• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.1-13
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• 2019

The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) resulted in the deposition of large quantities of radionuclides over parts of eastern Japan. Radioactive contaminants have been observed over a large area including forests, cities, rivers and lakes. Due to the strong adsorption of radioactive cesium by soil particles, radioactive cesium migrates with the eroded soil, follows the surface flow paths, and is delivered downstream of population-rich regions and eventually to coastal areas. In this study, we developed a model to simulate the transport of contaminated sediment in a watershed hydrological system and this model was compared with observation data from eroded soil observation instruments located at the Korea Atomic Energy Research Institute. Two methods were applied to analyze the soil particle size distribution of the collected soil samples, including standardized sieve analysis and image analysis methods. Numerical models were developed to simulate the movement of soil along with actual rainfall considering initial saturation, rainfall infiltration, multilayer and rain splash. In the 2019 study, a numerical model will be used to add rainfall shield effect by trees, evaporation effect and shield effects of surface water. An eroded soil observation instrument has been installed near the Wolsong nuclear power plant since 2018 and observation data are being continuously collected. Based on these observations data, we will develop the numerical model to analyze long-term behavior of radionuclides on land as they move from land to rivers, lakes and coastal areas.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.187-193
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• 2017

This study evaluated tidal stream energy resources according to tidal flow properties around Uido off the west coast of, Jeollanam-do, South Korea. A feasibility study was first carried out through the collection of bathymetry data and tidal phase information. For this simulation, a depth-averaged 2D ADCIRC (Advanced Circulation) model for real sea situations was applied to a Finite Element Method (FEM) approach for tides given the variation of tidal current speed. Hydrodynamics were simulated with 4 major tidal constituents (M2, S2, K1, and O1) after setting up 4 observation points. From the real depth-averaged model simulation results, it was found that the spring tide Higher High Water (HHW) and tidal current speed values at the 4 observation points were about 2.2 m and 1.33 m/s, respectively. The ADCIRC model results were analyzed with reference to the Korea Hydrographic and Oceanographic Agency's (KHOA) observed data for verification. Furthermore, using topographical characteristics via the Tidal Flux Method (TFM), tidal energy density distribution was calculated, indicating a maximum tidal energy density of about $1.75kW/m^2$ for the 5 assessment areas around Uido. The tidal energy density was evaluated with consideration given to topographical characteristics as well as tidal elevation and tidal current speed to determine an optimum tidal farm candidate.

• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.4
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• pp.130-145
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• 2016

Soil erosion processes are affected by weather factors, such as rainfall, temperature, wind, and humidity. Among these factors, rainfall directly influences soil erosion by breaking away soil particles. The kinetic energy of rainfall and water flow caused by rain entrains and transports soil particles downstream. Therefore, in order to estimate soil erosion, it is important to accurately determine the rainfall erosivity factor(R) in RUSLE(Revised Universal Soil Loss Equation). The objective of this study is to evaluate the average annual R using 14 years(2002~2015) of 1 minute rainfall data from 55 KMA(Korea Meteorological Administration) weather stations. The R results from 1 min rainfall were compared with previous R studies using 1 h rainfall data. The determination coefficients($R^2$) between R calculated using 1 min rainfall data and annual rainfall were 0.70-0.98. The estimation of 30 min rainfall intensity from 1 min rainfall data showed better $R^2$ results than results from 1 h rainfall data. For estimation of physical spatial rain erosivity(R), distribution of annual rainfall was estimated by IDW(Inverse Distance Weights) interpolation, taking elevation into consideration. Because of the computation burden, the R calculation process was programmed using the python GUI(Graphical User Interface) tool.

• Korean Journal of Ichthyology
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• v.31 no.2
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• pp.67-76
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• 2019

This study was conducted from 2017 to 2018 to determine habitat aspects of Acheilognathus signifier, an endangered species reintroduced (2010~2012) to Heukcheon Stream, a tributary of the Hangang River, Korea. A total of 329 individuals were collected in 2017 (two surveys) and 723 individuals were collected in 2018 (four surveys) at about 5 km habitat area, including the discharge station. A. signifier's habitat was about 0.4 to 1.2 meters deep in slow water flow upstream of the discharge area. It was a place with many boulders and cobbles. The spawning period was estimated from April to June in terms of spawning behavior and collected juvenile size. Sex ratio of females (438) and males (412) was 1 : 0.94. Estimated age of A. signifier based on their total length distribution during the spawning period (April) indicated that 1-, 2-, 3-year old groups and more than 4-year-old group were 32~43 mm, 50~61 mm, 62~75 mm, and 76~89 mm, respectively. Age-specific composition costs differed depending on the timing of the collection. They were relatively high in the order of first-year (juvenile)>third-year> and fourth-year or higher, showing a stable age structure. Thus, A. signifier reintroduced to Heukcheon Stream has successfully settled down and formed a stable population, showing a tendency to proliferate.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.12
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• pp.855-862
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• 2012

