• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.163-173
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• 2023

In this study, topographic change analysis was performed on the Nak-dong River estuary area. The factors affecting the changes in the bathymetry of the Nak-dong River estuary were analyzed using data from the discharge, suspended sediments, and rainfall of the Nak-dong River barrier as analysis data. As a result, erosion and sedimentation are judged to appear repeatedly due to complex effects such as discharge of the estuary barrier of the Nak-dong River and invasion of the open sea waves, and it is judged that there is no one-sided tendency. However, as a result of checking the data in the second half of 2020, it was possible to confirm a large amount of erosion, which is different from the past data. It is clear that this is a result beyond the trend of erosion in the first half and sedimentation in the second half. In the summer of 2020, the rainy season lasted for more than a month and torrential rains occurred, which seems to be due to about three times higher rainfall than other periods, and erosion is believed to have occurred as the discharge increased rapidly compared to the time deposited by river water outflow. In addition, compared to other times, the influence of many typhoons in the summer of 2020 is believed to have affected the topographical change at the mouth of the Nak-dong River.

• Journal of Marine Life Science
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• v.1 no.1
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• pp.1-7
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• 2016

In order to assess seasonal and geographical characteristics of pollutant Escherichia coli, we investigated its distribution in Nakdong River mouth and Busan coastal water from February 2013 to November 2015. The coastal area was divided into five different zones (I-V) based on the pollutant level and geographical characteristics. During the study periods, water temperature and salinity varied from 7.50 to 27.64℃ and 16.82 to 34.82 psu, respectively. The annual water temperature variation was characterized in temperate zone. The salinity was significantly (p<0.05) decreased in zone IV and zone III after heavy rain during summer season in 2014, resulting led to elevated E. coli biomass. The highest colony formation of E. coli was recorded at 6,000 cfu l^-1 during autumn at station 1 (zone I). On the other hands, during all seasons of 2015, E. coli abundances were kept to be low level in zone III. The E. coli was not significantly (p>0.05) correlated with water temperature. However, the salinity was significantly (r=-0.53, p<0.05) correlated with the E. coli, implying that salinity plays a crucial role in the proliferation of E. coli. Consequently, E. coli in western Busan coastal water might have been significantly promoted by pollutant sources from Nakdong Rive discharge during the spring and summer rainy seasons depending on annual rainfall variations. On the other hands, E. coli in station 1 (i.e., Suyeong Bay) was obviously high due to influences of discharge water from municipal wastewater treatment plant. However, there was no clear seasonality of E. coli.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.4
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• pp.340-345
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• 1995

Dispersion characteristics of surface discharge heat water in shallow region are investigated for coastal power plant with nearly constant depth of 20 meters by observing the seasonal depthwide temperature in several stations, which give or precise horizontal distribution and vertical structure of heat water. Surface discharged heat water in shallow coast in the Yellow Sea relies mainly on ambient tidal flow. so it behaves as free jet when the ambient now is strong and shows plumelike behavior during stagnant tide. According to observation the neat field region is estimated as 200-300 meters and shows distinct vertical profile and exponentially decreasing pattern from discharge point for this region. But there are no remarkable vertical distortion of temperature beyond 800 meters even though it is discharged from surface. Characteristic length scale model, CORMIX3, is applied and compared with the field date Overall tendency of CORMIX3 results resemble well with field data especially in near field and intermediate region.

• Journal of Navigation and Port Research
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• v.30 no.9
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• pp.755-762
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• 2006

When we consider to develop a new harbor, the most important factor, we think, is the lowest water depth of waterway and approaching channel for safe navigation of vessel. The existing harbors have been being dredged to meet the international trend of jumbo sized vessels by adopting the new design criteria. As the dredged materials over the expected at the design level were common and there are still lack of land based reclamation area, we have no choice to discharge the dredged materials in open sea area In this study, we analysed the behavior of discharged materials at the dumping area of offshore, which were collected from the dredging work at the waterway in Busan New Port. We measured the tidal currents and analyzed the waters of dumping site after the dumping work. These were used to evaluate the numerical models. Suspended Solids(SS) were introduced to the diffusion model. Because of the characteristic of the dumping site, the speed of initial diffusion and settle down of the discharged materials was so fast. Therefore, we believe that the dumped materials do not cause a significant impact to the marine environment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.377-387
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• 2021

