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31.
Dissolved and particulate concentrations of silver in Tokyo Bay estuarine waters and Japanese rivers were determined in this
study. The dissolved silver concentrations in the surface water of Tokyo Bay range from 5.9 to 15.1 pmol kg−1, which is comparable to those in the surface water of the Japan Sea, but two or three times higher than those in the surface
water of the open ocean. However, elevated concentrations of dissolved silver are not found in Tokyo Bay compared with those
in other highly urbanized estuaries, such as San Francisco Bay (20∼243 pmol kg−1). In the Tokyo Bay estuary, silver typically exhibits non-conservative mixing behavior, which is a common feature in the
other estuaries reported previously. Dissolved silver concentrations decrease with salinity from the rivers to the mouth of
Tokyo Bay. Silver is efficiently scavenged by suspended particulates, as evidenced by the high conditional distribution coefficients
for silver throughout the estuary (log Kd > 5.0 ± 0.6). The silver fluxes into Tokyo Bay via inflowing rivers and atmospheric deposition were estimated as 83 kg y−1 and 15 kg y−1, respectively. A simple budget calculation shows that the silver supplied from rivers and atmosphere must be rapidly scavenged
within the Tokyo Bay estuary. 相似文献
32.
Hedonic approaches based on spatial econometrics and spatial statistics: application to evaluation of project benefits 总被引:1,自引:0,他引:1
This study discusses the theoretical foundation of the application of spatial hedonic approaches—the hedonic approach employing
spatial econometrics or/and spatial statistics—to benefits evaluation. The study highlights the limitations of the spatial
econometrics approach since it uses a spatial weight matrix that is not employed by the spatial statistics approach. Further,
the study presents empirical analyses by applying the Spatial Autoregressive Error Model (SAEM), which is based on the spatial
econometrics approach, and the Spatial Process Model (SPM), which is based on the spatial statistics approach. SPMs are conducted
based on both isotropy and anisotropy and applied to different mesh sizes. The empirical analysis reveals that the estimated
benefits are quite different, especially between isotropic and anisotropic SPM and between isotropic SPM and SAEM; the estimated
benefits are similar for SAEM and anisotropic SPM. The study demonstrates that the mesh size does not affect the estimated
amount of benefits. Finally, the study provides a confidence interval for the estimated benefits and raises an issue with
regard to benefit evaluation. 相似文献
33.
The depositional environments and bivalve assemblages are determined for the Upper Cretaceous Hinoshima Formation of the Himenoura Group, Kamishima, Amakusa Islands, Kyushu, Japan. The Hinoshima Formation is characterized by a thick transgressive succession that varies from incised-valley-fill deposits to submarine slope deposits with high aggradation rates of depositional systems. The incised valley is filled with fluvial, bayhead delta, brackish-water estuary, and marine embayment deposits, and is overlain by thick slope deposits.Shallow marine bivalves are grouped into five fossil assemblages according to species composition: Glycymeris amakusensis (foreset beds of a bayhead delta), Nippononectes tamurai (foreset beds of a bayhead delta), Ezonuculana mactraeformis–Nucula formosa (central bay), Glycymeris amakusensis–Apiotrigonia minor (slope), and Inoceramus higoensis–Parvamussium yubarensis (slope). These bivalve assemblages all represent autochthonous and parautochthonous conditions except for a Glycymeris amakusensis–Apiotrigonia minor assemblage found in debris flow and slump deposits. The life habitats of these bivalves and the compositions of the assemblages are discussed in terms of the ecological history of fossil bivalves of the mid- to Late Cretaceous. 相似文献
34.
