研究者データベース

亀山 宗彦(カメヤマ ソオヒコ)
地球環境科学研究院 地球圏科学部門 化学物質循環学分野
准教授

基本情報

所属

  • 地球環境科学研究院 地球圏科学部門 化学物質循環学分野

職名

  • 准教授

学位

  • 博士(理学)(北海道大学)

ホームページURL

J-Global ID

研究キーワード

  • DMS   イソプレン   陽子移動反応-質量分析計   南大洋   温暖化   みらい   揮発性有機物(VOC)   二酸化炭素分圧   炭酸系   海洋酸性化   白鳳丸   

研究分野

  • 自然科学一般 / 宇宙惑星科学
  • 環境・農学 / 環境動態解析

職歴

  • 2015年04月 - 現在 北海道大学 地球環境科学研究科(研究院) 准教授
  • 2011年04月 - 2015年03月 北海道大学 地球環境科学研究科(研究院) 助教

学歴

  • 2004年04月 - 2007年03月   北海道大学   大学院理学研究科   地球惑星科学専攻 博士課程
  • 2002年04月 - 2004年03月   北海道大学   大学院理学研究科   地球惑星科学専攻 修士課程
  • 1998年04月 - 2002年03月   九州大学   理学部   地球惑星科学科

所属学協会

  • 日本大気化学会   米国地球物理学連合   日本海洋学会   日本地球化学会   

研究活動情報

論文

  • Jun Xia, Sohiko Kameyama, Florian Prodinger, Takashi Yoshida, Kyoung‐Ho Cho, Jinyoung Jung, Sung‐Ho Kang, Eun‐Jin Yang, Hiroyuki Ogata, Hisashi Endo
    Limnology and Oceanography 67 6 1343 - 1356 2022年06月
  • Robin Benard, Martine Lizotte, Maurice Levasseur, Michael Scarratt, Sonia Michaud, Michel Starr, Jean-Eric Tremblay, Ronald P. Kiene, Sohiko Kameyama
    ELEMENTA-SCIENCE OF THE ANTHROPOCENE 9 1 2021年04月 
    The objective of this study was to assess experimentally the potential impact of anthropogenic pH perturbation (ApHP) on concentrations of dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP), as well as processes governing the microbial cycling of sulfur compounds. A summer planktonic community from surface waters of the Lower St. Lawrence Estuary was monitored in microcosms over 12 days under three pCO(2) targets: 1 x pCO(2) (775 mu atm), 2 x pCO(2) (1,850 mu atm), and 3 x pCO(2) (2,700 mu atm). A mixed phytoplankton bloom comprised of diatoms and unidentified flagellates developed over the course of the experiment. The magnitude and timing of biomass buildup, measured by chlorophyll a concentration, changed in the 3 x pCO(2) treatment, reaching about half the peak chlorophyll a concentration measured in the 1 x pCO(2) treatment, with a 2-day lag. Doubling and tripling the pCO(2) resulted in a 15% and 40% decline in average concentrations of DMS compared to the control. Results from S-35-DMSPd uptake assays indicated that neither concentrations nor microbial scavenging efficiency of dissolved DMSP was affected by increased pCO(2). However, our results show a reduction of the mean microbial yield of DMS by 34% and 61% in the 2 x pCO(2) and 3 x pCO(2) treatments, respectively. DMS concentrations correlated positively with microbial yields of DMS (Spearman's rho = 0.65; P < 0.001), suggesting that the impact of ApHP on concentrations of DMS in diatom-dominated systems may be strongly linked with alterations of the microbial breakdown of dissolved DMSP. Findings from this study provide further empirical evidence of the sensitivity of the microbial DMSP switch under ApHP. Because even small modifications in microbial regulatory mechanisms of DMSP can elicit changes in atmospheric chemistry via dampened efflux of DMS, results from this study may contribute to a better comprehension of Earth's future climate.
  • Sakae Toyoda, Takahito Kakimoto, Kushi Kudo, Naohiro Yoshida, Daisuke Sasano, Naohiro Kosugi, Masao Ishii, Sohiko Kameyama, Mahomi Inagawa, Hisayuki Yoshikawa-Inoue, Shigeto Nishino, Akihiko Murata, Shigeyuki Ishidoya, Shinji Morimoto
    GLOBAL BIOGEOCHEMICAL CYCLES 35 4 2021年04月 
    Ocean-atmosphere gas exchange in the Arctic Ocean is sensitive to global warming because the decrease of sea-ice covered area enhances the exchange. Melting sea ice affects the vertical transport of dissolved gases. Few reports of Arctic Ocean studies have described observations of dissolved N2O or temporal variation of sea-to-atmosphere N2O flux. Therefore, production mechanisms of this greenhouse gas and the stratospheric ozone depleting gas remain unclear. We measured dissolved N2O and its isotopic signatures in the western Arctic shelf region of the Chukchi Sea and surrounding areas during September in 2014 and 2015. In the Chukchi Sea shelf, the N2O concentration was slightly higher than the value expected under sea-air equilibrium in the surface water. It increased with depth to 23 nmol kg(-1) in 2014, although it showed a vertically homogeneous distribution in 2015. Isotopocule ratios of N2O, which include N-15-site preference in the N2O molecule as well as elemental N and O isotope ratios, indicate that N2O in the Chukchi Sea shelf is a mixture of N2O produced in the bottom water and that of atmospheric origin. The isotopic signature of excess N2O (delta N-15(bulk) = -3.6 parts per thousand to -1.4 parts per thousand, delta O-18 = 61.5 parts per thousand-63.0 parts per thousand, SP = 38.7 parts per thousand-49.0 parts per thousand) suggests that it is produced by archeal or bacterial nitrification and that it is partly reduced by denitrification. Although further quantitative observations are necessary, the results confirmed that the western Arctic Ocean can act as a source of N2O to the atmosphere when sea-ice cover retreats and the pycnocline is weakened.
  • Yasunori Tohjima, Jiye Zeng, Tomoko Shirai, Yosuke Niwa, Shigeyuki Ishidoya, Fumikazu Taketani, Daisuke Sasano, Naohiro Kosugi, Sohiko Kameyama, Hisahiro Takashima, Hideki Nara, Shinji Morimoto
    POLAR SCIENCE 27 2021年03月 
    Atmospheric CH4 mole fractions were observed aboard the R/V Mirai sailing in waters off Alaska in the Arctic Ocean in September 2012-2017 to investigate the CH4 emissions from the surrounding region, especially from the East Siberian Arctic Shelf (ESAS). The synoptic-scale increases of CH4 were compared with simulated increases based on a Lagrangian Particle Dispersion Model and monthly CH4 flux maps determined by a global atmospheric inversion system. There were good agreements between the observed and simulated CH4 increases, suggesting the validity of CH4 fluxes from the surrounding areas of the cruise experiments. The CH4 emissions from the ESAS in September were further optimized in order to minimize the root mean square of the differences between the observed and simulated CH4 increases. The average (+/- 1s) of the resulting emission rates was 0.58 +/- 0.47 TgCH(4) yr(-1), which was much smaller than previously reported estimates. The individual optimized CH4 emissions varied from 0.1 +/- 0.3 to 1.3 +/- 0.4 TgCH(4) yr(-1), showing a positive correlation with the sea surface temperature and a negative correlation with the ice concentration of the ESAS area in September. These results suggest a possible enhancement of the CH4 emissions from the ESAS in a warmer future.
  • Siyuan Wang, Eric C. Apel, Rebecca H. Schwantes, Kelvin H. Bates, Daniel J. Jacob, Emily Fischer, Rebecca S. Hornbrook, Alan J. Hills, Louisa K. Emmons, Laura L. Pan, Shawn Honomichl, Simone Tilmes, Jean-Francois Lamarque, Mingxi Yang, Christa A. Marandino, Eric S. Saltzman, Warren de Bruyn, Sohiko Kameyama, Hiroshi Tanimoto, Yuko Omori, Samuel R. Hall, Kirk Ullmann, Thomas B. Ryerson, Chelsea R. Thompson, Jeff Peischl, Bruce C. Daube, Roisin Commane, Kathryn McKain, Colm Sweeney, Alexander B. Thames, David O. Miller, William H. Brune, Glenn S. Diskin, Joshua P. DiGangi, Steven C. Wofsy
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 125 15 2020年08月 
    Acetone is one of the most abundant oxygenated volatile organic compounds (VOCs) in the atmosphere. The oceans impose a strong control on atmospheric acetone, yet the oceanic fluxes of acetone remain poorly constrained. In this work, the global budget of acetone is evaluated using two global models: CAM-chem and GEOS-Chem. CAM-chem uses an online air-sea exchange framework to calculate the bidirectional oceanic acetone fluxes, which is coupled to a data-oriented machine-learning approach. The machine-learning algorithm is trained using a global suite of seawater acetone measurements. GEOS-Chem uses a fixed surface seawater concentration of acetone to calculate the oceanic fluxes. Both model simulations are compared to airborne observations from a recent global-scale, multiseasonal campaign, the NASA Atmospheric Tomography Mission (ATom). We find that both CAM-chem and GEOS-Chem capture the measured acetone vertical distributions in the remote atmosphere reasonably well. The combined observational and modeling analysis suggests that (i) the ocean strongly regulates the atmospheric budget of acetone. The tropical and subtropical oceans are mostly a net source of acetone, while the high-latitude oceans are a net sink. (ii) CMIP6 anthropogenic emission inventory may underestimate acetone and/or its precursors in the Northern Hemisphere. (iii) The MEGAN biogenic emissions model may overestimate acetone and/or its precursors, and/or the biogenic oxidation mechanisms may overestimate the acetone yields. (iv) The models consistently overestimate acetone in the upper troposphere-lower stratosphere over the Southern Ocean in austral winter. (v) Acetone contributes up to 30-40% of hydroxyl radical production in the tropical upper troposphere/lower stratosphere.Plain Language Summary Acetone is widely observed in the Earth's atmosphere, with mixing ratios ranging from parts-per-trillion levels in the stratosphere to parts-per-billion levels in polluted regions. Acetone is directly emitted from a wide variety of natural and anthropogenic sources and is also produced from the photochemical oxidation of a number of precursors. The role of the ocean is complicated; acetone is produced in the ocean from the photolysis of colored dissolved organic materials or from biological processes but is also removed via microbial uptake. Previous studies have found that the direction and magnitude of oceanic acetone fluxes vary dramatically with seasons and locations. In this work, we use a data-oriented machine-learning approach to predict the surface seawater concentration of acetone, leveraging in situ acetone measurements in the surface seawater around the globe. This machine learning-based approach shows promising potential and can be expanded to the bottom-up oceanic emissions of other climate-relevant compounds.
  • Jian-Long Li, Sohiko Kameyama, Gui-Peng Yang
    MARINE CHEMISTRY 222 2020年05月 
    Aqueous biogenic gases play an important role in the global environment. Here, we describe a novel method developed to determine trace levels of biogenic gases (isoprene and dimethyl sulfide, DMS) in situ, based on room temperature enrichment-thermal desorption. The two gases from seawater (isoprene: 630 mL; DMS: 20 mL) and the marine atmosphere (1 L) were adsorbed into a funnel-shaped quartz tube at room temperature, then thermally desorbed (358 degrees C) and introduced into a gas chromatograph-flame ionization detector (GC-FID) using a portable curie-point injector. A suitable adsorbent material (Carbopack X) was added to the adsorption tube to trap two the target compounds in a gas stream for the first time. Good reproducibility ( < 3%; < 1%), linearity (R-2 = 0.999; R-2 = 0.997), and low detection limits (0.5 pmol L-1; 0.07 nmol L-1) were obtained for isoprene and DMS, respectively. In addition, this method can be used for atmospheric isoprene and DMS quantization and involves an easier procedure than previous extraction techniques. The method was also applied for in situ seawater analysis off the coast of Hokkaido, Japan (isoprene: 27.54 +/- 0.46 pmol L-1), in the continental shelf area of the Bering Sea (isoprene: 42.55 +/- 16.24 pmol L-1; DMS: 5.20 +/- 3.29 nmol L-1), and for marine atmospheric analysis (average isoprene and DMS: 59 and 219 pptv, respectively) in the North Pacific. The results suggest that the method can be used successfully at room temperature, in place of traditional cryo-trapping techniques used to determine isoprene and DMS levels in seawater and the atmosphere.
  • Sohiko Kameyama, Maki Otomaru, Andrew McMinn, Koji Suzuki
    Journal of Phycology 2020年03月05日 [査読有り][通常論文]
  • Koji Sugie, Amane Fujiwara, Shigeto Nishino, Sohiko Kameyama, Naomi Harada
    FRONTIERS IN MARINE SCIENCE 6 2020年01月 
    The Arctic Ocean has been experiencing rapid warming, which accelerates sea ice melt. Further, the increasing area and duration of sea ice-free conditions enhance ocean uptake of CO2. We conducted two shipboard experiments in September 2015 and 2016 to examine the effects of temperature, CO2, and salinity on phytoplankton dynamics to better understand the impacts of rapid environmental changes on the Arctic ecosystem. Two temperature conditions (control: <3 and 5 degrees C above the control), two CO2 levels (control: similar to 300 and 300/450 mu atm above the control; i.e., 600/750 mu atm), and two salinity conditions (control: 29 in 2015 and 27 in 2016, and 1.4 below the control) conditions were fully factorially manipulated in eight treatments. Higher temperatures enhanced almost all phytoplankton traits in both experiments in terms of chl-a, accessory pigments and diatom biomass. The diatom diversity index decreased due to the replacement of chain-forming Thalassiosira spp. by solitary Cylindrotheca closterium or Pseudo-nitzschia spp. under higher temperature and lower salinity in combination. Higher CO2 levels significantly increased the growth of small-sized phytoplankton (<10 mu m) in both years. Decreased salinity had marginal effects but significantly increased the growth of small-sized phytoplankton under higher CO2 levels in terms of chl-a in 2015. Our results suggest that the smaller phytoplankton tend to dominate in the shelf edge region of the Chukchi Sea in the western Arctic Ocean under multiple environmental perturbations.
  • 「北極域の地球化学」特集序文
    大木淳之, 亀山宗彦
    地球化学 53 2020年01月 [査読有り][通常論文]
  • 北極域における臭素および有機硫黄化合物の生物地球化学
    亀山宗彦, 大木淳之, 野村大樹
    地球化学 2020年01月 [査読有り][通常論文]
  • Oanh Thi Ngoc Bui, Sohiko Kameyama, Yusuke Kawaguchi, Shigeto Nishino, Urumu Tsunogai, Hisayuki Yoshikawa-Inoue
    POLAR SCIENCE 22 2019年12月 
    We examined vertical profiles of methane (CH4) concentrations inside and outside of a warm-core eddy during a cruise of the R/V Mirai cruise (MR15-03 Leg. 1) in the Arctic Ocean in late summer/early fall 2015. Because a coherent mesoscale eddy is one of the possible mechanisms for transporting shelf water from the Chukchi Sea into the Canada Basin interior, we hypothesized that the warm-core eddy transported dissolved CH4 as well as nutrients and impacted the distribution of CH4. Seawater samples were therefore collected to obtain detailed vertical profiles of CH4 concentrations in the southwestern Canada Basin. We found high CH4 concentrations in bottom water on the shelf, which was located outside the warm-core eddy. The percent saturation in that water was as high as 947% of atmospheric CH4. We also found that sub-surface CH4 peaks within the radius of the maximum velocity of the eddy were broader at depth than those outside of the eddy. Lateral transport of the eddy was likely the controlling factor responsible for subsurface CH4 peaks within the warm-core eddy. Our study indicated that eddies play a crucial role in controlling and transporting CH4 laterally and vertically.
  • Oanh Thi Ngoc Bui, Kameyama Sohiko, Yoshikawa-Inoue Hisayuki, Ishii Masao, Sasano Daisuke, Uchida Hiroshi, Tsunogai Urumu
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 70 1 1 - 15 2018年08月06日 [査読有り][通常論文]
  • Yuko Omori, Hiroshi Tanimoto, Satoshi Inomata, Kohei Ikeda, Toru Iwata, Sohiko Kameyama, Mitsuo Uematsu, Toshitaka Gamo, Hiroshi Ogawa, Ken Furuya
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 122 13 7216 - 7231 2017年07月 [査読有り][通常論文]
     
