• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.58-58
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• 2010

The sediment geochemistry, including REE of surface and core samples in the western part off Jeju Island have been carried out in order to understand the provenance and hydrolic sorting. The sediment in the study area were primarily composed of coarse silt with a mean grain size of $2.8{\sim}82.8{\mu}m$. The ratios of TOC over total nitrogen (TN) showed that the study area sediments contained more organic matters of marine origin than those of terrigenous origin. The total A1203, Fe203, K20, MgO, and MnO contents and REE concentration of the fine sediments are higher than those of the coarse sediments. The higher Zr/Th and Zr/Yb ratios in coarse sediments relative to fine-grained detritus indicates sedimentary sorting. Grain size influence the REE concentrations of the study area sediment significantly. The < $63{\mu}m$ fraction of the sediment has higher REE concentration and different REE patterns when compared with those in bulk samples, due to the presence of REE-enrich heavy minerals. The REE distribution patterns of the western part of Jeju Island sediments are relatively enriched in most LREEs than the Yellow River sediment and depleted in the Changjiang River, but the LaN/YbN ratios are similar to the Changjiang sediment. The Eu/Eu* ratios ranged from 0.594~0.665(0.631) is much similar to the Yellow River sediment, possibly mixture of the sediments from these two rivers.

• Journal of the korean society of oceanography
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• v.32 no.3
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• pp.128-137
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• 1997

This study presents results from a detailed sedimentological investigation of surface sediments obtained from the Korea Strait region, the southern part of the East Sea (Sea of Japan). The distribution of different types of bottom sediments is controlled by the recent fine-grained sediment transport and deposition combined with the lowerings of sea level during the last glacial period, forming a diverse mixture of organic-rich fine-grained and shelly coarse-grained sediments. In comparison to high organic concentration of fine-grained sediments in the inner continental shelf and slope areas, the shell-rich coarse-grained sediments on the outer shelf are discernible being further modified. These coarse-grained sediments are confirmed as relict resulting from the sediment dynamics during the lower sea levels of the last glacial period. Clay mineral distribution of the fine-grained sediments gives information about the transport mechanism. Presence of present-day current system (the Tsushima Warm Current) is most probable source for the fine-grained particles into the open East Sea from the East China Sea, indicating that Holocene sediment dynamics may be used to explain the observed distribution of surface coarse-grained shell-rich sediments.

• Journal of the korean society of oceanography
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• v.34 no.4
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• pp.207-213
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• 1999

Sediment physical properties (compressional wave velocity, grain density, dry bulk density, and wet bulk density) are correlated to the paleoenvironmental parameters (coarse fraction, oxygen isotope, and planktonic foraminifera fragmentation) to reveal the possible interrelationship in the latest Quaternary sediments of the Ulleung Basin, the East Sea of Korea. Laboratory determinations of physical properties and paleoenvironmental parameters have been conducted on four piston core sediments. There are slight differences in the physical properties between glacial and interglacial period sediment sections. This is due to the large fraction of coarse grains of volcanic and terrigenous sediments relative to carbonate sediments. However, dry bulk density as an indicator of carbonate abundance in pelagic environment shows higher values at the lower part of cores, reflecting deeper CCD in the glacial period. Changes in velocity also relatively parallel to those in sediment coarse fraction, number of planktonic foraminifera, and wet bulk density. Therefore, we suggest that high-resolution physical properties may be used as a valuable tool for paleoenvironmental interpretation in the Ulleung Basin.

• Ocean Science Journal
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• v.41 no.3
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• pp.139-148
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• 2006

The distribution of the taxonomical composition and the density of meiobenthos depending on the sediment type has been studied in bottom sediments of Nha Trang Bay. The maximal population density and the taxonomical diversity were observed in the silted coarse and heterogeneous sand ($1031.4{\pm}419.7\;ind.\;10\;cm^{-2}$), whereas the minimal level of density and diversity ($588.1{\pm}152.5\;ind.\;10cm^{-2}$) was in the coarse and heterogeneous sand with shell debris and corals. The correlation between the median diameter of sediment particles and population density of meiobenthos has been revealed (r=0.82, p<0.05). In bottom sediments of Nha Trang Bay, twenty six taxonomic groups of meiobenthos were observed. Nematodes dominated in all sediment types. Representatives of four orders, twenty eight families and ninety seven genera of marine nematodes were identified. The vertical distribution of meiobenthos in different sediment types was considered. A sediment column (10 cm height) was sectioned by five 2 cm portions. In the last layer (8-10 cm) the most number of meiobenthic groups was found in sandy sediments. In the lower layers of silt sediments, only nematodes were found.

• Journal of Korea Water Resources Association
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• v.52 no.spc2
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• pp.835-844
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• 2019

This study dealt with a systematic approach for sediment replenishment works which defines the artificial supply of coarse sediment to downstream river channels of dams. That is an increasing practice in Japanese, American and European rivers for the purpose of compensating sediment deficits downstream and rehabilitating geomorphological habitats below dams. We introduced five main objectives of the sediment replenishment, simply from construction of artificial spawning redds for anadromous fish to restoration of fluvial geomorphological process of river system. Then we suggested determination of sediment size distribution and quantity of coarse sediment as well as selecting an effective implementation method in corresponding to specific objectives and local restrictions in the basin, reservoir and river.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.59-70
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• 1998

