• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.719-738
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• 2006

Simrad EM950 multibeam data and surficial sediment grab samples were acquired to correlate backscatter strength with surficial sediment properties in the eastern Yellow Sea which tidal sand ridges are dominantly developed. The study area is divided into the western sand ridge zone characterized by well sorted, fine sandy sediment, and the eastern non-sand ridge zone characterized by poorly sorted, medium sand with some gravels and shell fragments. In spite of minor difference in grain size between two zones, the variations of backscatter strength between two zones are distinct. Multibeam backscatter strength of study area shows good correlation with the grain size of surface sediment as well as the carbonate contents. High occurrence of carbonate shell fragments can increase grain size and bottom roughness. The dominance of higher backscatter strength in the eastern non-sand ridge zone may reflect the effects of coarse grain size and high shell fragments contents.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.12-16
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• 2002

Soil, ground water and sea bed are exposed to continuous accumulation of polluted materials causing serious environmental damage. It has been reported that such pollution causes a massive mortality of fish stock in rivers by the resuspension of toxic chemicals during strong wind conditions. Therefore, it becomes apparent that there is an immediate demand for the restoration treatment of polluted river bed (or sea bed) sediment layers. Pollution levels of major rivers and ports such as Pal-dang, Kyung-an rivers, Ma-san port are becoming public concern and are posing a serious environmental threat. In particular, the pollution of Shi-hwa river has become a nation wide issue for last few years. In spite of such public concern, the pollution level of such rivers or port are getting worse everyday. In this study, an environmentally sound engineering package is introduced which helps to restore the polluted river bed or sea bed sediments. This engineering package is consisted of a suction facility followed by a series of mechanical, chemical as well as biological treatment units. The suction facility is designed to minimize the secondary pollution due to the resuspension of toxic materials during suction. The sea bed cleaning engineering package is designed to be installed on the top of a floating barge. Such combination of environmental plant and shipbuilding technology provides a cost-effective solution, minimizing the cost involved in the transportation between suction and treatment facilities.

• Journal of the korean society of oceanography
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• v.39 no.1
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• pp.46-56
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• 2004

Spectral attenuation of light and upwelling radiance were measured in the western coast of Korea on board the R/V Inchon 888 of the Korean National Fisheries Research and Development Institute(NFRDI) during four seasons. The goal of these efforts was to determine the spatial and temporal distribution of the inherent and apparent optical properties of the water, and the factors that control their distribution. Our data indicate that while stratification of the water column, phytoplankton, and wind stress determined the vertical distribution of the optical parameters offshore, it was the tidal current and sediment type that controlled both the vertical and horizontal distribution in the coastal areas. These findings led to the development of a model that estimates the spectral attenuation of light with respect to depth and time for the Yellow Sea. The model integrates water leaving radiance from satellites, sediment types, current vectors, sigma-t, bathymetry, and in situ optical measurements in a learning algorithm capable of extracting optical properties with only knowledge of the environmental conditions of the Yellow Sea. The performance of the model decreases with increase in depth. The mean absolute percentage error (MAPE) of the model is 2% for the upper five meters, 8-10% between 6 and 50 meters, and 15% below 51 meters.

• Ocean and Polar Research
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• v.32 no.2
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• pp.145-156
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• 2010

This study investigated organic carbon fluxes in Ulleung Basin sediments, East Sea based on a chamber experiment and geochemical analyses. At depths greater than 2,000 m, Ulleung Basin sediments have high organic carbon contents (over 2.0%). Apparent sedimentation rates (ASR) calculated from excess $^{210}Pb$ activity distribution, varied from 0.036 to $0.047\;cm\;yr^{-1}$. The mass accumulation rates (MAR) calculated from porosity, grain density (GD), and ASR, ranged from 131 to $184\;g\;m^{-2}\;yr^{-1}$. These results were in agreement with sediment trap results obtained at a water depth of 2100 m. Input fluxes of organic carbon varied from 7.89 to $11.08\;gC\;m^{-2}\;yr^{-1}$ at the basin sediments, with an average of $9.56\;gC\;m^{-2}\;yr^{-1}$. Below a sediment depth of 15cm, burial fluxes of organic carbon ranged from 2.02 to $3.10\;gC\;m^{-2}\;yr^{-1}$. Within the basin sediments, regenerated fluxes of organic carbon estimated with oxygen consumption rate, varied from 6.22 to $6.90\;gC\;m^{-2}\;yr^{-1}$. However, the regenerated fluxes of organic carbon calculated by subtracting burial flux from input flux, varied from 5.87 to $7.98\;gC\;m^{-2}\;yr^{-1}$. Respectively, the proportions of the input flux, regenerated flux, and burial flux to the primary production ($233.6\;gC\;m^{-2}\;yr^{-1}$) in the Ulleung Basin were about 4.1%, 3.0%, and 1.1%. These proportions were extraordinarily higher than the average of world open ocean. Based upon these results, the Ulleung Basin might play an integral role in the deposition and removal of organic carbon.

