An accumulation model was used to analyze the TBT concentrations in seawater and sediments in Ise Bay and Mikawa Bay. Embedding a decomposition process, which considered aerobic and anaerobic conditions in sediments as well as the re-suspension process with current velocity above sediments, into the existing model more precisely predicted the observed phenomena. The calculated results of the TBT concentrations in water and sediments were compared to field data, which consequently validated the model. The TBT concentration in port of Yokkaichi was reduced during the period of 1992-2008 by 99.5% in seawater and by 28.5% in sediment. Hence, the model revealed a much longer persistence of TBT in sediments than that in water.
We measured tidal currents by using an electromagnetic current meter mooring in the Ariake Bay to clarify how heavy the sinker needs to be and how current meters should be moored for accurate current measuring. From the results, it is believed that there possibly occur 1 m/s over speeds of tidal currents in situ, and that the tilt of the current meter caused a decline of the observed speed. In addition, in cases where one observes tidal current by ACM-8M, a 10 kg sinker seemed to be insufficient to keep the current meter tilt to less than 20°, which is the limit of the clinometers installed, and furthermore mooring current meters in series encourages tilting. We recommend that the mooring of current meters in series should be avoid, the sinker should be connected close to the current meter, and that sinkers much heavier than 10 kg should be used.
We targeted Tokyo Bay to study the risk trade-off of substituting Copper pyrithione (CuPT) for Tri-butyltin (TBT) as an antifoulant. We estimated the ecological risk by assessing calcification of giant Pacific oysters (Crassostrea gigas). We estimated the environmental concentrations of TBT and CuPT using chemical fate model (FATE model). The risk assessment was used the uncertainty factor (UF) and margin of exposure ( MOE) method.
For TBT. the ecological risk was estimated by the no observed effect concentration (NOEC:0.001 μg・L^-1 : calcification of giant Pacific oysters) and the UF (10). As a result, a high risk level was shown for all sea areas of Tokyo Bay. For CuPT. the ecological risk was estimated by the no observed effect concentration (NOEC:0.25 μg •L^-1: Growth Reduction of Skeleionema costatum) and the UF (100). There is a high risk for the ports areas, but the risk was not of concern for other sea areas of the Bay. Regarding calcification of giant Pacific oysters, the risk was low for CuPT(EC50 11 μg・L^-1: UF10) though it was high for TBT (NOEC:0.001 μ• L＾-1:UF1) in all sea areas. It was suggested that the ecological risk to C. gigas in Tokyo Bay would greatly reduce by substituting TBT with CuPT. The risk evaluation of development inhibition of Bafununi Hemiceiurotuspulcherrimus) from CuPT NOEC: 1.0 μg. UF 10) was done for February 2007. which is the spawning season. The results show that the risk is low in all ea areas.
The Inertial Navigation System (INS) is one of navigation devices for moving objects, and it makes positioning without the communication with the external environment because it is composed of just internal sensors; gyros and accelerometers. Thus the moving object can move owing to the position data if it is equipped with the INS. And recently, the INS is applied as the navigation device for many autonomous underwater vehicles (AUVs). And they uses the position data outputted by the INS in order to understand its own current position in real time and cruise along the course line according to the position data. However it includes the error caused by the drift-bias error of the internal sensors, and the position error increases with the time. So it is very difficult for AUVs to cruise autonomously dependent only on the position data. We have proposed the method which improves the INS's performance owing to a rotational motion. In this method. The INS is rotated with one rotational axis according to some rules. This causes the cancellation of the drift-bias errors of the internal sensors and consequently the position error of the INS is decreased. In order to cause this effect, a precondition must be met. It is that a moving object keeps its own posture to horizontal. However, in reality. AUVs never keeps its own posture horizontal because they cruise with a roll motion as their body-specific behavior. In this paper, the reduction effect of the INS' s position error cased by this method is shown in experiments. And also, utility of this method if AUV's roll motion is applied to the INS while it is rotated is confirmed in experiments.
