• Journal of environmental and Sanitary engineering
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• v.15 no.4
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• pp.52-58
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• 2000

This study was carried out to investigate the contents of heavy metals with respect to the depth, particle size and Tessier et al. method in surface sediment of the Nakdong river. The contents of Cd, Cu & Pb were high or similar with increasing depth, but Mn & Zn were high to middle depth. Generally, the contents of heavy metals were found to be high as the particle size become more small and more deep. Because the more particle size was small, the specific surface area was large, the contents of heavy metals was high for increasing affinity. It was estimated that the types of heavy metals contained in surface sediment by Tessier et al. method was dissimilar with anaerobic condition, pH and degradation of organic matter, etc.

• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.78-85
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• 2010

This study investigates reducing characteristics for the spreading of dredged soil and the diffusion of contaminant by silt protector curtain through three dimensional numerical experiment. The numerical medel is modified by combining the sediment transport characteristics for cohesive sediment into the previously developed model. Several numerical experiments have been given in order to investigate the reducing effect of silt protector using two dimensional numerical channel model under various parameters such as upstream flow velocity, depth of silt curtain and the position of dumped materials. Through the evaluation of several simulation results, we knew that the careful design has to be given in the determination of depth and position of silt protector.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.2
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• pp.89-94
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• 1999

In this study small glass columns with 2.5cm inner diameter and 24.5cm length were used as many as the sample numbers to study the effects of initial pH, temperature, dissolved oxygen concentration, and sediment depth on the release of phosphorus from lake sediment. No phosphorus release occurred at $10^{\circ}C$ with all pHs, and release rate at $25^{\circ}C$ was higher than that at $35^{\circ}C$ with pH 4 and reverse trends were observed at pH 7 and 10. Under all conditions, DO concentrations were decreased and equilibrium was obtained after 4-8 days when phosphorus release started and the Do concentrations were less than 1 mg/l. Sediment depth had little effect on phosphorus release rate. It was found that relation between released SRP(Soluble Reactive Phosphorus) concentration and time was zero order reaction and reaction rate coefficients were obtained. The amount of phosphorus release from lake sediment can be predicted by considering these k values.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4E
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• pp.167-175
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• 2003

Shear wave velocity was measured and grain size analysis was conducted on two core samples obtained in unconsolidated marine sediments of the western continental margin, the East Sea. A pulse transmission technique based on the Hamilton frame was used to measure shear wave velocity. Duomorph ceramic bender transducer-receiver elements were used to generate and detect shear waves in sediment samples. Time delay was calculated by changing the sample length from the transducer-receiver element. Time delay is 43.18 μs and shear wave velocity (22.49 m/s) is calculated from the slope of regression line. Shear wave velocities of station 1 and 2 range from 8.9 to 19.0 m/s and from 8.8 to 22 mis, respectively. Shear wave velocities with depth in both cores are qualitatively in agreement with the compared model〔1〕, although the absolute value is different. The sediment type of two core samples is mud (mean grain size, 8-9Φ). Shear wave velocity generally increases with sediment depth, which is suggesting normally consolidated sediments. The complicated variation of velocity anisotropy with depth at station 2 is probably responsible for sediment disturbance by possible gas effect.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.4
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• pp.59-69
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• 1999

This study examines the existing theories related to detention basin and embodies the calculation process of sediment basin. It investigated the scale of sediment basin by actual measurement at Buju Mountain, Mokpo city which causes the environmental problems like erosion and outflow of sediment due to the excessive development, finds the problems of existing sediment basin by applying and analyzing the physical factors which affect the execution of sediment basin using GIS as the method establishing the scale of sediment basin embodied in this study and then suggests the oteimum scale. Comparing the surface area of the existing sediment basin and of the required one, all of the surface areas of the existing sediment basins were smaller than those of the required one. Therefore, it can be expected that the trap efficient of sediment will be declined. The required one. Therefore, it can be expected that the trap efficient of sediment will be declined. The required minimum depth was fully satisfied, but it is analyzed that the volume of sediment basin will affect the neighboring environment because it can not accomodate the inflow discharge volume except sediment basin C. It is consistent with the actual situation which causes a serious environmental problem due to the overflow of sediment basin during the heavy storm event except sediment basin C and also it verifies the validity of calculation process of establishing optimum sediment basin suggested in this study.

• Ocean and Polar Research
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• v.30 no.4
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• pp.537-543
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• 2008

The sediment resuspension and diffusion model is an integral part of a sediment transport and morphologic change model. We examined a vertical one-dimensional sediment resuspension and diffusion model using field data collected at about 10-m depth off the Saemangeun $4^{th}$ dike. The field data include waves, currents and suspended sediment concentration near the bed for about a day in May, 2007. The suspended sediment concentration obtained from the 1D model overestimated the observation about two orders of magnitude with single grain size and multiple grain sizes. The incorporation of the bed armoring effect, which adjusts the amount of suspended sediment with the available bed sediment, improved the agreement between the model and observation within a factor of two.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.77-88
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• 2007

