyarchaeol were detected in both the polar and neutral ether lipid fractions. Acyclic and cyclic biphytanes were also detected in both types of lipid fractions after treatment with HI/LiAlH4 for ether cleavage and alkylation. The delta C-13 values of archaeol, sn-2-hydroxyarchaeol, and sn-3-hydroxyarchaeol in the sample from 0.82 in below the seafloor were lower than -100 parts per thousand relative to PDB, indicating that diverse living methanotrophic archaea are present in the seep sediments. Biphytanes released from polar ether lipids in the same sample were less depleted in delta C-13 (-71 parts per thousand to -36 parts per thousand). The wide range of delta C-13 values suggests that the biphytanes were derived not only from methanotrophic but also from non-methanotrophic archaea, and that the relative contributions of the methanotrophic and non-methanotrophic archaea differed, depending on the biphytane compound. The vertical profiles and delta C-13 values of the neutral ether lipids were similar to those of the intact polar ether lipids, suggesting that neutral ether lipids derived from fossil archaea in the samples had mainly been lost by the time of sampling.

DOI： 10.1016/j.orggeochem.2006.09.002

Stable isotopic compositions of methane and carbon monoxide in the Suiyo hydrothermal plume, Izu-Bonin arc: Tracers for microbial consumption/production 査読有り

Tsunogai, U, Nakagawa, F, Gamo, T, Ishibashi, J

EARTH AND PLANETARY SCIENCE LETTERS 237 巻 ( 40972 ) 頁： 326-340 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

Effluent hydrothermal water samples in and around the water column of the Suiyo seamount caldera (ca. 2 km diameter), Izu-Bonin arc, were taken to determine concentrations and stable carbon isotopic compositions (delta¹³C) of methane (CH₄) and carbon monoxide (CO) in the plume. Venting fluids on the caldera floor (ca. 1370 m depth) were also examined, using the manned submersible Shinkai 2000, to compare the chemical composition and isotopic composition of CH₄ and CO with those in the hydrothermal plume. Strong CH₄ enrichment was detected not only in the water column within the caldera, but also on those outside the caldera at the depth of ca. I 100 m, the sill depth of the caldera wall. Within the plume, we also detected significant CO enrichment. The delta¹³C of CO in the plume, however, exhibited highly C-13-depleted values (-110 parts per thousand(VPDB) to -60 parts per thousand(VPDB)) compared with those in seafloor venting hydrothermal fluids (around - 31 parts per thousand(VPDB)). Besides, the plume samples exhibited higher CO/CH₄ ratios depending on the distance from the seafloor venting site. We conclude that in situ microbial activity in the plume causes the CO enrichment in the hydrothermal plume. The present results suggest that CO enrichment in deep sea water could act as a new tracer for unidentified seafloor hydrothermal activities, especially for detecting plumes distant from venting sites, as well as for quantifying in situ microbial activity related to CO production in hydrothermal plumes.

DOI： 10.1016/j.epsl.2005.05.042

溶存メタンを指標に用いた富山湾海底湧出地下水の地球化学的研究査読有り

亀山宗彦, 角皆　潤, 蒲生俊敬, 張　勁, 鈴木麻衣, 小山裕樹

地球化学 39 巻頁： 131-140 2005年8月

An analytical system for determining delta O-17 in CO2 using continuous flow-isotope ratio MS 査読有り

Kawagucci, S, Tsunogai, U, Kudo, S, Nakagawa, F, Honda, H , Aoki, S, Nakazawa, T, Gamo, T

ANALYTICAL CHEMISTRY 77 巻 ( 14 ) 頁： 4509-4514 2005年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

We developed a simple measurement system for delta¹⁷O in nanomole quantities of CO2 using continuous flow isotope ratio mass spectrometry (CF-IRMS). The analytical system consisted of a sample injection system, a helium-purged CO2 purification line, a capillary GC, a combustion unit, and CF-IRMS. A unique feature of the system is that we use molecular CO2 to determine the isotopic compositions including delta¹⁷O. The delta¹⁷O Of CO2 in a sample is calculated from the mass ratios of both 45/44 and 46/44 of two different kinds Of CO2, which have been purified quantitatively from different aliquots of a sample. While one aliquot (rCO₂) flows into IRMS directly, the other (eCO₂) flows through a CuO unit (900 degrees C) prior to injection into IRMS, to exchange oxygen atoms in the sample CO2 molecules with those in CuO for which we can assume Delta¹⁷O = 0. In our system, we introduce both rCO₂ and eCO₂ alternately to IRMS repeatedly by using an automatic multianalytical system to improve analytical precision statistically. The standard deviation of 0.35 parts per thousand for Delta¹⁷O can be realized using as little as 8.7 nmol CO2 in a similar to 3-h analysis. Based on this system, we have quantified delta¹⁷O in the stratospheric CO2 over Japan.