Caenorhabditis elegans, a free-living nematode mainly found in the soil pore water, roles the critical function in trophic levels, energy flow, and decomposition in soil ecosystem. C. elegans is commonly used species to test soil toxicity. Recently, they are employed broadly as a test organism in nanotoxicology. In this study, a review of the toxicity of nanomaterials for C. elegans was presented based on SCI (E) papers. The nanotoxicity studies using C. elegans have been reported in 20 instances including the mechanism of toxicity. Most studies used K-medium, S-medium, and NGM (Nematode Growth Medium) plate as an exposure medium to test toxicity of nanoparticles. The effects observed include anti aging, phototoxicity, genotoxicity, and dermal effects on C. elegans exposed to nanoparticles. We found that the toxic mechanisms were related with various aspects such as lifespan abnormality, oxidative stress, distribution of particles on inter-organisms, and stress-related gene analysis. C. elegans has advantage to test toxicity of nanoparticles due to various cellular activities, full genome information, and easy observation of transparent body. C. elegans was considered to be a good test species to evaluate the nanotoxicity.

• Journal of fish pathology
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• v.36 no.2
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• pp.251-261
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• 2023

Photobacterium sp. YW2207 was isolated from rainbow trout raised in a fish farm located in Yeongwol-gun, Gangwon Province, South Korea. Based on 16S rRNA sequence analysis and phylogenetic analysis, it was confirmed that Photobacterium sp. YW2207 showed 100% similarity with Photobacterium piscicola and Photobacterium phosphoreum, and 94.6% similarity with P. damselae subsp. damselae. Biochemical analysis revealed that Photobacterium sp. YW2207 is a Gram-negative, motile bacterium with a cell size of 1.5~3×3~5 ㎛. The bacteria were cultured on nutrient agar, brain heart infusion agar, Muller-Hinton agar, tryptic soy agar, and thiosulfate citrate bile sucrose agar with NaCl concentrations ranging from 0 to 2.5%. The API50CHE and API20E tests indicated lower utilization capabilities compared to the P. damselae strains provided in the API database. Furthermore, unlike most Photobacterium species, Photobacterium sp. YW2207 presented negative for catalase test. Results from the flow cytometric measurement indicated that Photobacterium sp. YW2207 exhibited a more diverse distribution of cell sizes and had larger cell sizes compared with P. damselae subsp. damselae. Minimum inhibitory concentration tests showed that Photobacterium sp. YW2207 had low susceptibility to β-Lactam and aminoglycoside antibiotics, while having high susceptibility to tetracycline, doxycycline, and quinolone antibiotics. Pathogenicity on rainbow trout revealed that an immersion of 1×10⁵ CFU/ml did not cause mortality or clinical symptoms.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.12
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• pp.655-663
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• 2017

It is difficult to manage hotspot area and to establish the reduction plan considering with spatial-distribution on Korea TMDLs (Total Maximun Daily Loads) system. To solve this problems, methods of Load Duration Curve (LDC) using long-term flow and water quality data, and spatial-analysis were applied on present TMDLs. Jinwi A watershed which is enforced TMDLs plan were selected to study area. Results of application of suggested methods in this study to Jinwi watershed, Hwangguji tributary was selected to hotspot area and Jinwi tributary was exclued. Also, middle area of Hwangguji tributary was needed a reduction plan for the protection of non-point source pollution. In downstream area, livestock manure should be managed additionally. The new methods suggested in this study were useful to increase healthiness for total watershed.

• Korean Journal of Environment and Ecology
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• v.37 no.2
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• pp.151-162
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• 2023

