• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.6
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• pp.390-399
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• 2012

This research observed the cross section current of 7 survey lines in Seokmo Channel of Gyeonggi bay with a lot of freshwater inflow and S-shaped for 13 hours during flood season and neap tide. We indicated the distribution of the current velocity by comprehending the speed and direction of the current velocity of each line during maximum flood, ebb tide and observed the distribution of salinity. Moreover, in order to understand what lateral momentum causes the lateral flow in each survey line, we practiced the momentum analysis through the observation data. As a result, the lateral baroclinic pressure gradient force and vertical friction of the Seokmo channel during neap tide were the strongest, and this is why the flow by the distribution of salinity and stratification most often occurs. In north of the Seokmo channel, where have wide intertidal and a lot of freshwater inflow, the secondary circulation is caused by balance of lateral baroclinic pressure gradient force and other forces, and the vertical friction was strong in the lines with small depth. On the other hand, in the southern part of the Seokmo channel where the water is deep and the waterway is curved, the advective acceleration and centrifugal force become stronger by the geographical causes during ebb and the influence of fresh water. Therefore, the lateral flow in the Seokmo channel was caused by the distribution of the momentum that differs by location, depth, curve, etc.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.497-502
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• 1996

Artificial fertilization of ice fish, Mypomesus transpaciticus nipponensis caught at Milyang-river and Osib-chun brook was performed in March 24, 1990, and the hatched larvae were reared for 25 days to describe the development of eggs and larvae. Fertilized eggs were spherical in shape, measuring $0.85\~1.05\;mm$ in diameter (mean: 0.97 mm) and translucent adhesive with many small-sized oil globules on the surface. Hatching in the indoor tank started from the 170 hours after fertilization under $16.5^{\circ}C$ water temperature. Newly-hatched larvae were measured $3.85\~4.25\;mm$ in total length (mean: 4.05 mm), and mouth and anus were not yet open. They had one yolk sac on the anterior part of abdomen, straight-type's notochord, and $52\~54$ myotomes. The larva of 5 days old transformed to postlarval stage and measured $5.20\~5.65\;mm$ (mean: 5.37 mm) in total length. As the yolk sac was completely absorbed, mouth and anus were open, and they fed rotifers vigorously. In 20 days after hatching, the larvae grew to 8.38 mm in TL, and the caudal notochord flex at $45^{\circ}$. In 25 days after hatching, total length reached 9.63 mm. The pan of the fin-fold of the future dorsal and anal fins became high.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.823-833
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• 1997

To clarify the annual reproductive cycle of the banded catfish, Pseudobagrus fulvidraco (Richardson), the seasonal changes in histological aspect of gonad and liver were examined. The adult fish was raptured from the upper stream of Young-San river, Chunnam in each month from May 1992 to June 1993. Based on the annual changes in GSI (gonadosomatic index), HSI (hepatosomatic index), CF (condition factor) and histological aspects of the gonads, the annual reproductive cycle were classified into 5 periods as follows: 1) Growing phase (from April to early May): The value of GSI increased and the size of oocytes in perinucleolus stage in oocytes increased gradually. Spermatogonia were developed actively from the epithelial tissues of seminiferous tubules. 2) Maturing phase (from Hay to early June): GSI levels increased rapidly in both sex. Oocytes at various developmental stages were observed. Appearance of active spermatogenesis were observed. 3) Mature and spawning phase (from June to August): High values of GSI remained static and oocytes accumulated significant quantitis of yolk globules. 4) Degenerating phase (from September to November): GSI levels decreased and ovaries were filled mostly with oocytes at the perinucleolus stage. Hepatic cells accumulated significant amounts of lipid droplets. 5) Resting period (from December to March) : Low values of GSI were kept and the size of oocytes at the perinucleolus stage did not increase. Spermatogenesis was not observed.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.3
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• pp.193-210
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• 2013

