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71.
Concentrations of persistent organochlorines (OCs) such as PCBs, DDTs, chlordanes (CHLs), HCHs and HCB were determined in the liver of bluefin tuna (Thunnus thynnus) collected from Japanese coastal waters in order to elucidate accumulation profiles and to evaluate the suitability of this species as a biomonitor for pollution in the open sea ecosystem. Concentrations of PCBs, DDTs and CHLs in bluefin tuna increased significantly with body length (30–190 cm). HCHs and HCB residues were comparable among all the sampling regions, and the levels of these chemicals did not show correlation with body length. These results suggest significance of dietary uptake of PCBs, DDTs and CHLs compared to the intake via the gill. On the other hand, equilibrium partitioning with ambient water is a major determinant of the levels of HCHs and HCB in tuna. Body-length normalized values (BLNV) of PCBs, DDTs and CHLs concentrations in bluefin tuna were calculated using the linear regression equation obtained from the plot of concentrations and body length. BLNV of these chemicals on a lipid wt basis, which was adjusted for 100 cm body length, were indicative of the present state water pollution by PCBs, DDTs and CHLs. These results suggest that bluefin tuna is a suitable bioindicator for monitoring OCs contamination in the open sea ecosystem. 相似文献
72.
The high frequency part (10 Hz50 Hz) of the one-dimensional wave spectrum was measured in a wind-wave channel under accurately controlled conditions. The results are compared with the spectral forms for the capillary range that have been proposed recently byPierson andStacy (1973) andToba (1973). In a general sense, fairly good agreement is found between the present results and those ofPierson andStacy (1973) and ofToba (1973). The spectrum in the capillary range is clearly wind speed dependent, and the spectral density in that range increases with increasing wind speed.However, closer examination shows systematic deviations of the present results from those previously proposed, particularly for high speed winds. 相似文献
73.
Information on the location and area for all MPAs in Japan was collected through a comprehensive survey targeting government officials and local stakeholders. It was verified that at least 1161 MPAs exist in Japan. Of these, 1055 are implemented in conjunction with fishery regulations in the form of no-take zones. More than 30% of the individual MPAs in Japan were established by self-imposed instruments agreed by members of fishery co-management organizations. It was suggested that the autonomous MPAs are not a product of simple altruism, but rather are logical extensions of the tenure system guaranteed by the government legal system. 相似文献
74.
Takashi Kudo Minoru Sasaki Yoshihiro Uchiyama Akifumi Nozawa Hisashi Sasaki Takeshi Tokizawa Shinji Takarada 《Island Arc》2007,16(1):133-155
Abstract The Hakkoda‐Towada caldera cluster (HTCC) is a typical Late Cenozoic caldera cluster located in the northern part of the Northeast Japan Arc. The HTCC consists of five caldera volcanoes, active between 3.5 Ma and present time. The felsic magmas can be classified into high‐K (HK‐) type and medium‐ to low‐K (MLK‐) type based on their whole‐rock chemistry. The HK‐type magmas are characterized by higher K2O and Rb contents and higher 87Sr/86Sr ratios than MLK‐type magmas. Both magmas cannot be derived from fractional crystallization of any basaltic magma in the HTCC. Assimilation‐fractional crystallization model calculations show that crustal assimilation is necessary for producing the felsic magmas, and HK‐type magmas are produced by higher degree of crustal assimilation with fractional crystallization than MLK‐type magmas. Although MLK‐type magmas were erupted throughout HTCC activity, HK‐type magmas were erupted only during the initial stage. The temporal variations of magma types suggest the large contribution of crustal components in the initial stage. A major volcanic hiatus of 3 my before the HTCC activity suggests a relatively cold crust in the initial stage. The cold crust probably promoted crustal assimilation and fractional crystallization, and caused the initial generation of HK‐type magmas. Subsequently, the repeated supply of mantle‐derived magmas raised temperature in the crust and formed relatively stable magma pathways. Such a later system produced MLK‐type magmas with lesser crustal components. The MLK‐type magmas are common and HK‐type magmas are exceptional during the Pliocene–Quaternary volcanism in the Northeast Japan Arc. This fact suggests that exceptional conditions are necessary for the production of HK‐type magmas. A relatively cold crust caused by a long volcanic hiatus (several million years) is considered as one of the probable conditions. Intensive crustal assimilation and fractional crystallization promoted by the cold crust may be necessary for the generation of highly evolved HK‐type felsic magmas. 相似文献
75.
