Anthropogenic trace metals in an ice core at Vestfonna,Svalbard, Norway

1　IntroductionAnicecoreobtainedfrom polarglaciersoricesheetsisoneofthemostimportantarchivestoreconstructpaleoclimaticandpaleoatmosphericcondition .Informationonpale o environmentcanbeextractedfromicecoresaschemicaland/orphysicalsignals.Amongthechemicalsignals,heavymetalsarenotedassignalsofterrestrialenvironmentalchangeandanthropogenicpollution (e.g .Murozumietal.1 969;NgandPatterson 1 981 ;Hongetal.1 994) .SinceconcentrationsofmostofthemetalsinpolarsnowincentralGreen landareatorbelowthepptl…     

High-sensitive measurement of uranium LIII-edge X-ray absorption near-edge structure (XANES) for the determination of the oxidation states of uranium in crustal materials

The uranium L_III-edge XANES spectra for natural rocks at the concentration range of 0.96–124 mg kg⁻¹ were measured using a log spiral bent crystal Laue analyzer (BCLA) combined with a multi-element Ge detector. It was found that the quality of the XANES spectra using the BCLA was greatly improved due to a reduction of interfering fluorescence from major components such as Rb and Sr. The ratio of signal to background intensities in the U L_III-edge XANES spectra increased by a factor of 2.9–17 with the use of the BCLA, which greatly enhanced the detection limit for the speciation of the oxidation states of U or the U(IV)/U(VI) ratio of natural samples. In addition, it was demonstrated that the fluorescence XANES method coupled with the BCLA enable determination of the speciation of U for various natural samples such as acidic igneous rocks, ferromanganese nodules, sediments, and some sedimentary rocks such as shale and limestone.     

In situ strength measurements on natural upper-mantle minerals

Using in situ strength measurements at pressures up to 10 GPa and at room temperature, 400, 600, and 700°C, we examined rheological properties of olivine, orthopyroxene, and chromian-spinel contained in a mantle-derived xenolith. Mineral strengths were estimated using widths of X-ray diffraction peaks as a function of pressure, temperature, and time. Differential stresses of all minerals increase with increasing pressure, but they decrease with increasing temperature because of elastic strain on compression and stress relaxation during heating. During compression at room temperature, all minerals deform plastically at differential stress of 4–6 GPa. During subsequent heating, thermally induced yielding is observed in olivine at 600°C. Neither orthopyroxene nor spinel shows complete stress relaxation, but both retain some stress even at 700°C. The strength of the minerals decreases in the order of chromian-spinel ≈ orthopyroxene > olivine for these conditions. This order of strength is consistent with the residual pressure of fluid inclusions in mantle xenoliths.     

Transfer of60Co from midwater squid to sperm whales

Sperm whales are notable squid-eaters. They feed mainly on medium to large-sized cephalopods at midwater levels and defecate near the surface. This suggests the existence of an upward transport of⁶⁰Co by sperm whales from the mesopelagic zone (150–1,200 m). To elucidate this squid-whale route for this artificial radionuclide,⁶⁰Co content was determined in squid and in predator whales captured by commercial whaling. In the Cephalopoda livers⁶⁰Co levels of 30–500 mBq kg^–1 wet were found and in the viscera of Odontoceti (toothed whales) 15–40 mBq kg^–1 wet. About 0.3% of⁸⁰Co ingested was estimated to be retained in a 23-year-old male sperm whale. In the livers of Bryde's whales,⁶⁰Co levels of 40–80 mBq kg^–1 wet were detected, but not in euphausiids and sardines, their possible prey. The level of Co in sperm whales was nearly the same as in Bryde's whales. Specific radioactivity⁶⁰Co/⁵⁹Co in mBq µg^–1 was several times higher in sperm whale (1.1–1.6) than in cephalopods (0.19–0.77). Eating prey with a high content of⁶⁰Co in the 1960's may have contributed to the present body burden in sperm whales with a long-life span. However, the origin of⁶⁰Co in Bryde's whales is unknown.     

