Application of a 3-D chemical fate prediction model (FATE3D) to predict dioxin concentrations in the Tokyo Bay

A 3-D chemical fate prediction model (FATE3D) was applied to predict the dioxin concentrations in the seawater of Tokyo Bay, Japan. The simulations were carried out for a period of one year (from September 2002 to August 2003). Parameters such as meteorological data, flow field conditions, concentrations and sinking rates of organic particulate matter, initial and boundary conditions, and loading fluxes and physico-chemical properties of dioxins were used as the model inputs.The simulation results compared favorably with the field measurements of dioxin concentrations in the bay for both the particulate and dissolved phases, indicating the validity and predictive capability of the model. Furthermore, the differences in the seasonal cycles and distributions between the particulate- and dissolved-phase dioxins in the bay were estimated from the simulation results.However, the particulate-phase dioxin concentrations in the bottom layers (+1 m from the bottom) were underestimated, probably because the resuspension process was not taken into account in the model. The improvement of the model's predictive capability, including the resuspension process, shall be the focus of our next study.     

Study on the chemical forms of radionuclides in seawater—I

The stability constants for sulfate, chloride and hydroxide ions with cerium (III) in the solution at ionic strength of 0.67 have been determined by cation exchange method, the values of ₁ and ₂ for sulfate complexes of cerium being 40±13 and 453±140, respectively and those for chloride complexes being 1.28±0.23 and 0.56±0.076, respectively. The values of ₁, ₂ and ₃ for hydroxide complexes of cerium were (4.5±0.9)×10⁷, (3.3±0.7)×10¹⁴ and (1.8±0.7)×10²³, respectively.Using the above constants the ratios of individual chemical species of¹⁴⁴Ce were calculated in a solution at ionic strength of 0.67 containing sulfate and chloride ions approximately the same as in seawater of 35 %. The result of calculation indicates that the dominant species of¹⁴⁴Ce in this solution is Ce(OH)₃ ⁰ at pH 8.     

Crustal structure and accurate hypocenter determination along the Longmenshan fault zone

Ｃｒｕｓｔａｌｓｔｒｕｃｔｕｒｅａｎｄａｃｃｕｒａｔｅｈｙｐｏｃｅｎｔｅｒｄｅ┐ｔｅｒｍｉｎａｔｉｏｎａｌｏｎｇｔｈｅＬｏｎｇｍｅｎｓｈａｎｆａｕｌｔｚｏｎｅＺＨＵＺＨＡＯ１）（赵珠）ＪＵＮＦＡＮ１）（范军）ＳＩ－ＨＵＡＺＨＥＮＧ２）（郑斯华）ＡＫ...     

Limestone of the Daiichi Kashima Seamount and the fate of a subducting guyot: fact and speculation from the Kaiko “Nautile” dives

The Daiichi-Kashima Seamount subducting in the Japan Trench has two reef-capped flat tops with different depths, which are bounded by a nearly straight scarp. The western (inboard) crest is 5300–5450 m deep, and the eastern (outboard) one is 3880–4000 m deep.

A variety of shallow-water reefoid limestones studied by the Kaiko “Nautile” dives not only confirms the similarity in thickness and lithologies, but also establishes an approximate biostratigraphic correlation between the two reefoid caps, based for the first time on the orbitolinid foraminifers (Orbitolina (Mesorbitolina) parva from the western block and O. (M.) texana from the eastern block).

This conclusion supports the interpretation that the present topography of the seamount has resulted from a subduction-induced faulting of a once single reef-capped guyot. A plausible scenario of the fate of a subducting Early Cretaceous guyot in the Western Pacific is outlined as exemplified by the Daiichi-Kashima Seamount.     

Influence of non-photosynthetic pigments on light absorption and quantum yield of photosynthesis in the western equatorial Pacific and the Subarctic North Pacific

Regional variations in the contribution of non-photosynthetic pigments (ā _np^*) to the total light absorption of phytoplankton (ā _ph^*) and its influence on the maximum quantum yield of photosynthesis (φ _m) were investigated. In the western equatorial Pacific, the surface ā _np^* : ā _ph^* ratio was higher in the western warm pool than that in the upwelling region. This difference appears to be attributable to severe nitrate depletion and higher percentage of prokaryotes, which can accumulate very high concentrations of zeaxanthin in the western warm pool. In the subarctic North Pacific, the ā _np^* : ā _ph^* ratio was expected to be higher in the Alaskan Gyre where the thermocline is sharper and iron limitation may possibly be more severe than in the Western Subarctic Gyre. However, the ratio was actually higher in the Western Subarctic Gyre, contradictory to our expectations. This east-west variation appears to be attributable to changes in the taxonomic composition; cyanobacteria were more abundant in the Western Subarctic Gyre. The values of ā _np^* : ā _ph^* and its vertical variations were relatively small in the subarctic North Pacific compared to those in the western equatorial Pacific. These inter-regional variations appear to be attributable to the lower solar radiation intensity, smaller percentage of cyanobacteria, and relatively strong vertical mixing in the subarctic North Pacific. The spatial variations in ā _np^* : ā _ph^* significantly influence φ _m. In comparison with φ _m based on the total light absorption (φ _{m ph}), the values corrected for the contribution of non-photosynthetic pigments (φ _{m ps}) showed an increase in both the western equatorial Pacific and the subarctic North Pacific.     

