• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.510-510
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• 2023

집중호우의 증가는 저수지 내 탁수의 증가로 이어지며, 저수지에서의 탁수 배제는 하천의 탁수 문제로 연결될 수 있다. 탁수의 발생은 정수처리 비용 증가와 하천 생태계 문제 등을 발생시키므로, 이에 대한 해결책이 지속적으로 요구되고 있다. 특히 낙동강 유역의 임하호는 태풍 및 집중호우 발생 시 고탁수의 유입 빈도가 높다. 탁수가 임하호에 유입되면 일반적으로 저수지 탁수 예측 수치해석을 수행하여 탁수의 저수지 내 탁수 거동과 방류량에 따른 탁수 저감 정도를 파악하고, 탁수 배제를 위한 저수지 운영계획을 수립한다. 그러나 방류된 고탁수의 하천 거동에 대한 수치해석은 국내에서는 수행하고 있지 않은 실정이다. 임하댐 하류에서 내성천합류부까지는 약 0.325 m³/s의 물을 취수하고 있으므로(2022년 기준), 하천의 탁수도 저수지 탁수와 동시에 고려되어야 할 필요가 있다. 저수지와 하천의 유사 거동 분석에 대해 격자 구성 등의 이유로 일반적으로 각각 다른 tool을 사용하고 있으나, 모델구축 및 입□출력 data의 변환 등 구축, 구동, 분석 과정 모두 효율적이지 못하다. 이에 본 연구에서는 하천과 저수지에서의 탁수 거동을 동시에 예측할 수 있는 일원화된 수치해석 모델을 구축(임하호~낙본C)하였다. 준3차원 모델인 EFDC를 이용하였으며, 격자는 저수지는 직사각격자, 하천은 Curvlinear를 적용하였다. 연직방향으로는 저수지와 하천의 수심 차이가 크므로 EFDC 내에 탑재되어 있는 𝜎-z(uniform)레이어 옵션을 선택하여, 저수지 연직 레이어는 40개, 하천은 2개로 구축되었다. 하천에서의 탁수 거동 예측은 지류의 유량, 탁도 등의 경계조건 data를 얻기가 쉽지 않기 때문에, 유량은 임하호 유입유량에 유역면적비를 적용하였으며, 탁도는 TSS(Total Suspended Solid)-SSC(Suspended Sediment Concentration)-유량의 관계를 각각 회귀분석 등을 통해 도출하여 연구 범위 내 7개 지류하천에 적용하였다. 모의 시기는 2개의 태풍으로 연속적인 탁수가 발생한 2020년 08~10월로 결정하였다. 모의 결과 저수지와 하천의 PBIAS는 각각 13.6과 8.4로(Very Good 등급) 하천과 저수지를 동시에 모의하는 탁수 예측의 적용 가능성은 충분한 것으로 확인되었다. 그러나 이벤트별 지류의 유량과 탁도는 일정한 관계로 계산될 수 없으므로, 향후 유역 모델과 연계하여 지류 유입 유량 및 탁도의 정확도를 개선할 것이다.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.30-36
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• 2017

SS(Suspended Solid) concentration by soil erosion into river at normal and flood season should be measured. However, to present the variation of SS due to various development project such as EIA(Environmental Impact Assessment), River Master Plan, and so on, it is necessary to estimate not measure SS, but there are not exist how to estimate SS. In the present study, therefore, we propose the hydrologic method of estimating SS concentration using the results of particular frequency flood discharge and sediment discharge by RUSLE method. SS consists of silty and clay soil and colloid particle etc. However, in the present study, silty and clay soils of sediment discharge except send set up SS standards. The flow discharge to estimate SS concentration are 1~2 years for normal season, 30~100 years for flood season. Meanwhile, analysis software for probable rainfall uses Fard2006, probable rainfalls under 2-year frequency are estimated using rainfall data and frequency factor of Gumbel distribution. The results of estimating SS concentration using runoff volume by sediment and flow discharges of silty and cray soils as above method show that reliable level of SS concentration is considered in predevelopment of natural condition and under development of barren condition. Especially, SS concentration takes notice that the value of sediment discharge makes a huge difference according to channel slope, it was confirmed that the value obtained by dividing the SS concentration by the channel slope is relatively constant even though the topographical factors are different. Therefore, if the present study will be proceeded for various watersheds, it will be developed as estimation method of SS concentration.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.4
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• pp.339-346
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• 1986

