Kiyoshi Takikawa

Polycyclic aromatic hydrocarbons in oysters and sediments from the Yatsushiro Sea, Japan: Comparison of potential risks among PAHs, dioxins and dioxin-like compounds in benthic organisms

Polycyclic aromatic hydrocarbons (PAHs) were analyzed in oysters collected from 18 stations in the Yatsushiro Sea, western Japan. PAHs were detected in all samples analyzed, and the highest concentration (mean 230 ng/g wet weight) was found in oysters from Tanoura Bay. The high molecular weight PAHs to low molecular weight PAHs ratios in oysters from Tanoura Bay were higher than at other stations. Sediment samples collected from 42 stations in Tanoura Bay were analyzed for PAHs to understand their concentrations and distribution. Higher concentrations were found in sediment samples at two stations in the southern inner bay (mean 30,200 ng/g dry weight), which were approximately two orders of magnitude higher than at a reference site. These observations strongly suggest severe contamination and significant sources of PAHs in Tanoura Bay. Dioxins and dioxin-like compounds (PCDFs, and non- and mono-ortho coplanar PCBs) were analyzed in sediments from eight stations in Tanoura Bay. The concentrations were comparable to, or lower than, at the reference sites, suggesting that there are no specific sources of these compounds in this bay. PAH, dioxins and dioxin-like compounds DR-CALUX relative potencies (REP) were applied to the sediment concentrations to evaluate the potential for toxicological effects on benthic organisms. PAHs made the highest contribution to the total REP concentration, supplying 99% of the total REP, followed by PCDDs (0.18%), PCDFs (0.04%), and PCBs (<0.001%). In this area, PAHs appear to be the most important Ah receptor binding chemicals for potential toxicity to benthic species.

Isolation and Evaluation of PAH Degrading Bacteria

Polycyclic aromatic hydrocarbons (PAHs) degrading bacteria can be isolated from polluted coastal environments. They were close to Burkholderia fungorum and Mycobacterium gilvum, and had nidA, nidA3, pdoA2, and pcaH genes. In the pyrene and fluoranthene degradation experiment using a minimum medium, B. fungorum isolate no. 1 and M. gilvum isolate no. 13 were able to degrade 98.6% + 1.9 of pyrene after 20 days, and 99.9% ± 0.1 after a 16-day incubation period, respectively. Moreover, fluoranthene could be consumed by B. fungorum isolate no. 1 and M. gilvum isolate no. 13 at the level of 99.6% ± 0.7 after 24 days, and 100% after a 28-day incubation period, respectively.

Internal characteristics and numerical analysis of plunging breaker on a slope

Abstract Many investigations about the direct measurements of velocities to clarify the internal mechanism of the breaker have been carried out as a result of recent progress in the measuring techniques. This research attempts to clarify the breaking wave transformation system on a slope by an experiment and numerical analysis. In an experiment, the velocities in the surf zone were measured directly using an electromagnetic current meter, and the space distribution characteristic of the vorticity ω = (∂u/∂y − ∂u/∂x) and the skewness γ = (∂u/∂y + ∂u/∂x) were examined. Also, occurrence situations of the vortices at the time of water mass inrush were measured by video tape recorder (VTR) image processing. However, because the breaker is a violent phenomenon that is entrained with plentiful bubbles, the extent to which we can clarify breaker transformation in experiments is limited. Numerical simulations are substituted for experiments as a method to clarify breaker transformation. In numerical analysis, finite amplitude wave analysis based on the potential theory (non-viscous fluid) is possible before wave breaking; however, the analysis must take into account the viscous fluid after breaking. So, we use the Reynolds equations to develop a numerical simulation system of the breaker transformation on a sloping bottom. The numerical energy dissipation model of the breaker was compared to the experimental results, and a modified Simplified Marker and Cell (SMAC) method is presented. The internal characteristics of the breaker transformation are described using application examples.

Open boundary treatment of the finite amplitude wave using the boundary element method

Abstract In this paper the boundary element method is applied to the analysis of non-linear free-surface waves. A particular concern is the treatment of open boundary at the input flow boundary and output flow boundary, which uses the mass-flux and energy-flux because of the continuity of fluid. By assuming the fluid to be inviscid and incompressible and the flow to be irrotational, the problem is formulated mathematically as a two-dimensional non-linear problem in terms of a velocity potential. The equation (Laplace equation) and the boundary conditions are transformed into two boundary integral equations. Due to the non-linearity of the problem, the incremental method is used in the numerical analysis. Numerical results obtained by the present boundary element method are compared with those obtained by the finite element method and also with the experimental values. Good agreements are obtained.

