[in Japanese]

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We have developed an analytical method for the determination of bioactive trace metals in seawater using a chelating column concentration-inductively coupled plasma mass spectrometry. Using new chelating columns containing oxine or ethylene diamine triacetic acid, we are studying on preconcentration of trace metals and removal of major salts, expecting further refinement of methodology. The new method will be applied to observation of bioactive trace metals in the eastern Pacific.

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Sediment core samples were collected at 37 stations in the western north Pacific in 1997 - 2004. Biogenic constituents were determined in the samples. Results of opal in the sediments and also settling particles which were collected by sediment traps at some stations were reported here. Opal concentrations does not vary, also many reports show decreasing profile with depth in the sediment. The opal concentration in the sediment is less than 10% in south of 30N and it is larger than 10% in north of 40N. Opal flux observed by sediment trap has similer tendency. Opal contents in settling particle corrected in deep ocean deeper than 4500m is two to three times higher than opal in the sediment.

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[in Japanese]

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In Tsugaru Strait and its mixed water region, concentrations of Ra-226, Ra-228 were measured and compared with distribution of the water masses. Ra-226, Ra-228 concentrations were different from Tsugaru warm current to Oyashio current, and it was possible to distinguish both waters clearly by radium isotopes. In addition, the relation with the path of Tsugaru warm current was discussed the seasonal variation of Ra-226, Ra-228 conncentrations in seawater sample collected from Rokkasho and Oma coast.

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[in Japanese]

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We propose a hypothesis that Ultra-H3 (Ultramafic rock, Hydrothermal activity, Hydrogen, and Hyper SLiME) linkage was responsible for the development of primitive life on the early Earth. In order to establish the Ultra-H3 linkage hypothesis, we plan experimental investigations of hydrothermal reactions among hydrothermal solution, ultramafic rocks, and microorganisms using newly designed hydrothermal apparatus with both flexible reaction-cell and fluid-flow systems. The hydrothermal experiments will be performed to resolve the following issues: 1) relationships between HyperSLiME activity and hydrogen concentration of hydrothermal fluid, 2) hydrothermal hydrogen-generation under the specific condition of the early Earth (e.g., low-O2, low-SO4, high-CO2, low-pH, and komatiitic rocks), and 3) probability of formation of organic compounds such as amino acids that are essential to cellular life during the hydrothermal reaction.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Mercury wet deposition is dependent on both the scavenging of divalent gaseous mercury (RGM) and atmospheric particulate mercury (Hg(p)) by precipitation. In this study, the contribution of Hg(p) scavenging to mercury wet deposition in Japan was estimated on the basis of the scavenging ratios of other trace elements (i.e., Cd, Cu, Mn, Ni, Pb, V) existing entirely in particulate form. Their wet deposition fluxes and atmospheric concentrations, which were measured concurrently from April 2004 to March 2005 at 10 sites, were used for this estimation. On average at 10 sites, the contribution of Hg(p) scavenging to the annual mercury deposition flux was 26%, suggesting that mercury wet deposition in Japan is dominated by RGM scavenging. This RGM should be originated mainly from the in situ oxidation of gaseous elemental mercury (Hg(0)) in the atmosphere.

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[in Japanese]

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14C variations of atmospheric CO2 as well as human carbonaceous materials such as collagen fractions from teeth and bone, hair, nail, etc., of modern humans are influenced by 14C produced artificially by nuclear bomb tests in the atmosphere from late 1950s to early 1960s. By careful investigation of 14C concentration of tree rings and human tissue samples formed in this time ranges, we can establish a relation between their 14C concentrations and calendar year. By applying this relation to a sample whose 14C concentration can be measured, we can estimate the formation age of the sample. We discuss the application of this dating method to forensic investigations.

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[in Japanese]

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Origin and depositional environment of black carbonaceous cherts in the c. 3.4Ga Strelley Pool Chert that contain diverse and large microfossils are discussed, based on occurrence, sedimentary geology, and characteristics of rare earth elements.

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[in Japanese]

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We have determined nitrogen isotopic composition of amino acids in Omul fish scales collected from Lake Baikal during 1945-1995 to study the food web structure in the surface water of the lake.

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Recently, deep-sea precious corals attract much attention because climatic information and the history of deep-ocean circulation changes could be obtained from those corals with huge geographic and depth ranges in the ocean. Oxygen and carbon isotopic ratios as well as elemental compositions incorporated in the calcite skeleton of these corals have been proposed as a method for obtaining information from intermediate and deep-water environments. In the present study, we analyzed stable isotope ratios and elemental composition, together with radiocarbon (14C) dating, of three specimens of deep-sea precious corals from NW Pacific. Also, we discussed the differences in isotopic characteristics among precious, cold-water and hermatipic corals from the viewpoint as paleo-environmental archives.

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The oxygen isotopic values of coral skeletons are definitely smaller than those synthesized under equilibrium condition. This difference has been called vital effect. This includes metabolic effect and kinetic effect. In this study we report the kinetic effects of carbon and oxygen isotopes on the cultivated corals.

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[in Japanese]

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Temporal variation of methan concentration in groundwater at Omaezaki 500m well will be reported. Groundwater is sampled by use of the circular pumping method, becuase the water level at this well is about -2m from ground level. Bubble gas and discharged gas by vapor-liquid equilibrium are assumed as dissolved gas. Gas composition of dissolved gas is analyzed by a quadrupole mass spectrometer evely 10 minutes. Methan concentration non-regularly increased. Factors of methan release will be discussed.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Since 2001, degassing operation is going on at Lakes Nyos and Monoun, Cameroon, where CO2 of mantle origin is accumulating at an alrming rate. In the present report, we will report how much gas has been removed by the degassing operation and its consequence in the future.

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[in Japanese]

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Degassing of volatile elements are occurring trough volcano, hot spring and natural gas in the Japanese Islands. Among the volatiles, helium-3 is the most important nuclide to show the mantle signature. The ratio of helium-3 to helium-4 of crustal and/or radiogenic origin is a useful parameter to study tectonic setting of the region. Geographical distribution of the helium isotopes has been investigated since middle 1980s. On the other hand, recent advance of earthquake research makes precise seismic tomography. We present here complies of helium isotope data in Japan and discuss their relation to the sesimic tomography.

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