Hitoshi Mukai

National Institute for Environmental Studies

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Yukihiro Nojiri

National Institute for Environmental Studies

Toshinobu Machida

National Institute for Environmental Studies

Yoko Yokouchi

National Institute for Environmental Studies

Minoru Yoneda

The University of Tokyo

Takakiyo Nakazawa

Tohoku University

Yukio Terao

National Institute for Environmental Studies

Kentaro Murano

Kyoto University

Takuya Saito

National Institute for Environmental Studies

Yasunori Tohjima

National Institute for Environmental Studies

Masao Uchida

Tokyo Medical Center

Cooperative Institutions

National Institute for Environmental Studies

The University of Tokyo

Japan Agency for Marine-Earth Science and Technology

Hokkaido University

Tohoku University

Nagoya University

University of Arizona

Japan Meteorological Agency

Japan Aerospace Exploration Agency

National Oceanic and Atmospheric Administration

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Compound-Specific Radiocarbon Ages of Fatty Acids in Marine Sediments from the Western North Pacific

Radiocarbon (2001)

Masao Uchida Yasuyuki Shibata Kimitaka Kawamura Yuichiro Kumamoto Minoru Yoneda

Compound-specific radiocarbon analysis of five fatty-acid biomarkers was conducted for marine sediments collected from the western North Pacific. The fatty acids (C 12 to C 34 ) showed a typical bimodal distribution pattern with two maxima at C 16 and C 26 . Their carbon isotopic compositions ranged from −25.1‰ (C 16 ) to −31.8‰ (C 28 ), suggesting that they derived from terrestrial higher plants and marine organisms. A large variations of 14 C ages were found among the fatty acids detected in the same sedimentary horizon of the core, ranging from 530 BP (C 18 ) to 3250 BP (C 28 ). The results of 14 C analysis of fatty acids could be divided into two groups, i.e., lower molecular weight (LMW) fatty acids (C 16 , C 18 ) derived from marine organisms and higher molecular weight (HMW) fatty acids (C 24 , C 26 , C 28 ) derived from terrestrial higher plants. The HMW fatty acids showed older ages, ranging from 2550 BP (C 24 ) to 3250 BP (C 28 ), than LMW fatty acids (530 BP [C 18 ] to 1,820 years BP [C 16 ]). On the other hand, bulk-phase total organic matter (TOM) showed the age of 2260 BP that is between those two groups, suggesting that it was likely a mixture of organic matter derived from marine and terrestrial sources. The compound specific 14 C ages and δ 13 C data of sedimentary fatty acids presented here could provide useful information to decipher the fate and transport process of terrestrial organic matter to marine sediments.

Sedimentary organic matter

10.1017/s0033822200041618

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Observational study of the short-lived ozone depleting substances, bromoform and dibromomethane

Japan Geoscience Union (2016)

Yoko Yokouchi Takuya Saito Jiye Zeng Hitoshi Mukai S. A. Montzka

Bromoform

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Trans-boundary and in-country transport of air pollutants observed in Kobe, Japan by high frequent filter pack sampling method

Journal of Atmospheric Chemistry (2016)

Masahide Aikawa Takatoshi Hiraki Yosuke Horie Ryouhei Nakatsubo Chisato Matsumura

Seasonality

Urban area

10.1007/s10874-016-9357-1

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Ecosystem‐scale carbon isotope ratio of respired CO₂ in cool‐temperate deciduous forests under Asian monsoon climate

Journal of Geophysical Research Atmospheres (2008)

Masao Uchida Miyuki Kondo Yukihiro Nojiri Hitoshi Mukai Shohei Murayama

The carbon isotopic ratio for ecosystem respiration ( δ 13 C R ) is an important parameter in isotopic mass balance models for the global carbon budget. Recent studies in North American and European temperate forests showed that δ 13 C R was controlled by stomatal regulation of gas exchange and associated changes in photosynthetic carbon isotope discrimination. In this model, δ 13 C R depends on the vapor pressure deficit (vpd) and precipitation (i.e., plant water availability). We investigated the monthly and annual variation in δ 13 C R and its controlling factors in two cool‐temperate deciduous forests in the monsoon climate area of Japan. The Keeling plot approach was used to evaluate variation in δ 13 C R . Overall, δ 13 C R varied from −24.1‰ to −29.7‰ and was most negative in late summer and autumn. The amplitude of the variation was 2.0‰ to 2.2‰ within a forest. In 1996, which had unusually little precipitation (63% of normal precipitation), δ 13 C R was correlated with vpd measured 7 d before sampling and monthly precipitation, consistent with predictions based on the stomatal regulation model. In contrast, δ 13 C R in 1995 was insensitive to vpd and precipitation, but was significantly correlated with air temperature, suggesting temperature control associated with variabilities in the decomposition of labile and recalcitrant pools of soil carbon and in the availability of recent photosynthate‐derived carbon for respiration. Variation in heterotrophic respiration rather than photosynthetic discrimination appeared to be the dominant factor governing δ 13 C R in our forests at near‐normal levels of precipitation. The results of our study can be used to better constrain future model estimates using δ 13 C R and ecosystem‐level discrimination in a temperate forest in the Asian monsoon region.

Temperate deciduous forest

Temperate forest

Temperate rainforest

10.1029/2007jg000574

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Aircraft measurements of the stable carbon isotopic ratio of atmospheric methane over Siberia

Global Biogeochemical Cycles (1996)

Satoshi Sugawara Takakiyo Nakazawa Gen Inoue Toshinobu Machida Hitoshi Mukai

Air samples collected using aircraft during the Siberian Terrestrial Ecosystem‐Atmosphere‐Cryosphere Experiments (STEACE) in the summer of 1993 and 1994 were analyzed for the carbon isotopic ratio, δ 13 C, of atmospheric CH 4 as well as for the CH 4 concentration. The CH 4 concentrations and δ 13 C values observed in the lower troposphere over wetlands in the West Siberian Lowland varied considerably, showing a clear negative correlation between the two components. From the relationships between measured values of the CH 4 concentration and δ 13 C, values of δ 13 C of CH 4 released from wetlands into the atmosphere were estimated to be −75 to −67‰. The results observed over oil wells and pipelines showed isotopic evidence for leakage of natural gas. Mean values of δ 13 C measured in the middle and upper troposphere over Siberia in the summer season were −47.9±0.3 and −47.8±0.2‰ for 1993 and 1994, respectively, which are quite similar to each other.

Isotopic ratio

Isotope Analysis

10.1029/96gb00038

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Flattening of the equatorial bulge of annual mean APO observed in the Western Pacific during the 09/10 El Nino event

Japan Geoscience Union (2014)

Yasunori Tohjima Hitoshi Mukai Toshinobu Machida Yukio Terao Yukihiro Nojiri

Flattening

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