• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.446-457
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• 2020

Crescentic sand bar in the coastal zone of eastern Korea is a common morphological feature and the rhythmic patterns exist constantly except for high wave energy events. However, four consecutive typhoons that directly and indirectly affected the East Sea of Korea from September to October in 2019 impacted the formation of longshore uniform sand bar and overall shoreline retreats (approx. 2 m) although repetitive erosion and accretion patterns exist near the shoreline. Widely used XBeach to predict storm erosions in the beach is utilized to investigate the morphological response to a series of storms and each storm impact (NE-E wave incidence). Several calibration processes for improved XBeach modeling are conducted by recently reported calibration methods and the optimal calibration set obtained is applied to the numerical simulation. Using observed wave, tide, and pre & post-storm bathymetries data with optimal calibration set for XBeach input, XBeach successfully reproduces erosion and accretion patterns near MSL (BSS = 0.77 (Erosion profile), 0.87 (Accretion profile)) and observed the formation of the longshore uniform sandbar. As a result of analysis of simulated total sediment transport vectors and bed level changes at each storm peak Hs, the incident wave direction contributes considerable impact to the behavior of crescentic sandbar. Moreover, not only the wave height but also storm duration affects the magnitude of the sediment transport. However, model results suggest that additional calibration processes are needed to predict the exact crest position of bar and bed level changes across the inner surfzone.

• Journal of Environmental Science International
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• v.14 no.12
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• pp.1129-1139
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• 2005

A series of experiments was conducted to identify the potential of five phytoplankton species as standard test species for marine ecotoxicological tests. The candidate phytoplankton species are Skeletonema costatum, Heterosigma akashiwo, Prorocentrum micans, Isochrysis galbana, and Tetraselmis suecica. Salinity tolerance and sensitivity on potassium dichromate as a reference material were identified. Toxicity of eleven ocean dumped sewage sludges and four red tide expellent extracts were estimated by the inhibition of population growth rates (PGR) of marine diatom S. costatum, While most species revealed relatively weak tolerance on salinity, T. suecica demonstrated the highest salinity tolerance ranged from $5\~35$ psu and the others $15\~35$ psu. H. akashiwo revealed the highest sensitivity as 72h $IC_{50}$=0.76mg/L and T. suecica the lowest as 72h $IC_{50}$=8.89mg/L on potassium dichromate. Sludge extracts from industrial waste, domestic sewage and livestock farm waste sludge showed high toxicity as 72h $IC_{50}$<$2\%$ and lowest toxicity from filtration bed sludge as 72h $IC_{50}$=$30.50\%$ NOEC (No Observed Effective Concentration) of sludge extract ranged from <$0.4\%$ to $1.6\%$ and this indicated high phytotoxicity of ocean dumped sewage sludge. The test sensitivity of phytoplankton PGR inhibition was much higher than those of marine rotifer Brachionus plicatilis mortality test and bioluminescent inhibition test by marine bacteria Vibrio fischeri, and comparable with the sea urchin (Strongylocentrotus intermedius) fertilization test. As a result the phytotoxicity test using phytoplankton PGR inhibition ($IC_{50}$) must be a useful tool for marine phyto-toxicological evaluation of ocean dumped materials.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.261-272
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• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• Journal of Soil and Groundwater Environment
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• v.9 no.3
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• pp.27-32
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• 2004

The oceanic tides have an effect on groundwater levels in coastal fractured rock aquifers. The observed groundwater table fluctuations caused by the effective stress through an aquifer are shown as sine curves similar with tidal fluctuation. To estimate a hydrogeologic parameter, tidal method is utilized with groundwater level fluctuations of two monitoring wells. Cross correlation function is used to calculate time lags between observed groundwater levels and tide, and the deeper well shows longer time lag. The storage coefficients calculated by using tidal efficiency and time lag show large differences. The storage coefficients obtained by using time lags are close to the result of slug test, and that of the deeper well shows closer value by slug test. The tidal efficiency is unsatisfied to apply in the tidal method because of an effect of phreatic aquifer and the vertical flow of groundwater through fractured confining bed. This tidal method can be an economical and effective way to define the parameter by considering the location of observation well and hydrogeologic characteristics of a coastal aquifer.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.115-125
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• 2004