DOI： 10.1021/ac050266u

海底熱水活動地帯の化学環境を明らかにする試み招待有り査読有り

石橋純一郎, 中村光一, 岡村慶, 下島公紀, 土岐知弘, 角皆　潤

海の研究 14 巻 ( 2 ) 頁： 251-266 2005年3月

記述言語：日本語

海底熱水活動地帯は高温で還元的な熱水と低温で酸化的な海水が混合する場である。熱水活動地帯の生態系機能を研究するうえで, 場所ごとに化学環境を明らかにしていくことは, 最も基本的な解析手法となる。近年, このような目的を目指した試料採取法の工夫がさかんに行なわれている。また, 試料採取と分析に頼る従来の研究を打破する手法として, 現場化学分析や化学センサーなどの技術を深海底で実用化して, さらに連続観測を行なうことも試みられている。アーキアン・パーク計画では, 化学環境の時空間変動を明らかにすることを目的として, 新しい発想に基づく様々な機器が開発されてきた。その結果, 水曜海山で行なわれた一連の研究から, この熱水地帯の化学環境がこの海域特有の強い底層流の時間変動と相関を持って変動していたことが示された。

化学トレーサーを用いた水曜海山熱水プルーム中における微生物活動の定量化招待有り査読有り

角皆　潤, 中川書子, 岡村　慶

海の研究 14 巻 ( 2 ) 頁： 279-295 2005年3月

担当区分：筆頭著者記述言語：日本語

本論文はアーキアン・パーク計画において行われた熱水プルーム中における微生物活動の解明に関する化学的調査の成果をまとめたもので, この調査によって水曜海山カルデラ内外の海水において微生物活動に関連する化学成分の濃度と一部の同位体組成の分布が定量された。また, カルデラ底に湧出する熱水の採取と分析も行なわれた。その結果, 熱水に由来する濁度異常やCH₄, Mn, Feの高濃度異常が, カルデラ内はもちろん, カルデラ外でも検出され, 熱水プルームがカルデラ壁上の鞍部を経由して外に漏出していることが判明した。また, 熱水由来のMnの約半分がカルデラ内で分解されているのに対して, CH₄は大部分が分解されずにそのまま外に漏出していることも明らかになった。さらに, 水曜海山の熱水プルームではCOも高濃度異常を示すことが明らかになったが, このCOは熱水に由来するのではなく, プルーム内部の微生物活動によって二次的に生成した可能性が高いと結論された。

A selective unsaturated hydrocarbon subtraction technique for stable carbon isotopic analysis of atmospheric methyl chloride, methyl bromide, and C(2)-C(5) saturated hydrocarbons using continuous-flow isotope ratio mass spectrometry 査読有り

Komatsu, DD, Tsunogai, U, Yamaguchi, J, Nakagawa, F

RAPID COMMUNICATIONS IN MASS SPECTROMETRY 19 巻 ( 4 ) 頁： 477-483 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

Using continuous-flow isotope ratio mass spectrometry, we have developed a new analytical system which enables us to determine the stable carbon isotopic composition of CH(3)Cl, CH(3)Br, and C(2)-C(5) saturated hydrocarbons in gas samples even if they contain substantial amounts of unsaturated hydrocarbons, using an I(2)O(5) reagent for their selective subtraction. The analytical precision of the delta¹³C determinations is better than 0.5parts per thousand for >300 pmolC injections and better than 5parts per thousand for 20 pmolC injections. Using the system, delta¹³C values for CH(3)Cl and CH(3)Br were found in burning exhaust that contain a substantial quantity of unsaturated hydrocarbons. CH(3)Cl and CH(3)Br measured in exhaust from burning rice plants exhibit highly ¹³C-depleted values of -56.6 +/- 1.3parts per thousand and -48.6 +/- 3.9parts per thousand, respectively, while saturated hydrocarbons exhibit delta¹³C values (-26.4 to -28.9parts per thousand) that are comparable with the total delta¹³C value of the parent material (rice plant; -28.0parts per thousand). Using the system, we can determine the delta¹³C values of methyl halides and hydrocarbons in many kinds of gas samples.

