A new fluorometric method of analysis of selenium in sea water

A new method of determination of selenium and separation of Se(IV) and Se(VI) in sea water is described. The selenium is determined by fluorometric method using Se-DAN complex in cyclohexane media. Prior to the fluorometric determination, Se(IV) is separated from sea water by means of Se(IV)-DDTC complex which is adsorbed on the macroreticular resin. As to the separation of the total selenium from sea water sample, the reduction and coprecipitation method is used. Se(VI) is determined with the same method as used for the total selenium after the separation of Se(IV). The average recoveries are 92.5±1.3% for Se(IV) and 97.4±0.9% for Se. The standard deviation of analytical results is below 10%.     

Relationship between atmospheric fluxes and concentrations of terrigenous materials in the surface air over the Japan Sea

Relationship between atmospheric deposition fluxes and concentrations of Si and²¹⁰Po in the surface air were examined through daily basis simultaneous observation at the coast of the Japan Sea. Both the Si and²¹⁰Po, the atmospheric fluxes were highly variable from day to day. According to correlation analysis, there was no significant correlation between flux and atmospheric concentration of these terrigenous materials in the surface air. On the other hand, flux of Si and²¹⁰Po significantly correlated to precipitation rate. These results indicate that the atmospheric flux of terrigenous material is not constantly proportional to atmospheric concentration in the surface air. This may be due to the deposition flux represents an integrated value throughout the air column of in-and below-cloud, while the air concentration represents only the environment of earth's surface.     

Community Structure and Dynamics of Phytoplankton in the Western Subarctic Pacific Ocean: A Synthesis

The phytoplankton community in the western subarctic Pacific (WSP) is composed mostly of pico- and nanophytoplankton. Chlorophyll a (Chl a) in the <2 μm size fraction accounted for more than half of the total Chl a in all seasons, with higher contributions of up to 75% of the total Chl a in summer and fall. The exception is the western boundary along the Kamchatka Peninsula and Kuril Islands and the Oyashio region where diatoms make up the majority of total Chl a during the spring bloom. Among the picophytoplankton, picoeukaryotes and Synechococcus are approximately equally abundant, but the former is more important in term of carbon biomass. Despite the lack of a clear seasonal variation in Chl a concentration, primary productivity showed a large seasonal variation, and was lowest in winter and highest in spring. Seasonal succession in the phytoplankton community is also evident with the abundance of diatoms peaking in May, followed by picoeukaryotes and Synechococcus in summer. The growth of phytoplankton (especially >10 μm cell size) in the western subarctic Pacific is often limited by iron bioavailability, and microzooplankton grazing keeps the standing stock of pico- and nano-phytoplankton low. Compared to the other HNLC regions (the eastern equatorial Pacific, the Southern Ocean, and the eastern subarctic Pacific), iron limitation in the Western Subarctic Gyre (WSG) may be less severe probably due to higher iron concentrations. The Oyashio region has similar physical condition, macronutrient supply and phytoplankton species compositions to the WSG, but much higher phytoplankton biomass and primary productivity. The difference between the Oyashio region and the WSG is also believed to be the results of difference in iron bioavailability in both regions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bioenhancement of cadmium transfer along a multi-level food chain

Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP - e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)-->Palaemonetes pugio (grass shrimp)-->Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including (109)Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 muM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus.     

Hydrography and budget of dissolved total nitrogen and dissolved oxygen in the stratified season in Mikawa Bay,Japan

Distributions of salinity, dissolved total nitrogen (DTN) and dissolved oxygen (DO) were observed once a month throughout a year in Mikawa Bay, one of the most eutrophic bays in Japan. Supply of freshwater, DTN and DO from the land and precipitation was estimated. Hydrography, circulation and transformation of DTN and DO during the stratified period were investigated simultaneously by a two-layered box model analysis dividing the bay into five boxes. The two-layered circulation was confirmed. In the upper layer of the river mouth regions, a high production of particulate organic nitrogen (PON) due to the strong upwelling together with the river inflow was found. On the other hand, in the lower layer of the bay mouth region, a high deposition of PON due to weak upwelling and sometimes downwelling and a high decomposition of PON due to the inflow of DO abundant water were also found. The reason why the eutrophication is more severe in the eastern part than in the north-western part of the bay is discussed.     