An experiment to measure the volume variation of bag net in a set-net by acoustic telemetry system was conducted in Jaran Bay, Gosung, Korea on 10 April to 23 April 2003. The long baseline telemetry system consists of three radio-acoustic linked positioning (RAP) buoys, a time controller with a personal computer and seven pingers. Six pingers were attached on the bottom of the bag-net and the other one was fixed on the sea bed. The results obtained are summarized as follows : 1. The average RAP buoy fixing errors of x-axis, y-axis, and z-axis were 0.2m, 0.4m, and 0.1m, respectively. 2. In the neap tide the minimum and maximum volume of the bag-net on 11 April 2003 were 4,173$m^3$(17:00) and 4,757$m^3$(12:00), respectively. The average current direction and speed at those times were 99.9$^{\circ}$, 12.9cm/s and 104.0$^{\circ}$, 2.4cm/s, respectively. 3. In the spring tide on 17 April 2003, the minimum and maximum volume were 2,016$m^3$(18:30) and 4,454$m^3$(15:00), respectively. The average current direction and speed at those times were 315.6$^{\circ}$, 16.1cm/s and 289.0$^{\circ}$, 5.7cm/s, respectively. 4. In conclusion the maximum variation of the volume on 17 April to 20 April 2003 was 3,552$m^3$ and it was larger 1.4 times than time on 11 April to 16 April 2003.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.107-116
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• 1999

To study the characters of surface sediment and to describe the seasonal depositional environment as a result of sedimentation process off Byun-San Peninsula, a total 61 samples of surface sediment (32 samples in summer; 29 samples in winter) were collected and analysed. A digitized depth data from sea chart and echosounding profiles along five trans-sections were helpful for understanding the morphological factors. The types classified by the characters of surface sediment are type I (sand, S), type II (silty sand, zS), and type ill (sandy silt, sZ). Mean grain size varies from 2.11 to 7.81 ${\Phi}$. The positive-skewness shows the typical tide-dominated environment. The sediment type of the northwestern stations is medium sand and the sorting value is 0.5~1.4 ${\Phi}$ of well/moderately sorted. Meanwhile, other stations are composed of muddy sands and sandy muds transported from rivers and offshore. These sediment types toward inshore change gradually from silty sand to sandy silt. According to the C/M diagram, there are three major transport modes of sediment: bed load (Mode A), graded suspension (Mode B), and suspension (Mode C), correlating with north-eastern sandy area, middle part of silty-sand area, and southern sandy-silt area, respectively. The result of Principal Component Analysis shows also similar pattern of sediment types. In result, sediment texture of type III tends to be finer and more poorly-sorted than that of type II and sediment facies are correlateed with sedimentation process.

• 한국해양학회지
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• v.28 no.3
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• pp.212-228
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• 1993

A chenier, about 860 m long, 30 to 60 m wide and 0.6∼1.6 m high, occurs on the upper muddy tidal flat in the Gomso bay, western coast of Korea, It consists of medium to fine sands and shells with small amounts of subangular gravels. Vertical sections across the chenier show gently landward dipping stratifications which include small-scale cross-bedded sets. the most probable source of the chenier is considered to be the intertidal sandy sediments. Vibracores taken along a line transversing the tidal flat reveal that the intertidal sand deposits are more than 5 m thick near the low-water line and become thinner toward the chenier. The most sand deposits are undertrain by tidal muds which occur behind the chenier as salt marsh deposits. C-14 age dating suggests that the sand deposits and the chenier are younger than about 1,800 years B.P. The chenier has originated from the intertidal sand shoals at the lower to mid sand flat, and has continuously moved landward. A series of aerial photographs (1967∼1989) reveal that intertidal sand shoals (predecessor of the western part of chenier) on the mid flat have continuously moved landward during the past two decades and ultimately attached to the eastern part of the chenier already anchored at the present position in the late 1960s. Repeated measurements (four times between 1991 and 1992) of morphological changes of the chenier indicate that the eastern two thirds of the chenier, mostly above the mean high water, has rarely moved whereas the western remainder below the mean high water, has moved continuously at a rate of 0.5 m/mo during the last two years (1991∼1992). This displacement rate has been considerably accelerated up to 1.0 m/mo in winter, and during a few days of typhoon in the summer of 1992 the displacement amounted to about 8∼11 m/mo for the entire chenier. these facts suggest that macro-tidal currents, coupled with winter-storm waves and infrequent strong typhoons, should play a major role for the formation and migration of chenier after 1,800 B.P., when the sea level already rose to the present position and thereafter remained constant.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.271-283
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• 2006