Role of dissolved silicate in the occurrence of a phytoplankton bloom

The spring bloom of phytoplankton was studied in March in Funka Bay, Japan, to test the Tsunogai (1979)'s hypothesis regarding the role of silicate in the bloom. The hypothesis comprises two parts. 1) Diatoms are predominant when all the physical and chemical conditions are adequate for plankton growth. 2) Since the Si:P ratio of the diatom body is usually much larger than that of sea water, flagellates (non-siliceous phytoplankton) replace diatoms after dissolved silicate in the sea water has been almost completely consumed by diatoms. At the end of the bloom in late March phosphate still remained in the water but silicate was exhausted and the main species of phytoplankton changed from diatoms to flagellates. Grazing pressure by zooplankton at this time was not so great. A model using the data on assimilation rates of silicate showed a dramatic change of silicate uptake in late March. Poison in scallops caused byProtogonyaulux sp. (dinoflagellates) rapidly increased from mid-April at all stations along the coast of Funka Bay. All of these findings support Tsunogai's hypothesis.     

The instability of viscous two-layer oscillatory flows

The instability of oscillatory flows in a two-layer fluid where the two layers differ in density and viscosity has been analysed using a perturbation method for long waves with special interest on effects of viscosity, time scale, density and depth of the fluid. The flow of a fluid with homogeneous density can be unstable, when the kinematic viscosity of the upper fluid layer is different from that of the lower one. Viscosity stratification results in unstable oscillatory flows. Two limiting cases of single-layer flow are also considered.     

Annual variation of methane in seawater in Funka bay,Japan

The concentration of methane in seawater was determined approximately once a month for one year from August 1990 to July 1991 at a station close to the center of Funka bay (92 m depth) and some supplementary observations were also carried out. The concentration of methane was usually increased with increasing depth, suggesting that methane was emitted from the bottom of the bay. While highly variable both spatially and temporally, the emission was intense in March and April, a period immediately after the spring bloom of phytoplankton. The maximum of methane found in the intermediate water suggests its source from the slope of the bay. The concentration of methane in the surface water changed seasonally and also interannually. The annually averaged flux of methane transferred to the atmosphere in the bay was estimated to be 6×10^–3 gCH₄m²/day. The coastal zone in the world may be a significant source of the atmospheric methane, although its source strength has yet to be accurately estimated from more data in different coastal seas.     

Detection of systematic errors in XBT data and their correction

Comparison experiment between XBT of T-7 probe and CTD was conducted at 15 stations in the sea area centered on 29°N, 135°E in December 1985. There were systematic errors in XBT temperature profiles in comparison with CTD temperature profiles. The main cause of errors was attributed to an error in the free-fall speed of the XBT probes which was provided by the XBT maker. A previous equation for depth correction proposed by Heinmilleret al. (1983) could not give effective correction for our data. A new equation between the probe depth and the elapsed time from landing of the probe on the water was obtained by the method of adjusting temperature gradients of XBT profiles to those of CTD profiles. This equation agreed with the theoretical result given by Seaver and Kuleshov (1982) much better than that of Heinmilleret al. (1983). Systematic errors due to a scatter of values of the reference resistance and variation of B-constant of thermistors used in XBT also seemed to exist. After an adjustment using the temperature difference between XBT and CTD in the mixed layer with depths of about 100 m, the standard deviation of temperature difference between XBT and CTD from the surface to the depth of 750 m was 0.14°C.     

Total amount of oceanic excess CO2 taken from the North Pacific subpolar region

Concentrations of total carbonate, alkalinity and dissolved oxygen were obtained near the 1973 GEOSECS stations in the North Pacific subpolar region north of 40°N along 175°E between 1993 and 1994. A difference of excess CO₂ content between the GEOSECS and our expeditions was estimated. The maximum difference in water column inventory of excess CO₂ has increased by about 280 gC m^–2 above 2000 m depth which apparently means an uptake of excess CO₂ taken from air to sea during the last two decades. An averaged value of the annual flux of excess CO₂ at 75–1000 m depth was 8.63±2.01 gC m^–2yr^–1 in the North Pacific subpolar region. By introducing the annual flux of excess CO₂ into a two-box model for the North Pacific subpolar region, a penetration factor of excess CO₂ from air to sea was obtained to be 1.08×10^–2 gC m^–3ppm^–1 in the North Pacific subpolar region. Based on this factor, the surface concentration of excess CO₂ in the North Pacific subpolar region was estimated to be 68 mole I^–1, suggesting that the North Pacific subpolar region absorbed atmospheric excess CO₂ more than the saturated concentration of excess CO₂. Total amount of excess CO₂ taken from the North Pacific subpolar region by 1993 was estimated to be 36.2×10¹⁵ gC, which was equal to about one tenth of that released by human activities after the preindustrial era.