This study aims to assess the slope stability variation of Jeollabuk-do drainage areas by RCM model outputs based on A1B climate change scenario and infinite slope stability model based on the specific catchment area concept. For this objective, we downscaled RCM data in time and space: from watershed scale to rain gauge scale in space and from monthly data to daily data in time and also developed the GIS-based infinite slope stability model based on the concept of specific catchment area to calculate spatially-distributed wetness index. For model parameterization, topographic, geologic, forestry digital map were used and model parameters were set up in format of grid cells($90m{\times}90m$). Finally, we applied the future daily rainfall data to the infinite slope stability model and then assess slope stability variation under the climate change scenario. This research consists of two papers: the first paper focuses on the methodologies of climate change scenario preparation and infinite slope stability model development.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.12
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• pp.657-667
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• 2015

Cyanobacteria frequently dominate the freshwater phytoplankton community in eutrophic waters. Cyanotoxins can be classified according to toxicity as neurotoxin (Anatoxin-a, Anatoxin-a(s), Saxitoxins) or hepatotoxin (microcystins, nodularin, cylindrospermopsin). Microcystins are present within cyanobacterial cells generally, and they are extracted by the damage of cell membrane. It has been reported that cyanotoxins caused adverse effects and they are acculmulated in aquatic oganisms of lake, river and ocean. In natural, microcystins are removed by biodegradation of microorganisms and/or feeding of predators. However, in process of water treatment, the use of copper sulfate to remove algal cells caused extraction of a mess of microcystins. Microcysitns are removed by physical, chemical and biological methods according to reports. The reduction of nutrients (N and P) inflow is basic method of prevention of cyanobacteria bloom formation. However, it is less effective than investigation because nutrients already present in the eutrophic lake. In natural lake, cyanobacteria bloom are not formed because macrophytes invade from coastal lake by eutrophication. Therefore, a coastal lake has to recover to prevent of cyanobacteria bloom formation.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.119-126
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• 2014

The object of this study was to evaluate the combined toxic interactions of the perfluorooctanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) with six heavy metals (Cu, Zn, Cr, Cd, Hg, and Pb). The individual and combined toxic effects were assessed using the Vibrio fischeri assay. In case of the individual toxicity, PFOA was higher toxic than PFOS and toxicity of PFOA and PFOS were lower than heavy metal. In the toxicity of heavy metals, the $Hg^{2+}$ was found to be most toxic followed by $Pb^{2+}$, $Cr^{6+}$, $Cu^{2+}$, $Zn^{2+}$, and $Cd^{2+}$. The combined toxicity of PFOA or PFOS with $Cr^{6+}$ were synergistic effect because the $EC_{50}$ mix values were less than 1 TU. PFOA + $Zn^{2+}$, PFOS + $Zn^{2+}$, PFOA + $Cd^{2+}$ and PFOS + $Cd^{2+}$ produced addictive effect. Except in these case, all of binary mixtures show antagonistic effect. This study proved potential risk of coexistent with perfluorinated compounds and heavy metals in water environment.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.1
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• pp.58-66
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• 2014

Water pollution problems of urban rivers due to the urbanization and industrialization have been the subject of public attention. In particular, considering the fact that the characteristics of water cycle of each basin change dramatically through the development of new towns, a large number of concerns about future water quality have been raised. However, reasonable measures to predict future water quality quantitatively have not been presented by this moment. In this study, by the linkage of annual unit load generation based on long-term monitoring results of the ministry of environment (MOE) to a semi-distributed rainfall runoff model, SWMM (Storm Water Management Model), we proposed a new methodology to estimate future water quality macroscopically and testified it to verify its applicability for the estimation of future water quality of a small watershed at G new town. As a result of the estimation using Y-EMC (Yearly based Event Mean Concentration), future water quality were simulated as BOD 18.7, T-N 16.1 and T-P 0.85 mg/L respectively which could not achieve the grade III of domestic river life guidance and these criteria could be satisfied by the reduction of domestic wastewater discharge load by over 80%. The results of this study are shown to be utilized for one of basic tools to estimate and manage water quality of urban rivers in the course of new town developments.