DOI： 10.1002/rcm.1795

Automobile exhaust as a source of C-13- and D-enriched atmospheric methane in urban areas 査読有り

Nakagawa, F, Tsunogai, U, Komatsu, DD, Yamada, K, Yoshida, N , Moriizumi, J, Nagamine, K, Iida, T, Ikebe, Y

ORGANIC GEOCHEMISTRY 36 巻 ( 5 ) 頁： 727-738 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The stable carbon and hydrogen isotopic compositions (delta¹³C and delta D, respectively) of methane (CH₄) in automobile exhaust were determined in order to quantify by mass balance the contribution from this source to atmospheric CH₄ in an urban area of Nagoya, Japan. Both delta¹³C and delta D values of CH₄ in automobile exhaust increased in accordance with the model year of the engine, probably as a result of isotope fractionation effects associated with oxidation over metal catalysts in the catalytic converter of modern vehicles. Thus, CH₄ emissions from recent automobiles exhibit conspicuous C-13 and D enrichment compared to the flux from other major anthropogenic sources, such as natural gas leakage, landfills and rice paddies. Using average delta¹³C and delta D CH₄ values estimated for local sources, automobile exhaust in Nagoya, Japan, was determined to contribute significant amounts (up to 30 %) of CH₄ to the troposphere in the study area.

DOI： 10.1016/j.orggeochem.2005.01.003

Characterization of C-1-metabolizing prokaryotic communities in methane seep habitats at the Kuroshima Knoll, southern Ryukyu arc, by analyzing pmoA, mmoX, mxaF, mcrA, and 16S rRNA genes 査読有り

Inagaki, F, Tsunogai, U, Suzuki, M, Kosaka, A, Machiyama, H , Takai, K, Nunoura, T, Nealson, KH, Horikoshi, K

APPLIED AND ENVIRONMENTAL MICROBIOLOGY 70 巻 ( 12 ) 頁： 7445-7455 2004年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Increasing levels Of CO₂ in the atmosphere are expected to cause climatic change with negative effects on the earth's ecosystems and human society. Consequently, a variety of CO₂ disposal options are discussed, including injection into the deep ocean. Because the dissolution Of CO₂ in seawater will decrease ambient pH considerably, negative consequences for deep-water ecosystems have been predicted. Hence, ecosystems associated with natural CO₂ reservoirs in the deep sea, and the dynamics of gaseous, liquid, and solid CO₂ in such environments, are of great interest to science and society. We report here a biogeochemical and microbiological characterization of a microbial community inhabiting deep-sea sediments overlying a natural CO₂ lake at the Yonaguni Knoll IV hydrothermal field, southern Okinawa Trough. We found high abundances (> 10(9) CM(-3)) of microbial cells in sediment pavements above the CO₂ lake, decreasing to strikingly low cell numbers (107 CM-3) at the liquid CO₂/CO₂-hydrate interface. The key groups in these sediments were as follows: (i) the anaerobic methanotrophic archaea ANME-2c and the Eel-2 group of Deltaproteobacteria and (ii) sulfur-metabolizing chemolithotrophs within the Gamma- and Epsilonproteobacteria. The detection of functional genes related to one-carbon assimilation and the presence of highly ¹³C-depleted archaeal and bacterial lipid biomarkers suggest that microorganisms assimilating CO₂ and/or CH₄ dominate the liquid CO₂ and CO₂-hydrate-bearing sediments. Clearly, the Yonaguni Knoll is an exceptional natural laboratory for the study of consequences of CO₂ disposal as well as of natural CO₂ reservoirs as potential microbial habitats on early Earth and other celestial bodies.

