• Fisheries and Aquatic Sciences
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• v.4 no.4
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• pp.201-207
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• 2001

To study the distribution of organophosphorus pesticides which are extensively used for agriculture in Korea. Sea water samples were taken from 4 coastal areas during May and August of 1997 and sediment samples were collected from two coastal areas in August of 1997. These samples were analyzed using a Gas Chromatography/Nitrogen Phosphorus Detector (GC/NPD). In August the most commonly found organophosphorus pesticides in the surface waters of Kunsan area were IBP < S-Benzyl O,O-di-isopropyl phosphorothioate > $(m=432.5ng\;L^{-1})$ and EDDP < O-ethyl S,S-diphenyl phosphorodithioate > $(m=37.4ng\;L^{-1}) $ which are largely used between June and September to prevent rice blast disease. In Danghang Bay, dry fields located near the mouth of the estuary seemed to affect the concentrations of certain organophosphorus pesticides in the surface waters. Since organophosphorus pesticides applied in the watershed are rapidly decomposed while being transported along freshwater streams, watershed size is not proportional to the concentrations of these pesticides in the coastal waters. Pesticides concentrations measured in August were compared with those in May. IBP concentrations in coastal waters were about an order of magnitude higher in August than in May. Temporal and geographical distribution of individual organophosphorus pesticides is likely to be affected by types of agricultural practices in the watershed. Chloropyrifos was the most important of the organophosphorus pesticides in the sediments of the study area because of its persistent nature and high affinity to particulates.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.1
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• pp.38-44
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• 1991

A simple box model was applied to the sedimentation of fine-grained sediments in a rectangular basin. Using the model explanation of the net depositional process of One-grained sediments in a small tide-dominated rocky embayment was possible by a careful evaluation of coefficients for erosion and deposition. For a basin with an inlet through which the exchange of suspended sediments occurs between open sea. the model shows that the time-averaged concentration of suspended sediments for a tidal cycle reaches a steady state initial abrupt change in concentration. During a tidal cycle deposition of sediments seems to occur when the magnitude of tidal currents is substantially low near the slack waters. Resuspension and erosion of bottom sediments take place near the peak of tidal currents. For a depositional basin. Gamagyang Bay, the duration and the maximum rate of deposition appear to be longer and higher than those of erosion. which accounts for the net deposition of fine-grained sediments. The time-averaged concentration of suspended sediment in the basin is slightly lower than that of the open water due to the net deposition. The instantaneous concentration of suspended sediments showed the maximum value about an hour before high water and the minimum about an hour after low water.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.4
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• pp.343-349
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• 2011

Seabed topography and marine site survey should be performed first in the design and construction of marine structures. We could successfully acquire the seafloor topography information can be obtained by bathymetric survey and side scan sonar and the sediment layer thickness and 3D bedrock depth by seismic reflection. It is necessary to apply carry out the integrated interpretation to each other in the ocean civil Eng. In this paper, we have obtained information on the sea bottom topography and water depth at the same time using interferometer technique and on the basement depth by seismic reflection. We have performed to assess the proposed method on the seafloor topographic survey with bedrock.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.5-12
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• 2011

This study was focused on the reactivity of furnace slag against cadmium to design the vertical drain method with reactive column for improving contaminated sea shore sediment. The kinetic sorption test was performed by changing the initial concentration and pH. Using pseudo-second-order model, the reactivity of furnace slag was quantitatively analyzed. Equilibrium removal amount ($q_e$) of furnace slag increased and rate constant ($k_2$) decreased with the increase of initial cadmium concentration. With the increase of pH, the equilibrium removal amount ($q_e$) and rate constant ($k_2$) increased in the same initial concentration. Required retention time was related to the inverse of the product of the equilibrium removal amount ($q_e$) multiplied by rate constant ($k_2$). The required retention time could be used to design the length of reactive column.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.4
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• pp.372-389
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• 2008

In this study, we formed a detailed grid at the estuary area of the Nakdong and collected the surface sediments. Particle size analysis and comparison with existing data were conducted to investigate the characteristics of seasonal and long-term changes in the sediments. As a result of investigation, the distribution of the sediments showed a great change per season and was greatly influenced by the quantity of outfall discharge at the Nakdong estuary barrier and the incident wave climate. The sandy sediments showed dominant movement toward the front of Jinwoodo west of the estuary area of the Nakdong due to the influence of the ENE wave, the annually-dominant wave. And the muddy sediments showed deposition by being moved toward the deep open sea along with a current. The present conditions of the sediments at the estuary area of the Nakdong showed great differences from the results of previous studies.

• Ocean Science Journal
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• v.42 no.1
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• pp.31-39
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• 2007