Preserved paleo-oceanic plateaus in accretionary complexes: Implications for the contributions of the Pacific superplume to global environmental change

We have reinvestigated the mid-Cretaceous plume pulse in relation to paleo-oceanic plateaus from accretionary prisms in the circum-Pacific region, and we have correlated the Pacific superplume activity with catastrophic environmental changes since the Neoproterozoic. The Paleo-oceanic plateaus are dated at 75–150 Ma; they were generated in the Pacific superplume region and are preserved in accretionary prisms. The volcanic edifice composed of both modern and paleo-oceanic plateaus is up to 10.7 × 10⁶ km² in area and 19.1 × 10⁷ km³ in volume. The degassing rate of CO₂ (0.82 − 1.1 × 10¹⁸ mol/m.y.) suggests a significant impact on Cretaceous global warming. The synchronous occurrence of paleo-oceanic plateaus in accretionary complexes indicates that Pacific superplume pulse activities roughly coincided at the Permo-Triassic boundary and the Vendian–Cambrian boundary interval. The CO₂ expelled by the Pacific superplume probably contributed to environmental catastrophes. The initiation of the Pacific superplume contributed to the snowball Earth event near the Vendian–Cambrian boundary; this was one of the most dramatic events in Earth's history. The scale of the Pacific superplume activity roughly corresponds to the scale of drastic environmental change.     

Dynamic data integration for structural modeling: model screening approach using a distance-based model parameterization

This paper proposes a novel history-matching method where reservoir structure is inverted from dynamic fluid flow response. The proposed workflow consists of searching for models that match production history from a large set of prior structural model realizations. This prior set represents the reservoir structural uncertainty because of interpretation uncertainty on seismic sections. To make such a search effective, we introduce a parameter space defined with a “similarity distance” for accommodating this large set of realizations. The inverse solutions are found using a stochastic search method. Realistic reservoir examples are presented to prove the applicability of the proposed method.     

Preparation of a New Geological Survey of Japan Geochemical Reference Material: Coral JCp-1

A new geochemical reference material, coral Porites sp. JCp-1 has been prepared by the Geological Survey of Japan (GSJ). Provisional values for twenty one major, minor and trace elements are presented. The homogeneity tests showed that all elements studied are considered to be homogeneously distributed.     

Thermodynamic modelling of sodic pyroxene solid-solution and its application in a garnet-omphacite-kyanite-coesite geothermobarometer for UHP metamorphic rocks

A garnet-omphacite-kyanite-coesite geothermobarometer is constructed to estimate the peak metamorphic pressure of ultrahigh-pressure (UHP) eclogites. For this we use a quaternary regular solution model for garnet, and propose a new model for sodic pyroxene that assumes double site solid-solution (Na,Ca)^M2(Al,Fe³⁺,Fe²⁺,Mg)^M1Si₂O₆, where cations in the M2- and the M1-sites mix randomly but with inter-site interactions, not only between nearest neighboring cations but also between next nearest neighboring cations. In the new model, overall excess interaction parameters are quantitatively deduced from the previous experimental data and critical temperature, and the activity of the jadeite component agrees reasonably with that based on the Landau theory. Furthermore, the relations of the calculated order parameter to temperature and composition are consistent with other experimental works. These facts support the usefulness of the new model. Application of our geothermobarometer to kyanite eclogite gave metamorphic conditions around 3.4 GPa and 800 ^∘C for both samples from the Dora Maira Massif, Western Alps, and from Rongcheng County, in the Su-Lu region of eastern China. Received: 30 December 1996 / Accepted: 25 August 1997     

Bathymetric and geochemical investigation of Kawah Ijen Crater Lake, East Java, Indonesia

A bathymetric survey of Kawah Ijen crater lake was conducted by acoustic sounding in 1996 to compare the lake morphology with those measured in 1922, 1925 and 1938, and to calculate the present lake volume. Even though the lake experienced several hydrothermal eruptions, the maximum depth became shallower (182 m) than before (200 m), resulting in a reduced lake volume (3.0×10⁷ m³).Fifty-two major and minor constituents including rare earth elements and polythionates (PT) of the lake waters at various depths were determined by ICP-AES, ICP-MS and HPLC, respectively. These ions except for several volatile elements are taken up by lake fringe through congruent dissolution of pyroclastics of Kawah Ijen volcano. Most ions are homogeneously distributed throughout the lake, although PT showed a considerable vertical variation. Rare earth elements (REE) in the Kawah Ijen water as well as those from other hyper-acidic crater lakes show distribution patterns likely due to the three rock dissolution (preferential, congruent and residual) types, and their logarithmic concentrations linearly depend upon the pH values of the lake waters.Using the PT degradation kinetics data, production rates of PT, injection rates of SO₂ and H₂S into the lake were estimated to be 114, 86 and 30 tons/day, respectively. Also travel time of the spring water at the Banyupahit Riverhead from Kawah Ijen was estimated to be 600–1000 days through the consideration of decreasing rates of PT. Molten sulfur stocks containing Sn, Cu, Bi sulfides and Pb-barite exposed on the inner crater slope were presumed to be extinct molten sulfur pools at the former lake bottom. This was strongly supported by the barite precipitation temperature estimated through the consideration of the temperature dependence of Pb-chlorocomplex formation.