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排序方式: 共有1210条查询结果,搜索用时 15 毫秒
1.
1 IntroductionAnicecoreobtainedfrom polarglaciersoricesheetsisoneofthemostimportantarchivestoreconstructpaleoclimaticandpaleoatmosphericcondition .Informationonpale o environmentcanbeextractedfromicecoresaschemicaland/orphysicalsignals.Amongthechemicalsignals,heavymetalsarenotedassignalsofterrestrialenvironmentalchangeandanthropogenicpollution (e.g .Murozumietal.1 969;NgandPatterson 1 981 ;Hongetal.1 994) .SinceconcentrationsofmostofthemetalsinpolarsnowincentralGreen landareatorbelowthepptl… 相似文献
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3.
Yuhei Yamamoto Yoshio Takahashi Yutaka Kanai Yoshio Watanabe Tomoya Uruga Hajime Tanida Yasuko Terada Hiroshi Shimizu 《Applied Geochemistry》2008,23(8):2452-2461
The uranium LIII-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 LIII-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. 相似文献
4.
Takeshi Umezu Hiroshi Ebihara Yōko Minamisako Hiroshi Watanabe 《Journal of Oceanography》1984,40(5):382-390
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. 相似文献
5.
Akio Maeda Kazuki Uejima Toru Yamashiro Masahito Sakurai Hiroshi Ichikawa Masaki Chaen Keisuke Taira Shinjirou Mizuno 《Journal of Oceanography》1996,52(3):375-388
An excitation of inertial oscillation in the upper layer east of course of Typhoon 9019 was fortuitously observed at three surface buoys deployed during the Ocean Mixed Layer Experiment (OMLET). The observed inertial oscillation was compared with wind fluctuation measured at Ocean Weather Station T (29°N, 135°E) which was placed at the center of a triangle with three vertexes occupied by the respective surface buoys. Inertial oscillation is effectively excited in the mixed layer at the eastern margin of the typhoon by a rapid decrease of wind rather than by prevailing strong wind. It is shown by means of a least square deviation that the inertial oscillation observed in the mixed layer has a period of 23.9 hours shorter than the local inertial period of 24.7 hours. This shorter period suggests that the inertial oscillation has the finite velocities of phase and group as an inertial internal wave. A theoretically obtained ratio of vertical component of group velocity to that of phase velocity, approximately agrees with observed value. The inertial internal wave is excited by fluctuation of divergence with near inertial period in the mixed layer. 相似文献
6.
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. 相似文献
7.
Shuichi Watanabe Naoto Higashitani Nobuo Tsurushima Shizuo Tsunogai 《Journal of Oceanography》1994,50(4):415-421
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. 相似文献
8.
The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands 总被引:3,自引:0,他引:3
In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i 相似文献
9.
Joji Ishizaka Yasuhisa Kitaura Yasuharu Touke Hiroaki Sasaki Akihiko Tanaka Hiroshi Murakami Toshikazu Suzuki Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2006,62(1):37-45
High resolution SeaWiFS data was used to detect red tide events that occurred in the Ariake Sound, Japan, a small embayment
known as one of the most productive areas in Japan. SeaWiFS chlorophyll data clearly showed that a large red tide event, which
damaged seaweed (Nori) cultures, started early in December 2000 in Isahaya Bay, expanded to the whole sound and persisted
to the end of February 2001. The monthly average of SeaWiFS data from May 1998 to December 2001 indicated that the chlorophyll
peaks appeared twice a year, in early summer and in fall, after the peaks of rain and river discharge. The SeaWiFS data showed
that the red tide event during 2000–2001 winter was part of the fall bloom; however, it started later and continued significantly
longer than other years. Satellite ocean color data is useful to detect the red tide; however the algorithms require improvement
to accurately estimate chlorophyll in highly turbid water and in red tide areas. 相似文献
10.
Yutaka W. Watanabe Yoshiyuki Takahashi Takashi Kitao Koh Harada 《Journal of Oceanography》1996,52(3):301-312
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. 相似文献