Many techniques are being developed in the world wide to prevent marine organism's transportation with ballast waters of ships. This study was conducted to know the availability of sodium pyrithione (NaPT) and chlorine dioxide (ClO2) for ballast water treatment. The concentrations of 3 mg/1 and 9 mg/1 of NaPT and 3 mg/l of ClO2 were prepared with sea water which was taken from Tokyo bay. These were incubated at 20 ± 1 ℃ and dark for 7 days. After 4 hours of the incubation, the number of heterotrophic bacteria deceased from 2.9 x 105 CFU/ml to 70 CFU/ml in the sea water containing C102. But more than 2.9 x 105 CFU /ml of heterotrophic bacteria was detected in the all sea waters after 7 days of the incubation. The chlorophyll a in the sea water containing ClO2 was almost disappeared after one day of the incubation. At 7th day of this study, each 800 ml of the sea water was divided into two groups, and 1.2 mgs of ClO2s were added to one group of the sea waters (”ClO2 additional group” and ”CｌO2 non additional group”). These were incubated at 20 ± 11C and a 12 hours cycle of light and dark for 43 days. Besides, each 5 ml of the sea water was injected into 100 ml of f/2 mediums to confirm existence of survived phytoplankton after 4 hours of the incubation. The increasing of chlorophyll a in the f/2 mediums were observed in both groups of control (only sea water at beginning of this study) and 3 mg/1 of C102 on ”CｌO2 non additional group”. The result of 43 days incubation showed existence of survived phytoplankton in all sea waters, and the lowest cell density of phytoplankton in 3 mg/1 of CI02 on ”CｌO2 additional group”. From these results, although heterotrophic bacteria and phytoplankton were not extinguished by NaPT and ClO2 under this experimental condition, it seems that ClO2 is available for ballast water treatment.
A new ecosystem model - the first model describing the ecological connectivity consisting of both benthic-pelagic and central baytidal flat ecosystem coupling while describing the vertical micro-scale in the benthic ecosystem, simultaneously - was developed and applied to Tokyo Bay (Sohma et al. 2005a). The model permits the prediction/evaluation of the effects of environmental measures, such as tidal flat restoration, sand capping, dredging, and nutrients load reduction from rivers, on the hypoxic estuary from the perspectives of (1) the whole estuary composed of temporal-spatial mutual linkage of benthic-pelagic or central baytidal flat ecosystems (holistic approach) , and (2) each biochemical and physical process contributing to oxygen production/consumption (elemental approach) . The model outputs demonstrated the significant ecosystem responses as follows. First, the oxygen consumption in the benthic system during summer was quite low due to low level of dissolved oxygen (hypoxia), although reduced substances. Mn^2+, Fe^2+ and S^2- were highly produced and accumulated in the pore water. This result denotes importance to use the oxygen consumption rate under the high level of dissolved oxygen as the index of hypoxia potential. Second, both the tidal flat creation and nutrients load reduction decreased the anoxic water volume and mass of detritus in Tokyo Bay. However, the tidal flats creation led to the higher biomassof benthic fauna, while the nutrients load reduction led to the lower biomass of them compared to the existing situation. This result clarifies the differences from the measure aimed at a ”bountiful ocean: a non-hypoxic and rich production of higher level trophic biology” to the measure just aimed at a ”clear ocean: a non-hypoxic and low level of particulate organic matter” and also the differences from a bountiful ecosystem to a higher water quality. Lastly, in the simulation, Tokyo Bay reproducing reclaimed tidal flats (earlier Tokyo Bay system) prevented the increase of oxygen consumption potential (hypoxia potential) and the decrease of the higher trophic production to red tide compared to the existing Tokyo Bay system with reclamation of tidal flats. This result demonstrates the higher ecosystem tolerance of the earlier Tokyo Bay to red tide, and tidal flats function of keeping an optimized ecological balance to the environmental perturbation.