DOI： 10.1128/AEM.70.12.7445-7455.2004

Detection of low-chloride fluids beneath a cold seep field on the Nankai accretionary wedge off Kumano, south of Japan 査読有り

Toki, T, Tsunogai, U, Gamo, T, Kuramoto, S, Ashi, J

EARTH AND PLANETARY SCIENCE LETTERS 228 巻 ( 40910 ) 頁： 37-47 2004年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Chemical and isotopic characteristics were determined for interstitial waters extracted from surface sediments in and around dense biological communities on the seafloor of the Nankai accretionary prism off Kumano, south of Japan. We found the following unique features when compared with usual interstitial water samples of normal seafloor in those of samples from bacterial mats on the Oomine Ridge, one of the outer ridge in the Nankai accretionary prism: (1) significant depletion of chloride concentration (maximum 10% depletion from bottom seawater), (2) high concentrations of CH₄ and SigmaCO₂ (more than 660 mumol/kg and 60 mmol/kg, respectively), (3) sulfate depletion (more than 90% depletion compared to bottom seawater), and (4) deltaDH₂O and delta(18)O(H2O) depletion [more than 4parts per thousand and 0.7parts per thousand depletion, respectively, compared to standard mean ocean water (SMOW)]. The highest CH₄ value among these samples was comparable to the highest value so far reported at one of the most active seep areas in the Nankai Trough, suggesting that these sites should also be regarded as one of the most active seep sites in the Nankai Trough. The chemical compositions of the samples taken from the Oomine Ridge strongly suggest that the fluid originates not from normal sediment-seawater interaction at the sediment surface of hemipelagic environments, but from active seepage of fluids that are rich in CH₄ and SigmaCO₂, depleted in Cl- and SO42-, and low in deltaD(H2O) and delta(18)O(H2O) compared to normal seawater. Values for the carbon isotopic composition (delta¹³C(CH₄)) of the dissolved methane in the interstitial fluid [less than -70parts per thousand PeeDee Belemnite (PDB)] and for the C2H6/CH₄ ratio (less than 10(-3)) suggest that the methane originates from microbial production in a relatively shallow layer of sediment, not from the deep sedimentary layer of higher temperature than 60 degreesC at the depthof more than 300 m below the seafloor. The Cl-=0 mmol/kg extrapolated end-member deltaD(H2O) and delta(18)O(H2O) values of low-chloride fluids were -46+7parts per thousand and -6.3+0.7parts per thousand SMOW, respectively, suggesting that land-derived groundwater could be one of the possible sources for the low-Cl- fluids. Depth profiles of chloride concentrations of interstitial fluids show the heterogeneity of end members ad upward sluid velocities suggest active fluid seepage on the Oomine Ridge seems to be a localized phenomenon. Assuming steady-state emission of fluid from the cold seep vent, upward fluid flow velocities from the seeping vent are estimated to be 40-200 cm year(-1), comparable to the previously reported values within the bacterial mats in Nankai Trough accretionary wedge. Development of bacterial mat might favor slower advection, which might allow longer time for diagenetic reactions in the vent conduits, and consequently, carry more reductive compounds in the fluids.

DOI： 10.1016/j.epsl.2004.09.007

Geochemical and microbiological evidence for a hydrogen-based, hyperthermophilic subsurface lithoautotrophic microbial ecosystem (HyperSLiME) beneath an active deep-sea hydrothermal field 査読有り

Takai, K, Gamo, T, Tsunogai, U, Nakayama, N, Hirayama, H, Nealson, KH, Horikoshi, K

EXTREMOPHILES 8 巻 ( 4 ) 頁： 269-282 2004年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

Subsurface microbial communities supported by geologically and abiologically derived hydrogen and carbon dioxide from the Earth's interior are of great interest, not only with regard to the nature of primitive life on Earth, but as potential analogs for extraterrestrial life. Here, for the first time, we present geochemical and microbiological evidence pointing to the existence of hyperthermophilic subsurface lithoautotrophic microbial ecosystem (HyperSLiME) dominated by hyperthermophilic methanogens beneath an active deep-sea hydrothermal field in the Central Indian Ridge. Geochemical and isotopic analyses of gaseous components in the hydrothermal fluids revealed heterogeneity of both concentration and carbon isotopic compositions of methane between the main hydrothermal vent (0.08 mM and -13.8parts per thousand PDB, respectively) and the adjacent divergent vent site (0.2 mM and -18.5parts per thousand PDB, respectively), representing potential subsurface microbial methanogenesis, at least in the divergent vent emitting more C-13-depleted methane. Extremely high abundance of magmatic energy sources such as hydrogen (2.5 mM) in the fluids also encourages a hydrogen-based, lithoautotrophic microbial activity. Both cultivation and cultivation-independent molecular analyses suggested the predominance of Methanococcales members in the superheated hydrothermal emissions and chimney interiors along with the other major microbial components of Thermococcales members. These results imply that a HyperSLiME, consisting of methanogens and fermenters, occurs in this tectonically active subsurface zone, strongly supporting the existence of hydrogen-driven subsurface microbial communities.

