• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.1
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• pp.49-54
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• 2003

This study was conducted to evaluate characteristics of particle composition and organic matter distribution for tidal flat sediments in the Saemankeum area. The tidal flat sediments consist of predominantly sand and a little of silt, whereas the content of clay was very low. The analyzed values of particles of tidal flat sediments were in the range of $4.60\~10.90\;{\phi}$ for mean size and $-0.1\~1.75\;{\phi}$ for sorting and $-1.0\~0.92\;{\phi}$ for skewness and $0.27\~6.75\;{\phi}$ for kurtosis. The tidal flat sediments are interpreted as representing significant effect of the environmental change due to the construction of Saemankeum embankment. The ORP was in the range of -133$\~$200 (mean 73) mV. But 24 stations of the total stations showed reduction condition, The concentration of CODs was in the range of 17.54$\~$6,176.3 mg/kg. The ratio of C/S was 0.02$\~$0.45 (mean 0.24). And the Saemankeum tidal flat sediment was a little effected by input organic pollutants from upper site area. Conclusively, conservation of the Saemankeum tidal flat sediment was requested because it is for the growing fishery and low organic matter.

• Analytical Science and Technology
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• v.30 no.5
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• pp.262-269
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• 2017

The concentration of natural radioactivity in the sediment of the Geum River was investigated. The river and lake sediment samples were collected at 23 points during September to November, 2015 and March to April, 2015, respectively. The gamma-rays emitted from the $^{226}Ra$ and $^{232}Th$ decay series and $^{40}K$ were measured with a high purity germanium (HPGe) gamma detector. The average radioactivity concentrations of the $^{226}Ra$, $^{232}Th$ decay series and $^{40}K$ for the river sediment was found to be $15.6{\pm}0.6$, $33.8{\pm}1.2$, $789.8{\pm}26.0Bq/kg$, respectively, while for the lake sediment, the concentrations were $17.1{\pm}0.5$, $37.8{\pm}1.1$, $269.4{\pm}9.6Bq/kg$, respectively. Spearman's correlation was conducted to compare the radioactivity concentration and properties of the sediment. The radioactivity concentration of the $^{232}Th$ decay series showed a negative correlation with the particle size of the sediment, and was measured to be higher than the $^{226}Ra$ decay series according to mobility of the radionuclides. The radioactivity concentration of $^{40}K$ showed a negative correlation with organic matter content. The concentration of $^{40}K$ in the lake sediment was lower than that in the river sediment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.680-687
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• 1999

To understand the role of shelf sediment in phosphorus biogeochemical cycle, we carried out sequential sediment extraction (SEDEX) of P and porewater analysis on 14 core samples collected in the South Sea of Korea, SEDEX classified P-pools into 5 phases and results are grouped into two categories: reactive P (loosely sorbed-P and Fe bound-P) and refractory P (detrital inorganic-p, authigenic mineral-P and organic-P). Total P concentrations are decreased with sediment depth in all samples as a result of dissolution to porewater. Reactive P comprises about $20\~50\%$ of total P, and iron bound-P is the major form consisting $70\~80\%$ of reactive P-pool. Iron bound-P decreases sharply with depth. Depth profiles of dissolved P concentration in porewater show mirror image of iron bound-P, revealing the role of FeOOH as a regulator of reactive P supply to overlying water column. Authigenic mineral-P consists less than $5\%$ of total P, thus removal of reactive P by converting into refractory P seems inefficient in shelf sediment. This implies that continental shelf sediment sequesters P temporarily rather than permanently. Results show local variation. Nakdong estuary receiving large amount of terrigenous input shows the highest concentration of total P and reactive P. Here iron oxyhydroxides at the surface sediment control the water column flux of P from sediment. Although total P content at the surface is comparable (500$\~$600 ${\mu}g{\cdot}g^{-1}$) between the South Sea and East China Sea, the former contains more iron bound-P and less derital inorganic-P than the latter. Reasons for the difference seem due in part to particle texture, and to biological productivity which depends roughly on the distance from land.

