• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.1
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• pp.1-12
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• 2021

To investigate the effect of freshwater discharge on the seawater circulation in the semi-closed harbor, a 3-D hydrodynamic model was applied to the International Ferry Terminal (IFT). The model run is conducted for 45 days (from May 15 to June 30, 2020), and the reproducibility of the model for time-spatial variability of current velocity and salinity was verified by comparison with model results and observation data. There are two sources of freshwater towards inside of the IFT: Han River and water reservoir located in the eastern part of IFT. In residual current velocity results, the two-layer circulation (the seaward flow near surface and the landward flow near bottom)derived from the horizontal salinity gradient in only considering the discharge from a Han River is more developed than that considering both the Han River and water reservoir. This suggests that the impact of freshwater from the reservoir is greater in the IFT areas than that from a Han River. Additionally, the two-layer circulation is stronger in the IFT located in southern part than Incheon South Port located in northern part. This process is formed by the interaction between tidal current propagating into the port and freshwater discharge from a water reservoir, and flow with a low salinity (near 0 psu) is delivered into the IFT. This low salinity distribution reinforces the horizontal stratification in front of the IFT, and maintains a two-layer circulation. Therefore, local sources of freshwater input are considered to estimate for mass transport process associated with the seawater circulation within the harbor and It is necessary to perform a numerical model according to the real-time freshwater flow rate discharged.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.536-544
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• 2001

Three harmful algal bloom species with similar morphology, Cochlodinium polykrikoides, Gyodinium impudicum and Gymodinium catenatum have damaged to aquatic animals or human health by either making massive blooms or intoxication of shellfishes in a food chain. Eco-physiological and hydrodynamic studies on the harmful algae offer useful informations in the understanding their bloom mechanism by giving promising data for the prediction and modelling of harmful algal blooms event. Thus, we studied the abundance of these species in the coastal area of South Sea of Korea and their effects of temperature, salinity, irradiance and nutrient on the growth for the isolates. The timing for initial appearance of the three species around the coastal area of Namhaedo, Narodo and Wando was between Bate July and late August in 1999 when water temperature ranged from $22.8^{\circ}C\;to\;26.5^{\circ}C$ Vegetative cells of C. polykrikoides and G. impudicum were abundant until late September when water temperature had been dropped to less than $23^{\circ}C$. By contrast, vegetative cell of G. catenatum disappeared before early September, showing shorter period of abundance than the other two species in the South Sea. Both G. impudicum and G. catenatum revealed comparatively low density with a maximal cell density of 3,460 cells/L and 440 cells/L, respectively without making any bloom, while C. polykrikoides made massive blooms with a maximal cell density more than $40\times10^6$cells/L, The three species showed a better growth at the relatively higher water temperature ranging from 22 to $28^{\circ}C$ with their maximal growth rate at $25^{\circ}C$ in culture, which almost corresponded with the water temperature during the outbreak of C. polykrikoides in the coastal area of South Sea. Also, they all showed a relatively higher growth at the salinity from 30 to $35\%$. Specially, G. impudicum showed the euryhalic characteristics among the species, On the other hand, growth rate of G. catenatum decreased sharply with the increase of water temperature at the experimental ranges more than $35\%$. The higher of light intensities showed the better growth rates for the three species, Moreover, C. polykrikoides and G. impudirum continued their exponential growth even at 7,500 lux, the highest level of light intensity in the experiment, Therefore, It is assumed that C. polykrikoides has a physiological capability to adapt and utilize higher irradiance resulting in the higher growth rate without any photo inhibition response at the sea surface where there is usually strong irradiance during its blooming season. Although C. poiykikoides and G. impudicum continued their linear growth with the increase of nitrate ($NO_3^-$) and ammonium ($NH_4^-$) concentrations at less than the $40{\mu}M$, they didn't show any significant differences in growth rates with the increase of nitrate and ammonium concentrations at more than $40{\mu}M$, signifying that the nitrogen critical point for the growth of the two species stands between 13.5 and $40{\mu}M$. Also, even though both of the two species continued their linear growth with the increase of phosphate ($PO_4^{2-}$) concentrations at less than the $4.05{\mu}M$, there were no any significant differences in growth rates with the increase of phosphate concentrations at more than $4.05{\mu}M$, signifying that the phosphate critical point for the growth of the two species stands between 1.35 and $4.05{\mu}M$. On the other hand, C. polykrikoides has made blooms at the oligotrophic environment near Narodo and Namhaedo where the concentration of DIN and DIP are less than 1.2 and $0.3{\mu}M$, respectively. We attributed this phenomenon to its own ecological characteristics of diel vertical migration through which C. polykrikoides could uptake enough nutrients from the deep sea water near bottom during the night time irrespective of the lower nutrient pools in the surface water.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.770-774
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• 2009