DOI： 10.1007/s00792-004-0386-3

Stable isotopic compositions and fractionations of carbon monoxide at coastal and open ocean stations in the Pacific 査読有り

Nakagawa, F, Tsunogai, U, Gamo, T, Yoshida, N

JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 109 巻 ( C6 ) 2004年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

Included in this report are the results of the first isotopic studies of seawater-dissolved carbon monoxide ( CO). Large variations in both carbon and oxygen isotopic compositions (delta¹³C: -44.7 similar to -21.1parts per thousand PDB, and delta(18)O: + 8.7 similar to + 32.9parts per thousandSMOW) were observed in seawater-dissolved CO due to the combination of isotopically light CO production in seawater and the enrichment of heavy isotopes during the microbial consumption of CO. Compared with the total delta¹³C value of dissolved organic matter (DOM), the isotopic compositions of the photochemically produced CO in seawater are depleted in C-13 by more than 20parts per thousand, probably due to large fractionation processes during the photochemical production of CO from DOM. In addition, the isotopic fractionation factors resulting from the microbial oxidation of CO in seawater were estimated to be 1.005 +/- 0.002 and 1.006 +/- 0.002 for carbon (alpha(c)) and oxygen (alpha(o)) based on the incubation experiments. By calculating the weighted mean of the isotopic composition of CO according to the CO concentration observed in surface seawater, the mean delta¹³C and delta(18)O for CO emitted from the oceans were estimated to be -40parts per thousand PDB and + 15parts per thousand SMOW, respectively. Oceanic CO is a unique source of C-13 and O-18-depleted CO relative to that of fossil fuel combustion and biomass burning, which will help us create a better isotopic mass balance for both global and local CO budget.

DOI： 10.1029/2001JC001108

Geophysical and geochemical observations on actively seeping hydrocarbon gases on the south-eastern Yellow Sea continental shelf 査読有り

Jeong, KS, Cho, JH, Kim, SR, Hyun, S, Tsunogai, U

GEO-MARINE LETTERS 24 巻 ( 1 ) 頁： 53-62 2004年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

In the southeastern Yellow Sea, active seepage of hydrocarbon gases has been observed by high-resolution (3.5 kHz) seismic profiling both in 1987 and 2001, occurring through a large number of plumes from the topmost pre-Holocene sedimentary layer. It is strong enough to compensate for current speed, extending vertically up to the sea surface. The gas seepage often appears to be explosive to form craters and diapirs, although pockmarks are rare due to the redistribution of mobile palimpsest sands. In core-top seawater and sediments, the gases are characterized by high amounts of C-2, homogenous delta¹³C(1) values and a large difference (19.7parts per thousand on average) between delta¹³C(1) (-55.2 to -53.6parts per thousand PDB) and delta¹³C(2) (-36.8 to -32.5parts per thousand PDB) values. The gases are considered to be generated with a smaller amount of C-1 at the early thermal cracking stage of labile source materials, after which the C-2 gas is enriched in C-13 by diffusion or biological alternation at the generation or accumulation site. The homogenous delta¹³C(1) values may be one of the geochemical characteristics of gases acquired at depth which are less altered in the case of rapid diffusive gas migration to the seafloor.

DOI： 10.1007/s00367-003-0164-8

Stable carbon and oxygen isotopic determination of sub-microgram quantities of CaCO₃ to analyze individual foraminiferal shells 査読有り

Ishimura, T, Tsunogai, U, Gamo, T

RAPID COMMUNICATIONS IN MASS SPECTROMETRY 18 巻 ( 23 ) 頁： 2883-2888 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

We have developed an analytical system to determine stable isotopic compositions (delta¹³C and delta¹⁸O) of sub-microgram quantities of CaCO₃ for the purpose of analyzing individual foraminiferal shells, using continuous-flow isotope ratio mass spectrometry (CF-IRMS). The system consists of a microvolume CaCO₃ decomposition tube, stainless steel CO₂ purification vacuum line with a quantity-regulating unit, helium-purged CO₂ purification line, gas chromatograph, and a CF-IRMS system. By using this system, we can determine stable carbon and oxygen isotopic compositions as low as 0.2 µg of CaCO₃, with standard deviations of +/-0.10 parts per thousand for delta¹³C and +/-0.18parts per thousand for delta¹⁸O within a 4-h reaction time and 30-min analysis period.