    Exchange of dimethyl sulfide (DMS) between the surface ocean and the lower atmosphere was examined by using proton transfer reaction-mass spectrometry coupled with the gradient flux (PTR-MS/GF) system. We deployed the PTR-MS/GF system and observed vertical gradients of atmospheric DMS just above the sea surface in the subtropical and transitional South Pacific Ocean and the subarctic North Pacific Ocean. In total, we obtained 370 in situ profiles, and of these we used 46 data sets to calculate the sea-to-air flux of DMS. The DMS flux determined was in the range from 1.9 to 31 mu mol m(-2) d(-1) and increased with wind speed and biological activity, in reasonable accordance with previous observations in the open ocean. The gas transfer velocity of DMS derived from the PTR-MS/GF measurements was similar to either that of DMS determined by the eddy covariance technique or that of insoluble gases derived from the dual tracer experiments, depending on the observation sites located in different geographic regions. When atmospheric conditions were strongly stable during the daytime in the subtropical ocean, the PTR-MS/GF observations captured a daytime versus nighttime difference in DMS mixing ratios in the surface air overlying the ocean surface. The difference was mainly due to the sea-to-air DMS emissions and stable atmospheric conditions, thus affecting the gradient of DMS. This indicates that the DMS gradient is strongly controlled by diurnal variations in the vertical structure of the lower atmosphere above the ocean surface.
  • BUI THI NGOC OANH, 亀山 宗彦, 川口 悠介, 笹野 大輔, 石井 雅男, 西野 茂人, 小杉 如央, 角皆 潤, 吉川 久幸
    日本地球化学会年会要旨集 64 241 - 241 一般社団法人日本地球化学会 2017年 