A study on eutrophication in the downstream of the Nakdong River was conducted from October 1983 to September 1984. Nutrients concentration of the samples in this area was usually high and the nitrogen ratio to the phosphorus was as very high as $63.5{\sim}119.6$. The concentration of nutrients was in the range of $0.22{\sim}173{\mu}g-at/l$ for ammonia nitrogen, $26.7{\sim}187{\mu}g-at/l$ for nitrate nitrogen, $1.07{\sim}8.22{\mu}g-at/l$ for nitrite nitrogen, $58.7{\sim}231{\mu}g-at/l$ for total inorganic nitrogen and $0.44{\sim}4.43{\mu}g-at/l$ for phosphate phosphorus. The concentration of chlorophyll-a was in the range of $1.8{\sim}75.2\;mg/m^3$. Correlationship between concentration of nutrients and chlorophyll-a was not found. The concentrations of total suspended solid were in the range of $10.7{\sim}45.9\;ppm$, and $16.2{\sim}35.2\%$ of the total suspended solid was consisted of volatile suspended solid. According to the state of lacustrine nutrition, the state of the downstream of Nakdong River was equivalent to the eutrophication state in term of chlorophyll-a and inorganic nitrogen, and mid-nutritional state in term of phosphate.

• Journal of Korea Water Resources Association
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• v.50 no.11
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• pp.715-723
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• 2017

Extracellular Polymeric Substances (EPS) in the water environment assemble fine, colloidal particles, such as clays, microorganisms and biomass, in large flocs, which are eventually subject to sedimentation and deposition and determine water/sediment quality and quantity. This study hence aimed to investigate the way that water and colloidal chemistry affects EPS-mediated flocculation of colloidal particles, using a jar-test experiment. Especially, ionic strength, divalent cation and humic substances concentrations were selected as experimental variables in the jar-test experiments, to elucidate their effects on EPS-mediated flocculation. A higher ionic strength increased flocculation capability, reducing electrostatic repulsion between EPS-attached colloidal particles and enhancing particle aggregation. 0.1 M NaCl ionic strength had higher flocculation capability, with 3 times larger floc size and 2.5 times lower suspended solid concentration, than 0.001 M NaCl. Divalent cations, such as $Ca^{2+}$, built divalent cationic bridges between colloidal particles and EPS (i.e., $colloid-Ca^{2+}-EPS$ or $EPS-Ca^{2+}-EPS$) and hence made colloidal particles to build into large, settelable flocs. A small $Ca^{2+}$ concentration enhanced flocculation capability, reducing suspended solid concentration 20 times lower than the initial dosed concentration. However, humic substances, adsorbed on colloidal particles, reduced flocculation, because they blocked EPS adsorption on colloidal particles and increased negative charges and electrostatic repulsion of colloidal particles. Suspended solid concentration in the tests with humic substances remained as high as the initial dosed concentration, indicating stabilization rather than flocculation. Findings about EPS-mediated flocculation in this research will be used for better understanding the fate and transport of colloidal particles in the water environment and for developing the best management practices for water/sediment quality.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.3
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• pp.140-148
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• 2017

The effectiveness of the first flush treatment system using settling process was evaluated to reduce urban nonpoint source pollutant loads to surface water during storm events. A pilot scale system was constructed and tested in the field and surface runoff samples were collected automatically according to pre-defined conditions. Nine rainfall events were tested and average removal efficiencies of TSS (Total Suspended Solid), TP (Total Phosphorus) and TN (Total Nitrogen) were evaluated as 87.4%, 75.3%, and 43.6%, respectively. Concentration and removal efficiency of pollutants were found to be affected by an amount of rainfall and rainfall intensities of the respective events. This seemed to be caused by the greater particulate fractions of first flushed samples than the samples collected in later time periods during the same rainfall events. The study showed that it is possible to remove a significant portion of the nonpoint source pollutant loads in initial rainfall runoff by using a simple settling process for TSS and TP without requiring additional power or chemicals.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.563-570
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• 2019