DOI： 10.1002/rcm.1701

Discovery of a new hydrothermal venting site in the southernmost Mariana Arc: Al-rich hydrothermal plumes and white smoker activity associated with biogenic methane 査読有り

Gamo, T, Masuda, H, Yamanaka, T, Okamura, K, Ishibashi, J , Nakayama, E, Obata, H, Shitashima, K, Nishio, Y, Hasumoto, H, Watanabe, M, Mitsuzawa, K, Seama, N, Tsunogai, U, Kouzuma, F, Sano, Y

GEOCHEMICAL JOURNAL 38 巻 ( 6 ) 頁： 527-534 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

This paper reports a series of studies leading to the discovery of a submarine hydrothermal field (called Nakayama Field) at an arc seamount (12degrees43' N, 143degrees32' E) in the southernmost part of the Mariana Trough, western Pacific Ocean. We first detected hydrothermal plumes characterized by water column anomalies of temperature, light transmission, Mn, Fe, Al, O-2, CH₄, and delta¹³C of CH₄ above the summit caldera of the seamount. Then deep-tow camera surveys confirmed the existence of hydrothermal activity inside the caldera, and an ROV dive finally discovered white smoker-type fluid venting associated with vent fauna. A high concentration of aluminum in the plume and white smoker-type emissions imply acidic hydrothermal activity similar to that observed at the DESMOS Caldera in the eastern Manus Basin, Papua New Guinea. Anomalously low delta¹³C (CH₄) of -38parts per thousand of a vent fluid sample compared to other arc hydrothermal systems along the Izu-Bonin and Mariana Arcs suggests an incorporation of biogenic methane based on a subsurface microbial ecosystem.

An updated estimation of the stable carbon and oxygen isotopic compositions of automobile CO emissions 査読有り

Tsunogai, U, Hachisu, Y, Komatsu, DD, Nakagawa, F, Gamo, T , Akiyama, K

ATMOSPHERIC ENVIRONMENT 37 巻 ( 35 ) 頁： 4901-4910 2003年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

We estimate up-to-date values of the average isotopic compositions of CO emitted from automobiles. In the estimation, we determined the isotopic compositions of CO in tail pipe exhaust for four gasoline automobiles and two diesel automobiles under varying conditions of both idling and running. While the dependence on the automobile manufacturer is little, each automobile equipped with functional catalytic converter exhibits a large temporal delta¹³C and delta(18)O variation. They tend to show C-13 and O-18 enrichment in accordance with the reduction of CO in exhaust, suggesting that the functional catalytic converter in engines enhances the delta¹³C and delta(18)O values of CO from tail pipes through a kinetic isotope effect during CO destruction. Assuming that automobiles run a modeled driving cycle, we estimated the average delta¹³C and delta(18)O of CO to be -23.8 +/- 0.8parts per thousand(PDB) and +25.3 +/- 1.0parts per thousand(SMOW), respectively, for recent gasoline automobiles, and -19.5 +/- 0.7parts per thousand(PDB) and +15.1 +/- 1.0parts per thousand(SMOW), respectively, for recent diesel automobiles. While the delta¹³C and delta(18)O values of recent gasoline automobiles coincide well with the isotopic compositions of source CO in present trunk road atmosphere estimated in this study, those are +4-+6parts per thousand (delta¹³C) and +1-+3parts per thousand (delta(18)O) higher than those reported previously and also those emitted from old, non-catalyst automobiles determined in this study. Recent improvements in functional catalytic converters have enhanced and will enhance the delta¹³C and delta(18)O values of CO from automobiles.