    北極海は地球温暖化に対して最も鋭敏に応答する海域であるといわれている。メタンは温室効果をはじめとした大気環境に影響を及ぼす気体成分であり、北極域はメタンの大きなソースであることが指摘されていながら北極海での観測は十分になされていない。本研究では2015年に海洋研究開発機構の「みらい」MR15-03航海でカナダ海盆における詳細な溶存メタン分布を明らかにした。この溶存メタンの分布と海洋の暖水渦や生物学的パラメーターとの関係性について検討を行った。

  • 大森 裕子, 谷本 浩志, 猪俣 敏, 池田 恒平, 岩田 徹, 亀山 宗彦, 植松 光夫, 蒲生 俊敬, 小川 浩史, 古谷 研
    日本地球化学会年会要旨集 64 238 - 238 一般社団法人日本地球化学会 2017年 

    硫化ジメチル(DMS)は、海洋微生物によって生成され、大気中に放出されると雲形成に寄与する。そのため、地球の気候システムを理解する上で、海洋から大気へのDMSの放出量の把握は極めて重要である。近年、我々の研究グループは、オンライン質量分析計と微気象学的手法の一つである傾度法を組み合わせた海洋-大気間のフラックスの実計測法を確立した。本研究では、南北太平洋で実施した海洋-大気間のDMSフラックスの実計測の観測結果について報告する。

  • Yuko Omori, Hiroshi Tanimoto, Satoshi Inomata, Kohei Ikeda, Toru Iwata, Sohiko Kameyama, Mitsuo Uematsu, Toshitaka Gamo, Hiroshi Ogawa, Ken Furuya
    Journal of Geophysical Research 122 13 7216 - 7231 2017年 [査読有り][通常論文]
     
    Exchange of dimethyl sulfide (DMS) between the surface ocean and the lower atmosphere was examined by using proton transfer reaction-mass spectrometry coupled with the gradient flux (PTR-MS/GF) system. We deployed the PTR-MS/GF system and observed vertical gradients of atmospheric DMS just above the sea surface in the subtropical and transitional South Pacific Ocean and the subarctic North Pacific Ocean. In total, we obtained 370 in situ profiles, and of these we used 46 data sets to calculate the sea-to-air flux of DMS. The DMS flux determined was in the range from 1.9 to 31 µmol m-2 d-1 and increased with wind speed and biological activity, in reasonable accordance with previous observations in the open ocean. The gas transfer velocity of DMS derived from the PTR-MS/GF measurements was similar to either that of DMS determined by the eddy covariance technique or that of insoluble gases derived from the dual tracer experiments, depending on the observation sites located in different geographic regions. When atmospheric conditions were strongly stable during the daytime in the subtropical ocean, the PTR-MS/GF observations captured a daytime versus nighttime difference in DMS mixing ratios in the surface air overlying the ocean surface. The difference was mainly due to the sea-to-air DMS emissions and stable atmospheric conditions, thus affecting the gradient of DMS. This indicates that the DMS gradient is strongly controlled by diurnal variations in the vertical structure of the lower atmosphere above the ocean surface.
  • 亀山 宗彦, 谷本 浩志, 猪俣 敏, 大森 裕子, 笹野 大輔, 石井 雅男, ブイ ティ オック オアン, 吉川 久幸
    日本地球化学会年会要旨集 63 93 - 93 日本地球化学会 2016年 

    大気微量気体成分の動態を考える上で、海洋表層は大気-海洋間気体交換により重要な放出源・吸収源となりうる。近年、大気化学の分野で気相中の微量気体を連続的に測定する技術を海洋表層水中の微量気体の連続測定に応用する試みが始まっている。我々は対象化学種のイオン化に化学イオン化の一つである陽子移動反応を用いた、気相中のVOCのリアルタイム計測が可能な技術である陽子移動反応質量分析計(PTR-MS)を大気海洋境界層のVOC測定に応用した研究を行っている。また、最近では赤外吸収を行う気体種に高い感度を持つキャビティリングダウン分光法(CRDS)を用いた溶存メタンの高分解能測定にも取り組んでいる。本発表ではこれらの新規実験系を用いた研究の概要と近年の具体的な研究例を紹介する。

  • Yingshun Cui, Shotaro Suzuki, Yuko Omori, Shu-Kuan Wong, Minoru Ijichi, Ryo Kaneko, Sohiko Kameyama, Hiroshi Tanimoto, Koji Hamasaki
    APPLIED AND ENVIRONMENTAL MICROBIOLOGY 81 12 4184 - 4194 2015年06月 [査読有り][通常論文]
     
    Dimethylsulfoniopropionate (DMSP) is mainly produced by marine phytoplankton but is released into the microbial food web and degraded by marine bacteria to dimethyl sulfide (DMS) and other products. To reveal the abundance and distribution of bacterial DMSP degradation genes and the corresponding bacterial communities in relation to DMS and DMSP concentrations in seawater, we collected surface seawater samples from DMS hot spot sites during a cruise across the Pacific Ocean. We analyzed the genes encoding DMSP lyase (dddP) and DMSP demethylase (dmdA), which are responsible for the transformation of DMSP to DMS and DMSP assimilation, respectively. The averaged abundance (+/- standard deviation) of these DMSP degradation genes relative to that of the 16S rRNA genes was 33% +/- 12%. The abundances of these genes showed large spatial variations. dddP genes showed more variation in abundances than dmdA genes. Multidimensional analysis based on the abundances of DMSP degradation genes and environmental factors revealed that the distribution pattern of these genes was influenced by chlorophyll a concentrations and temperatures. dddP genes, dmdA subclade C/2 genes, and dmdA subclade D genes exhibited significant correlations with the marine Roseobacter clade, SAR11 subgroup Ib, and SAR11 subgroup Ia, respectively. SAR11 subgroups Ia and Ib, which possessed dmdA genes, were suggested to be the main potential DMSP consumers. The Roseobacter clade members possessing dddP genes in oligotrophic subtropical regions were possible DMS producers. These results suggest that DMSP degradation genes are abundant and widely distributed in the surface seawater and that the marine bacteria possessing these genes influence the degradation of DMSP and regulate the emissions of DMS in subtropical gyres of the Pacific Ocean.
  • 亀山宗彦
    地球化学 48 2 53 - 66 2014年06月25日 [査読無し][通常論文]
  • Sohiko Kameyama, Satoshi Yoshida, Hiroshi Tanimoto, Satoshi Inomata, Koji Suzuki, Hisayuki Yoshikawa-Inoue
    JOURNAL OF OCEANOGRAPHY 70 3 225 - 239 2014年06月 [査読有り][通常論文]
     
    We measured dissolved isoprene (2-methyl-1,3-butadiene; C5H8) concentrations in a broad area of the southern Indian Ocean and in the Indian sector of the Southern Ocean from 35A degrees S to 64A degrees S and from 37A degrees E to 111A degrees E during austral summer 2010-2011. Isoprene concentrations were continuously measured by use of a proton-transfer-reaction mass spectrometer combined with a bubbling-type equilibrator. Concentrations of isoprene and its emission flux throughout the study period ranged from 0.2 to 395 pmol L-1 and from 181 to 313 nmol m(-2) day(-1), respectively, the averages being generally higher than those of previous studies. Although we found a significant linear positive relationship between isoprene and chlorophyll-a concentrations (r (2) = 0.37, n = 36, P < 0.001), the correlation coefficient was lower than previously reported. In contrast, in the high-latitude area (> 53A degrees S) we identified a significant negative correlation (r (2) = 0.59, n = 1263, P < 0.001) between isoprene and the temperature-normalized partial pressure of carbon dioxide (n-pCO(2)), used as an indicator of net community production in this study. This suggests that residence times and factors controlling variations in isoprene and n-pCO(2) are similar within a physically stable water column.
  • Hiroshi Tanimoto, Sohiko Kameyama, Toru Iwata, Satoshi Inomata, Yuko Omori
    ENVIRONMENTAL SCIENCE & TECHNOLOGY 48 1 526 - 533 2014年01月 [査読有り][通常論文]
     
    We developed a new method for in situ measurement of air sea fluxes of multiple volatile organic compounds (VOCs) by combining proton transfer reaction-mass spectrometry (PTR-MS) and gradient flux (GF) technique. The PTR-MS/GF system was first deployed to determine the air sea flux of VOCs in the open ocean of the western Pacific, in addition to carbon dioxide and water vapor. Each profiling at seven heights from the ocean surface up to 14 m took 7 min. In total, 34 vertical profiles of VOCs in the marine atmosphere just above the ocean surface were obtained. The vertical gradient observed was significant for dimethyl sulfide (DMS) and acetone with the best-fit curves on quasi-logarithmic relationship. The mean fluxes of DMS and acetone were 5.5 +/- 1.5 and 2.7 +/- 1.3 mu mol/m(2)/day, respectively. These fluxes are in general in accordance with those reported by previous expeditions.
  • Sohiko Kameyama, Hiroshi Tanimoto, Satoshi Inomata, Hisayuki Yoshikawa-Inoue, Urumu Tsunogai, Atsushi Tsuda, Mitsuo Uematsu, Masao Ishii, Daisuke Sasano, Koji Suzuki, Yuichi Nosaka
    GEOPHYSICAL RESEARCH LETTERS 40 15 3986 - 3990 2013年08月 [査読有り][通常論文]
     