• Parasites, Hosts and Diseases
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• v.51 no.3
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• pp.305-311
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• 2013

In this study, we found that Haplorchis taichui, a heterophyid intestinal fluke, is highly prevalent, with heavy worm loads, among riparian people in Saravane and Champasak province, Lao PDR. Fecal specimens were collected from 1,460 people (717 men and 743 women) in 12 riparian (Mekong river) districts and were examined by the Kato-Katz fecal smear technique. The overall helminth egg positive rate was 78.8% and 66.4% in Saravane and Champasak province, respectively. The positive rate for small trematode eggs (STE), which included H. taichui and other heterophyids, Opisthorchis viverrini, and lecithodendriids, was 69.9% and 46.3% in Saravane and Champasak province, respectively. To obtain adult flukes, 30 STE-positive people were treated with 40 mg/kg praziquantel and then purged. Whole diarrheic stools were collected 4-5 times for each person and searched for fluke specimens using a stereomicroscope. Mixed infections with various species of trematodes (H. taichui, Haplorchis pumilio, O. viverrini, Prosthodendrium molenkampi, Centrocestus formosanus, and Echinochasmus japonicus) and a species of cestode (Taenia saginata) were found. However, the worm load was exceptionally high for H. taichui compared with other trematode species, with an average of 21,565 and 12,079 specimens per infected person in Saravane and Champasak province, respectively, followed by H. pumilio (41.9 and 22.5, respectively) and O. viverrini (9.4 and 1.5, respectively). These results show that diverse species of intestinal and liver flukes are prevalent among riparian people in Saravane and Champasak province, Lao PDR, with H. taichui being the exceptionally dominant species.

• Journal of Korean Society on Water Environment
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• v.36 no.4
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• pp.284-299
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• 2020

Dam reservoirs play a particularly crucial role in processing the allochthonous and the autochthonous dissolved (DOC) and the particulate (POC) organic carbon and in the budget of global carbon cycle. However, the complex physical and biogeochemical processes make it difficult to capture the temporal and spatial dynamics of the DOC and the POC in reservoirs. The purpose of this study was to simulate the dynamics of the DOC and the POC in Daecheong Reservoir using the 3-D hydrodynamics and water quality model (AEM3D), and to quantify the mass balance through the source and sink fluxes analysis. The AEM3D model was calibrated using field data collected in 2017 and showed reasonable performance in the water temperature and the water quality simulations. The results showed that the allochthonous and autochthonous proportions of the annual total organic carbon (TOC) loads in the reservoir were 55.5% and 44.5%, respectively. In season, the allochthonous loading was the highest (72.7%) in summer, while in autumn, the autochthonous loading was the majority (77.1%) because of the basal metabolism of the phytoplankton. The amount of the DOC discharged to downstream of the dam was similar to the allochthonous load into the reservoir. However, the POC was removed by approximately 96.6% in the reservoir mainly by the sedimentation. The POC sedimentation flux was 36.21 g-C/㎡/yr. In terms of space, the contribution rate of the autochthonous organic carbon loading was high in order of the riverine zone, the transitional zone, and the lacustrine zone. The results of the study provide important information on the TOC management in the watersheds with extensive stagnant water, such as dam reservoirs and weir pools.

• Korean Journal of Ecology and Environment
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• v.51 no.1
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• pp.1-15
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• 2018

With land-use (cover) and water quality, the distributional characteristics of epilithic diatom communities were studied with 193 samples from estuaries of Korean peninsula between 2015 and 2016. Of total 394 taxa classified, Nitzschia perminuta (19.6%) and N. inconspicua (14.0%) were the 1st and 2nd dominant species. Using a cluster analysis, the epilithic diatom communities of Korean estuaries were divided into four groups (G1-G4). Ecological characteristics of each group were followed: G1 was located in estuaries of the East Sea, and characterized by high forest land-use and high DO and low nutrients; G2 was the eastern part of the South Sea, and characterized by low turbidity and nutrients; G3 was the western part of the South Sea, and characterized by high agriculture, low electric conductivity and low salinity; G4 was the Yellow Sea, and characterized by high nutrients. The environmental factors having significant correlation with diatom distributions were as follows: TN to G1, turbidity to G2, agriculture to G3, and TP to G4. Moreover, the important factors affecting the occurrence of indicator species were forest land-use for Fragilaria construens var. venter in G1, turbidity for Rhoicosphenia abbreviata in G2, urban land- use and total phosphorus (TP) for Bacillaria paradoxa and Hantzschia amphioxys of G3, and TP and turbidity for N. ovalis and Stephanodiscus invistatus of G4. These results collectively indicate that the distribution of epilithic diatom communities in Korean peninsula was largely effected by water quality and land cover/use.