Subsurface structure exploration of wide landslide area by Aerial electromagnetic exploration

Aerial electromagnetic exploration obtains the ground resistivity of a wide area by measuring the intensity of a secondary magnetic field induced in the ground by a primary magnetic field. We conducted the AEM exploration in the Yamakoshi Village where was dameged by the Mid Niigata Prefecture Earthquake in 2004, for the landslide hazard assessment. The apparent resistivity distribution in the survey area differ between the Imogawa River Basin and the Asahigawa River Basin, and the former shows high resistivity and the later shows low resistivity with 30 -m as the boundary. In the high resistivity zone that corresponds to the sandy rock distribution area, the large landslide blocks show lower resisitivity than in the surrounding ground. In sandy rock distribution areas, it is possible for the relatively low resistivity parts to be an index of the instability of slopes, even in landslide blocks where deformation has not yet appeared.     

黑濑川地体源于亚洲大陆东缘何处？

The point at issue: The Kurosegawa Terrane is composed of continental fragments transecting Mesozoic terranes of accretionary complex in Southwest Japan (Fig. 1). It is an attenuated tectonic sliver and considered to be allochthonous with respect to the main part of Southwest Japan. The problem of which continental block in the East Asian continental margin is the source of the Kurosegawa Terrane has puzzled Japanese geologists for many years. Firstly, we try to approach this issue based on the analysis of fusulinacean assemblage in accreted terranes composed of subduction complex in the Pacific Rim. Secondly, by applying the result of this analysis we try to locate the source of the continental fragments of the Kurosegawa Terrane. Thirdly, we try to prove its validity with a new paleomagnetic study.     

Experimental studies on debris flow with logs focusing on specific weight difference of log species

There are many experimental approaches,field investigations and numerical calculations for movements of woods in a clear water and debris flow.However,kinematic conditions for accumulated logs and the interactions between a main flow and logs have not been fully evaluated.Mitigations for woods need taking into account the characteristics of tree species such as conifer and broad-leaf trees and of shapes such as root swells and crown.In the present study,we focus on the differences in specific weight of conifer and broad-leaf trees with some moisture in a sediment-water mixture flow with narrow flow width,and consider that conifer and broad-leaf tree are floating and submerged solid phase,respectively.Flume tests are conducted in steady flow of clear and debris flow over a rigid bed in order to evaluate conifer and broad-leaf tree movement in clear water and debris flow.Experimental data indicates that dimensionless transverse diffusion coefficient can be 0.1 to 0.4 and 0.3 to 0.9 in flow direction.Those diffusive characteristics seem to be independent of Reynolds number and Froude number,but dependent of bed slope,i.e.,gravity,though detailed considerations are needed to discuss about flow characteristics such as spatial eddy structures,momentum transfer induced by interactions of logs and so on.     

Evaluation of the structural damage of high‐rise reinforced concrete buildings using ambient vibrations recorded before and after damage

Evaluation of the degrees of structural damage suffered by high‐rise residential buildings after being subjected to strong ground motions is extremely important to the development of life continuity planning for building residents. However, these evaluations cannot be based on strong‐motion records alone, because earthquake observation equipment is not installed in most such buildings in Japan. In this study, we propose simple equations for estimating the stiffness degradation rate and the peak inter‐story drift ratio (PIDR) by using ambient vibration records instead of strong‐motion records when high‐rise RC buildings are subjected to a severe earthquake. More specifically, we propose one equation that relates the square root of the stiffness degradation rate, which is the ratio of natural frequencies at the maximum response to the preliminary tremor response (elastic state), in strong‐motion records with the ratio of natural frequencies identified from ambient vibrations before and after damage was suffered. We also propose an equation that relates the PIDR with the stiffness degradation rate on the basis of the stiffness‐degrading bilinear restoring force characteristic derived from the strong‐motion records of 13 high‐rise buildings for the 1995 Hyogoken‐Nanbu Earthquake (Mw 6.9) and the 2011 Tohoku‐Oki Earthquake (Mw 9.0). Copyright © 2015 John Wiley & Sons, Ltd.