A systematic water quality survey was conducted in August, 2005 for a drinking water supply reservoir (the Jeolgol reseuoir located in an island), which is at an early stage of impoundment, to investigate the causes of water color deterioration of the reservoir and the clogging of filter beds of a water treatment plant. The reservoir shape was simple and its average depth was 5.5 m, increasing from upreservoir toward the downreservoir end near the dam. Dissolved oxygen (DO) and chloropllyll-a (chi-a) showed a large variation while water temperature had a smaller range. Transparency ranged from 0.6 to 0.9 m (average 0.7 m). The average value of turbidity was 9.3 NTU, ranging from 8.0 ${\sim}$ 12.1 NTU. The transparency and the turbidity appear to be affected by a combination of biological and non-biological factors. The poor transparency was explained by an increase of inorganic colloids and algal bloom in the reservoir. The blockage of the filter bed was attributed to the oversupply of phytoplanktons from the reservoir. The range and the average concentration of chi-a within the reservoir were 31.6 ${\sim}$ 258.9 ${\mu}g\;L^{-1}$, 123.6 ${\mu}g\;L^{-1}$ for the upper layer, and 17.0 ${\sim}$ 37.4 ${\mu}g\;L^{-1}$, 26.5 ${\mu}g\;L^{-1}$ for the bottom layer, respectively. A predominant species contributing the algal bloom was Dinophyceae, Peridinium bipes f. occultatum. The distribution of Peridinium spp. was correlated with chi-a concentrations. The standing crop of phytoplankton was highest in the upreservoir with $8.5\;{\times}\;103\;cells\;mL^{-1}$ and it decreased toward the downresevoir. Synedra of Bacillariophyceae and Microcystis aeruginosa of Cyanophyceae appeared to contribute to the algal bloom, although they are not dominated. It is mostly likely that sloped farmlands located in the watershed of the reservoir caused water quality problems because they may contain a significant amount of the nutrients originated from fertilizers. In addition, the aerators installed in the reservoir and a shortage of the inflowing water may be related to the poor water quality. A long-term monitoring and an integrated management plan for the water quality of the watersheds and the reservoir may be required to improve the water quality of the reservoir.

• Journal of the Korean Chemical Society
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• v.8 no.4
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• pp.192-199
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• 1964

Seasonal variations of the contents of some chemical constituents of the estuary water at two definite stations of the laver bed in Nack Dong River have been determined over one tidal cycle in spring tide from Nov. 1962 to Oct. 1963. The ranges of annual variations of the contents at station 1 and station 2 are as follows: water temp. $2.2-30.8^{\circ}C$, $3.3-28.0^{\circ}C$; pH 7.8-8.5, 7.9-8.4; chlorosity 0.025-19.66 g/l, 4.31-19.56 g/l; magnesium 0.00355-1.565 g/l, -1.524 g/l; calcium 0.00557-0.482 g/l, - -0.590 g/l; saturation % of dissolved oxygen 71.8-123.2%, 88.2-113.8%; silicate-Si 8.00-125.5 ${\mu}$g-at./l, 6.70-100.5 ${\mu}$g-at./l; phosphate-P 0.12-1.47 ${\mu}$g-at./l, 0.11-1.09 ${\mu}$g-at./l; ammonia-N 4.88-25.45 ${\mu}$g-at./l, 4.12-17.58 ${\mu}$g-at./l; nitrite-N 0.07-0.75 ${\mu}$g-at./l, 0.08-0.58 ${\mu}$g-at./l; nitrate-N 2.11-6.89 ${\mu}$g-at./l, 1.85-7.43 ${\mu}$g-at./l each. The annual tidal variations of the constituents at station 1 are more remarkable than of station 2. The chlorosity, magnesium and calcium contents are decreased nearing the slack after ebb, and increased abruptly then one hour after the slack. The contents of the other constituents are varied according to the chlorosity variety. The values of pH, chlorosity, magnesium and calcium contents are lower in summer than winter, while the difference of seasonal variations of the % saturation of dissolved oxygen is not remarkable. The phosphate-P and total nitrogen contents have a tendency of increasing within a definite range, while the silicate-Si increase proportionally, to the increasing of mixing percentage of fresh water. The average values of Si/P and N/P are several times greater than of the normal in sea water. The chemical composition considered from the value of Mg/Cl or Ca/Cl of estuarine water varies according to the variety of chlorosity, even at the high chlorosity of 19 g/l.