• Korean Journal of Ecology and Environment
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• v.52 no.4
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• pp.316-323
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• 2019

This study was carried out to investigate sedimentary environment changes in Nakdong River sediments. For this purpose, sediments at six sites upstream of Gangjeong-Goryung Weir in the middle of the Nakdong River were collected before and after the rainy season. Particles size, IL, TOC, TN, TP, and SRP were analyzed for the sediment environment. The changes in the watershed environment before and after the rainy season (precipitation, discharge, and SS concentration) were investigated. After the rainy season, the amount of precipitation and discharge increased more than three times, and the average concentration of SS in the stream increased more than two times. Fine grained sediment and the concentrations of IL, TOC, TN, TP, SRP were increased after the rainy season. As a result of sediment contamination assessment, IL was 19~68% of the reference value, TN and TP were 21~76% and 21~58% of the reference value. The result showed strong correlation between particle size (Silt+Clay) and organic contents of sediment (IL, TOC, TN, TP and SRP). It is considered that the change of the river watershed environment (precipitation, discharge) is an important factor of the change of sedimentation environment.

• Journal of Korea Water Resources Association
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• v.33 no.5
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• pp.581-592
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• 2000

Turbulence structure and suspended sediment transport capacity in vegetated open-channel flows are investigated numerically in the present paper. The $\textsc{k}-\;\varepsilon$ model is employed for the turbulence closure. Mean velocity and turbulence characteristics including turbulence intensity, Reynolds stress, and production and dissipation of turbulence kinetic energy are evaluated and compared with measurement data available in the literature. The numerical results show that mean velocity is diminished due to the drag provided by vegetation, which results in the reduction of turbulence intensity and Reynolds stress. For submerged vegetation, the shear at the top of vegetation dominates turbulence production, and the turbulence production within vegetation is characterized by wakes. For emergent condition, it is observed that the turbulence generation is dominated by wakes within vegetation. In general, simulated profiles compares favorably to measured data. Computed values of eddy viscosity are used to solve the conservation equation for suspended sediment, yielding sediment concentration more uniform over the depth compared with the one in the plain channel. The simulation reveals that the suspended load decreases as the vegetation density increases and the suspended load increases as the particle diameter decreases for the same vegetation density.

• Journal of Wetlands Research
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• v.16 no.4
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• pp.477-486
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• 2014

Integrated sand control including sediment discharge from hinterland rivers is necessary to maintain coastal sand resources over a long term. In this regard, the following subjects should be considered; efficient ways to transfer discharged sand from a river to the neighboring coast, measures to improve storage efficiency of the discharged sand at the river delta and/or river terrace, measures to prevent the sand resources from being discharged into the deep sea during flooding. From the 1997 to January 2004, the jetty of 156 m length was constructed the Heoya-river mouth to protect the blockade of river mouth. Several tests were carried out to investigate the characteristics of sediment transport and morphological change due to the construction of the jetty at the Heoya-river mouth. Firstly, The sand discharge from Heoya river is quantified by one-dimensional numerical analysis assuming the mixed sand of three different particle diameters. Also the numerical mode system, which predicts the sea bed changes obtained from the Bailard's energy model(1981), was combined with the wave, wave-induced currents and sediment transport models. Then, to understand the changes to the blockade of the river mouth, several aerial photographs were compared, which showed that the changes were significant.

• Journal of Korea Water Resources Association
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• v.54 no.3
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• pp.167-179
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• 2021

In order to characterize the mixing process of confluence for understanding the impacts of a river on the other river, it has been crucial to analyze the spatial mixing patterns for main streams depending on various inflow conditions of tributaries. However, most conventional studies have mostly relied upon hydraulic or water quality numerical models for understanding mixing pattern analysis of confluences, due to the difficulties to acquire a wide spatial range of in-situ data for characterizing mixing process. In this study, backscatters (or SNR) measured from ADCPs were particularly used to track sediment mixing assuming that it could be a surrogate to estimate the suspended sediment concentration. Raw backscatter data were corrected by considering the beam spreading and absorption by water. Also, an optical Laser diffraction instrument (LISST) was used to verify the method of acoustic backscatter and to collect the particle size distribution of main stream and tributary. In addition, image-based spatial distributions of sediment mixture in the confluence were monitored in various flow conditions by using an unmanned aerial vehicle (UAV), which were compared with the spatial distribution of acoustic backscatter. As results, we found that when acoustic backscatter by ADCPs were well processed, they could be proper indicators to identify the spatial patterns of the three-dimensional mixing process between two rivers. For this study, flow and sediment mixing characteristics were investigated in the confluence between Nakdong and Nam river.