Red tide has caused massive fish kills in Korean coastal waters with devastating economic loss in the aquaculture industry since 1995. Remote sensing technique has shown to be effective for the detection of red tide in wide areas, where the absorption property of red tide water plays a central role in understanding the red tide reflectance. This study analyzed the optical absorption property of sea waters dominated by the dinoflagellate specie of Alexandirum affine, off the Tongyeong area in August, 2017. Water samples collected from 20 stations in the ship-based campaign were measured for absorption by pigment, suspended solid, and dissolved organic matter, with the corresponding water quality variables such as chlorophyll concentration and total suspended solid. The analysis showed that Alexandrium-dominated water exhibits strong absorption in the spectral range below 400 nm unlike that of diatom-dominated waters, and greater fluctuations in the range of 400 nm - 500 nm. The packaging effect in pigment absorption was stronger in Alexandrium-dominated waters, and the exponent in the absorption by detritus and gelbstoff is disparate for diatom and Alexandrium. In the model for the detritus and gelbstoff absorption (a_dg(λ)=a_dg(λ₀)e^-s(λ-λ₀)), the optimal exponent coefficient(s) for the Alexandrium was close to 0.01 rather than to 0.015, which was commonly use for modelling diatom waters.

• Journal of Environmental Science International
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• v.15 no.3
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• pp.271-278
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• 2006

To investigate the variations of physico-chemical factors and microbial population, in ten stations at water region of coastal area of Chagwi-Do, Nutritive salts, water temperature, transparency, suspended solid, salinity, COD, DO, pH, heterotrophic bacteria, coliform group and Vibrio spp. were analysed three times in September, November in 2004 and February in 2005. Heterotrophic bacteria in surface water was $3.5X10^1{\sim}1.16X10^3cfu/ml,\;1.0X10^2{\sim}5.2X10^1cfu/ml\;2.0X10^1{\sim}7.6X10^1cfu/ml$ and bottom water counted $7.0X10^2{\sim}1.0X10^3cfu/ml,\;1.4X10^1{\sim}2.5X10^2cfu/ml\;2.0X10^2{\sim}4.2X10^1cfu/ml$ in September, November in 2004 and February in 2005, respectively. The cell number of total coliform bacteria in the surface water amounted to $0{\sim}4.3X10^2cfu/ml,\;0{\sim}6.0X10^1cfu/ml,\;0{\sim}1.0X10^1cfu/ml$ and bottom water amounted $0{\sim}2.2X10^2cfu/ml,\;0{\sim}5.4X0^2cfu/ml,\;0{\sim}2.0X10^1cfu/ml$ in September, November in 2004 and February in 2005, respectively. As for Vibrio spp., the cell number in the surface water was $1.0X10^1{\sim}2.5X10^2cfu/ml,\;1.0X10^1{\sim}2.0X10^1cfu/ml,\;0cfu/ml$ and bottom water counted $1.0X10^1{\sim}5.2X10^2cfu/ml,\;0cfu/ml,\;2.0X10^1cfu/ml$ in September, November in 2004 and February in 2005, respectively.