한강하구 일대는 세계최대 규모의 갯벌이 조성되어 해양생태계에서 중요한 역할을 수행하는 곳이다. 육상기원의 퇴적물이 흐름이 완만한 하구 주변부에 퇴적되어 대규모의 갯벌을 생성하여 육상에서 유입되는 많은 유기물이 집중되고 탁도가 높아 대량의 플랑크톤과 같은 일차생산자가 상대적으로 부족한 대신에 담수 유입이 많아 하구와의 거리에 따른 일정한 염분 구배를 가지고 있어 더욱 다양한 환경이 조성되어 있음에도 1980년대 후반부터 각종 매립사업과 한강종합개발사업($1982{\sim}1986$)이 실시되어 한강하구의 습지가 줄어들고, 해안침식, 토사유입, 퇴적, 적조현상, 갯벌 및 해수오염과 같은 결과를 가져왔다. 1990년대에는 한강하구지역에서 퇴적으로 인한 홍수 예방과 건설골재 확보를 위한 준설이 활발히 이루어졌으나, 이로 인한 습지생물 서식처 파괴와 같은 환경영향이 우려되어 현재는 실시하지 않고 있다. 무차별적인 개발계획으로 매년 홍수 때마다 피해를 입는 김포일대, 한강과 임진강 지역의 수위 및 흐름 영향을 살펴보고 향후 대책 수립을 검토해야 한다. 이에 본 연구에서는 한강하구의 유사이송에 의한 수리학적 특성을 분석하기 위해 상류로부터 이송되어온 유사에 대하여 시간적 흐름특성을 통하여 조성된 한강하구의 특징을 분석하였고, 지형변화 분석을 위해 MIKE 21 프로그램의 이동상 해석모듈을 사용하여 지형변화에 따른 한강하구에서의 홍수기 하상변화와 유수 흐름 및 수위등의 변화를 모의하였다. 그 결과 예성강과 한강의 유수흐름은 청주초를 통하여 외해로 유출되고 이 흐름은 대부분 강화도와 교동도 사이의 교동수로로 유출되는 것으로 나타났으며, 염하수로 합류부 및 임진강 합류부에서는 침식 및 퇴적이 활발히 일어나는 것으로 모의되었다. 향후 수리학적 특성변화에 따른 유사의 퇴적 및 세굴에 의한 한강하구 지역의 지형변화를 분석하여, 주변 환경영향에 대한 대책 수립을 검토해야 할 것이다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.4
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• pp.335-343
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• 2016

The spatio-temporal distribution of jellyfish in Masan Bay was investigated in this study using a numerical model. First, a three-dimensional hydrodynamic model (POM) was constructed,taking into account residual flows, tides, temperature, salinity, and wind effects. A particle tracking model based on residual flow was then used to investigate the jellyfish present in Masan Port, referred to as the Heavy Industry and Gapo New Port in Masan. Jellyfish distribution was concentrated with maximum (2,533 individual) in the North Sea near Machang Bridge. Itcan be concluded that this concentration was due to multi-directional residual flows and topography effects. Residual flow currents are a dominant factor in understanding the aggregation of jellyfish, and this study used a numerical simulation of tide-induced residual currents, wind-driven currents and density currents in distinct cases to thoroughly address the topic. As a result, wind-driven currents (effect of the wind) was found to be superior to other components as an influence on the distribution of jellyfish near Machang Bridge and Modo in Masan Bay.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.2
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• pp.61-66
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• 2015

In this study, manufacture of kitchen garden soil and its application on the growth of Lettuce has been performed. The optimal ratio of various raw materials for pH, total nitrogen, phosphate, cations, and salt content was found to be 49 : 35 : 10 : 5 : 1(w/w) in peatmoss, livestock manure, cocopeat, zeolite, and microbial fertilizer, respectively. In the growth experiment using Lettuce, the manufactured soil obtained 21% & 20% increase in leaf length and width, 17% increase in chlorophyll, and 22% in biomass, compared to the control.

