• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.15-22
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• 2009

This study reports the serial use of a 3-D hydrodynamic model, EFDC-Hydro and a dynamic water quality model WASP7.2 that are maintained by USEPA. The 48 km section of the Geum River downstream between Daechung Dam and Gongju was selected as a sample study site. Topographical information was used to accurately represent morphology of the study site and boundary conditions were derived from governmental databases including WAMIS by Ministry of Land and Ocean and WEIS by Ministry of Environment. EFDC-Hydro was successfully calibrated for observed water level and WASP was calibrated using monthly observed water quality data obtained from the above sources. It was found that the current water quality target of BOD for the Geum River-H point could not be met on monthly basis though every other tributary of the area would meet its own water quality target as assigned in Korean TMDL. This study proposed the new target BOD water quality for the Gabcheon and Mihocheon as 4.3 and 3.6 mg/l, respectively so that the Geum River-H point can meet the target. When Sejong City is constructed, it is estimated that effluent discharge limit of BOD must be less than 4.5 mg/l to meet water quality of the point. This study shows that it is possible to carry out more precise modeling considering both water movement and water kinetics by using EFDC and WASP simultaneously.

• Journal of Environmental Science International
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• v.23 no.6
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• pp.1183-1197
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• 2014

Doam Bay is an estuary where harmful algal blooms (HABs) such as red tides develop frequently in summer. The bay also is influenced by freshwater inflow from Tamjin River in upper regions as well as from an artificial lake in lower regions. Phytoplankton size and species composition were investigated at six stations located in the lower regions in April, June and July, 2007. Physical properties (temperature, salinity and SS) were intensively measured for 3 days (5 occasions) after the freshwater discharges from the dike. The freshwater discharge affected temperature, salinity and turbidity in the study sites adjacent to the freshwater lake. Phytoplankton biomass was larger in April than June and it increased more in July. An explicit shift of species composition was observed. Diatoms were dominant in April and June (>70%) whereas their abundances greatly decreased and chlorophytes increased in July. Pseudo-nitzschia sp. was dominant at all stations (except St. 2) and this change was also detected in ecological indices such as diversity and dominance index.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.71-78
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• 2012

Rainfall infiltration test under one dimensional condition is conducted to evaluate the effect of rainfall intensity on seepage velocity and infiltration characteristics for initial unsaturated sediment. Experimental results are compared with those numerical simulations with respect to variations of pore water pressure, degree of saturation and discharge velocity with time, and both results give good agreement. High rainfall intensity tends to increase seepage velocity almost linearly. But it shows rapid increase as rainfall intensity approaches saturated hydraulic conductivity of the sediment. In addition, the upper part of wetting front depth is partially saturated, not fully. Therefore, actual wetting front depth is considered to advance faster than theoretical prediction, which leads to slope instability of unsaturated slope due to surface rainfall.

• Journal of the Korean earth science society
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• v.26 no.7
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• pp.714-724
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• 2005

The East Sea, a semi-enclosed marginal sea with shallow straits in the northwest Pacific, is marked by the nearly geographic isolation and the low sea surface salinity during the last glacial maximum (LGM). The East Sea might have the only connection to the open ocean through the Korea Strait with a sill depth of 130 m, allowing the paleo-Tsushima Water to enter the sea during the LGM. The low paleosalinity associated with abnormally light $\delta^{18}O$ values of planktonic foraminifera is interpreted to have resulted from river discharge and precipitation. Nevertheless, two LGM features in the East Sea are disputable. This study attempts to estimate volume transport of the paleo-Tsushima Water via the Korea Strait and further examines its effect on the low sea surface salinity (SSS) during the lowest sea level of the LGM. The East Sea was not completely isolated, but partially linked to the northern East China Sea through the Korea Strait during the LGM. The volume transport of the paleo-Tsushima Water during the LGM is calculated approximately$(0.5\~2.1)\times10^{12}m^3/yr$ on the basis of the selected seismic reflection profiles along with bathymetry and current data. The annual influx of the paleo-Tsushima Water is low, compared to the 100 m-thick surface water volume $(about\;79.75\times10^{12}m^3)$ in the East Sea. The paleo-Tsushima Water influx might have changed the surface water properties within a geologically short time, potentially decreasing sea surface salinity. However, the effect of volume transport on the low sea surface salinity essentially depends on freshwater amounts within the paleo-Tsushima Water and excessive evaporation during the glacial lowstands of sea level. Even though the paleo-Tsushima Water is assumed to have been entirely freshwater at that time period, it would annually reduce only about 1‰ of salinity in the surface water of the East Sea. Thus, the paleo-Tsushima Water influx itself might not be large enough to significantly reduce the paleosalinity of about 100 m-thick surface layer during the LGM. This further suggests contribution of additional river discharges from nearby fluvial systems (e.g. the Amur River) to freshen the surface water.