This study investigated the characteristics of fish communities and inhabiting status of the endangered species, Rhodeus pseudosericeus, in the Geumdang Stream in Korea from March to October 2021. A total of 1,698 fish in 5 families and 25 species were collected from 7 survey stations during the survey period. The dominant species was Zacco platypus (relative abundance, 46.5%), and the subdominant species was Squalidus gracilis majimae (16.7%), followed by Rhynchocypris oxycephalus (12.0%), Z. koreanus (5.7%), Pungtungia herzi (3.2%), R. pseudosericeus (2.0%), R. notatus (1.9%), and Acheilognathus rhombeus (1.8%). Nine Korean endemic species (36.0%) were collected, including R. pseudosericeus, R. uyekii, Sarcocheilichthys variegatus wakiyae, Microphysogobio yaluensis, S. gracilis majimae, Z. koreanus, Cobitis nalbanti, Iksookimia koreensis, and Odontobutis interrupta. An exotic species, Micropterus salmoides, designated as an invasive alien species (IAS), was collected downstream. The investigation of the habitat patterns of the endangered species (class II), Rhodeus pseudosericeus, showed a habitat range of about 6 to 7 km in the middle of Geumdang Stream (RP-1 to RP-4), and this species inhabited the edge with water depths of 0.3 through 1.0 m with slow water flow and many aquatic plants. According to the community analysis results, the overall dominance and evenness indexes were low, while diversity and richness indexes were high, and the cluster structure was largely divided into upstream and middle-downstream areas. The river health (fish assessment index) evaluated using fish was assessed as good (3 stations), normal (3 stations), and bad (1 station), and water quality was evaluated as good both upstream and downstream. Compared to previous studies, the number of species was relatively similar, and among the species that appeared in the past, 13 species did not appear in this survey, while 6 species appeared for the first time in this survey. Disturbance factors included river construction, many weirs, and the appearance of the ecosystem-disturbing species, M. salmoides. Since Geumdang Strem has high conservation value because it is home to many species in the Acheilognathinae subfamily, including the endangered species R. pseudosericeus, continuous attention and systematic conservation measures are required.

• Economic and Environmental Geology
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• v.41 no.4
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• pp.405-425
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• 2008

In order to investigate the amounts of trace elements flowing into reservoir, and to elucidate the relationship between trace element mobility and fraction size, the stream water and sediment samples were collected from thirty-two sites of the 3rd or 4th order stream within watershed surrounding the Juam reservoir. Chemical analyses of trace elements (As, Cd, Cr, Cu, Ni, Pb and Zn) for all samples were completed, and additionally cationi and anion for stream water samples. Considering the distribution of rocks and contamination sources in watershed, the eight stream sediments were selected from typical sites representing study areas, and we determined the concentrations of trace elements according to size fractions ($2\;mm{\sim}200\;{\mu}m$, $200{\sim}100\;{\mu}m$, $100{\sim}50\;{\mu}m$, $50{\sim}20\;{\mu}m$ and < $20\;{\mu}m$). The correlation relationships between concentrations and size fractions of stream sediments were important to identify the hydro-geochemical behavior of trace elements that flow into Juam reservoir. Stream waters showed four water types (Ca-Mg-$HCO_3$, Ca-Na-$HCO_3$-Cl, Ca-Na-$HCO_3-SO_4$, Ca-Na-$HCO_3$) depending on pollution sources such as coal mine, metal mine, farm-land and dwellings. Concentrations of trace elements increased clearly with the decrease in size fractions of stream sediments. Concentrations of Cu, Pb and Zn increased dramatically in silt size (< $20\;{\mu}m$) fraction, while As had high concentrations in sand size ($2\;mm{\sim}100\;{\mu}m$) fraction in downstream sediments of metal mines. These indicate that Cu, Zn, and Pb moved into Juam reservoir easily in the adsorbed form on silt size grain in sediments, and As was transported as As-bearing mineral facies, resulting in its less chance to reach into Juam reservoir.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.29-46
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• 2004

It is important to identify geometries of fracture that act as a conduit of fluid flow for characterization of ground water flow in fractured rock. Fracture geometries control hydraulic conductivity and stream lines in a rock mass. However, we have difficulties to acquire whole geometric data of fractures in a field scale because of discontinuous distribution of outcrops and impossibility of continuous collecting of subsurface data. Therefore, it is needed to develop a method to describe whole feature of a target fracture geometry. This study suggests a new approach to develop a method to characterize on the whole feature of a target fracture geometry based on the Fourier transform. After sampling of specimens along a target fracture from borehole cores, effective frequencies among roughness components were selected by the Fourier transform on each specimen. Then, the selected effective frequencies were averaged on each frequency. Because the averaged spectrum includes all the frequency profiles of each specimen, it shows the representative components of the fracture roughness of the target fracture. The inverse Fourier transform is conducted to reconstruct an averaged whole roughness feature after low pass filtering. The reconstructed roughness feature also shows the representative roughness of the target subsurface fracture including the geometrical characteristics of each specimen. It also means that overall roughness feature by scaling up of a fracture. In order to identify the characteristics of permeability coefficients along the target fracture, fracture models were constructed based on the reconstructed roughness feature. The computation of permeability coefficient was performed by the homogenization analysis that can calculate accurate permeability coefficients with full consideration of fracture geometry. The results show a range between $10^{-4}{\;}and{\;}10^{-3}{\;}cm/sec$, indicating reasonable values of permeability coefficient along a large fracture. This approach will be effectively applied to the analysis of permeability characteristics along a large fracture as well as identification of the whole feature of a fracture in a field scale.