Two-dimensional trend-vector model of sediment transport is first tested in the tidal flat of Garolim Bay, mid-western coast of the Korean Peninsula. Three major parameters of surface sediment, i.e., mean grain size, sorting and skewness, are used for defining the best-fitting transport trend-vector on the sand ridge and muddy sand flat. These trend vectors are compared with the real transport directions determined from morphology, field observation and bedforms. The 15 possible cases of trend vectors are calculated from total sediments. In order to find the role of coarse sediments, trend vectors from sediments coarser than < 4.5 ${\phi}$, (sand size) are separately calculated from those of total sediments. As compared with the real directions, the best-fitting transport-vector model is the "case M" of coarse sediments which is the combined trend vectors of two cases: (1) finer, better sorted and more negatively skewed and (2) coarser, better sorted and more positively skewed. This indicates sand-size grains are formed by simpler hydrodynamic processes than total sediments. Transported sediment grains are better sorted than the source sediment grains. This indicates that consistent hydrodynamic energy can make sediment grains better sorted, regardless of complicated mechanisms of sediment transport. Consequently, both transported vector model and real transported direction show that the source of sediments are located outside of bay (offshore Yellow Sea) and in the baymouth. These source sediments are transported through the East Main Tidal Channel adjacent the baymouth. Some are transported from the subtidal zone to the upper tidal flat, but others are transported farther to the south, reaching the south tidal channel in the study area. Also, coarse sediment grains on the sand ridge are originally from the baymouth, and transported through the subtidal zone to the south tidal channel. These coarse sediments are moved to the northeast, but could not pass the small north tidal channel. It is interpreted that the great amount of coarse sediments is returned back to the outside of the bay (Yellow Sea) again through the baymouth during the ebb tide. The distribution of muddy sand in the northeastern part of study area may result from the mixing of two sediment transport mechanisms, i.e., suspension and bedload processes. The landward movement of sand ridge and the formation of the north tidal channel are formed either by the supply of coarse sediments originating from the baymouth and outside of the bay (subaqueous sand ridges including Jang-An-Tae) or by the recent relative sea-level rise.

• 한국해양학회지
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• v.25 no.1
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• pp.26-35
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• 1990

Sound velocities and attenuation coefficients of marine surface sediments were calculated from insitu acoustic experiments on 4 nearshore areas off Pohang, Pusan Yeosu, and Kunsan around the Korean Peninsula. The relationship between these values and physical properties of sediments was examined and attenuation mechanism was analysed using the estimated gas content. Sound velocities and attenuation coefficients ranging from 1470 to 1616 m/sec and 0.0565 to 0.6604 dB/kHz-m, respectively, are well related to sediment types. The attenuation coefficient is maximum in coarse silts, and the sound velocity increases with density. The gas content estimated less than 8 ppm increases with the decreasing sediment grain size. When the sediment size is greater than fine sand, sound attenuation is mostly due to friction losses, and probably negligible viscous loss remains unchanged with the varying physical properties of sediments. The maximum attenuation in coarse silts result from both friction loss and cohesion of finer sediments between the contacts of silt grains. The cohesion begins to be the dominant dissipative process with decreasing grain size from medium and fine silts.

• Journal of Marine Life Science
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• v.3 no.1
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• pp.38-43
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• 2018

The polychaetes are the dominant species in the benthic communities, and play an important role in improving the sediment quality through the action of ingesting organic materials. We evaluated the improvement ability of rockworm Marphysa sanguinea for the removal of organic matter. We used the three types of sediment (S1: coarse sand, S2: fine sand, S3: muddy sand), and analyzed TOC of seawater and sediment. Rockworm was effective in eliminating organic matter in the three types of sediment and the larger the particle, the higher the removal rate. Removal ability of rockworm for organic matter in sediment were calculated with 3.9856 ppm g^-1d^-1 in coarse sand, 2.8021 ppm g^-1d^-1 in fine sand, and 28.1142 ppm g^-1d^-1 in muddy sand. The results show that rockworm contributes to the removal of organic matter in the various sediment types.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.245-250
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• 2004

Farmers typically apply the dressed soil (coarse saprolite) for various reasons in the sloped upland with high altitude in Kangwon province. However, little researches on the impacts of application of dressed soil in uplands were conducted. Therefore, it is necessary to assess soil quality in this area and to study adverse effects on soil and water due to application of dressed soil. Coarse saprolite itself showed signiScantly poor chemical properties, Particularly P and organic matter contents were not enough for crops to grow. With respect to biological qualities such as enzyme activity and microbial population, coarse saprolite itself showed poor qualities. For example, bacterial population in coarse saprolite contains six times or ten times smaller populations. Based on survey at Jawoon-ri in Hongchon-gun, this region is susceptible for soil erosion due to massive amounts of coarse saprolite application, undesirably long slope length, etc. When weestimated soil loss, more than 40% of farming field in this region exceeded $11.2MT\;ha^{-1}\;yr^{-1}$. According to experiment by installing sediment basins. the sediment basin with up-down tillage and application with dressed soil had the highest soil loss and runofT, while the sediment basin with contour tillage and without soil dressing showed the lowest soil erosion and runoff.

• Proceedings of the Korea Water Resources Association Conference
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• 1984.07a
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• pp.7-21
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• 1984

Entrainment and deposition experiments were counducted in fresh water on four groups of sediments: three well-defined sediments of uniform composition and narrow-size distribution (1 to 9 um, 10 to 50 um, and 50 to 90 um), and a fourth group which was a mixture of these three sediments. In the entrainment experiments and at a particular stress, the steady-state suspended sediment concentration of the coarse group was the lowest while the concentrations of the fine and medium groups were higher that that of the coarse group but were similar to each other. Deposition experiments generally showed an exponential decrease of suspended sediment concentration with time with the decay time being a function of particle size and applied stress.