Crustal model of the Bransfield Rift, West Antarctica, from detailed OBS refraction experiments 总被引:2,自引:0,他引:2
M. Grad H. Shiobara T. Janik A. Guterch H. Shimamura 《Geophysical Journal International》1997,130(2):506-518
The first detailed deep seismic refraction study in the Bransfield Strait, West Antarctica, using sensitive OBSs (ocean bottom seismographs) was carried out successfully during the Antarctic summer of 1990/1991. The experiment focused on the deep crustal structure beneath the axis of the Bransfield Rift. Seismic profile DSS-20 was located exactly in the Bransfield Trough, which is suspected to be a young rift system. Along the profile, five OBSs were deployed at spacings of 50-70 km. 51 shots were fired along the 310 km profile. This paper gives the first presentation of the results. A detailed model of the crustal structure was obtained by modelling the observed traveltimes and amplitudes using a 2-D ray-tracing technique. The uppermost (sedimentary?) cover, with velocities of 2.0-5.5 km s−1 , reaches a depth of up to 8 km. Below this, a complex with velocities of 6.4-6.8 km s−1 is observed. The presence of a high-velocity body, with V p = 7.3-7.7 km s−1 , was detected in the 14-32 km depth range in the central part of the profile. These inhomogeneities can be interpreted as a stage of back-arc spreading and stretching of the continental crust, coinciding with the Deception-Bridgeman volcanic line. Velocities of 8.1 km s−1 , characteristic of the Moho, are observed along the profile at a depth of 30-32 km. 相似文献
35.
Planform evolution of deltas with graded alluvial topsets: Insights from three‐dimensional tank experiments,geometric considerations and field applications
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Tetsuji Muto Ryuji Furubayashi Arti Tomer Tomoyuki Sato Wonsuck Kim Hajime Naruse Gary Parker 《Sedimentology》2016,63(7):2158-2189
The profile of a river that conveys sediment without net deposition and net erosion is referred to as ‘graded’ with respect to vertical aggradation of the river segment. Three experimental series, designed in terms of the autostratigraphic view of alluvial grade, were conducted to clarify the diagnostic spatial behaviour of graded alluvial–deltaic rivers: an ‘R series’, which utilized a moving boundary setting with a stationary base level; an ‘F series’ in a fixed boundary setting with a stationary base level to produce ‘forced grade’; and an ‘M series’ in a moving boundary setting with constant base‐level fall to produce ‘autogenic grade.’ The results of the three experimental series, combined with geometrical modelling of the effects of basin water depth and other experimental data, suggest the following: (i) in a graded alluvial–deltaic system, lateral shifting and avulsing of active distributary channels are suppressed regardless of whether the downstream boundary of the deltaic system is fixed; (ii) in a delta with a downstream‐fixed boundary, the graded streams are stabilized within a valley that is incised in the axial part of the delta plain, whereby the alluvial plain outside the valley is abandoned and terraced; (iii) in moving boundary settings, the graded river simply extends basinward as a linearly elongated channel and lobe system without cutting a valley; and (iv) a modern forced‐graded alluvial river is most likely to be found in a valley incised into a fan delta in front of very deep water, and the stratigraphic signal of fossil autogenic‐graded rivers will be found in deltaic successions that accumulated in the outer to marginal areas of deltaic continental shelves during sea‐level falls. This renewed autostratigraphic view of alluvial grade suggests a thorough reconsideration of the conventional understanding that an alluvial river feeding a progradational delta is graded with a stationary base level. 相似文献
36.
Gravity and S-wave modelling across the Jan Mayen Ridge,North Atlantic; implications for crustal lithology 总被引:1,自引:0,他引:1
Rolf Mjelde Inger Eckhoff Ståle Solbakken Shuichi Kodaira Hideki Shimamura Karl Gunnarsson Ayako Nakanishi Hajime Shiobara 《Marine Geophysical Researches》2007,28(1):27-41
The horizontal components from fourteen Ocean Bottom Seismometers deployed along four profiles focused along the western margin
of the Jan Mayen microcontinent, North Atlantic, have been modelled with regard to S-waves, based on P-wave models obtained
earlier. The seismic models have furthermore been constrained by 2D gravity modelling. High V
p/V
s-ratios (2.3–7.9) within the Cenozoic sedimentary section are attributed to significant porosities, whereas V
p/V
s-ratios in the order of 1.9–2.2 for the Mesozoic and Paleozoic sedimentary rocks indicate shale-dominated lithology throughout
the area. The eastern side of the Jan Mayen Ridge is interpreted as a passive, volcanic margin, based on relatively high crustal
V
p/V
s-ratios (1.9), whereas lower V
p/V
s-ratios (1.75–1.8) suggest the presence of intermediate composition crust and non-volcanic margin on the western side of the
ridge. In the westernmost part of the Jan Mayen Basin, slightly increased upper mantle V
p/V
s-ratios may indicate some degree of serpentization of upper mantle peridotites. 相似文献
37.