Fecal contamination levels of discharge water from inland pollution sources were investigated in Iwon-myeon (Taean-gun), South Korea. Gram-negative bacteria were isolated during the investigation and the antimicrobial resistance patterns of the isolates were examined to estimate their impact on the coastal environment. The ranges of total coliform and fecal coliform of 12 samples from four major inland pollution sources were 79-490,000 MPN/100 mL and 2.0-490,000 MPN/100 mL, respectively, with the highest level of fecal contamination at Station No. 3. A total of 137 strains (14 genus) were isolated, of which 86 strains (62.8%) were Enterobacteriaceae. The identified isolates were as follows: Pseudomonas spp. (35 strains), Klebsiella spp. (20 strains), Serratia spp. (20 strains), and Escherichia spp. (19 strains). The isolated Gram-negative bacteria showed the highest antimicrobial resistance to ampicillin (81.8%), followed by amoxicillin/clavulanic acid (64.2%), ceftiofur (61.3%), and cefoxitin (59.1%). Antimicrobials in which less than 10% of isolates showed antimicrobial resistance were ciprofloxacin (3.6%) and gentamicin (2.2%). Resistance to one or more antimicrobials was observed in 121 strains (88.3%) and 84 strains (61.3%) showed a tendency for multiple antimicrobial resistance.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.348-354
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• 2001

This study was conducted to estimation of change characteristics for water quality by the dyke gate operation in the Keum River estuary. The estimation data made use of surveyed data in Keum River estuary by NERDI (National Fisheries Research and Development Institute) during $1990\~1999$. Shown to compare water quality changes at st. A and st. D in Figure 1, the concentrations of TSS, COD and nutrients at st. A were as high as about $2\~4$ times than those at st. D due to affection of fresh water discharge in the Keum River. The percentages of water quality change at surface water by dyke gate operation in the Keum River estuary were shown that TSS (Total Suspended Solid) was decrease to $56\%,\;47\%$ at st. A and D, and COD (Chemical Oxygen Demand) was increase to $68\%,\;71\%$ at st. A and D, respectively. The changes percentage of DIN (Dissolved Inorganic Nitrogen) by dyke gate operation in the Keum River estuary were increase high to $95\%$ at surface water and $7\sim30\%$ at bottom water, but those of DIP (Dissolved Inorganic Phosphorus) were increase to $2.8\sim8.6\%$ at surface water and $28\%$ at bottom water. The range of fluctuation for water quality at each station by dyke gate operation has shown that salinity and TSS are little better than before dyke gate operation, but COD show highly fluctuation. Also we studied estimation of characteristics of water quality change by the season, COD was increased except the summer, TSS was decreased to all season. DIN was increased to about $61\sim172.1\%$ for all season, but DIP was increased to the spring and decreased to the autumn, DIN enrichment in the estuary by dyke gate operation are interpreted to improvement of organic matter decomposition and nitrification by increasing the residence time and to increase nutrient flux in sediments due to decreasing dissolved oxygen and increasing a deposit matter.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.295-311
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• 1994

A comprehensive in-situ tests are performed to define the hydrogeologic and hydrodispersive characteristics such as hydraulic conductivities, longitudinal dispersivity, and average linear velocities as well as conducting flow-net analysis at the study area. The results show that the study area is very heterogeneous so that hydraulic conductivities range from $6.45{\times}10^{-7}$ to $1.15{\times}10^{-5}m/s$ with average linear velocities of 0.34~0.62m/day. Whole groundwater in upper-most aquifer is discharging into the sea with specific discharge rate of $7.2{\times}10^{-3}$ to $1.3{\times}10^{-2}m/day$. The longitudinal dispersivity of the aquifer is estimated about 4.8m through In-situ injection phase test. The area is highly vulnerable to potential contaminant sources due to it's high value of DRASTIC index ranging from 139 to 155 and also under water table condition with very shallow groundwater level. To delineate contaminant plumes of toxic NaOH and carcinogenic benzene when these substances are assumed to be leaked through existing TSDF at the study area by unexpected accidents or spill, Aquifer Simulation Model (ASM) including Flow and Transport Model is used. Te simulated results reveal that the size of NaOH plume after 5 years continuous leak is about $250{\times}100m$ and benzene after 10 years, $490{\times}100m$. When the groundwater is abstracted about 50 days, which is maximum continuously sustained no-precipitation period during 30 years, with pumping rate of $100m^3/day$, THWELL program shows that the groundwater is adversly affected by sea water intrusion.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.2
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• pp.103-111
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• 2013

