Hirotsugu Minami

Hydrate‐bearing structures in the Sea of Okhotsk

Gas hydrates are natural gas reservoirs in ice-like crystalline solids, and are stable in pore spaces of submarine sediments in water depths greater than about 300–500 m. They have been recovered in many of the worlds oceans, both at larger sub-bottom depths (up to 450 m) by drilling and near the seafloor in shallow cores by gravity-coring. In the latter case, the gas hydrates are related to the sites of enhanced seepage such as cold seeps and mud volcanoes [Ginsburg and Soloviev, 1998]. Multidisciplinary field investigations during the two cruises have revealed new, large hydrate-bearing seepage structures in the Sea of Okhotsk, a northwestern marginal sea of the Pacific Ocean (Figure l). The Derugin Basin at the central part of the Sea of Okhotsk, the zone of intensive gas seepage and hydrate accumulation, was studied during two cruises of the R/V Akademik M.A. Lavrentyev (LV) of the Russian Academy of Sciences (RAS), in August and October 2003 within the framework of the CHAOS project (hydroCarbon Hydrate Accumulations in the Okhotsk Sea) supported by funding agencies in five nations.

A new solid-liquid extraction sampling technique for direct determination of trace elements in biological materials by graphite furnace atomic absorption spectrometry

Abstract A new solid-liquid extraction sampling technique with graphite furnace atomic absorption spectrometry is based on the quantitative extraction of the element of interest from the biological powdered samples into a liquid phase of 1 mol 1 −1 nitric acid solution. Examinations of the conditions for sample preparation using solid-liquid extraction (i.e. the effect of concentration of nitric acid, sample mass and ultrasonication time on the extraction) have been carried out in order to obtain 100% extraction of cadmium, copper, lead and manganese from powdered biological samples to the liquid phase. 100% of extraction of these metals is successfully carried out using 1 mol 1 −1 nitric acid, and separation of solid phase and liquid phase is done by using a centrifuge (20 min, 4000 rev min −1 ). The proposed method is applied to the determination of cadmium and lead at 0.1 μ g −1 levels and of copper and manganese at 10 μ g −1 levels in powdered biological samples. These analytical results are ascertained by microwave induced nitrogen plasma-mass spectrometry. Detection limits for cadmium, copper, lead and manganese are, respectively, 0.012 μ g −1 , 0.829 μ g −1 , 0.082 μ g −1 and 0.125 μ g −1 in solid samples, when 50 mg of powdered biological samples is extracted in 5 ml of 1 mol 1 −1 nitric acid and then 10 μ l of extracted solution is measured. Precisions of the determination (relative standard deviation at five determinations) of cadmium, copper, lead and manganese are 3.4%, 3.1%, 3.9% and 3.1%, respectively.

Crystallization of authigenic carbonates in mud volcanoes at Lake Baikal

This paper presents data on authigenic siderite first found in surface sediments from mud volcanoes in the Central (K-2) and Southern (Malen’kii) basins of Lake Baikal. Ca is the predominant cation, which substitutes Fe in the crystalline lattice of siderite. The enrichment of the carbonates in the 13C isotope (from +3.3 to +6.8‰ for the Malen’kii volcano and from +17.7 to +21.9‰ for K-2) results from the crystallization of the carbonates during methane generation via the bacterial destruction of organic matter (acetate). The overall depletion of the carbonates in 18O is mainly inherited from the isotopic composition of Baikal water.

Gas hydrate forming fluids on the NE Sakhalin slope, Sea of Okhotsk

Abstract An area of focused fluid venting off NE Sakhalin, Sea of Okhotsk, was investigated in 2003 during the 31st and 32nd international expeditions of R/V Akademik M. A. Lavrentyev within the framework of the CHAOS Project. More than 40 structures related to seafloor gas venting were discovered and gas hydrates were sampled from three of these: CHAOS, Hieroglyph and Kitami. Geochemical analyses were used to define the mechanisms of gas hydrate accumulation and the sources of fluids involved. Chemical and isotopic analyses of the interstitial and hydrate waters suggest that hydrates were formed from seawater (or in-situ pore water) and an ascending fluid enriched in salts. Hydrate formation occurs at locations of the most intensive saline water upflow, and this is probably a function of the gas solubility in water in equilibrium with hydrate. The water involved in gas hydrate formation consists of about 70% pore water derived from the host sediment and 30% from the ascending fluid. The overall isotopic composition of the ‘fluid’ taking part in hydrate formation was calculated as δ2H≈−11‰ and δ18O≈−1.5‰.