Following a successful bathymetric mapping demonstration in a previous study, the potential of airborne EM for seafloor characterisation has been investigated. The sediment thickness inferred from 1D inversion of helicopter-borne time-domain electromagnetic (TEM) data has been compared with estimates based on marine seismic studies. Generally, the two estimates of sediment thickness, and hence depth to resistive bedrock, were in reasonable agreement when the seawater was ${\sim}20\;m$ deep and the sediment was less than ${\sim}40\;m$ thick. Inversion of noisy synthetic data showed that recovered models closely resemble the true models, even when the starting model is dissimilar to the true model, in keeping with the uniqueness theorem for EM soundings. The standard deviations associated with shallow seawater depths inferred from noisy synthetic data are about ${\pm}5\;%$ of depth, comparable with the errors of approximately ${\pm}1\;m$ arising during inversion of real data. The corresponding uncertainty in depth-to-bedrock estimates, based on synthetic data inversion, is of order of ${\pm}10\;%$. The mean inverted depths of both seawater and sediment inferred from noisy synthetic data are accurate to ${\sim}1\;m$, illustrating the improvement in accuracy resulting from stacking. It is concluded that a carefully calibrated airborne TEM system has potential for surveying sediment thickness and bedrock topography, and for characterising seafloor resistivity in shallow coastal waters.

• Ocean and Polar Research
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• v.28 no.4
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• pp.475-484
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• 2006

In order to reveal the vertical variation of physical properties in deep-sea sediments, deep-sea sediment cores were collected at 78 stations using a multiple corer in the KR5 area, one of the Korea contract areas for manganese nodule exploration, located in the northeast equatorial Pacific. Based on the color of sediments, sampled sediment cores were characterized into three lithologic units (unit 1,2, and 3). In all sediment cores, three units appear systematically; unit 1 lies at the top of cores and unit 2 and/or unit 3 appear to underlie unit 1 or alternate with unit 3. Unit 1 layer from the top of cores shows dark grayish brown to dark brown with mean thickness of 10.2cm. Unit 2 and 3 layers show very dark brown to black color and yellowish brown to brown color, respectively. According to the physical properties of the deep-sea sediment cores, sediment column can be divided into three sections. Section A $(0{\sim}15cm)$ in subbottom depth consists mostly of unit 1. Mean values of physical properties of section B $(15{\sim}30cm)$ in subbottom depth are similar to those of section C (>30 cm) in subbottom depth. However, the physical properties of section B were more variable than those of section C because of the high activity of bioturbation in section B. These results will provide valuable information for selecting suitable sites for mining manganese nodules in the Korea contract areas.

• Analytical Science and Technology
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• v.19 no.1
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• pp.45-49
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• 2006

Drilled sediment core was acquired from Jinheung catchment which was located at Jeollabuk-do Jeongeup city. Elements concentration variation were studied by neutron activation analysis using sediment core by divided 1 cm depth interval. The concentration of major element such as Na, K were increased but Fe was decrease with depth. Minimum elements concentration and particle size were observed at 17 cm depth. This depth was considered 1969 year which was great dry year recorded from the rain fall data and the sedimentation rate was calculated $0.197g{\cdot}cm^{-2}{\cdot}year^{-1}$.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.53-60
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• 2010

In the present study, experiments have been performed to investigate the possibility of removing Cochlodinium polykrikoides using the dredged sediment from a coastal fishery and then to derive the optimal conditions; the amount and particle size of dredged sediment besprinkled into water, the thermal treatment, the types and amounts of additives, and the depth profile of Cochlodinium polykrikoides. Results showed that the optimal amount of dredged sediment besprinkled into water was 6~10 g/L, and the removal efficiency of Cochlodinium polykrikoides after the reaction time for 60 min was 73~93%. Note that, in the real sea water, it is necessary to besprinkle 6~10 $kg/m^3$ of dry dredged sediment on a unit area (1 $m^2$). With decreasing particle size, Cochlodinium polykrikoides could be more efficiently removed. The removal efficiency was 93% with the dredged sediment smaller than 100 ${\mu}m$, whereas it was 51% with that of 100 ${\mu}m$ ${\mu}m$. Since most of dredged sediment (over 90%) was smaller than 100 ${\mu}m$, high efficiency could be obtained by besprinkling only the dredged sediment without pre-treatment. CaO was found to be an effective additive in promoting the removal efficiency (up to 99%). The optimal amount of additive was 5~10%, however, it was necessary to use as small amount of an additive as possible in order to avoid the sharp increase in pH. The removal efficiency increased with increasing depth profile of Cochlodinium polykrikoides. The removal efficiency was 83% at 5 cm depth, whereas it was 93% at 50 cm depth. In the sea water, red tide occurred within 3 m depth, and furthermore most Cochlodinium polykrikoides existed within 1 m depth. It was, therefore, expected that higher removal efficiency of Cochlodinium polykrikoides could be obtained when the dredged sediment was besprinkled into the sea water. The removal efficiency of Cochlodinium polykrikoides was up to 93% when the dredged sediment (<100 ${\mu}m$) was besprinkled into water at the ratio of 10 g/L. This result was comparable to that obtained with loess (90~97%). All the results in the present study indicated that the dredged sediment from a coastal fishery could be successfully used as a substitute of loess for removing the red tide alga.