• Korean journal of food and cookery science
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• v.30 no.5
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• pp.526-530
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• 2014

The effect of roasting on particle size distribution, water-holding capacity, and viscosity of sunsik was investigated in this study using non-roasted one as control. Roasting increased the size of particles in sunsik, in particular, particles larger than $1{\mu}m$ in diameter, indicating that roasted sunsik is likely to sediment faster, thereby decreasing the time to maintain dispersibility when mixing with water. Roasting also increased the water-holding capacity of sunsik, indicating that polymerization occurred greater than a pyrolysis during roasting, leading to increased viscosity in roasted sunsik. These results indicate that the roasting affected the dispersibility and viscosity of sunsik by increasing particle size and water-holding capacity, respectively.

• Journal of Ocean Engineering and Technology
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• v.25 no.5
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• pp.15-20
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• 2011

This study carried out a series of experiments involving impact tests (Drop Weight type & Charpy type with a standard specimen and newly designed I-type specimen), hardness tests, and fracture surface observations of French-made roll shell steel (F), abnormal roll shell steel (M), reheated roll shell steel (R), and S25C steel under heat treatment conditiAn experimental study was carried out to study the solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. The lift forces acting on a fluidized particle play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport, the cleaning of particles from surfaces, etc. In this study a clear acrylic pipe was used to observe the movement of solid particles. Annular velocities varied from 0.4 to 1.2 m/s. The effect of the annulus inclination and drill pipe rotation on the carrying capacity of a drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully-developed flows of water and aqueous solutions of CMC (sodium carboxymethyl cellulose) and bentonite. The rotation of the inner cylinder was efficient at carrying particles to some degree. For a higher particle volume concentration, the hydraulic pressure loss of the mixture flow increased because of the friction between the wall and solids or between solids.

• Ocean and Polar Research
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• v.24 no.2
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• pp.123-134
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• 2002

Seasonal variations of settling particles and metal fluxes were monitored at a nearshore site of Marian Cove, King Geroge Island, Antarctica from 28th February 1998 to 22nd January 2000. Near-bottom sediment traps were deployed at 30m water depth of the cove, and sampling bottles were recovered every month by SCUBA divers. Total particulate flux and metal concentrations were determined from the samples. Total particulate flux showed a distinct seasonality, high in austral summer and low in austral winter: the highest flux $(21.97g\;m^{-2}d^{-1})$ was found in February of 1999, and the lowest $(2.47g\;m^{-2}d^{-1})$ in September of 1998, when sea surface was frozen completely. Lithogenic particle flux accounted for 90% of the total flux, and showed a significantly negative correlation with the thickness of snow accumulation around the study site. It was suggested that the most of the lithogenic particles trapped in the bottles was transported by melt water stream from the surrounding land. Fluxes of Al, Fe, Ti, Mn, Zn, Cii, Co, Ni, Cr, Cd, and Pb showed similar seasonal variations with the total flux, and their averaged fluxes were 34000, 9000,960, 180, 13.8, 17.6, 3.0,2.1, 5.4, 0.02, and $1.5nmol\;m^{-2}d^{-1}$ respectively. Among the metals, Cu and Cd showed the most noticeable seasonal patterns. The Cd flux correlated positively with the fluxes of biogenic components while the Cu flux correlated with both the lithogenic and biogenic particle fluxes. The Cu flux peak in the late summer is likely related to a substantial amount of inflow of ice melt water laden with Cu-enriched lithogenic particles. On the other hands, the Cd flux peak in the early spring may be associated with the unusually early occurred phytoplankton bloom.