    Although much attention has been paid to describing the distribution of oceanic dimethyl sulfide (DMS) concentrations, establishing robust relationships between DMS concentrations and biological, physical, and chemical variables is still challenging. Previous studies have proposed semiempirical parameterizations by combining multiple physical and biogeochemical parameters to better understand and reproduce the global distribution of sea surface DMS. However, none of these parameterization schemes could reconcile regionally elevated DMS peaks found in high-resolution DMS measurements made in the western subarctic Pacific. Here we found that DMS concentrations are highly correlated with the net community production, a parameter that integrates biological activity over time. We anticipate that this relationship may be exportable to other regions with high primary productivity, such as the Southern Ocean or upwelling regions, and can be used as an important parameterization scheme, combined with solar radiation dose relationship.
  • Yuko Omori, Hiroshi Tanimoto, Satoshi Inomata, Sohiko Kameyama, Shintaro Takao, Koji Suzuki
    Limnology and Oceanography: Methods 11 549 - 560 2013年 [査読有り][通常論文]
     
    New, highly time-resolved techniques for measuring dimethyl sulfide (DMS) concentrations in seawater provide the opportunity to greatly increase the size of the DMS concentration database. However, lack of community-level quality control raises concerns about the quality of data obtained by these new techniques and their consistency with data obtained by existing techniques. One of the concerns is that the new techniques use a continuous flow of unfiltered seawater as a sample. Phytoplankton in unfiltered seawater might produce DMS in the sample, resulting in inaccurate DMS concentrations. Here, in our equilibrator inlet-proton transfer reaction-mass spectrometry technique, unfiltered seawater is continuously supplied to the equilibrator, and dissolved DMS is extracted into a bubbling gas and detected by the mass spectrometry. To investigate the possible artifact from using unfiltered seawater and the magnitude of its effects, we conducted laboratory experiments in a closed system at equilibrium, focusing on the effects of sample filtration and gas bubbling on the temporal variation of DMS concentrations in coastal seawater samples dominated by diatoms. With N2 as the bubbling gas, DMS concentration increased with time in unfiltered seawater but not in filtered seawater. DMS concentration increased when unfiltered seawater was bubbled with N2 but not when it was bubbled with air, and the increase occurred just after dissolved O2 was depleted in the seawater in the equilibrator. These results indicate that O2 depletion artificially increased DMS concentrations in unfiltered seawater bubbled with N2. This artifact could be avoided by maintaining aerobic conditions in the equilibrator. © 2013, by the American Society of Limnology and Oceanography, Inc.
  • 吉川 久幸, 亀山 宗彦, 吉田 怜, 緑川 貴, 石井 雅男, 笹野 大輔, 中岡 慎一郎, 橋田 元
    日本地球化学会年会要旨集 58 44 - 44 日本地球化学会 2011年 
    気象研究所や国立極地研によって取得されてきたインド洋・太平洋セクターでの海洋二酸化炭素分圧等の炭酸系観測データを用いて、季節変化、長期的な傾向について解析してきた結果を発表する。特に、夏季に昭和基地沖の季節海氷域で得られた熱力学が支配的な海洋二酸化炭素分圧の空間分布と太平洋・インド洋セクターの海洋二酸化炭素分圧とpHの長期的傾向について詳しく述べる。
  • Sohiko Kameyama, Hiroshi Tanimoto, Satoshi Inomata, Koji Suzuki, Daisuke D. Komatsu, Akinari Hirota, Uta Konno, Urumu Tsunogai
    GEOCHEMICAL JOURNAL 45 5 355 - 363 2011年 [査読有り][通常論文]
     
    Emission of trace gases from the marine diatom Thalassiosira pseudonana (CCMP 1335) was continuously monitored with a proton transfer reaction-mass spectrometry (PTR-MS) in an axenic batch culture system under a 13:11-h light:dark cycle. Substantial increases in the signals at m/z 49, 63, and 69, attributable to methanethiol, dimethyl sulfide (DMS), and isoprene, respectively, were observed in response to increases in cell density. Signals at m/z 69 showed diurnal variations throughout the experiment whereas those at m/z 49 were more pronounced at the beginning of the incubation. Interestingly, the signals at m/z 49 and 69 changed immediately following the light-dark and dark-light transitions, suggesting that light plays a crucial role in the production of methanethiol and isoprene. However, in the latter half of the experiment, methanethiol showed negligible diurnal variations regardless of light conditions, suggesting the production of methanethiol from enzymatic cleavage of DMS. The trend ill signals at m/z 63 was similar to that of the abundance of senescent cells plus cell debris rather than vegetative cells. The results suggest that aging or death of phytoplankton cells could also substantially control DMS production in natural waters along with the other microbial processes related to bacteria and zooplankton.
  • Atsushi Ooki, Atsushi Tsuda, Sohiko Kameyama, Shigenobu Takeda, Sachihiko Itoh, Toshio Suga, Hirofumi Tazoe, Ayako Okubo, Yoko Yokouchi
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 115 2010年10月 [査読有り][通常論文]
     
    The partial pressures of methyl halides (CH3X; X = Cl, Br, or I) and of CHClF2 (HCFC-22), which are all volatile organic compounds (VOCs), were measured in the air of the marine boundary layer (pVOC(air)) and in surface seawater (pVOC(water)) during a cruise from the subarctic to subtropical regions of the northwest Pacific in summer of 2008. In the northern transition water (TWN) with high biological activity, high levels of the three CH(3)Xs in surface seawater were frequently observed, probably owing to their enhanced production by phytoplankton. Supersaturation of CH3Br was only present in TWN water, with a saturation anomaly (SCH3Br) of 0.95 [SCH3X = (pCH(3)X(water) - pCH(3)X(air))/pCH(3)X(air)]. The highest saturation anomalies for CH3Cl (SCH3Cl = 1.6) and CH3I (SCH3I = 91) were found in the southern subtropical water (STS) with low biological production south of the subtropical front. We found that the molar concentrations of CH3Cl (CCH3Cl) and CH3I (CCH3I) sharply increased with increasing sea surface temperature (SST) in the subtropical waters. The maximum CCH3Cl (144 pmol l(-1)) was present in STS water at SST = 30 degrees C and is 1.5 times the value extrapolated from the previously reported relationship between CCH3Cl and SST. Photochemical production might have contributed to the production of CH3Cl and CH3I in STS water.
  • Sohiko Kameyama, Hiroshi Tanimoto, Satoshi Inomata, Urumu Tsunogai, Atsushi Ooki, Shigenobu Takeda, Hajime Obata, Atsushi Tsuda, Mitsuo Uematsu
    MARINE CHEMISTRY 122 1-4 59 - 73 2010年10月 [査読有り][通常論文]
     
    We developed an equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) system for high-resolution measurement of the concentrations of multiple volatile organic compounds (VOCs) dissolved in seawater. The equilibration of five VOCs (isoprene, propene, acetone, acetaldehyde, and methanol) between seawater samples and the carrier gas, and the response time of the system, were evaluated by means of a series of laboratory experiments. Although equilibrium between the seawater sample and the carrier gas in the equilibrator was not achieved for isoprene and propene (likely because of their low water solubility), the other species did reach equilibrium. The EI-PTR-MS system was deployed during a research cruise in the western North Pacific Ocean. Evaluation of several seawater sampling methods indicated that there was no significant contamination from the sampling apparatus for the target VOCs. For isoprene, comparison of EI-PTR-MS measurements with measurements obtained with a membrane equilibrator-gas chromatography/mass spectrometry system showed generally good agreement (R-2=0.79). EI-PTR-MS captured the temporal variations of dissolved VOCs, including small-scale variability, which demonstrates that the performance of the EI-PTR-MS system was sufficient for simultaneous and continuous measurements of multiple VOCs of environmental importance in seawater. (C) 2010 Elsevier B.V. All rights reserved.
  • Atsushi Ooki, Atsushi Tsuda, Sohiko Kameyama, Shigenobu Takeda, Sachihiko Itoh, Toshio Suga, Hirofumi Tazoe, Ayako Okubo, Yoko Yokouchi
    Journal of Geophysical Research: Oceans 115 10 2010年 [査読有り][通常論文]
     