DOI： 10.1016/j.atmosenv.2003.08.008

潜水調査船用多連式ガスタイト海底湧水採取装置の開発査読有り

角皆　潤, 土岐知弘, 中山典子, 蒲生俊敬, 加藤博之, 金子　将

地球化学 37 巻 ( 3 ) 頁： 101-109 2003年8月

Stable isotope evidence for a putative endosymbiont-based lithotrophic Bathymodiolus sp mussel community atop a serpentine seamount 査読有り

Yamanaka, T, Mizota, C, Satake, H, Kouzuma, F, Gamo, T, Tsunogai, U, Miwa, T, Fujioka, K

GEOMICROBIOLOGY JOURNAL 20 巻 ( 3 ) 頁： 185-197 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

A putative endosymbiont-based benthic animal community composed of at least two kinds of bivalves has been found atop the South Chamorro serpentine seamount in the Mariana fore-arc, western Pacific. Multiple stable isotopic analyses ( hydrogen, carbon, nitrogen, and sulfur) were carried out on the soft tissues of an undescribed mussel species belonging to the genus Bathymodiolus. Markedly higher stable carbon (delta¹³C: -21.4 to -18.9 % vs. PDB) and lower sulfur (delta(34)S: +10.2 to +10.6 % vs. CDT) isotopic compositions of the mussel tissues suggested that they utilized both methane and sulfide as nutrient sources of carbon and sulfur. Analyses of in situ shimmering water and clayey sediment under the mussel bed supported these findings. These results strongly suggest that the mussels harbored both methanotrophic and thioautotrophic bacterial symbionts in their gills. This is the first stable isotopic evidence of a dual symbiotic Bathymodiolus sp. in the western Pacific. It is proposed that the major substrates for energy acquisition-methane and hydrogen sulfide-may be responsible for results from serpentinization in the lower crust. This abiotic process would be followed by abiotic or archaeal methane production and bacterial sulfate-reduction as evidenced by high delta¹³C value (-14.6 %) of methane in the shimmering water and low delta(34)S value (-32.3 %) of sulfides in the immediate sediments, respectively. Due to the very low organic matter content (0.5 mg C/g dry sediment) of the immediate sediment, it is further proposed that sulfate-reduction occurred using hydrogen (or possibly methane) as an electron donor. Thus, the mussel community living independently of magmatism and sedimentary organic matter is a lithotrophic animal community.

DOI： 10.1080/01490450390206674

海水中のメタンを指標に用いた三宅島周辺における火山活動調査の結果について査読有り

土岐知弘, 角皆　潤, 蒲生俊敬, 皆川昌幸

火山 48 巻 ( 1 ) 頁： 63-67 2003年

A simple method for oxygen-18 determination of milligram quantities of water using NaHCO₃ reagent 査読有り

Ijiri, A, Tsunogai, U, Gamo, T

RAPID COMMUNICATIONS IN MASS SPECTROMETRY 17 巻 ( 13 ) 頁： 1472-1478 2003年

記述言語：英語掲載種別：研究論文（学術雑誌）

This paper presents a modified H₂O-CO₂ equilibration method for stable oxygen isotopic composition (delta¹⁸O) analysis of water. This method enables rapid and simple delta¹⁸O analysis of milligram quantities of water, by employing solid reagent NaHCO₃ as the CO₂ Source, a small (0.6 mL) glass vial for the equilibration chamber, and an isotope-monitoring gas chromatography/mass spectrometry (irm-GC/MS) system for delta¹⁸O(CO₂) analysis. This method has several advantages, including simple handling for the H₂O-CO₂ equilibration (without purging and/or evacuation treatments), rapid and easy delta¹⁸O analysis of equilibrated CO₂, and highly sensitive and highly precise delta¹⁸O analysis of H₂O, using samples as small as 10 mg and with a precision of less than +/-0.12parts per thousand. The time needed to attain oxygen isotopic equilibration between CO₂ and water is also comparable (17 h for 10 mg H₂O and 10 h for 100 mg H₂O) to other previous methods using CO₂ gas for the CO₂ source. The extent of delta¹⁸O variation of sample water from its initial delta¹⁸O value due to isotope exchange with added NaHCO₃ is also discussed. It is concluded that the correction needed is negligible (less than 0.1parts per thousand) as long as the oxygen atom ratio (O-NaHCO₃/O-H₂O) is less than 3.3 +/- 10^-3 and provided the delta¹⁸O(H₂O) determination is made by comparing delta¹⁸O of CO₂ equilibrated with sample water and that equilibrated with standard water of a moderately close delta¹⁸O value, less than 30parts per thousand difference.

DOI： 10.1002/rcm.1081

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