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51.
52.
Millennial‐scale stratigraphy of a tide‐dominated incised valley during the last 14 kyr: Spatial and quantitative reconstruction in the Tokyo Lowland,central Japan
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Susumu Tanabe Toshimichi Nakanishi Yoshiro Ishihara Rei Nakashima 《Sedimentology》2015,62(7):1837-1872
Spatial and quantitative analysis of infilling processes of the tide‐dominated incised valleys beneath the Tokyo Lowland during the last 14 kyr was undertaken by using data from 18 sediment cores, 467 radiocarbon dates and 6100 borehole logs. The post‐Last Glacial Maximum valley fills consist of braided river, meandering river, estuary, spit and delta systems in ascending order. The boundary between the estuary and delta systems is regarded as the maximum flooding surface. The maximum flooding surface beneath the Tokyo Lowland is dated at 8 ka in the Arakawa Valley and 7 ka in the Nakagawa Valley. This age difference is due to the migration of the Tone River from the Arakawa Valley to the Nakagawa Valley at 5 ka, and suggests that the widely held view that the global initiation of deltas coincided with the abrupt rise of sea‐level at 9 to 8 ka is true only where there has been steady sediment supply from major rivers. The meandering river system is dominated by sheet‐like sands that were deposited during lateral migration of channels during the Younger Dryas and isolated vertical sands within muds that reflect vertical aggradation of channels before and after the Younger Dryas. The transition between these channel geometries is controlled by a threshold sea‐level rise of 4 to 7 mm yr?1. Before migration of the Tone River at 5 ka, the tide‐dominated bay in the Nakagawa Valley was filled by upward‐fining laterally accreting muds. The muds accreted from the margin to the axis of the bay. Such lateral accretion of suspended particles derived from outside the bay has been documented in other tide‐dominated coastal environments and is probably common in other similar settings. After the migration of the Tone River, the bay was filled by upward‐coarsening deltaic sediments. 相似文献
53.
Sohiko Kameyama Urumu Tsunogai Fumiko Nakagawa Motoki Sasakawa Daisuke D. Komatsu Akira Ijiri Junko Yamaguchi Takeo Horiguchi Hiroshi Kawamura Aika Yamaguchi Atsushi Tsuda 《Marine Chemistry》2009,115(1-2):92-101
During the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study ΙΙ (SEEDS-II), we monitored variations in the concentrations of non-methane hydrocarbons (NMHCs), CH3Cl, N2O, and CH4 within a phytoplankton bloom. Stable isotopic compositions were also determined to evaluate the sources of the variations. Although there was little variation in either the concentrations or the stable isotopic compositions of alkenes, CH3Cl, N2O, and CH4 during the 23-day observation period, alkane concentrations increased substantially as the phytoplankton bloomed. The column-integrated quantities of alkanes increased to 3 times pre-bloom levels for C2H6, 5 times for C3H8, and 20 times for n-C4H10. The δ13C values of both C2H6 and C3H8 remained almost constant while concentrations increased, whereas that of n-C4H10 increased by about 12‰. To evaluate the sources of the alkanes produced during the bloom, we compared their δ13C values with those of alkanes produced in axenic phytoplankton cultures in our laboratory. We concluded that during the SEEDS-ΙΙ experiment the major portions of C2H6 and C3H8 were produced during the autolysis of diatoms cells, whereas n-C4H10 was produced during autolysis of other phytoplankton cells such as cryptophytes and dinoflagellates. 相似文献
54.