To understand the transport process of lithogenic particles in the ocean, we measured the grain size distributions of lithogenic
particles and measured the opal, La, Yb, Th, and Sc concentrations of the settling particles collected from time-series sediment
traps at Sta. KNOT (44°N, 155°E, water depth 5320 m) from June 2002 to May 2004. The annual mean lithogenic particle flux
observed at the lower sediment trap (5100 m) was twice as high as that at the upper sediment trap (770 m). The contribution
of Asian loess estimated by the La/Yb and the Th/Sc ratios in the lower layer was greater than that in the upper layer. The
fluxes of small lithogenic particles with sizes of 3–4 μm at the lower layer (5 to 65 mg/m2/day) were approximately four times larger than that at the upper layer (0.6 to 27 mg/m2/day). These results indicate that the horizontal addition of small particle sizes of Asian loess is a main factor in the
increase of lithogenic particles at the lower layer. The temporal variations in the small lithogenic particle flux at the
lower layer had a positive correlation with those at the upper layer (r = 0.71). The small lithogenic particle fluxes showed
a strong positive correlation with the opal fluxes (r = 0.9). We therefore conclude that the small lithogenic particles were
laterally transported and scavenged by the formation of aggregates with opal. 相似文献
76.
Joh Koenigsberger 《International Journal of Earth Sciences》1912,3(5-6):319-323
Ohne Zusammenfassung 相似文献
77.
Natural groundwater of a gas field utilizable for a bioremediation of trichloroethylene-contamination 总被引:1,自引:0,他引:1
Mio?TakeuchiEmail author Kenji?Nanba Ken?Furuya Hisashi?Nirei Mitsuo?Yoshida 《Environmental Geology》2004,45(7):891-898
Groundwater from a shallow aquifer in Mobara, a city in a natural gas field in Chiba Prefecture, Japan, was found to contain a significant amount of dissolved methane (<3.1 mM) along with nitrate, phosphate and methane-oxidizing bacteria (methanotrophs, <9.9×106 MPN ml–1) which can degrade trichloroethylene (TCE). This water exhibited high methanotroph growth activity and rapid degradation of TCE. This water was introduced into a TCE-contaminated aquifer. The concentration of TCE at the monitoring well 2 m down-gradient of the injection pit decreased from 128 g L–1 before the injection to less than the lower detection limit of 12.5 g L–1 after the injection, while it decreased only slightly (to 86 g L–1) when control water was injected. These results demonstrate the feasibility of utilizing a natural groundwater resource containing methane and methanotrophs without any additives for bioremediation of a TCE-contaminated site. 相似文献
78.
Various wind velocitiesu
*,U
/2,U
andU
10 are correlated to the measured growth rate of water waves , whereu
* is the friction velocity of the wind, andU
/2,U
andU
10 are the wind speeds respectively at the heights /2, and 10m above sea surface (: wave length). It is shown that within a range of the dimensionless wind speed, 0.1<u
* /C<0.6, there are no appreciable differences in the correlations, whereC is the phase velocity of water waves. The present relation between andU
shows qualitatively similar properties as the one obtained by Al'Zanaidi and Hui (1984); the growth rate for waves with rough surface is larger than that with smooth surface. However, our present relations give, for the both waves with different surface roughness, larger values by factors 1.71.8 than those given by Al'Zanaidi and Hui's relation. 相似文献
79.
A two-way nested model has been constructed and applied to the idealized ocean where a uniform mean flow impinges on the isolated
Gaussian-shaped seamount and produces two eddies (cold and warm) in the depths. The performance of the nested model has been
evaluated subjectively and objectively. Both subjective and objective analyses confirm the traditional view that the nested
model can well capture the performance of isolated eddies. Objective analysis, however, reveals some quantitatively important
features of a two-way nested model. One is penetration of improved features into the coarse domain and another is the deterioration
of mean flow field inside the nested area, neither of which is clear from subjective analysis. With successful application
of two-way nested model to the seamount problem, we expect that such a nested model will also be applicable to other oceanic
phenomena, particularly to some coastal problems whose time scale is short and where the topographic effects are dominant. 相似文献
80.
船舶螺旋桨尾流场的数值分析 总被引:16,自引:1,他引:16
利用基于速度势的低阶面元法计算船舶螺旋桨的尾流场。采用计算较为简捷的关于扰动速度势的基本积分微分方程,并采用双曲面形状的面凶以消除面元间的缝隙。Newton-Raphson迭代过程被用来在桨叶随边满足压力Kutta条件,使桨叶面上表面的压力在随边有良好的一致性。在计算面元的影响系数时,应用了Morino导出的解析计算公式,加快了数值计算的速度。从解面元法的基本积分方程得到的偶极强度和源汇强度,直接求得尾流场的速度分布。 相似文献