• Ocean and Polar Research
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• v.36 no.4
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• pp.395-405
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• 2014

A 570 cm-long sediment core was retrieved at $9^{\circ}57^{\prime}N$ and $131^{\circ}42^{\prime}W$ in 5,080 m water depth from the northeast equatorial Pacific and its stratigraphy was established with $^{10}Be/^9Be$ and paleomagnetic measurements. Successive AF demagnetization reveals eight geomagnetic field reversals. In the reference geologic time scale, the eight reversal events correspond to an age of about 4.5 Ma. However, $^{10}Be/^9Be$-based age yields 9.5 Ma at a depth of 372 cm. Such a large discrepancy in determined ages is attributed to an extremely low sedimentation rate, 0.4 mm/kyr on average, of the study core and resultant loss or smoothing of geomagnetic fields. The composite age model reveals a wide range in the sedimentation rate - varying from 0.1 to 2.4 mm/kyr. However, the sedimentation rate shows systematic variation depending on sedimentary facies (Unit II and III), which suggests that each lithologic unit has a unique provenance and transport mechanism. At depths of 110-80 cm with a sedimentation rate of about 0.1 mm/kyr, ancient geomagnetic field reversal events of at least a 1.8 Myr time span have not been recorded, which indicates the probable existence of a hiatus in the interval. Such a sedimentary hiatus is observed widely in the deep-sea sediments of the NE equatorial Pacific.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.96-108
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• 1998

The management of water quality and fishery resources with a major environmental problem in eutrophic coastal sea is studied. The numerical experiments using the water-sediment quality model (WSQM) were carried out for the management of water quality at the Seto Inland Sea in Japan. The results of long-term water quality simulation showed responses of seawater quality to input loads to vary in different localities. A formula roughly forecasting water qualify to estimate the effect of loading abatement was proposed. The simulation for the improvement of seawater quality showed the abatements of nutrient loads such as total phosphorus (TP) and total nitrogen (TN) as well as organic loads such as chemical oxygen demand (COD) to be peformed in the eastern Seto Inland Sea from Bisan Seto to Osaka Bay. On the other hand, it is indicated that the increase of loading leads to the increase of primary production. while not straightly to the increase of fish production for the catch of fisheries.

• Journal of the korean society of oceanography
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• v.33 no.4
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• pp.185-195
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• 1998

Two piston cores (94PC-2 and 95PC-4) taken from the East Sea (Sea of Japan) are studied to evaluate the paleoceanographic changes and its interaction with climatic variation. The bulk geochemistry of the non-biogenic fractions of 54 sediment samples is determined using X-ray fluorescence. Four geochemical stratigraphic units at both core sediments are recognized based on the variations in major element concentration. These chemical stratigraphic units correspond well with the sedimentological and paleontological facies. Source materials are considered as basic and/or intermediate rocks judging from silica content. A distinctive boundary around 11 kyr may correspond to Younger Dryas event. The switch of most major elements at this level and the distinctive changes in concentration of typical terrigenous elements (TiO$_2$ and Al$_2$O$_3$) are the strong evidence for the difference in sources of terrigenous materials. The weathering indices exhibit high degree in Core 94PC-2 and low degree in Core 95PC-4. The changes in weathering degree can be distinguished by the lowest value occurred at 11 kyr in Core 94PC-2 and by a gradual decrease from top to bottom in Core 95PC-4. The profiles of potassium and sodium exhibit specific excursions between the Holocene and the late Pleistocene. This implies that sediments of the two cores originating from different sources with different weathering degrees. The distinct two-group distributions in K$_2$O/CaO vs. Na$_2$O/K$_2$O also support the difference in provenance of aluminosilicate materials at the boundary of 11 kyr. Thus, supply patterns of terrigenous materials are stable in Holocene and more complicated in the last glacial period.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.1
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• pp.14-20
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• 1997

The southwestern continental shelf of the East Sea, Korea developed mud deposits as a belt in the inner shelf area from Pusan to Pohang. The general surface sediments consist of very poorly to poorly sorted muddy sediment. The differences of physical, geological and geomorphic conditions in the study area may control and produce distinctive foraminiferal populations. To establish a baseline of environment for the muddy sediments in the southwestern continental shelf of the East Sea, 17 stations were sampled and proved to contain 45 species of living benthic foraminifera. Analysis of the foraminiferal populations in cluster analysis recognized to five habitat zones. These habitat zones contain distinctive cooccurrences of the entire occurring species. Foraminiferal community composition appeared to be closely interrelated of water masses, depths, nutrients and sediment characters.

• Economic and Environmental Geology
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• v.37 no.2
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• pp.235-244
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• 2004

The shear strength of deep-sea core sediments from the nofheast equatorial Pacific was measured in various conditions to ensure precision of results. The comparison items were 1) two different measuring systems (hand-held vane and motorized vane), 2) in different places of on-board immediately after collecting the core samples and on-land laboratories after storing these samples for three months in a cold room, 3) two different core samples from a multiple corer within a sampling station, and 4) four different measuring points (holes) from a core sample. In this experiment, the values of shear strength in deep-sea sediments show significant change with depth which increase toward the bottom of core. Also, the results of two cores recovered at the same station indicate that vertical variation of shear strength is mainly caused by the change of physical properties. They strongly support the fact that the difference of vue syrtem and/or experimental conditions are not major factor in the variation of geotechnical properties.

• Journal of the Korean earth science society
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• v.37 no.6
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• pp.325-331
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• 2016

Three diatom assemblage zones were erected from HMB-103 core sediment of the Heuksan Mud Belt. The paleoenvironmental changes were reconstructed basing on diatom analyses using indicator species, cold and warm water species, and salinity. Seventy-six species belonging to 41 genera were identified in the core sediments. The number of diatom valves per gram of dry sediment ranged from 0.1 to $15.4{\times}10^4g^{-1}$. As a result, diatom assemblage I in about 45,000 yr B.P showed a high abundance in cold species indicating a major influence by the Korea Coastal Current. Diatom assemblage II from 14,000 to 11,646 yr B.P is characterized by rare abundance and indicative of the cold periods at Younger Dryas with the lower sea-level. However, diatom assemblage III from 11,646 yr B.P to Holocene was more affected by the Yellow Sea Warm Current while the progressive sea level rise.