Measurement of Halogenated Dicarboxylic Acids in the Arctic Aerosols at Polar Sunrise     

M. Narukawa  K. Kawamura  H. Hatsushika  K. Yamazaki  S.-M. Li  J. W. Bottenheim  K. G. Anlauf 《Journal of Atmospheric Chemistry》2003,44(3):323-335

Halogenated dicarboxylic acids, such as bromomalonic (Br-C₃), chlorosuccinic (Cl-C₄) and bromosuccinic (Br-C₄) acids, have been measured, for the first time, in the arctic aerosols during the polar sunrise experiment ALERT2000 (February to May). They were detected in the light spring, but not in the dark winter. Concentration ranges of halogenated diacids in the spring were 0.11–0.68 ng m^–3 for Br-C₃ diacid, 0.04–0.10 ng m^–3 for Cl-C₄ diacid and 0.12–0.20 ng m^–3 for Br-C₄ diacid. Those of Br-C₃ diacid increased from late April to early May, whereas Cl-C₄ diacid decreased. In contrast, Br-C₄ diacid showed maximum concentrations in the middle of the experiment. A strong negative correlation (R = –0.98) was obtained between Br-C₃ and Cl-C₄ diacids. Concentrations of methanesulfonic acid (MSA) also increased from late April to early May whereas those of Cl^– ion decreased. A strong positive correlation was found between Cl-C₄ diacid and Cl^– ion (R = 0.99) and between Br-C₃ diacid and MSA (R = 0.96). These results suggest that Br-C₃ diacid is primarily derived from marine biogenic source, whereas Cl-C₄ diacid is secondarily formed by heterogeneous reaction involving halogen chemistry on sea salt. Satellite images of sea ice concentrations and backward air mass trajectories suggest that the aerosols containing halogenated diacids were transported over the sampling sites from the Arctic Ocean covered with sea ice.  相似文献   

Configuration of subducting Philippine Sea plate and crustal structure in the central Japan region     

Takashi Iidaka  Tetsuya Takeda  Eiji Kurashimo  Tomonori Kawamura  Yoshiyuki Kaneda  Takaya Iwasaki 《Tectonophysics》2004,388(1-4):7

A seismic experiment with six explosive sources and 391 seismic stations was conducted in August 2001 in the central Japan region. The crustal velocity structure for the central part of Japan and configuration of the subducting Philippine Sea plate were revealed. A large lateral variation of the thickness of the sedimentary layer was observed, and the P-wave velocity values below the sedimentary layer obtained were 5.3–5.8 km/s. P-wave velocity values for the lower part of upper crust and lower crust were estimated to be 6.0–6.4 and 6.6–6.8 km/s, respectively. The reflected wave from the upper boundary of the subducting Philippine Sea plate was observed on the record sections of several shots. The configuration of the subducting Philippine Sea slab was revealed for depths of 20–35 km. The dip angle of the Philippine Sea plate was estimated to be 26° for a depth range of about 20–26 km. Below this depth, the upper boundary of the subducting Philippine Sea plate is distorted over a depth range of 26–33 km. A large variation of the reflected-wave amplitude with depth along the subducting plate was observed. At a depth of about 20–26 km, the amplitude of the reflected wave is not large, and is explained by the reflected wave at the upper boundary of the subducting oceanic crust. However, the reflected wave from reflection points deeper than 26 km showed a large amplitude that cannot be explained by several reliable velocity models. Some unique seismic structures have to be considered to explain the observed data. Such unique structures will provide important information to know the mechanism of inter-plate earthquakes.  相似文献   

Conversion of sedimentary fatty acids from extractable (unbound + bound) to tightly bound form during mild heating     

Kimitaka Kawamura  Ryoshi Ishiwatari 《Organic Geochemistry》1985,8(3):197-201

Prolonged heating (1–248 days) of a recent sediment was conducted under mild conditions (65 and 83°C) to understand the thermal behavior of extractable (unbound and bound) fatty acids (C_12C32). In the course of the heating, the concentrations of saturated and monounsaturated fatty acids first decreased, and then increased. This indicates that extractable fatty acids can be converted to a tightly bound form upon heating, before fatty acids are extensively released from sediment matrices. Changes in molecular distributions of extractable fatty acids upon heating were also observed. The higher molecular weight fatty acids (?C₂₀) are more likely to become tightly bound than are lower molecular weight (<C₂₀). Monounsaturated fatty acids (C_16:1 and C_18:1) are more easily converted to the tightly bound form than polyunsaturated fatty acids (C_18:2 and C_18:3). These differences probably reflect their mode of occurrence in sediments, which are closely related to their origin.  相似文献   

Molecular clouds and star formation in the Magellanic Clouds and the Milky Way     

Akiko Kawamura 《Astrophysics and Space Science》2008,313(1-3):145-151

Star formation is a fundamental process that dominates the life-cycle of various matters in galaxies: Stars are formed in molecular clouds, and the formed stars often affect the surrounding materials strongly via their UV photons, stellar winds, and supernova explosions. It is therefore revealing the distribution and properties of molecular gas in a galaxy is crucial to investigate the star formation history and galaxy evolution. Recent progress in developing millimeter and sub-millimeter wave receiver systems has enabled us to rapidly increase our knowledge on molecular clouds. In this proceedings, the recent results from the surveys of the molecular clouds in the Milky Way and the Magellanic Clouds as well as the Galactic center as the most active regions in the Milky Way are presented. The high sensitivity with unrivaled high resolution of ALMA will play a key role in detecting denser gas that is tightly connected to star formation.  相似文献   

Assessing impervious area ratios of grid-based land-use classifications on the example of an urban watershed     

Tatsuya Koga  Akira Kawamura  Hideo Amaguchi  Hiroto Tanouchi 《水文科学杂志》2016,61(9):1728-1739

ABSTRACT

When applying a distributed hydrological model in urban watersheds, grid-based land-use classification data with 10 m resolution are typically used in Japan. For urban hydrological models, the estimation of the impervious area ratio (IAR) of each land-use classification is a crucial factor for accurate runoff analysis. In order to assess the IAR accurately, we created a set of vector-based “urban landscape GIS delineation” data for a typical urban watershed in Tokyo. By superimposing the vector-based delineation map on the grid-based map, the IAR of each grid-based land-use classification was estimated, after calculating the IARs of all grid cells in the entire urban watershed. As a result, we were able to calculate the frequency distribution of IAR for each land-use classification, as well as the spatial distribution of IARs for the urban watershed. It is evident from the results that the reference values of IAR for the land-use classifications were estimated very roughly and inherited errors of between about 7% and 70%, which corresponds to more than 100 mm increase of direct runoff for the 1500 mm annual average precipitation.