    The partial pressures of methyl halides (CH3X X = Cl, Br, or I) and of CHClF2 (HCFC-22), which are all volatile organic compounds (VOCs), were measured in the air of the marine boundary layer (pVOC air) and in surface seawater (pVOCwater) during a cruise from the subarctic to subtropical regions of the northwest Pacific in summer of 2008. In the northern transition water (TWN) with high biological activity, high levels of the three CH3Xs in surface seawater were frequently observed, probably owing to their enhanced production by phytoplankton. Supersaturation of CH3Br was only present in TW N water, with a saturation anomaly (SCH3Br) of 0.95 [SCH3X = (pCH3Xwater - pCH3X air)/pCH3Xair]. The highest saturation anomalies for CH3Cl (SCH3Cl = 1.6) and CH3I (SCH3I = 91) were found in the southern subtropical water (ST S) with low biological production south of the subtropical front. We found that the molar concentrations of CH3Cl (CCH3Cl) and CH3I (CCH3I) sharply increased with increasing sea surface temperature (SST) in the subtropical waters. The maximum CCH3Cl (144 pmol l-1) was present in STS water at SST = 30°C and is 1.5 times the value extrapolated from the previously reported relationship between CCH3Cl and SST. Photochemical production might have contributed to the production of CH3Cl and CH3I in ST S water. Copyright 2010 by the American Geophysical Union.
  • U. Tsunogai, A. Kosaka, N. Nakayama, D. D. Komatsu, U. Konno, S. Kameyama, F. Nakagawa, H. Sumino, K. Nagao, K. Fujikura, H. Machiyama
    GEOCHEMICAL JOURNAL 44 6 461 - 476 2010年 [査読無し][通常論文]
     
    Seafloor sec ping methane bubbles were successfully sampled on the summit area of the Kuroshima Knoll (depth of ca 640 m) using the gas-tight sampler WHATS attached to the Shinkai 2000 To evaluate the origin of the bubbles and verify that the dissociation of methane hydrate was actually in progress the chemical and isotopic composition of the samples wen analyzed The major component of the gas bubbles was methane (C-1) with traces of CO2 (67 +/- 16 ppmv) and helium (11 +/- 1 ppmv He-4/Ne-20 = 320) having a moderate He-3/He-4 ratio (0 44R(a)) C-1 was enriched relative to other hydrocarbons (C-1/(C-2+C-3) > 3000) The delta C-13 values for C-1 (-40 1 parts per thousand(VPDB)) C-2 (-28 3 parts per thousand(VPDB)) and C-5 (-28 0 parts per thousand(VPDB)) were similar to those of hydrocarbons produced by thermal decomposition of organic matter The contribution of the mantle derived He-3 enriched component in coexisting helium also supports thermogenic generation On the other hand the other light hydrocarbons showed an unusual C-13 enrichment in C-3 (-19 1 parts per thousand(VPDB)) ISO-C-4 (-22 4 parts per thousand(VPDB)) and n-C-4 (-19 9 parts per thousand(VPDB)) C-3 and C-4 had been fractionated both chemically and isotopically through subsequent microbial destruction during the long storage from Miocene in the gas reservoir In addition the anaerobic oxidation of CH4 within shallow sediments removed about 20% of CH4, until seepage into ocean water column Regarding the contribution of gases originating from hydrate dissociation to the bubbles observed helium amount in the bubbles suggests that methane hydrate is considered to be a minor contributor to the bubbles at least at present Direct leakage of gases from deep reservoirs is a more plausible for the source Regarding the fate of the hydrocarbons in the bubbles in the water column, all rising bubbles at Kuroshima Knoll dissolved within 140 m of the seafloor After the dissolution the plume spreads horizontally along with the surface of equal density in the water column, while the concentrations decrease through dilution by eddy diffusion rather than by oxidation
  • Sohiko Kameyama, Hiroshi Tanimoto, Satoshi Inomata, Urumu Tsunogai, Atsushi Ooki, Yoko Yokouchi, Shigenobu Takeda, Hajime Obata, Mitsuo Uematsu
    ANALYTICAL CHEMISTRY 81 21 9021 - 9026 2009年11月 [査読有り][通常論文]
     
    We developed an equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) method for fast detection of dimethyl sulfide (DAIS) dissolved in seawater. Dissolved DMS extracted by bubbling pure nitrogen through the sample was continuously directed to the PTR-MS instrument. The equilibration of DMS between seawater and the carrier gas, and the response time of the system, were evaluated in the laboratory. DMS reached equilibrium with an overall response time of 1 min. The detection limit (50 pmol L-1 at 5 s integration) was sufficient for detection of DMS concentrations in the open ocean. The EI-PTR-MS instrument was deployed during a research cruise in the western North Pacific Ocean. Comparison of the EI-PTR-MS results with results obtained by means of membrane tube equilibrator-gas chromatography/mass spectrometry agreed reasonably well on average (R-2 = 0.99). EI-PTR-MS captured temporal variations of dissolved DMS concentrations, including elevated peaks associated with patches of high biogenic activity. These results demonstrate that the EI-PTR-MS technique was effective for highly time-resolved measurements of DMS in the open ocean. Further measurements will improve our understanding of the biogeochemical mechanisms of the production, consumption, and distribution of DMS on the ocean surface and, hence, the air-sea flux of DMS, which is a climatically important species.
  • Sohiko Kameyama, Urumu Tsunogai, Fumiko Nakagawa, Motoki Sasakawa, Daisuke D. Komatsu, Akira Ijiri, Junko Yamaguchi, Takeo Horiguchi, Hiroshi Kawamura, Aika Yamaguchi, Atsushi Tsuda
    MARINE CHEMISTRY 115 1-2 92 - 101 2009年06月 [査読有り][通常論文]
     
    During the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study II (SEEDS-II), we monitored variations in the concentrations of non-methane hydrocarbons (NMHCs), CH3Cl. N2O. and CH4 within a phytoplankton bloom. Stable isotopic compositions were also determined to evaluate the sources of the variations. Although there was little variation in either the concentrations or the stable isotopic compositions of alkenes, CH3Cl, N2O. and CH4 during the 23-day observation period, alkane concentrations increased substantially as the phytoplankton bloomed. The column-integrated quantities of alkanes increased to 3 times pre-bloom levels for C2H6, 5 times for C3H8. and 20 times for n-C4H10. The delta C-13 values of both C2H6 and C3H8 remained almost constant while concentrations increased, whereas that of n-C4H10 increased by about 12 parts per thousand. To evaluate the sources of the alkanes produced during the bloom, we compared their delta C-13 values with those of alkanes produced in axenic phytoplankton cultures in our laboratory. We concluded that during the SEEDS-II experiment the major portions of C2H6 and C3H8 were produced during the autolysis of diatoms cells, whereas n-C4H10 was produced during autolysis of other phytoplankton cells such as cryptophytes and dinoflagellates. (C) 2009 Elsevier B.V. All rights reserved.
  • Sohiko Kameyama, Satoshi Inomata, Hiroshi Tanimoto
    INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 276 1 49 - 55 2008年09月 [査読有り][通常論文]
     
    The proton-transfer reactions of H3O+ with ethylbenzene and deuterium-labeled ethylbenzenes were systematically investigated by means of proton-transfer reaction mass spectrometry. The branching ratios for the formation of protonated ethylbenzenes and for fragmentation reactions involving elimination of ethylene from the protonated molecules, accompanied by hydrogen migration from the alpha position or the beta position of the ethyl group, were determined as a function of the mean relative center-of-mass kinetic energies of the reactants (K-cm). The branching ratio for the intact protonated molecule decreased with increasing relative kinetic energy: the branching ratio decreased from 0.87 at K-cm = 0.19 eV to 0.05 at K-cm =036 eV, and in turn the ratio for ethylene elimination increased from 0.13 to 0.95. The branching ratios determined for partially deuterium-labeled ethylbenzenes were consistent with one another as well as with the ratios for unlabeled ethylbenzene. The fraction of H migration from the alpha position increased with increasing K-cm (from 0.13 +/- 0.01 at K-cm = 0.19 eV to 0.24 +/- 0.01 at K-cm = 0.36 eV) and appeared to saturate at similar to 0.24 at K-cm values above 0.28 eV. (C) 2008 Elsevier B.V. All rights reserved.
  • Motoki Sasakawa, Urumu Tsunogai, Sohiko Kameyama, Fumiko Nakagawa, Yukihiro Nojiri, Atsushi Tsuda
    Journal of Geophysical Research: Oceans 113 3 2008年03月08日 [査読有り][通常論文]
     