• Korean Journal of Environmental Biology
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• v.18 no.1
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• pp.21-31
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• 2000

We investigated seasonal variation of microalgal assemblages, sea water temperature, salinity and suspended solid and the parameters measured daily from January 1998 to October 1999 at a nearshore shallow-water in Marian Cove, Maxwell Bay, King George Island, the Antarctic. Annual mean surface water temperature was -0.3$0^{\circ}C$ and the highest water temperature was 4.53$^{\circ}C$ (22 January 1999) and the lowest water temperature was -2.07$^{\circ}C$ (23 August 1998). Annual mean salinity was 33.38 psu, ranging from 42.80 psu (6 January 1999) to 19.50 psu (6 June 1999). Annual mean suspended solid (SS) during two years was 34.14 mgㆍ1$^{-1}$, ranging from 60.62 mgㆍ1$^{-1}$(7 March 1998) to 12.90 mgㆍ1$^{-1}$ (26 December 1998). Chlorophyll $\alpha$ (Chl $\alpha$) concentrations were measured in order to know seasonal variations of microalgae in the surface seawater. Annual mean of total Chl a concentration was 0.55$\mu\textrm{g}$ㆍ1$^{-1}$, the highest Chl $\alpha$ concentration (12.16$\mu\textrm{g}$ㆍ1$^{-1}$) appeared in 4 October 1998, the lowest Chl $\alpha$ concentration appeared 0.19$\mu\textrm{g}$ㆍ1$^{-1}$, Monthly mean total Chl $\alpha$ concentration was high in October 1998 (1.32$\mu\textrm{g}$ㆍ1$^{-1}$) and low in July on 1998 (0.28$\mu\textrm{g}$ㆍ1$^{-1}$). Annual mean nano-sized Chl $\alpha$ concentration was 0.40$\mu\textrm{g}$ㆍ1$^{-1}$, monthly mean nano -sized Chl $\alpha$ concentration was high in November 1998 (0.90$\mu\textrm{g}$ㆍ1$^{-1}$), and low in July 1999 (0.22$\mu\textrm{g}$ㆍ1$^{-1}$). Annual mean micro-sized Chl $\alpha$ concentration was 0.15$\mu\textrm{g}$ㆍ1$^{-1}$ monthly mean micro-sized Chl $\alpha$ concentration was high in October 1998 (0.81$\mu\textrm{g}$ㆍ1$^{-1}$), and low July 1998, January, February and September 1999 (0.05$\mu\textrm{g}$ㆍ1$^{-1}$). More than 65% of total Chl $\alpha$ was concentrated during spring and summer time between October and March. Microalgal variation appeared to be due to physical factors of seawater in the Antarctic nearshore from 1998 to 1999. The reason why micro-sized Chl $\alpha$ did not increase during austral summer was the bay had been frozen by decrease of water temperature. We think that total microalgal abundance was decreased because the summer microalgal abundance was determined by variation of water temperature during winter season. [Chl $\alpha$ concentration, Microalgal assembalges, Seasonal variation, the Antarctic nearshore].

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.21-26
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• 2002

The behavior of the biological water treatment process on start-up operation was evaluated in the integrated recirculating aquaculture system consisting of a double drain type rearing tank ($2.5 m^3$), a sedimentation tank, a floating bead filter, a foam separator and a rotating biological contactor. A system was stocked with nile tilapia (Oreochromis niloticus) at an initial rearing density of $2\%$ for 2 weeks for acclimated rotating biological contactor. The total ammonia nitrogen (TAN) level increased to $13.6 g/m^3$ on day 4 after adding feed and was decreased to $0.3 g/m^3$ on day 7. The total suspended solid was completely removed during overall experimental period.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.27-34
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• 2002

The performances of fish culture were evaluated in the integrated recirculating aquaculture system consisting of a double drain type rearing tank ($2.5 m^3$), a sedimentation tank, a floating bead filter, a foam separator and a rotating biological contactor. A system was stocked with nile tilapia at an initial rearing densities of $5\%$ (A), $5\%$ (B) and $7\%$ (C) oyer 30 days. Feed coefficient was 1.62, 1,79 and 1.80 and average daily growth rate was $0.452\%$, 0.u5% and $0.423\%$, respectively. The level of TAN was maintained below $1 g/m^3$ for $5\%$ of initial rearing density and $2-4 g/m^3$ for $7\%$. The dissolved oxygen level ($2-4 g/m^3$) was not optimum but should not be inhibitory to fish growth. The total suspended solid was completely removed during overall experimental period.