• Journal of the Korean Wood Science and Technology
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• v.33 no.3 s.131
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• pp.53-63
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• 2005

This study attempted to obtain the basic data of utilizable possibility of preservative treated wood as a material used in a marine ranch. To evaluate the leaching stability of CCA-, CCFZ-, and ACQ-treated woods in seawater, the specimens treated with 2% and 3% (w/v) of CCA, CCFZ, and ACQ were exposed to deionized water, synthetic seawater and natural seawater for 41 days and then each component released was periodically determined. There was little amount of copper and chromium released from CCA-treated wood exposed in both deionized and seawater. Although relatively large amount of arsenic was released from CCA-treated wood, the release rate in seawater was lower than that in deionized water. The release rate of chromium and zinc from CCFZ-treated wood were somewhat greater in deionized water, but lower in seawater than in deionized water. Retention level and salinity of synthetic seawater had little effect on the release rate of components. The ACQ-treated wood had greater copper release than CCA- and CCFZ-treated wood, and the amount of copper released did not affected by leaching media used.

• Korean Journal of Ichthyology
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• v.8 no.1
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• pp.9-13
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• 1996

To study on the growth of young stage Acanthopagrus schlegelii, samples were collected from the shallow waters off Kunsan, Korea from July to December, 1995. The planctonic larvae of Acanthopagrus schlegelii were collected in early June. The young fish of 12.7~26.6 mm in total length began to appear in the shallow water in late June. They grew up 19.9~51.4 mm in middle July, 24.8~75.0 mm in late July, 63.3~79.6mm in middle August. A. schlegelii disappear from the shallow water after middle August, and began to be collected in the outer bay off Kokunsan Isls. by long back net. This species that had spawned from Kunsan coast in late June to middle August grew up to 100mm in total length in December of that year.

• 한국해양학회지
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• v.28 no.4
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• pp.292-304
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• 1993

The east Sea circulation is numerically modeled with refined grid resolution elaborated open boundary condition, and by directly imposing the measured surface temperature and salinity typical the east Korean Warm current are clearer than those in previous works. among others, The Ulleung warm Water and the Intermediate Water of minimum salinity are nicely reproduced. The latter is formed in the northern/northwestern coastal region in winter and is advocated southward by strong under-current. the former is associated with a locally generated anti-cyclonic gyres. The model indicates strong seasonal variation of Nearshore Current along the Japanese coast from wintertime barotropic to summertime baroclinic structures. the associated strong reversed under-cur-rent in summer is not well understood. Global circulation pattern is characterized by two regions of cyclonic and anti-cyclonic gyres in the north and south, respectively. The presence of these gyres indicates importance of local dynamics in East Sea circulation. This model, however, does not completely resolve the problem of overshooting of the East Korean Warm current.

• Membrane Journal
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• v.21 no.3
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• pp.236-246
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• 2011

In this study, we used prepared a cylindrical module consisting 100 hollow fibers of commercialized (hydrophobic) polyethylene membrane of $0.4{\mu}m$ pore size and systematically studied performance of direct contact membrane distillation (DCMD) and sweep gas membrane distillation (SGMD) in terms of variation of permeate flux and salt rejection with respect to temperature drop across the membrane, salt concentrations in feed, and flow rates of cooling water and sweep gas. SGMD was regarded as DCMD with a sweep gas layer between permeate-side membrane surface and cooling water. Sweep gas flow decreases the permeate flux from that of DCMD by providing an additional gas-layer resistance. We compared DCMD and SGMD performance by using mass balance with a fitting parameter (${\omega}$), indicating fraction of permeate flow rate.

• 한국해양학회지
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• v.24 no.3
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• pp.121-131
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• 1989

Cold water observed at sea surface near the southeastern coast of Korea in summers 1982 and 1983 was studied by using data of hydrography, sea level, wind and satellite image. In summer season when water column shows 3-layered structure a "full" upwelling occurs by southwesterly transient wind continuing for several days. During upwelling event, surface water of high temperature moved offshore, middle water of low temperature outcropped to the sea surface, and sea level was lowered, however, equilibrium depth of surface layer was not changed. It may be concluded that cold water at the surface originates from middle layer and strong surface front is a result of surfacing of seasonal thermocline. In order to see the relationship between position of surface front and wind input, a model of Csanady (1982) was applied in a rigid lid approximation. The results show that frontal position can be determined by wind input and water structure near the southeastern coast of Korea. Cold water in summer can appear at the sea surface only when there is wind larger than a minimum wind impulse of order $10m^2/sec$.