The occurrence of To-Nankai and Nankai earthquakes are very urgent and they accompany with tsunamis. Historically, tsunami damage was huge in comparison with earthquake damage. Therefore, how to reduce the tsunami damage is essential. This expands with the damage link of the earthquakes and tsunamis, and. up to now. has become a super-large area disaster that has not been experienced. Moreover, last 60 years, our social structure has rapidly changed and social vulnerability has also increased year by year. Especially, the lifeline damage controls the progress condition of the recovery works of the stricken area. If we take the electricity as the most important lifeline, the area under the jurisdiction of the Chubu Electric Power Co. Inc. in the electric supply could face a long-term power failure due to the occurrence of Tokai. To-Nankai and Nankai earthquakes. In this region,, c.a. 92% of the total power generation are supplied by thermal and nuclear power plants that are located where the ground shaking has been estimated as six minus or more in the JMA (Japan Meteorological Agency) seismic intensity scale. We proposed the following efforts to reduce damage 1) Early dispatch of tsunami warning to residents at the every corner who are generally at the end of the reach of the official information path.. 2) Utilization of measured seismic intensity meter located in every municipality to image coming tsunamis. 3) Promotion of hazard map circulation and education of residents who has difficulties to adjust themselves to the risk. 4) Senior citizen measures to reduce damage through reiterated evacuation drills, encouragement of mutual disaster mitigation planning in the local community, etc.. 5) Subways and underground shopping center measures because to cope with inundation disaster of a new type that we have never experienced before, and 6) Measures to people at recreation or sport in seashore, river terrace, and holm that hazardous zones of tsunamis..
In Japan extensive seismic networks have been constructed nationwide composed of high sensitivity seismographic network (Hinet). broadband seismographic network (F-net) and strong motion seismographic network (K-NET) as well as those by JMA and by universities. As a practical application of those data MEXT.JMA and NGOs are cooperating to develop an earthquake early warning system (EEW) since 2003 for the purpose of providing estimated seismic parameters to general public and prescribed users concerned with seismic risk reduction.
Onceearthquakes occur those focal parameters are calculated as soon as enough number (smallest number is one) of observation sites sense seismic waves, and are revised successively as seismic signals are received at larger number of observation sites in time. The transmitted parameters are used by application systems at sites to arrival time and seismic strength information in order for automatic or semi-automatic actions of various disaster mitigation countermeasures.
Many of applications systems have been developed under the coordination of consortium of concerned organizations and private companies(Real- time Earthquake Information Consortium: REIC). At present we are in the full stage both of the prescribed utilization and of the general usage through television and radio starting from October 1. Full adoption of the system is thought to reduce a large portion of damages induced by major disastrous earthquakes (several tens percents) .
The precise real-time and long-term monitoring capability on seafloor is effective to understand and forecast the mega-thrust earthquake activity near plate boundary accurately. The deployment of high density real-time seafloor sensor network is suggested to realize this requirement. The maintenance of large scale (high density) system extend over a long period of time is one of a great challenge of underwater technology. There are results that have already been used in-line sensor equipped submarine cable observatories for 30 years in Japan. However, these conventional high reliability seafloor real-time observation systems design are not suit for keeping up a large scale system long time. A noble system design concept and practical system management is necessary to make the seafloor sensor network turn into a reality. To aims at the improvement of observation capability of the Nankai trough, the project DONET (Development of Dense Ocean-floor Network System for Earthquakes and Tsunamis) is funded by MEXT (Ministry of Education. Culture. Sports. Science and Technology) and performed by JAMSTEC (Japan Agency for Marine-earth Science and Technology) from 2006. The DONET is mainly focuses to monitor the earthquake, tsunami and crustal movement on seafloor that related to the activity of plate boundary. This network is scheduling to install at least 20 sensor units on seafloor. which will be deployed at the interval of 15-20 km to obtain a precise monitoring ability
that surpasses the land base earthquakes observation network. The growth in sensor unit exerts a large influence on the decrease in total system reliability because of the sensors are most critical parts of the system to secure the reliability. A new design approach is necessary to surely manage a large scale system for long observation period (20-30 years). Replaceable, maintenanceable and extendable system configuration, and redundancy for the internal or external system failure are key technologies to provide for this network development. The concept of DONET is consists of three system component with different reliability. High reliability backbone cable system, replaceable science node, and extendable advanced sensor unit are major component of this system. Twenty sensor units will be installed in the seismogenic zone with mega-thrust earthquakes in the four year period from 2006.