• Spatial Information Research
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• v.21 no.5
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• pp.15-22
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• 2013

The purpose of this work is to investigate correlation between $CO_2$ concentration and NDVI (Normalized Difference Vegetation Index) in North East Asia. Geographically weighted regression techniques were used to evaluate the spatial relationships between GOSAT (Greenhouse Observing SATellite) $CO_2$ measurement and MODIS (Moderate Resolution Imaging Spectroradiometer) vegetation index. The results reveals that $CO_2$ concentration to be negatively associated with NDVI. The analysis of Global Morans' I index and Anselin Local Morasn's I showed spatial autocorrelation between the overall spatial pattern of $CO_2$ and NDVI. Ultimately, there were clustered patterns in both data sets. The results show that carbon dioxide concentration shows non-random distribution patterns in relation to NDVI clusters, which proves that intense development activities such as deforestation are influencing carbon dioxide emission across the area of analysis. However, as the concentration of carbon dioxide varies depending on a variety of factors such as artificial sources, plant respiration, and the absorption and discharge of the ocean, follow-up studies are required to evaluate the correlations among more related variables.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.1
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• pp.1-13
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• 2016

Physiological response of fish and bivalve was estimated to identify the physiological changes of test species by lowering water temperature due to the abrupt stop of cooling water discharge from power plant. The experiment was conducted by two conditions; fall and winter by decreasing water temperature ($2^{\circ}C$/2 days) from $26^{\circ}C$ to $17^{\circ}C$ for fall scenario and from $15^{\circ}C$ to $9^{\circ}C$ for winter scenario, respectively. Test organisms were parrot fish (Oplegnathus fasciantus) and bivalve (Gomphina melanaegis), and end points were mortality for both species, hematocrit and cortisol for fish, and hemolymph and superoxide dismutase(SOD) for bivalve. 48/96hr mortality test revealed no mortality for fish and 47% mortality for bivalve at 96hr/$26^{\circ}C$ only. Significant increases of hematocrit and cortisol were found at fishes exposed to $26^{\circ}C$ (high temperature) and lower temperature ($9{\sim}13^{\circ}C$), respectively. Hemolymph and SOD for bivalve tended to decrease by lowering water temperature from 15 to $9^{\circ}C$ (winter scenario) and no changes from 26 to $17^{\circ}C$ (fall scenario). Fall scenario (from 15 to $9^{\circ}C$) showed more significant changes of physiological response than winter cases (26 to $17^{\circ}C$).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.2
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• pp.129-135
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• 2003

Species composition and seasonal variations in abundance of fishes in the Nakdong River estuary were investigated using an otter trawl seasonally from September 2001 to July 2002. These data were compared with those obtained before the construction of the estuary barrage in 1987. A total of 3,648 fishes that comprised 30 species in 21 families were collected. Acanthogobius flavimanus and Leiognathus nuchalis predominated, and they were responsible for $71.2\%\;and\;67.8\%$ in the number of individuals and biomass, respectively. The next abundant fish species were Platycephalus indicus and Liparis tanakai. Compared with data obtained before the construction of the estuary barrage in 1987, abundances of Acanthogobius flavimanus, Platycephajus indicus, Liparis tanakai, Tridentiger trigonocephalus and Lateolabrax japonicus increased, while those of Pholis fangi, Repomucenus valenciennei, Sardineila zunasi and Scomber japonicus decreased. These results seems to be related to change of sediment environment caused by irregular discharge of freshwater with variation of sea water movement in the Nakdong River estuary.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.1
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• pp.35-44
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• 2000

The winter case of the near-field dilution at the Masan outfalls has been studied by field measurements and CORMIX model simulations. Dilution rates of the wastewater discharge in winter were obtained by a salinity deficit method using the field data observed in the neap tidal period of February, 1999. The observed dilution rates in winter season were found to be very high in the range of 90～130 due to the isopycnal mixing of ambient density compared with the summer range of 30～40 under weak neap tidal currents. The results of CORMIX model simulations also show that the winter dilution rates under a weak ambient current(Ua=6.0ms/s) were increased by 3-fold of the summer dilution rates. However, the difference between two seasons becomes small by 30% under a strong current(Ua=15.5cm/s). This result indicates that the dilution and hydrodynamic mixing process of the effluents are more influenced by ambient crossflow condition than by ambient density stratification at the outfalls site.

• Journal of Navigation and Port Research
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• v.41 no.4
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• pp.243-250
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• 2017

Seaports are not longer considered to be single entities for which the main activity is to load and discharge cargo, but rather as fundamental hubs within a complex supply chain serving global production networks. From a public perspective, they hold a key role in terms of their economic impact at the local, regional and national level by generating value added activity and employment. This issue is becoming increasingly pivotal for ports and their stakeholders. The objective of the study is to estimate a regression model of the value added activity and employment figures of 17 Italian ports for which there are no publications available. Concerning port system reform in Italy, the research intends to provide policy makers with a tool to measure the effects produced by ports and their importance to local communities and regions. The paper finds that in all Italian ports, the direct effects are larger than the indirect effects, and the bigger socio-economic effects are found in the biggest ports.

• Spatial Information Research
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• v.20 no.5
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• pp.1-13
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• 2012

This study intends to evaluate the seasonal flow direction of carbon dioxide in Northeast Asia by using GOSAT, the first Greenhouse Observing SATellite, in an attempt to overcome costly, laborious and time consuming ground observation which has been frequently pointed out in existing studies. For this purpose, missing values were supplemented by applying the Kriging interpolation and the overall flow direction of carbon dioxide was determined through anisotoropy semi-variogram. As a result, it was found that the overall spatial distribution of carbon dioxide in Northeast Asia varies depending on the latitude, and that carbon dioxide mainly flows southeast or east in spring, autumn and winter, but northeast or north in summer. Similar to the flow of monsoons in Northeast Asia, these results show that carbon dioxide flows mainly from the west to the east, which proves that carbon dioxide discharged from China is influencing even the Korean Peninsula and Japan. However, as the flow of carbon dioxide varies depending on a variety of factors such as artificial sources, plant respiration, and the absorption and discharge of the ocean, follow-up studies are requested to evaluate such variables and the correlations.