The Algal Growth Potential (AGP) of water samples collected off Gamagori in Mikawa Bay was measured from May 1978 through February 1979, and the limiting nutrient was determined using regression analysis and enrichment bioassays. The surface and bottom water samples had AGP that produced increments of chemical oxygen demand (COD) of 2.1 mg l–1 and 3.1 mg l–1, respectively, on average. These values ofCOD correspond to 46% and 97% of the average COD values of the raw water samples at the surface and bottom, respectively. Seasonal changes of AGP showed a close correlation with those of dissolved inorganic nitrogen (DIN) concentration. Enrichment bioassays showed that DIN was the most deficient nutrient. The DIN:phosphate-phosphorus (PO4
3–-P) ratios and DIN: dissolved phosphorus (DP) ratios in the water samples were below the cellular N:P ratios of the natural algal populations. These results suggest that AGP was mainly limited by DIN concentration. 相似文献
38.
In the current record taken in Uchuimi Bay during summer in 1990, we find anomalous features that the tidal currents during spring and neap tides are quite different in both speed and direction, and the transition between them takes place suddenly. Relation between the variation of tidal current and the observed internal tide is examined, but they are poorly correlated. By examining the direction and phase of the current, it is inferred that these anomalous features are caused by the influence of topographic eddies formed perioidically in Uchiumi Bay. 相似文献
39.
Hajime Kawakami Makio C. Honda Masahide Wakita Shuichi Watanabe 《Journal of Oceanography》2007,63(6):967-982
Time-series measurements of dissolved inorganic carbon (DIC) and nutrient concentrations were conducted in the northwestern
North Pacific from October 2002 to August 2004. Assuming that data obtained in different years represented time-series seasonal
data for a single year, vertical distributions of DIC and nutrients showed large seasonal variabilities in the surface layer
(∼100 m). Seasonal variabilities in normalized DIC (nDIC) and nitrate concentrations at the sea surface were estimated to
be 81–113 μmol kg−1 and 12.7–15.7 μmol kg−1, respectively, in the Western Subarctic Gyre. The variability in nutrients between May and July was generally at least double
that in other seasons. In the Western Subarctic Gyre, estimations based on statistical analyses revealed that seasonal new
production was 39–61 gC m−2 and tended to be higher in the southwestern regions or coastal regions. The seasonal new productions in the northwestern
North Pacific were two or more times higher than in the North Pacific subtropical gyre and the northeastern North Pacific.
It is likely that this difference is due to spatial variations in the concentrations of trace metals and the species of phytoplankton
present. In addition, from estimations of surface pCO2 it was verified that the Western Subarctic Gyre is a source of atmospheric CO2 between February and May and a sink for CO2 between July and October. 相似文献
40.
Precise Positioning of Ocean Bottom Seismometer by Using Acoustic Transponder and CTD 总被引:1,自引:0,他引:1
Shiobara Hajime Nakanishi Ayako Shimamura Hideki Mjelde Rolf Kanazawa Toshihiko Berg Eivind W. 《Marine Geophysical Researches》1997,19(3):199-209
We have obtained precise estimates of the position of Ocean Bottom Seismometers (OBS) on the sea bottom. Such estimates are usually uncertain due to their free falling deployment. This uncertainty is small enough, or is correctable, with OBS spacing of more than 10 km usually employed in crustal studies. But, for example, if the spacing is only 200 m for OBS reflection studies, estimates of the position with an accuracy of the order of 10 m or more is required.The determination was carried out with the slant range data, ship position data and a 1D acoustic velocity structure calculated from Conductivity–Temperature–Depth (CTD) data, if they are available. The slant range data were obtained by an acoustic transponder system designed for the sinker releasing of the OBS or travel time data of direct water wave arrivals by airgun shooting. The ship position data was obtained by a single GPS or DGPS. The method of calculation was similar to those used for earthquake hypocenter determination.The results indicate that the accuracy of determined OBS positions is enough for present OBS experiments, which becomes order of 1 m by using the DGPS and of less than 10 m by using the single GPS, if we measure the distance from several positions at the sea surface by using a transponder system which is not designed for the precise ranging. The geometry of calling positions is most important to determine the OBS position, even if we use the data with larger error, such as the direct water wave arrival data. The 1D acoustic velocity structure should be required for the correct depth of the OBS. Although it is rare that we use a CTD, even an empirical velocity structure works well. 相似文献