    We collected samples of seawater, zooplankton, and sinking particles in the northwestern North Pacific to determine the source of excess CH4 over the saturation value in equilibrium with the atmospheric CH4 in the oxygenated open ocean, using stable carbon isotope as a tracer. We found that subsurface (∼100 m depth) seawater is supersaturated (up to 12%) with 13C-enriched CH4 (up to -33.1‰) relative to surface seawater in equilibrium with the atmosphere (-47‰ suggesting that in situ addition of 13C-enriched CH4 must be responsible for CH4 enrichment at depth. The δ13C of CH4 emitted from sinking particles (from -36.7 ± 1.2‰ to +5.9 ± 7.5‰) is within the range of that of excess CH4 in seawater, suggesting that the major source of subsurface excess CH4 is sinking particles. The unusually 13C-enriched δ13C composition of CH4 emitted from sinking particles suggests that active microbial CH4 oxidation occurs within the oxic/anoxic boundary of these particles. On the basis of the Rayleigh equation, we estimated that at least 62% of CH4 produced within the anoxic center of sinking particles is oxidized within 100 m of the surface. Copyright 2008 by the American Geophysical Union.
  • Motoki Sasakawa, Urumu Tsunogai, Sohiko Kameyama, Fumiko Nakagawa, Yukihiro Nojiri, Atsushi Tsuda
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 113 C3 2008年03月 [査読有り][通常論文]
     
    We collected samples of seawater, zooplankton, and sinking particles in the northwestern North Pacific to determine the source of excess CH(4) over the saturation value in equilibrium with the atmospheric CH(4) in the oxygenated open ocean, using stable carbon isotope as a tracer. We found that subsurface (similar to 100 m depth) seawater is supersaturated (up to 12%) with (13)C-enriched CH(4) (up to -33.1%) relative to surface seawater in equilibrium with the atmosphere (-47%), suggesting that in situ addition of (13)C-enriched CH(4) must be responsible for CH(4) enrichment at depth. The delta(13)C of CH(4) emitted from sinking particles (from -36.7 +/- 1.2% to +5.9 +/- 7.5%) is within the range of that of excess CH(4) in seawater, suggesting that the major source of subsurface excess CH(4) is sinking particles. The unusually (13)C-enriched delta(13)C composition of CH(4) emitted from sinking particles suggests that active microbial CH(4) oxidation occurs within the oxic/anoxic boundary of these particles. On the basis of the Rayleigh equation, we estimated that at least 62% of CH(4) produced within the anoxic center of sinking particles is oxidized within 100 m of the surface.
  • S. Inomata, H. Tanimoto, S. Kameyama, U. Tsunogai, H. Irie, Y. Kanaya, Z. Wang
    ATMOSPHERIC CHEMISTRY AND PHYSICS 8 2 273 - 284 2008年 
    Formaldehyde (HCHO), the most abundant carbonyl compound in the atmosphere, is generated as an intermediate product in the oxidation of nonmethane hydrocarbons. Proton transfer reaction mass spectrometry (PTR-MS) has the capability to detect HCHO from ion signals at m/z 31 with high time-resolution. However, the detection sensitivity is low compared to other detectable species, and is considerably affected by humidity, due to back reactions between protonated HCHO and water vapor prior to analysis. We performed a laboratory calibration of PTR-MS for HCHO and examined the detection sensitivity and humidity dependence at various field strengths. Subsequently, we deployed the PTR-MS instrument in a field campaign at Mount Tai in China in June 2006 to measure HCHO in various meteorological and photochemical conditions; we also conducted intercomparison measurements by Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS). Correction of interference in the m/z 31 signals by fragments from proton transfer reactions with methyl hydroperoxide, methanol, and ethanol greatly improves agreement between the two methods, giving the correlation [HCHO](MAX-DOAS)=(0.99 +/- 0.16) [HCHO](PTR-MS)+(0.02 +/- 0.38), where error limits represent 95% confidence levels.
  • Atsushi Tsuda, Shigenobu Takeda, Hiroaki Saito, Jun Nishioka, Isao Kudo, Yukihiro Nojiri, Koji Suzuki, Mitsuo Uematsu, Mark L. Wells, Daisuke Tsumune, Takeshi Yoshimura, Tatsuo Aono, Takafumi Aramaki, William P. Cochlan, Maki Hayakawa, Keiri Imai, Tomoshi Isada, Yoko Iwamoto, William K. Johnson, Sohiko Kameyama, Shungo Kato, Hiroshi Kiyosawa, Yoshiko Kondo, Maurice Levasseur, Ryuji J. Machida, Ippei Nagao, Fumiko Nakagawa, Takahiro Nakanish, Seiji Nakatsuka, Akira Narita, Yoshifumi Noiri, Hajime Obata, Hiroshi Ogawa, Kenji Oguma, Tsuneo Ono, Tomofumi Sakuragi, Motoki Sasakawa, Mitsuhide Sato, Akifumi Shimamoto, Hyoe Takata, Charles G. Trick, Yutaka W. Watanabe, Chi Shing Wong, Naoki Yoshie
    JOURNAL OF OCEANOGRAPHY 63 6 983 - 994 2007年12月 [査読有り][通常論文]
     
    mesoscale iron-enrichment study (SEEDS II) was carried out in the western subarctic Pacific in the summer of 2004. The iron patch was traced for 26 days, which included observations of the development and the decline of the bloom by mapping with sulfur hexafluoride. The experiment was conducted at almost the same location and the same season as SEEDS (previous iron-enrichment experiment). However, the results were very different between SEEDS and SEEDS II. A high accumulation of phytoplankton biomass (similar to 18 mg chl m(-3)) was characteristic of SEEDS. In contrast, in SEEDS II, the surface chlorophyll-a accumulation was lower, 0.8 to 2.48 mg m(-3), with no prominent diatom bloom. Photosynthetic competence in terms of F-v/F-m for the total phytoplankton community in the surface waters increased after the iron enrichments and returned to the ambient level by day 20. These results suggest that the photosynthetic physiology of the phytoplankton assemblage was improved by the iron enrichments and returned to an iron-stressed condition during the declining phase of the bloom. Pico-phytoplankton (< 2 mu m) became dominant in the chlorophyll-a size distribution after the bloom. We observed a nitrate drawdown of 3.8 mu M in the patch (day 21), but there was no difference in silicic acid concentration between inside and outside the patch. Mesozooplankton (copepod) biomass was three to five times higher during the bloom-development phase in SEEDS II than in SEEDS. The copepod biomass increased exponentially. The grazing rate estimation indicates that the copepod grazing prevented the formation of an extensive diatom bloom, which was observed in SEEDS, and led to the change to a pico-phytoplankton dominated community towards the end of the experiment.
  • 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 3 131 - 140 日本地球化学会 2005年08月20日 [査読無し][通常論文]
     
    We present here a geochemical study on the SGD in the Toyama Bay using CH4 and its carbon isotope ratio as tracers. We found that all SGD fluids and many of land groundwaters contain less methane than natural water in equilibrium with atmospheric CH4. Theδ13C values of CH4 in the SGD fluids range from -50 to -20‰ VPDB, almost comparable or slightly higher than that of atmospheric CH4. The results suggest that most of methane in the SGD fluids had been derived from the atmosphere and a part of the CH4 is oxidized in the course of groundwater flow through the aquifer, with no CH4 production t...
  • 亀山 宗彦, 下山 正一, 宮部 俊輔, 宮田 雄一郎, 山 哲男, 岩野 英樹, 檀原 徹, 遠藤 邦彦, 松隈 明彦
    第四紀研究 44 1 15 - 29 日本第四紀学会 2005年02月01日 [査読無し][通常論文]

その他活動・業績

  • 杉江恒二, 亀山宗彦, 芳村毅, 内田裕, 西岡純, 原田尚美, 村田昌彦 日本海洋学会大会講演要旨集 2016 2016年
  • 崔英順, 鈴木翔太郎, 大森裕子, ウオン クワンシュー, 伊知地稔, 金子亮, 亀山宗彦, 谷本浩志, 浜崎恒二 日本海洋学会大会講演要旨集 2014 127 2014年09月01日 [査読無し][通常論文]
  • Tanimoto, H, S. Kameyama, Y. Omori, S. Inomata, U. Tsunogai Western Pacific Air-Sea Interaction Study (Eds. M. Uematsu, Y. Yokouchi, Y. W. Watanabe, S. Takeda, and Y. Yamanaka), TERRAPUB 89-115 2014年03月12日 [査読有り][通常論文]
  • 佐藤 晋太郎, 角皆 潤, 中川 書子, 小松 大祐, 亀山 宗彦, 今野 祐多 日本地球化学会年会要旨集 58 (0) 192 -192 2011年 [査読無し][通常論文]
     
    微生物によるメタン酸化時の水素同位体分別係数は,Coleman et al. (1981)によって室内実験にて求められたが,天然環境下で検証した例は少ない.本研究は天然環境下のメタン酸化における水素同位体分別を定量化する事を目的とした.熱水は海水中に放出され,有意なメタンの濃度異常を示す熱水プルームとして検出される.鳩間海丘は南部沖縄トラフに位置する海底火山であり,熱水プルーム中では希釈を上回るスピードでメタンが酸化分解され,水素同位体分別を定量するには最適である.分析は連続フロー型質量分析計にて測定を行った.結果,水素同位体分別係数は1.100であり,Coleman et al.(1981)の結果である1.103とほぼ一致した.炭素同位体分別係数(1.009)と比較すると,水素同位体比の変化率が炭素同位体比と比べて約10 倍になり,これも室内実験の結果と良く一致した.
  • 亀山 宗彦, 谷本 浩志, 猪俣 敏, 奥沢 和浩, 角皆 潤, 石井 雅男, 笹野 大輔, 吉川 久幸 日本地球化学会年会要旨集 58 (0) 46 -46 2011年 [査読無し][通常論文]
     
