Hiromune Yokoki

Heavy metal contamination of coastal lagoon sediments: Fongafale Islet, Funafuti Atoll, Tuvalu

To evaluate contamination of coastal sediments along Fongafale Islet, Central Pacific, a field survey was conducted in densely populated, sparsely populated, open dumping and undisturbed natural areas. Current measurements in shallow water of the lagoon indicated that contaminants from the densely populated area would only be transported for a small proportion of a tidal cycle. Acid-volatile sulfides were detected in both the intertidal beach and nearshore zones of the densely populated area, whereas these were no detection in the other areas. This observation lends support to argument that the coastal pollution mechanism that during ebb tide, domestic wastewater leaking from poorly constructed sanitary facilities seeps into the coast. The total concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were relatively high in all of the areas except the undisturbed natural area. The indices of contamination factor, pollution load index and geoaccumulation index were indicative of heavy metal pollution in the three areas. The densely populated area has the most significant contamination; domestic wastewater led to significant contamination of coastal sediments with Cr, Zn, Cu, Pb and Cd. The open dumping area is noteworthy with respect to Mn and Ni, which can be derived from disposed batteries.

Anthropogenic impacts on water quality of the lagoonal coast of Fongafale Islet, Funafuti Atoll, Tuvalu

Water pollution, evident by negative values of redox potential in waters, occurs at the lagoonal coast located near the densely populated area of Fongafale Islet on Funafuti Atoll, Tuvalu, Central Pacific. Sediment microbial quinone analysis revealed that these coastal sediments exhibit 2.7–10.4 times more microbial biomass, significantly different microbial community structure and low microbial diversity, when compared to an undisturbed natural coastal sediment. Thus, the pollution is chronic. By considering the total land use/coverage on the islet, the situation of septic tank installations, temporal changes in water redox potential and Escherichia coli numbers in the coastal waters and the spatial distribution of acid volatile sulfide in the sediments, we conclude that domestic wastewater is the primary source of pollution. This pollution is proposed to occur via the following mechanism: during ebb tides, domestic wastewater leaking from bottomless septic tanks and pit toilets run off into the lagoonal coast. Tide changes control the pollution load of domestic wastewater.

COMPLEX PRINCIPAL COMPONENT ANALYSIS TO CHARACTERIZE BEACH TOPOGRAPHIC CHANGE IN SILT ISLAND, GERMANY

Complex principal component analysis is a useful method to statistically extract dominant patterns of beach topographic change from a number of topographic survey data. However, the results of the statistical method are often vague since they are averaged values for a whole region. To overcome such vagueness, “local ratio of contribution” is used in the present study, which identifies the most dominant mode of topographic change at each point of the region. This method was applied to beach topographic data obtained in Sylt Island, Germany, and the characteristics of topographic change after beach nourishment was extracted.

A METHOD FOR ESTIMATING DIRECTIONAL SPECTRA IN A FIELD OF INCIDENT AND REFLECTED WAVES

A study of alternatives including a shoreline evolution numerical modelization has been carried out in order to both diagnose the erosion problem at the beaches located between Cambrils Harbour and Pixerota delta (Tarragona, Spain) and select nourishment alternatives.Engineers and scientists at the U.S. Army Engineer Waterways Experiment Station (WES) are developing a Rapidly Installed Breakwater (RIB) System specifically designed to address problems associated with the militarys efforts to offload ships during Logistics Over The Shore (LOTS) operations. Problems arise with these operations when seas become energetic and limit capabilities of crane operators and stevedore crews. The RIB System is designed to solve this problem by creating a pool of calmer water where these operations occur so that crews can continue to function. A series of small-scale laboratory experiments conducted in 1995 and 1996 at WESs facilities in Vicksburg, Miss., and at the O. H. Hinsdale Wave Research Laboratory at Oregon State University in Corvallis, laid the groundwork for the RIB System development and yielded an optimum RIB System configuration known as the Double Delta. Laboratory results, obtained with the Double Delta configuration, showed that wave heights could be reduced by more than 80 percent. During the spring and summer of 1996, a mid-scale RIB System successfully demonstrated its capabilities during a field deployment, with wave height reduction on the order of 75 percent. Based on these results, it is believed that the RIB System will be integrated into the Armys LOTS asset inventory and become a key part of the solution to the militarys LOTS problems.

95. NUMERICAL CALCULATION OF THE SEDIMENT TRANSPORTS ALONG THE LAGOONAL COAST ON MAJURO ATOLL

Atoll islands are low-lying and consist of the biological organisms such as corals and foraminifers. These islands have high vulnerability to the coastal erosion and need the conservation plan. Sato and Yokoki (2008) developed the sediment transport model in Majuro atoll. Although they had a good agreement with realistic sediment volume change, the extreme large accretion and erosion were also calculated at some points. Toward accurate estimation of future land changes, we improved the model by considering the interaction between waves and land changes in this study. The calculated results showed no extreme accretion and erosion and better agreement with the realistic sediment volume during 10 years. The present model enabled reasonable estimation for the future land change in Majuro atoll.