Alkalinization and acidification of stream water with changes in atmospheric deposition in a tropical dry evergreen forest of northeastern Thailand
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Hiroyuki Sase Jesada Luangjame Hathairatana Garivait Bopit Kietvuttinon Thiti Visaratana Masato Kamisako Ryo Kobayashi Seiichi Ohta Junko Shindo Kentaro Hayashi Hideshige Toda Kazuhide Matsuda 《水文研究》2017,31(4):836-846
Field surveys on atmospheric deposition and stream water chemistry were conducted in an evergreen forest in northeastern Thailand characterized by a tropical savanna climate with distinct dry and wet seasons. Atmospheric deposition of ion constituents by throughfall and stemflow was shown to increase in the beginning and end of the wet season, reflecting the precipitation pattern. The pH and electrical conductivity of stream water increased with alkalinity and base cation concentrations due to mineralization of organic matter by the first rain and retention of anions in soil during the start of the wet season. After initial alkalinization, the pH and alkalinity declined rapidly with the highest SO42? concentration displayed in the middle towards the end of the wet season. The magnitude of peaks in SO42? concentration (13.5–60.6 μmolc/L) reflects deposition during the first 2 months of the wet season (March and April) in respective years (60.8–170 molc/ha). Release of SO42? with H+, which is retained in soil during the early wet season, may cause acidification later in the season. The deposition and concentration of SO42? declined over 6 years. However, the pH of stream water declined with increasing concentrations of SO42? and other major ions. The release of materials accumulated in the ecosystem was facilitated by the decrease in SO42? concentration/deposition and increased precipitation in the middle–late wet season. The retention‐release cycle of SO42? largely contributed to both seasonal and interannual variations in stream water chemistry in the tropical savanna climate studied. 相似文献
55.
Junko Mochizuki 《Climate Policy》2013,13(6):1337-1349
After years of discussions and trials, Japan's domestic emissions trading scheme remains purely voluntary. The newly elected Democratic Party of Japan (DPJ) has taken a firmer stance on climate change, initially intending to establish a nationwide mandatory cap-and-trade as early as 2011. This has promoted several questions regarding the possible designs and feasibility of such a scheme. This article describes the key features of the two trial schemes implemented, thus far, assesses the effectiveness of their implementation and discusses what will be the likely areas of contention should the Japanese government introduce a mandatory cap-and-trade in the future. The analyses indicate that the initial years of ‘Japan's Voluntary Emissions Trading Scheme’ (JVETS) implementation have shown positive performance, although its scale has remained limited. The ‘Trial Implementation of an Integrated Domestic Market for Emissions Trading’ emerged as a hybrid scheme, one that incorporated varying interests. Significant institutional developments have taken place in recent years, however the effectiveness of the present trial scheme also seems restricted. 相似文献
56.
Reiji Kubota Takashi Kunito Junko Fujihara Shinsuke Tanabe Jian Yang Nobuyuki Miyazaki 《Marine pollution bulletin》2005,51(8-12):845
Concentrations of total arsenic and individual arsenic compounds were determined in liver, muscle, kidney and blubber of mother and fetus of Dall’s porpoises collected from off Sanriku, Japan, in the year 2000 to characterize the placental transfer of arsenic to fetus in cetaceans. Arsenic was detected in all the tissues of Dall’s porpoises. Total arsenic concentrations in liver, kidney, muscle and blubber were 0.76, 0.69, 0.35 and 0.55 μg/g wet wt, respectively, for mother and 0.28, 0.23, 0.26 and 0.07 μg/g wet wt, respectively, for fetus. In all the tissues, concentrations of total arsenic in mother Dall’s porpoise were higher than in fetus. Arsenic speciation revealed that arsenobetaine was the major arsenic compound in liver, kidney and muscle of both mother and fetus. The percentage of arsenobetaine to total arsenic ranged from 76.0 to 91.0% in the tissues. Dimethylarsinic acid, arsenocholine, methylarsonic acid and an unidentified arsenic compound were also detected in tissues of both mother and fetus as minor constituents, whereas tetramethylarsonium ion was not detected in tissues of the fetus. These results suggest that arsenobetaine, dimethylarsinic acid, arsenocholine and methylarsonic acid are transferable from mother to fetus in Dall’s porpoises. To our knowledge, this is the first report on placental transfer of arsenic compounds to fetus in marine mammals. 相似文献
57.
58.