    海洋は大気DMSの主要な放出源であり、植物プランクトン生体内で作られるDMSPがDMSの主な前駆体物質といわれているが、DMSの生成・消失には様々な生物地球化学過程が関係するため極めて複雑であり、その包括的な理解には至っていない。生成・消失過程の理解は今後の地球環境変化に対する海洋から大気へのDMS放出量の変化の見積もりを行うためにも重要な課題である。我々はバブリング型気液平衡器とPTR-MSを組み合わせた溶存揮発性有機化合物の連続定量装置(EI-PTR-MS)を開発し、北太平洋高生物生産海域で高時空間分解能のDMS濃度分布を取得した。本研究ではDMSの濃度分布と<I>p</I>CO<sub>2</sub>の連続測定から計算される純群集生産との間に良い相関(r<sup>2</sup> = 0.68、n = 279)があり、純群集生産が本研究海域のDMSの分布を決めるキーパラメータとなる可能性を見出した。
  • 亀山 宗彦, 猪俣 敏, 谷本 浩志, 角皆 潤 日本地球化学会年会要旨集 54 (0) 143 -143 2007年 [査読無し][通常論文]
     
    PTR-MSは近年大気中における多成分VOCの連続観測に用いられており、これまで自動車排ガスやバイオマスバーニング起源などからのVOC濃度を連続的に観測するためにしばしば使われてきた。一方、海洋表層からもVOCが大気中に放出されているという知見が得られているにもかかわらず、PTR-MSを用いた研究は洋上大気中のVOCを連続的に観測し海洋からの放出を算出するにとどまっており、溶存VOCを直接PTR-MSを使って測定した例はほとんどない。PTR-MSによる溶存VOC定量に関する課題として、数種類のVOCについてPTR-MSによる検出感度に湿度依存性があることが挙げられる。海水から抽出される気体には水蒸気が多く混在すると予想され、溶存VOCの定量に向けて湿度依存性の評価は不可欠である。本研究ではこの湿度依存性について数種のVOCを用いて室内実験をおこなったので、その結果と今後の展望を紹介する。
  • 角皆 潤, 中川 書子, 笹川 基樹, 亀山 宗彦 環境循環系診断のための同位体トレーサー技術 (筑波大学陸域環境研究センター電子モノグラフ No. 2) 47 -53 2006年 [査読無し][通常論文]
  • 亀山 宗彦, 井口 剛一郎, 中川 書子, 角皆 潤, 蒲生 俊敬, 野入 善史, 永延 幹男 日本地球化学会年会要旨集 53 (0) 198 -198 2006年 [査読無し][通常論文]
     
    メタンは重要な温室効果ガスであり、海洋はその放出源といわれている。これまで海洋亜表層にはメタンが過飽和になる層が普遍的に存在する事が知られていた。しかし、本研究で南極・ロス海におけるメタンの分布を測定したところ、他の海域よりも顕著な過飽和はみられず、むしろ未飽和になっている測点が多く存在した。これはこの海域がメタンの放出源ではなく吸収源になっている可能性を示唆する。本発表では濃度の議論と共に同位体比を用いて過飽和メタンの欠如の原因を明らかにする。
  • 角皆潤, 中川書子, 笹川基樹, 亀山宗彦, 小松大祐, 山口潤子, 川口慎介 日本海洋学会大会講演要旨集 2005 2005年
  • 亀山 宗彦, 中川 書子, 笹川 基樹, 角皆 潤, 蒲生 俊敬, 野尻 幸宏 日本地球化学会年会要旨集 52 (0) 39 -39 2005年 [査読無し][通常論文]
     
    本研究で研究対象としているメタンおよび亜酸化窒素は重要な温室効果気体である。それぞれの気体の大気への放出源の中でも海洋が占める割合は大きいが、その見積もりの幅は大きい。これを明らかにするために非常に重要となる海洋中の濃度・同位体比分布は海洋環境によって異なり、より広範囲、より詳細な分布およびその成因を知ることが必要である。本研究では北太平洋HNLC海域、東太平洋湧昇域、南極海さらにインド洋のメタンおよび亜酸化窒素の濃度・同位体比の分布、およびセディメントトラップとプランクトンネットを用いて採取した試料の濃度測定結果から考察した海洋分布の成因について報告する。
  • 前川 健二, 土岐 知弘, 亀山 宗彦, 角皆 潤, 中川 書子, 徐 垣, 芦 寿一郎, 木下 正高 日本地球化学会年会要旨集 52 (0) 40 -40 2005年 [査読無し][通常論文]
     
    本研究はJAMSTECの「かいよう」航海KY03-11、KY04-11において東京大学海洋研究所所有のNSS(Navigable Sampling System)で採取した相模湾初島南東沖、南海トラフ第二渥美海丘、熊野泥火山の堆積物の間隙水と海水試料の化学分析をし、湧水や泥火山のメタンフラックスを知る事を目的としている。 近年、メタンは温暖化物質として、また海底資源として注目を集めており、現在の海底から海水中へのメタンフラックスを求める事が重要である。海底からのメタン放出は特異的なサイトを中心に起きている事が近年の研究で明らかになりつつあり、従来の観測機器で正確な海底を捉える事ができない為本研究ではピンポイントで目的サイトの試料採取できるNSSを用いた研究を行った。 今回、塩化物イオン,メタン,全炭酸濃度及びメタンと全炭酸の炭素同位体比を測定する事で初島及び熊野泥火山におけるプルームと間隙水のメタンのエンドメンバーとフラックスを比較する。
  • 小松 大祐, 山口 潤子, 古用 啓介, 中川 書子, 亀山 宗彦, 笹川 基樹, 角皆 潤 日本地球化学会年会要旨集 52 (0) 87 -87 2005年 [査読無し][通常論文]
     
    海洋に溶存する塩化メチルの安定炭素同位体比分析法を開発した。塩化メチルの炭素同位体比を分析できれば、これまでの濃度のみの観測では得られなかった反応・分解の反応経路に関する情報が得られる可能性がある。本研究では従来よりも保存性、耐久性に優れ、かつ低予算でC<SUB>2</SUB>-C<SUB>5</SUB>の炭化水素及び塩化メチルを抽出、濃縮する方法を開発し、炭素同位体比を分析した。KH04-3航海で得られた東部北太平洋の表層数十メートルの試料を用いて溶存塩化メチルの濃度及び安定炭素同位体比を測定した結果、海水中で塩化メチルは生物によって分解されている可能性が高いことが分かった。
  • 山口 潤子, 小松 大祐, 角皆 潤, 中川 書子, 笹川 基樹, 亀山 宗彦 日本地球化学会年会要旨集 51 (0) 122 -122 2004年 [査読無し][通常論文]
     
    海洋表層では様々な地球化学的過程が存在しており、その結果として海洋表層中ではさまざまな溶存軽炭化水素が生成・消費されていると考えられる。炭素安定同位体比はその過程の解析において有効な指標となる可能性がある。本研究では、世界で始めて海洋表層中の溶存軽炭化水素の炭素安定同位体比を測定したので、その結果について報告する。
  • 笹川 基樹, 亀山 宗彦, 川口 慎介, 中川 書子, 角皆 潤, 野尻 幸宏 日本地球化学会年会要旨集 51 (0) 183 -183 2004年 [査読無し][通常論文]
     
    大気中のメタンは二酸化炭素の数10倍のGWP(地球温暖化ポテンシャル)を持ち、二酸化炭素に次ぐ温室効果気体である。また大気中メタン濃度の過去50年の平均増加率は二酸化炭素よりも大きいため、地球温暖化に対する影響は更に大きくなることが予想される。自然起源のメタンは人為起源をあわせた全球フラックスのうちの約30 %を占める。外洋の表層海水中には、大気の溶解平衡よりも数%から数10 %程度過剰のメタンが溶存していて大気への放出源となっており、そのフラックスは自然起源メタンの30 %前後を占めると見積もられている。この海洋表層のメタンは微生物起源と考えられているが、通常メタン生成細菌によるメタン生成は嫌気的環境下に限られ、好気的環境の海洋表層・亜表層では起こりえない。この矛盾を解決するメタンの放出源として、沈降有機物粒子や動物プランクトンなどの体内に形成されるミクロな還元環境が注目されている。ここでメタンが生産され海水中に供給されるという仮説だが、まだ明確な知見は得られていない。メタンの供給源を明らかにすることは、海洋におけるメタンの挙動や海洋から大気へのフラックスを見積もる上でも不可欠であると考えられる。さらに海水中のメタンを指標として用いることで逆に動物プランクトンの体内の生物地球化学的過程について考察できる可能性もある。そこで本研究では、2004年7/13-8/27に北部北太平洋において行われた白鳳丸KH04-3次航海で、同位体指標を併用してメタンの起源を考察する実験を行った。まず表層から水深300 mまでの計11層の海水試料を採取した。同時にセジメントトラップ(水深40m, 70m, 100m)を設置し各層に沈降する粒子から放出されるメタンを採取した。投入してから3、4日おきに引き上げ、トラップ内で沈降する粒子からのメタンを濃縮した滅菌高塩海水試料水を分取した。更に動物プランクトンに内包されるメタンを調べるため、NORPACネットにより水深150 m以浅のプランクトン試料も採取し放出されたメタンを分取した。これらの試料についてメタン濃度測定の他、メタンの炭素安定同位体比、亜酸化窒素の濃度・同位体比を測定し、海洋亜表層におけるメタンの起源を考察した。
  • 亀山 宗彦, 川口 慎介, 中川 書子, 笹川 基樹, 角皆 潤 日本地球化学会年会要旨集 51 (0) 184 -184 2004年 [査読無し][通常論文]
     