Synergistic Extraction of Lanthanides(III) with N‐p‐Methoxybenzoyl‐N‐Phenylhydroxylamine and Neutral Nitrogen Donors

Abstract We investigated the extraction equilibrium behavior of a series of trivalent lanthanide ions, (M3+), La, Pr, Eu, Ho, and Yb, from tartrate aqueous solutions using a chloroform solution containing N‐p‐methoxybenzoyl‐N‐phenylhydroxylamine (Methoxy‐BPHA or HL) combined with an adductant, 1,10‐phenanthroline (phen) or 2,2′‐bipyridyl (bipy). The synergistic species extracted were found to be {ML2(phen)(HL)}+(1/2)Tar2− and {ML2(bipy)(HL)2}+(1/2)Tar2−, where Tar2− is the tartrate ion. The stoichiometry, the extraction constants, and the separation factors of these systems were determined. We discuss the extractability and the separation factors in comparison with self‐adduct chelates, ML3(HL)2,(o), which were formed in the absence of phen or bipy.

Sequentially sampled gas hydrate water, coupled with pore water and bottom water isotopic and ionic signatures at the Kukuy mud volcano, Lake Baikal: ambiguous deep-rooted source of hydrate-forming water

The isotopic and ionic composition of pure gas hydrate (GH) water was examined for GHs recovered in three gravity cores (165–193 cm length) from the Kukuy K-9 mud volcano (MV) in Lake Baikal. A massive GH sample from core St6GC4 (143–165 cm core depth interval) was dissociated progressively over 6 h in a closed glass chamber, and 11 sequentially collected fractions of dissociated GH water analyzed. Their hydrogen and oxygen isotopic compositions, and the concentrations of Cl– and HCO3– remained essentially constant over time, except that the fraction collected during the first 50 minutes deviated partly from this pattern. Fraction #1 had a substantially higher Cl– concentration, similar to that of pore water sampled immediately above (135–142 cm core depth) the main GH-bearing interval in that core. Like the subsequent fractions, however, the HCO3– concentration was markedly lower than that of pore water. For the GH water fractions #2 to #11, an essentially constant HCO3–/Cl– ratio of 305 differed markedly from downcore pore water HCO3–/Cl– ratios of 63–99. Evidently, contamination of the extracted GH water by ambient pore water probably adhered to the massive GH sample was satisfactorily restricted to the initial phase of GH dissociation. The hydrogen and oxygen isotopic composition of hydrate-forming water was estimated using the measured isotopic composition of extracted GH water combined with known isotopic fractionation factors between GH and GH-forming water. Estimated δD of −126 to −133‰ and δ18O of −15.7 to −16.7‰ differed partly from the corresponding signatures of ambient pore water (δD of −123‰, δ18O of −15.6‰) and of lake bottom water (δD of −121‰, δ18O of −15.8‰) at the St6GC4 coring site, suggesting that the GH was not formed from those waters. Observations of breccias in that core point to a possible deep-rooted water source, consistent with published thermal measurements for the neighboring Kukuy K-2 MV. By contrast, the pore waters of core St6GC4 and also of the neighboring cores GC2 and GC3 from the Kukuy K-9 MV show neither isotopic nor ionic evidence of such a source (e.g., elevated sulfate concentration). These findings constrain GH formation to earlier times, but a deep-rooted source of hydrate-forming water remains ambiguous. A possible long-term dampening of key deep-water source signatures deserves further attention, notably in terms of diffusion and/or advection, as well as anaerobic oxidation of methane.