In this study, field measurements were conducted in the section about 7 km from sea dike to westward. The observations of along channel current were carried out, and water temperature and salinity were measured simultaneously at 10 stations during one tidal cycle, and sampling interval is 1 hour. The maximum ebb current is about 1.5 m/s at the surface layer but flood current is 0.4 m/s at the bottom layer during discharge period. Residual current during river discharge shows two layer structures which is typical characteristic of the estuary system. On the other hand, residual current during a period with no discharge has shown multi-layer structure different from general estuarine systems. The distribution of high salinity can be seen at the bottom layer as the effect of discharge does not reach down to the bottom layer during discharge. As a result, freshwater is not effected at the bottom layer during observation, and mixing of surface layer to bottom layer is reduced by stratification.

• Journal of Aquaculture
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• v.22 no.1
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• pp.42-50
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• 2009

Shrimp farming which is entirely conducted in outdoor ponds in the west coast of Korea has been suffered from mass mortality due to viral epizootics. Intensive indoor shrimp culture under limited water exchange can solve these problems of outdoor ponds including viral transmission from environment, pollution due to discharge of rearing water, low productivity and limited culture period. In this study, juvenile L. vannamei (B.W. 0.08-0.09 g) was stocked with $3,000-5,455/m^3$ in density in four raceway tanks (two $12.9\;m^2$, two $18\;m^2$ tanks) and cultured for 42 days with 2.7-3.4% of daily water exchange. Results from four tanks showed FCR of 0.79-1.29, survival of 38.2-48.0%, and yields of $2.49-4.22\;kg/m^3$ which is consistent with 12-20 and 8-14 times higher than those of commercial shrimp hatchery and outdoor pond in Korea, respectively. Concentrations of total ammonia nitrogen in all four tanks were 1.11-1.42 ppm in mean level and did not exceed 6.0 ppm (0.096 ppm of $NH_3$) which is still acceptable levels for shrimp growth. During the culture trial, concentration of $NO_2$-N rapidly increased from stocking, resulting in mean concentration of 18.45-22.07 ppm. It also exceeded 10 ppm over four weeks and maintained at 35-45 ppm for four days in all tanks, accounting for low survival of shrimp due to long-term exposure to high concentration of $NO_2$-N. Nevertheless, the results with survival rate over 38% from raceways which experienced the extreme $NO_2$-N levels suggests that under "biofloc system" white shrimp can acclimate to high $NO_2$-N concentration to some degree.

• 한국해양학회지
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• v.21 no.1
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• pp.56-71
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• 1986

In order to clarify the influence of environmental factors on the phytoplankton cmmunity in Kyeonggi Bay, the hydrological and water quality data were obtained from 20cruises from May, 1981, to September, 1982 in this bay. Physical conditions at the mouth of the bay are more stable than those at the head of the bay. Temperatures and salinities of the upper part of the bay show great seasonal fluctuations due to the river discharge. By the extending effects of freshwater, a weak two-layer flow system is formed from the upper part of the bay to Palmi Island. In summer thermal stratification are formed in the middle and outer parts of the bay. In winter, However, the temperature shows no vertical temperature gradient. The inner bay and the vicinity area of Incheon Harbour are relatively polluted and eutrophicated due to both the runoff of freshwater from the Han River and the waste discharge from Incheon industrial complex. However, except the polluted area, the study areas are well oxygenated with more than 90% saturation.