    近年、温室効果気体の中で最も濃度の高い二酸化炭素を減少させるために、富栄養でありながら鉄が欠乏している海域に鉄を散布し植物プランクトンを増殖させ、炭素を固定させるという試みがなされている。植物プランクトンの増殖に伴い生物活動が活発になると考えられ、様々な生物化学的な反応により生成・消滅する化学成分の挙動を把握するために非常によい環境にあるといえる。本研究では、船上で鉄散布に伴う温室効果気体濃度の変化を測定するため、溶存気体自動抽出装置(AMEXs:Automatic Methane and nitrous oxide EXtraction System)を開発した。本発表ではその測定法と、実際の船上分析結果を亜酸化窒素について紹介する。
  • S Kameyama, U Tsunogai, T Gamo, J Zhang, M Suzuki GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A197 -A197 2003年09月 [査読無し][通常論文]
  • 亀山 宗彦, 角皆 潤, 蒲生 俊敬, 張 勁, 鈴木 麻衣 日本地球化学会年会要旨集 49 (0) 40 -40 2002年 [査読無し][通常論文]
     
    本研究では富山湾の黒部川・片貝川両扇状地の沿岸で沿岸湧出海底地下水と周辺海水のサンプリングおよびメタン濃度の分析をおこなった。湧水のメタンの濃度を測定するとその濃度は周辺海水より有意に低いことがわかった。また、表層水のメタン濃度は外洋の表層の値に比べ高い値を示した。今回の発表ではこれらの特徴を示す原因などについて述べる予定である。

受賞

  • 2013年09月 日本地球化学会 奨励賞
     高時間分解能分析法を用いた海洋表層における揮発性有機化合物に関する研究 
    受賞者: 亀山宗彦
  • 2012年11月 テクノオーシャン・ネットワーク 海のフロンティアを拓く岡村健二賞
     
    受賞者: 亀山宗彦
  • 2004年03月 第 2 回北海道大学地球化学優秀修士論文賞(角皆賞)
     「溶存気体成分を指標に用いた海底湧出 地下水の地球化学的研究 
    受賞者: 亀山宗彦

共同研究・競争的資金等の研究課題

  • サンゴが雲を作り気候を変化させているのか?遺伝子解析技術を用いた検証
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2020年07月 -2023年03月 
    代表者 : 新里 宙也, 山下 洋, 鈴木 豪, 亀山 宗彦
  • 精密試料採取手法に基づく北極海の海氷域における硫黄循環像の解明
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 亀山 宗彦, 浜崎 恒二
     
    2019年度はこれまで測定することが出来なかった溶存硫黄化合物の測定手法の確立を行った。その結果、メタンチオールの検出が可能となり、過去に報告されているサンプル処理方法を用いれば既存のシステムで検出可能なジメチルスルホキシドと合わせて、本研究で目的としている溶存硫黄化合物全てを検出することが可能となった。 本来2019年度に本研究課題に係る乗船機会を得る予定だったが、韓国極地研究所(KOPRI)Araonの定員が満たされていたため参加することができなかった。2020年度の航海で確実に乗船ができるようにKOPRIを訪問し北極海航海のプロジェクトマネージャーや実務を行う研究者と直接議論するなどし調整を行った。 本研究でマイクロレイヤー試料採取に使用する予定の採取装置は共同研究者の浜崎が所持しているが、2019年度に行われた航海後にメンテナンスを行っている。2020年度の航海に向けて浜崎の研究室において研究打ち合わせを行い、試料採取方法等の確認を行った。 2020年度は8月の航海に向けて6月を目途に研究機材をKOPRIに発送する予定である。その後、8月上旬から下旬にかけて観測航海を北極海にて行う。本航海では計画書に記載された海氷周辺環境における硫黄化合物及びその循環に強く影響するジメチルスルフォニオプロピオネート(DMSP)分解酵素等の分布を明らかにするための試料採取を行う。本年度は最終年度であるので、得られた成果を年度終盤に行われる学会等で発表する予定である。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 吉川 久幸, 小杉 如央, 村田 昌彦, 亀山 宗彦, 石井 雅男, 笹野 大輔
     
    北極海の夏季海氷面積の減少は、地球温暖化に起因すると考えられている。この海域における気候変動・変化に関連する化学物質、すなわち揮発性有機化合物(VOC)や温室効果ガス(CO2及びCH4)の大気-海洋間の交換の実態を把握し、将来予測に資するため、海洋地球研究船「みらい」(研究開発機構)において平成26年度~28年度にかけて北極海海洋観測を実施した。その結果、カナダ海盆においては海氷融解水が表層の成層を強化し、水面下30mくらいの活発な生物活動にもかかわらず大気-海洋間の気体交換を抑制する役割を果たしていることが明らかになった。
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2015年 -2016年 
    代表者 : 亀山 宗彦
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2011年05月 -2014年03月 
    代表者 : 吉川 久幸, 緑川 貴, 笹野 大輔, 村田 昌彦, 亀山 宗彦, 橋田 元
     
    本研究は、南大洋における二酸化炭素(CO2)および揮発性有機化合物 (volatile organic compounds, VOC)の大気-海洋間交換と、その変動要因(特に生物活動の影響)を解明することを目的として開始した。2012年度には、海洋地球研究船「みらい」に前年度開発したシステムを搭載し、南大洋広域で11月から2月まで海洋CO2・メタン(CH4)分圧、VOCなどの観測を行った。その結果、南緯60度以南の高緯度海域では海氷融解、鉛直・水平混合、生物活動などの影響によりCO2とCH4の吸収域、放出域が混在していること、VOCは生物活動に起因して亜表層で極大となっていることが分かった。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2010年 -2012年 
    代表者 : 亀山 宗彦
     
    本研究では硫化ジメチル(DMS)及びイソプレンが大気環境に与える影響を評価するために、膜平衡器を使った海水中の溶存DMS及びイソプレンの簡易連続測定法の開発を行った。イソプレンは標準海水の作成が困難であり平衡到達度を評価することができなかったが、DMSは平衡到達度80%に達する抽出が可能となり、海水中のDMSの連続測定が可能となった。今後本研究で開発した装置を用いた高分解能測定によってDMSおよびイソプレンの洋上大気環境への影響評価が進むことが期待される。
  • 安定同位体比を用いた海洋におけるメタンと亜酸化窒素の挙動および生成過程の解明
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2006年 -2007年 
    代表者 : 亀山 宗彦
     
    本研究の研究目的は「海水中のメタン・亜酸化窒素の挙動(分布)を明らかにすること」、「海洋中のメタン・亜酸化窒素の放出源となっている可能性が大きい沈降粒子および動・植物プランクトンについてその影響を評価すること」の2点である。このうち本年度では動・植物プランクトンから放出される亜酸化窒素に関する実験をおこなった。KT05-26次航海、MR06-04次航海で採取したプランクトン培養試料中の亜酸化窒素の濃度及び窒素・酸素安定同位体比測定をおこなった。この測定をおこなう前に新しい測定システムの適用に関する基礎実験もあわせておこなった。この実験結果から、動物プランクトンからはメタンの放出がなく、一方亜酸化窒素の放出がみられた。この結果は、両航海の試料で確認でき、動物プランクトンからの亜酸化窒素放出が海域を問わず普遍的に起きている可能性が示唆される。また、平成19年度は成果を学会・学術雑誌にて発表をおこなうことを目標としていた。本研究で得られた結果の一部はSasakawa et al.(2008)として国際誌Journal of Geophysical Research-Oceanに掲載された。また、その他の結果を国際誌Journal of Geophysical Research-Oceanに投稿したが受理には至らず、他国際誌への再投稿に向けて現在も原稿を校正中である。本研究課題に関連した国内外の学会発表を計4回おこない、また関連研究プロジェクトであるSOLAS(Surface Ocean-Lower Atmosphere Study)が主催したサマースクールにも参加し研究成果を発表した。

教育活動情報

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    キーワード : environments, natural sciences
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  • 国際交流Ⅱ
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    開講学部 : 国際本部
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