Synergistic Extraction of Lanthanides(III) by Mixtures of N‐p‐Methoxybenzoyl‐N‐phenylhydroxylamine and 1,10‐Phenanthroline

Abstract We conducted a study on the equilibrium extraction behavior of the trivalent lanthanide ions (M3+), La, Pr, Eu, Ho, and Yb, from tartrate aqueous solutions into chloroform solutions containing N‐p‐methoxybenzoyl‐N‐phenylhydroxylamine (Methoxy‐BPHA, HL) and 1,10‐phenanthroline (phen). The synergistic species extracted was found to be {ML2(phen) (HL)}+(1/2)Tar2−, where Tar2− is tartrate ion. The extraction constants were calculated. The extraction separation behavior and extractability of lanthanides are discussed in comparison with the self‐adducted chelate, ML3(HL)2, which was extracted in the absence of phen, and synergistic extraction by mixtures of other extractants such as 2‐thenoyltrifluoroacetone, and neutral donors.

Spectrophotometic Determination Of Tin In Steels With2-(5-Nltro-2-Pyridylazo)-5-[N-n-Propyl-N-(3-Sulfopropyl)Amino]phenol

ABSTRACT A highly sensitive azo dye, 2-(5-nitro-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (Nitro-PAPS), is used as a colorimetric reagent for the determination of tin(IV) content. Nitro-PAPS reacts with tin(IV) to form a water-soluble complex in 1.0 M acetic acid. Full color development is attained within 5 minutes, and maintains constant absorbance for at least 24 hours. The apparent molar absorptivity is 7.7 x 104 dm3 mol−1 cm−1 at a maximum wavelength of 580 ran. Beers law is obeyed for tin(IV) in the range of 0-1.2 μg ml−1. The proposed method is successfully applied to the determination of trace amounts of tin in steels.

Possible variation in methane flux caused by gas hydrate formation on the northeastern continental slope off Sakhalin Island, Russia

The Sakhalin Slope Gas Hydrate Project (SSGH) is an international collaborative effort by scientists from Japan, Korea, and Russia to investigate natural gas hydrates (GHs) that have accumulated on the continental slope off Sakhalin Island, Okhotsk Sea. From 2009 to 2011, field operations of the SSGH-09, -10, and -11 projects were conducted. GH-bearing and -free sediment cores were retrieved using steel hydro- and gravity corers. The concentrations of sulfate ions in sediment pore waters were measured to investigate sulfate concentration–depth profiles. Seventeen cores showed linear depth profiles of sulfate concentrations. In contrast, eight cores and two cores showed concave-up and -down profiles plausibly explained by sudden increase and decrease in methane flux from below, respectively, presumably caused by the formation of gas hydrate adjacent to the core sampling sites.

Determination of zinc in marine/lacustrine sediments by graphite furnace atomic absorption spectrometry using Pd/Mg chemical modifier and slurry sampling

Effectiveness of Pd/Mg chemical modifier for the accurate direct determination of zinc in marine/lacustrine sediments by graphite furnace atomic absorption spectrometry (GF-AAS) using slurry samples was evaluated. A calibration curve prepared by aqueous zinc standard solution with addition of Pd/Mg chemical modifier is used to determine the zinc concentration in the sediment. The accuracy of the proposed method was confirmed using Certified Reference Materials, NMIJ CRM 7303-a (lacustrine sediment) from National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Japan, and MESS-3 (marine sediment) and PACS-2 (marine sediment) from National Research Council, Canada. The analytical results obtained by employing Pd/Mg modifier are in good agreement with the certified values of all the reference sediment materials. Although for NRC MESS-3 an accurate determination of zinc is achieved even without the chemical modifier, the use of Pd/Mg chemical modifier is recommended as it leads to establishment of a reliable and accurate direct analytical method. One quantitative analysis takes less than 15 minutes after we obtain dried sediment samples, which is several tens of times faster than conventional analytical methods using acid digested sample solutions. The detection limits are 0.13 µg g−1 (213.9 nm) and 16 µg g−1 (307.6 nm), respectively, in sediment samples, when 40 mg of dried powdered samples are suspended in 20 mL of 0.1 mol L−1 nitric acid and a 10 µl portion of the slurry sample is measured. The precision of the proposed method is 8–15% (RSD).