Distributional characteristics of dinoflagellate cysts in surface sediments were investigated in relation to environmental factors in the eastern part of Geoje Island, Korea. Samples were collected from 10 stations in February of 2004 and water temperature and salinity were measured in February, May, September and November of 2004. Total 30 taxa of dinoflagellate cysts were identified representing 19 genera, 28 species and 2 unidentified species. Among these dinoflagellate cysts, Brigantedinium spp. of which relative proportion in th e total dinoflagellate cysts was 23.5%, was the most abundant at all stations except St. 1, and was followed by Spiniferites bulloideus (8.6%), Lingulodinium machaerophorum (8.2%) and Diplopsalis lenticula (6.7%). In addition, ellipsoidal cysts of the genus Alexandrium (Alexandrium catenella - tamarense type) and Gymnodinium catenatum, known to be causative organisms for PSP, occurred with high concentrations. Scrippsiella trochoidea was also found; however, its cyst concentration was low. Generally, species composition in the study area was similar to these reported from Jinhae Bay and Busan Harbor and several dinoflagellate cysts reflected the eutrophic condition. Cyst distribution in th e eastern part of Geoje Island seems to be influenced by the Tsushima Warm Current flowing from the southwest. The mean water temperature was $12.0^{\circ}C$ in February, $14.7^{\circ}C$ in May, $20.9^{\circ}C$ in September and $17.2^{\circ}C$ in November, which was most favorable for Alexandrium spp. growth. The abundances of dinoflagellate cysts rang e d from 528 to 2,834 cysts/g dry sediment. Higher concentrations were recognized in sediments of west area of the Jisimdo than at other stations. The cyst composition of this area was closely related to these of Jinhae Bay and Busan Harbor from which currents flow into this area. Higher cyst concentration in the west area of Jisimdo might be due to formation of the gyre.

• The Journal of the Acoustical Society of Korea
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• v.13 no.3
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• pp.5-15
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• 1994

In order to examine the propagation loss associated with water depth and bottom sediment type, an acoustic experiment was conducted in the Southeast Sea of Korea. A sound source was towed along the pre-defined tracks in about 5kts and the signal was simultaneously received at three bottom-moored hydrophones. The propagation loss of sound wave traveling along the isodepth was compared with that crossing the isodepth. The former case shows, in general, less loss than the latter. This trend is stronger as the distance between a source and a receiver increases. When sound wave propagates across the isodepth, we also find that the propagation loss is influenced by the upsloping and downslopoing conditions of wave propagtion. In general, the propagation loss under downsloping condition is smaller than that of upsloping condition, and the differences are as large as 10dB in some cases. However, little difference are found in the propagation loss depending on the bottom types : gravelly sand and sand-silt-clay. Meanwhile, the optimum propagation frequencies are found within range of 130-255Hz.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.838-846
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• 2007

A measurement system of tri-axial pressure was designed and constructed to measure permeability and resistivity under changing confining pressure. The system was designed to measure the permeability and resistivity of a core simultaneously, consisting of tri-axial supporting device and sets of dual-flow measurement. In this measurement system the permeability and resistivity of a sample can be directly measured and porosity can be obtained using Archie's laws. As for physical properties, artificial core samples are made from mixtures of standard commercial sand and mud of illite. In-situ sediment cores were sampled at the water-depth of 1,800m in the Ulleung Basin East Sea. In order to investigate the effects of confining pressure changes on physical properties, permeability and resistivity changes were monitored with increasing confining pressure. In this study, it was found that with the increase of confining pressure, permeability and porosity tend to decrease and resistivity tend to increase exponentially.

• Ocean and Polar Research
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• v.33 no.4
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• pp.421-434
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• 2011

Although thermal effluent from coastal power plants affects marine ecosystems, few studies have examined the spatiotemporal distribution of macrobenthic communities in a coastal area of Korea with thermal discharge. This study analyzed the species composition and abundance of a macrobenthic community in relation to environmental variables for a period of 1 year. In total 334 macrobenthic faunal species were collected; the mean density was 3,221 ind/$m^2$. The number of species and the density of macrobenthic fauna increased with distance from the thermal discharge site. Cluster analysis indicated that the macrobenthic community could be divided into two groups: group I in shallow (< 30 m deep) and group II in the outer areas (> 30 m deep). Group I showed the lowest species density and diversity. Four polychaetes, including Magelona japonica, Spiophanes bombyx, Scolotoma longifolia and Chaetozone setosa, all of which have been dominant species since 1987, exhibited higher mean densities in the area distant from the thermal discharge (the outer and north areas). Conversely, the warm-adapted and opportunistic species, such as the amphipods Urothoe convexa and Mandibulophoxus mai, the bivalve Felaniella sowerbyi, and the polychaete Rhynchospio sp., were more abundant in the thermal discharge region. The results of this study indicate that thermal effluent influences macrobenthic communities in the shallow area, while other environmental variables, such as depth, sediment grain size, and TOC, are more important determinants of the macrobenthic communities in deeper regions (> 30 m deep).

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.75-82
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• 2020

The Daehang-ri intertidal flat located the just outside of the Saemangeum dike has been reported to show new-developing flats. Based on the topographic surveys of 21 times from 2000 to 2016 by a leveling method every year, this site clearly shows variation of deposition/erosion in time and space. Deposition has consistently occurred at the rate of +3.75 cm per year at the area along the dike (Zone 1), and this tidal flat is expanding and prograding seaward. In the area of far from the dike (Zone 2), on the other hand, erosion prevails at the rate of -2.38 cm per year, and this zone tends to retreat landward. However, the erosional trend of Zone 2 has slightly slowed down since 2014. As a whole from 2000 to 2016, net deposition is recorded over 3.0 m at the upper beach and the area adjacent to the dike (Zone 1), while erosion up to 1.0 m in Zone 2. In conclusion, the results at the Daehang-ri intertidal flat clearly revealed that its topographic changes were induced by the artificial structures and water masses through its sluice gate. Counter-clockwise gyre newly created after the sea dikes construction probably results in relocating of sediment outside the dike 1 by transportation of materials eroded from the south to the north along the coast.