Assessment of the spatial distribution of submarine groundwater discharge (SGD) along the Yatsushiro Inland Sea coastline, SW Japan, using 222Rn method

Abstract A towing method using 222Rn can detect SGD signals in coastal areas. This study aims to evaluate the impact of topography and hydrology on SGD spatial distribution and the estimation of SGD patches along the coastlines. For this, we tried to determine the SGD signals in the study area and the maximum depth where the SGD rate is significant. The study conducted along the Yatsushiro Sea coastline, SW Japan. The estimated SGD distribution pattern suggests that the local topographic and geological settings govern the occurrence of SGD (recirculated seawater (RSGD) and terrestrially derived groundwater (FSGD)) as the primary deriving forces.

FORECASTING OF DAMAGE LEVEL OF MARITIME STRUCUTRES CAUSED BY TYPHOONS BASED ON IMPROVED EWE METHOD

The aim is to forecast the damage length of damaged maritime structures at each coast for each pass of a typhoon of the equivalent wave energy of a typhoon at a latitude of 30˚N using the so-called equivalent wave energy (EWE) method, which has been improved. EWE of typhoons is defined based on the maximum wind speed and the duration of wind blowing of the typhoon. Using the data on the damage length of maritime structures by typhoons and the path and the equivalent wave energy of typhoons, the vulnerability of coastal regions along the coastline of Japan for 13 groups of typhoon with different paths is estimated. The improved EWE method has been upgraded in comparison with EWE method and it will be used to estimate the damage length of damaged maritime structures that will occur along the coast at a latitude of 30˚ N before a typhoon strikes. The forecasting method reported here will be used for the purpose of coastal zone management in disaster prevention works. Further, it provides useful for information of storm warning and evacuation of residents along coastlines.

APPLICABILITY OF RECYCLED FINE AGGREGATE BY PULSED POWER TO OVERLAYING SAND MATERIAL

Ariake Bay and Yatsushiro Bay, a typical closed bay on the west of the Kyushu Island, is a sea area where a vast tidal flat develops. Recently, various environmental degradations are reported occur in Ariake Bay and Yatsushiro Bay, as red tidal and anoxic water. Especially, a rapid decrease in the short-necked clam’s fish catch is a problem since the latter half of the 1980s. The natural sand is insufficient, even though the sand overlying is done as a rehabilitation technology. In this study, we tried the bioassay for short-necked clams that used the recycled fine aggregate by pulse power aim at application of the sand overlying material. As the result, the possibility that the recycled fine aggregate by pulse power was able to be applied to the sand overlying material was suggested.

Field Study on Characteristic of Thermal in Bottom Mud at Tidal Flat

It is difficult to clarify the environmental condition in tidal flat because of the complicated interaction of atmosphere, sea water, land and creature. The thermal environment is an important factor in water quality closed relationship phytoplankton growth and activated biological. The objective of this study is to grasp the characteristic thermal from field observation and calculate the numerical thermal model simulation in the bottom mud at tidal flat. The thermal water or bottom was observed at four sites that were different in the ground level and the meteorological variables in the inter-tidal zone near Kumamoto Port. As a result, the thermal in bottom was depended on tide change and the numerical thermal model improved the accuracy with a scheme thermal diffusion.

ONE CONSIDERATION CONCERNING ABOUT TOPOGRAPHY CHANGE AND HABITAT IN FRONT OF COASTAL EMBANKMENT IN ARIAKE SEA

The natural coastline has been almost replaced by the concrete construct on such as coastal embankment for the land reclamation and disaster prevention in Ariake Sea. The natural habitat for benthos and salt plant had been getting loss; and then the environmental deterioration becoming advanced in Ariake Sea. Agricultural Administration Office promoted the harmony with disaster prevention and environment using embankment and jetty in Tamana Yokoshima coast. In this study, firstly searched the volume of sediment movement at the jetty area by the river and tidal flow and confirm the stability performance in sediment, which the benthos could be alive. And then, modeling the Habitat Suitable Index by using the topography, bottom quality and benthos calculate the habitat environment in the feature.

THE CHARACTERISTICS OF SPATIAL DISTRIBUTION OF HABITAT AT “THE ARTIFICIAL SHORELINE”, IN KUMAMOTO PORT

Ariake Bay, a typical closed bay on the west of the Kyushu Island, is a sea area where a vast tidal flat develops. Recently, various environmental degradations are reported occur in Ariake Bay, as red tidal and anoxic water. In this study, the ecosystem formation process by recovery of shoreline, the aim in this method is to establish the technology that can artificially restore the tidal flat and the shoreline in front of embankment development and to recover and maintain the ecosystem, was investigated in Ariake Bay. We investigated the characteristics of spatial distribution of habitat from relation to topography, sediment and distribution situation of benthos. As the result, the peculiar environment such as water-route influences distribution situation of benthos.