地球化学
Online ISSN : 2188-5923
Print ISSN : 0386-4073
ISSN-L : 0386-4073
34 巻, 3 号
「21世紀初頭の海洋地球化学の研究」特集号
選択された号の論文の7件中1~7を表示しています
「21世紀初頭の海洋地球化学の研究」総説
  • 角皆 静男
    2000 年 34 巻 3 号 p. 125-134
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    Marine Chemistry in Japan in the 20th century has been reviewed. The subjects discussed are fractionation of sea salt particles, contribution of dry fallout, sulfur compounds in the maritime air, residence time of tropospheric aerosols, vertical eddy diffusivity of the Pacific Deep Water, mechanism removing chemical substances from seawater, sediment trap experiments, sites of organic matter decomposition, influence of atmospheric fallout on marine ecosystem, role of Si in marine ecosystem, corals and CO2, the western North Pacific and CO2, Pacific Intermediate Water absorbing atmospheric CO2, marginal seas absorbing atmospheric CO2, gas exchange velocities at the surface, genesis of manganese nodules, and paleoclimate from Marine Chemistry.
  • 長沼 毅
    2000 年 34 巻 3 号 p. 135-141
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    Microbial respiration is versatile in exploiting terminal electron acceptors (TEAs). In addition to dioxygen (O2), prokaryotic microorganisms utilize nitrate, sulfate, carbon dioxide, etc, as TEAs. Respiration using nitrate as a TEA, or denitrification, results in the release of dinitrogen (N2). Oceanic denitrification is largely limited to the oxygen minimal layer, which is developed below photosynthetic zone; bottom waters are relatively rich in dioxygen, thus 'peak minimum' in dioxygen concentration is formed. However, denitrification is thought to have been a predominant process during the past oceanic anoxic events (OAEs), and denitrification must have been closely coupled with microbial nitrogen fixation. Therefore, a 'short-circuit' cycling of nitrogen is presumed for the biogeochemistry during the past OAE periods. Respiration using sulfate as a TEA, or sulfate reduction, is also thought to have been a major process during the OAEs. Sulfate reduction using methane results in carbonate rock formation, as seen in modern methane-rich cold seeps. This serves as an effective methane-trap, lowering the amount of methane to be released into the hydro-atmosphere. Influence of microbial versatility in TEA utilization on biogeochemical cyclings, along with other examples, is discussed.
  • 岡田 尚武
    2000 年 34 巻 3 号 p. 143-148
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    Material cycle in present ocean represents only one phase of the progressively changing ocean material cycle system, and a through evaluation of the system in different time periods under different oceanic/climatic modes is important to understand comprehensively the biological role in the global ocean material cycle. Current knowledge on the biotic role and environmental control during the formation of Cretaceous organic carbon-rich sediments and black shales is briefly reviewed. This paper has also reviewed recent studies on the contribution of biological PIC (particulate inorganic carbon), particularly of coccolithophores, to the present global ocean carbon cycle. Also, the importance of the role of the newly found underground biosphere in the oceanic material cycle is emphasized.
  • 益田 晴恵
    2000 年 34 巻 3 号 p. 149-151
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    Important future subjects of the marine-chemistry and related scientific fields are summarized. It is urgently needed to precisely estimate rules of the ocean to preserve the physico-chemical condition of the Earth's system and foresee the future impact to our environment. Thus, in addition to the knowledge of the present situation of marine chemistry and circulating systems, we have to understand the history and causes and results of the historic events which changed the oceanic and earth's environments. Also, we have to acceralate collaboration of the scientific projects and basic education, and to interchange scientist in the different fields.
  • 川幡 穂高
    2000 年 34 巻 3 号 p. 153-160
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    Owing to continuous increase in carbon dioxide and other greenhouse gas (e.g., methane) emissions due to human activities, especially global warming is now being more seriously addressed world wide because it may lead to the climatic change in future. Therefore it is important to study the relationship between the climatic change and global carbon cycle. In the first step, the material transport in the oceans affected by large scale climatic changes such as ENSO (El Niño/Southern Oscillation) and Asian monsoon should be investigated. By obtaining algorithm and relative parameters for the estimation of chlorophyll-a standing stock and primary production from the satellite data, we will get time-series global map on primary production. And the combination of satellite imagery analysis and the sediment trap experiments will provide important information on the fluctuation of biological pump, responding to these cyclic climatic change. The fluctuations in SST and SSS (sea surface temperature and salinity) over the last 200-300 years will be estimated by the analysis of coral annual banding. During glacial times, the Indonesian maritime continent may play an important role in the global conveyer current. The current from the Pacific to the Indian ocean passing through the straits in the region, might change substantially during glacial low sea levels when the Sunda and Sahul platforms were emergent. These studies will enable us to answer what kind of role the Pacific has played in the change in climate, ocean environments and material cycle.
  • 野崎 義行
    2000 年 34 巻 3 号 p. 161-167
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    This article briefly reviews the recent advances in research on the concentration and distribution of the elements in the ocean. Since the last compilation of North Pacific vertical profiles of elements on a periodic table (Nozaki, EOS 78, 221,1997), new data have become available for Nb, Ta, and Os in the literature. Those are shown graphically, and the conservativeness of Os in seawter is examined. We have still lack of knowledge on the fluxes to and out of the ocean for many elements including the above. Chemical speciation and relative importance of complexation with organic ligands in seawater are very obscure as yet for many trace metals. Iron, which plays an important role in the oceanic biogeochemistry of plankton growth and carbon cycling, is not an exemption. Coupling of radionuclide tracers which can provide time-scales and the spatial variations of concentration reflected by the strength of sources and sinks with an isotopic "finger print" should help solve some of the issues generated on the dynamic aspects of elements in the ocean. A case study for Nd by Amakawa et al. (2000) is also briefly outlined.
1998年度日本地球化学会奨励賞受賞記念論文
  • 鍵 裕之
    2000 年 34 巻 3 号 p. 169-189
    発行日: 2000/08/23
    公開日: 2017/01/02
    ジャーナル フリー
    This paper reviews three topics on the spectroscopic approach to the natural carbonaceous materials, especially focuses on photoluminescence (PL) spectroscopy of natural polycrystalline diamonds and Raman spectra deciphering chemical structure of graphite. The first topic is characteristic PL spectra of carbonado natural polycrystalline diamond whose origin has been in enigma. We have shown that carbonado from Central African Republic can be grouped into two groups according to the structure of PL spectra. PL of carbonado resulted from radiation-induced damage and interaction with thermal fluids. Carbon isotope composition, thermal behavior, REE abundance correlate with PL. We suggested that the characteristics of carbonado were induced at the last stage by reaction with thermal fluids. The second is micro Raman spectroscopy characterizing the chemical structure of graphitic material in ureilite. We proposed array plots between Raman frequency of E2g mode of graphite and intensity ratio of G-band to D-band. The distribution in the array plots was proved to be closely linked to the extent of shock which ureilites suffered. The third is on the technical caution on micro-Raman spectroscopy. Laser-induced heating during measurements of micro-Raman spectra, in some cases, gives rise to considering downshifts in Raman spectra of powder samples. We showed that the intensity ratio of Stokes line to Anti-Stokes line is potential to monitor the temperature of sample surface to cancel out the artificial downshifts. Furthermore, we demonstrated that the stacking sequences of graphite did not affect the intralayer vibrational frequency.
feedback
Top