T. Etoh M. Nakanishi 《Stochastic Environmental Research and Risk Assessment (SERRA)》1987,1(2):117-126
The expression of equi-risk line derived by the authors represents the relationship between discharge capacityy
0
u
and storage capacityz
0
u
to keep flood frequency under a certain risk level represented by the return periodT, i.e.,z
0/z
0
u
={(y
0
u
–y
0
u
)/y
0
u
}
S
, wherey
0
u
andz
0
u
areT-year probability peak discharge and total volume of a hydrograph. The shape parametersS is evaluated in this paper for various release rules of the storage facilities and correlations of durations and peaks of hydrographs. The expression forS is:
, whereS
0 andS
are the values ofS forp=0 and , andp is the exponent of a general storage-release relation,q=az'
p, wherea is the storage constant, andz' andq are the volume of stored water and the corresponding release. The values ofS
0 andS
are expressed in terms of the correlation coefficient of durations and peaks of inflow hydrographs. 相似文献
59.
Seiichi Miura Shuichi Kodaira Ayako Nakanishi Tetsuro Tsuru Narumi Takahashi Naoshi Hirata Yoshiyuki Kaneda 《Tectonophysics》2003,363(1-2):79-102
The Japan Trench is a plate convergent zone where the Pacific Plate is subducting below the Japanese islands. Many earthquakes occur associated with plate convergence, and the hypocenter distribution is variable along the Japan Trench. In order to investigate the detailed structure in the southern Japan Trench and to understand the variation of seismicity around the Japan Trench, a wide-angle seismic survey was conducted in the southern Japan Trench fore-arc region in 1998. Ocean bottom seismometers (15) were deployed on two seismic lines: one parallel to the trench axis and one perpendicular. Velocity structures along two seismic lines were determined by velocity modeling of travel time ray-tracing method. Results from the experiment show that the island arc Moho is 18–20 km in depth and consists of four layers: Tertiary and Cretaceous sedimentary rocks, island arc upper and lower crust. The uppermost mantle of the island arc (mantle wedge) extends to 110 km landward of the trench axis. The P-wave velocity of the mantle wedge is laterally heterogeneous: 7.4 km/s at the tip of the mantle wedge and 7.9 km/s below the coastline. An interplate layer is constrained in the subducting oceanic crust. The thickness of the interplate layer is about 1 km for a velocity of 4 km/s. Interplate layer at the plate boundary may cause weak interplate coupling and low seismicity near the trench axis. Low P-wave velocity mantle wedge is also consistent with weak interplate coupling. Thick interplate layer and heterogeneous P-wave velocity of mantle wedge may be associated with the variation of seismic activity. 相似文献
60.
Norikazu Kinoshita Yuko Sato Takeyasu Yamagata Hisao Nagai Akihiko Yokoyama Takashi Nakanishi 《Journal of Oceanography》2007,63(5):813-820
In order to estimate the deposition rate of extraterrestrial material onto a manganese crust in a search for supernova debris,
we analyzed the contents of 10Be, 230Th, 231Pa, and 239,240Pu in a sample of manganese crust collected from the North Pacific Ocean. On the basis of the depth profile of 10Be, the growth rate of the manganese crust was determined to be 2.3 mm Myr−1. The uptake rates of 10Be, 230Th, and 231Pa onto the manganese crust were estimated to be 0.22–0.44%, 0.11–0.73%, and 1.4–4.5%, respectively, as compared to the deposition
rates onto the deep-sea sediments near the sampling station, while that for 239,240Pu was 0.14% as compared to the total inventory of seawater and sediment column. Assuming that sinking particles represent
0.11–4.5% of the uptake rates, the deposition rate of extraterrestrial material onto the manganese crust was estimated to
be 2–800 μg cm−2Myr−1 according to the uptake of 10Be onto the manganese crust. Further, our estimate is similar to the value of 9–90 μg cm− 2Myr−1 obtained using the integrated global production rate of 10Be and the deposition rate of 10Be onto the manganese crust. 相似文献