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Ra K.,Marine Environments and Conservation Research Division | Kim J.-K.,Marine Environments and Conservation Research Division | Hong S.H.,South Sea Research Institute | Hong S.H.,Korean University of Science and Technology | And 10 more authors.
Ocean Science Journal | Year: 2014

Heavy metal concentrations in the surface sediments of specially managed Ulsan Bay were investigated to determine metal distribution, pollution status and its ecological risk using pollution indices (enrichment factor and geo-accumulation index), potential ecological risk index and sediment quality guidelines (SQGs). The order of mean concentration (mg/kg) of metals was Zn (361.9) > Cu (95.6) > Pb (90.7) > Cr (64.7) > Ni (32.2) > Co (16.6) > As (15.8) > Cd (0.40) > Hg (0.16) in sediments of Ulsan Bay. Spatial distribution of metals in sediments showed a significantly higher concentration near industrial complexes, indicating that metal pollution is caused by anthropogenic sources. The results of enrichment factor (EF) and geo-accumulation index (Igeo) showed that sediments were significantly accumulated with Cu, Zn, As, Cd, Pb and Hg, indicating moderate to very severe enrichment (pollution) by these metals. Based on the potential ecological risk index, Hg and Cd posed a very high and a considerable potential ecological risk. Cu and As posed a moderate potential ecological risk, while, other metals (Cr, Co, Ni, Zn and Pb) rarely posed any potential ecological risk to the coastal environments. The sediments in Ulsan Bay showed a very high level of ecological risk, dominated by Hg and Cd. Metal concentrations in sediments were 80% for Cu, 96.7% for Zn, 50% for As, 70% for Pb and 50% for Hg above the threshold effects level (TEL), respectively. © KSO, KIOST and Springer 2014.

Kang S.K.,Ocean Circulation and Climate Research Division | Jung K.T.,Marine Environments and Conservation Research Division | Yum K.-D.,Ocean energy | Lee K.-S.,Ocean energy | And 2 more authors.
Ocean Science Journal | Year: 2012

Uldolmok waterway, located between an island off the southwestern tip of Korean peninsula and mainland, is famous for its strong tidal current that has a maximum current of about 6. 0m/s. A series of field observations along with numerical modeling have been carried out in order to understand the tidal dynamics in terms of the force balance along the whole waterway and the energy balance in the narrowest part of the waterway. First, analysis of the ADCP current and the tide level variation data reveals that the tidal dynamics along the total waterway (channel) is balanced dominantly between the pressure gradient and linear bottom frictional forces, with the phase lag of sea level difference for the semi-diurnal constituents leading the current phase about by 10°. Secondly, the result of the numerical modeling reveals that the tidal energy flux vector flows toward the narrowest section, indicating that there should be related nonlinear processes. Through the numerical model experiment with multi-components, the convergence of (M2 + S2) tidal energy flux of 6. 68 × 107 Joule/s in the narrow area of the Uldolmok waterway is explained mainly by the energy consumption of 73% through the nonlinear generation of shallow water components and by the bottom frictional energy dissipation of 27%. This reveals that the remarkably strong nonlinear process dominates in the narrowest section of the Uldolmok waterway, compared with other areas, such as Yellow and East China Seas where the total M2 energy flux through the open boundary is balanced in terms of the bottom dissipation (Kang et al. 2003; Choi 1980). © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Kang J.,Marine Environments and Conservation Research Division | Choi M.-S.,Chungnam National University | Jeong K.-S.,Marine Environments and Conservation Research Division | Lee C.-B.,Seoul National University
Ocean Science Journal | Year: 2014

Total dissolvable metals (Co, Ni, Cu, Cd, and Pb) in both surface waters and the water columns were acquired in the southern East/Japan Sea during a cruise around the Ulleung Basin in June 2001 to understand the spatial distributions of the metals. Concentrations in offshore surface waters were found to be Co 60 ± 12 pM, Ni 2.16 ± 0.25 nM, Cu 1.85 ± 0.55 nM, Cd 0.134 ± 0.018 nM, and Pb 155 ± 40 pM. Spatial distributions in surface waters showed that metal levels were generally enhanced at coastal sites in both Korea and Japan, where the metal distributions indicated complex patterns due to inputs, biogeochemical processes, and physical factors including upwelling. The Co distributions in the water columns seemed to be influenced predominantly by surface and bottom inputs, scavenged rather than regenerated at depth. For Cd, there was generally good agreement between the Cd and PO4 depth distributions, in agreement with the literature. The Cd/PO4 ratio from the water columns was found to be 0.133-0.203, lower than that in other marginal seas (e.g. the East/South China Seas and the Philippine Sea) of the western Pacific Ocean; this might be a result of the fast ventilation rate in this sea. The vertical Pb profile showed typical scavenged-type behavior with a surface maximum and deep minimum. From a comparison of inputs from the atmosphere and the Tsushima Warm Current, atmospheric deposition is substantial enough that it cannot be ignored, and its role in metal cycling is more significant in the offshore zone. © 2014 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Lee H.J.,Marine Environments and Conservation Research Division
Ocean Science Journal | Year: 2014

Sediment dynamical processes began to be systematically monitored in the west coast of Korea facing the eastern Yellow Sea in the 1990s. The early investigations were largely conducted aboard vessels that provided results where the resolution was highly restricted in both temporal and spatial aspects. However, full-fledged autonomous instruments introduced early in the 2000s allowed for a quantum leap in the level of this sub-field of sedimentology. The investigated sites include various environments such as estuaries, bays, tidal flats, beaches, and offshore deposits. Among them, a total of seven sites were selected for the review: Han estuary, Daeho tidal flats, Garolim Bay, Saemangeum Region, Byunsan Beach, Gomso Bay, and Huksan Mud Belt. The major results from each site were briefly summarized. The summary clearly demonstrates that wind-generated currents and waves particularly during winter should be carefully considered in interpreting sedimentary environments. This is because winter-season processes interrupt or actively displace much of the sediments worked by tidal currents in the remaining seasons. The summary hence suggests that seasonal investigations of sediment dynamics are necessary to understand shallow-water sedimentation in the west coast of Korea that is governed complicatedly by two major forcing agents: waves and tidal currents. © 2014 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Suh Y.J.,Marine Environments and Conservation Research Division | Suh Y.J.,University of Cincinnati | Hyun S.,Marine Environments and Conservation Research Division | Park C.,Office of the Vice President for Research
Ocean Science Journal | Year: 2013

Two piston cores (DD09-ST21, DD09-ST39B) from the northeastern Ulleung Basin in the East Sea were obtained to investigate variations in the biogenic components (calcium carbonate, organic carbon) and biogeochemical processes (δ13C and δ15N). The two cores had distinctive characteristics in terms of surface production, preservation and dissolution capacity of carbonate, and redox conditions of bottom-water. Core DD09-ST21 was characterized by an oxygen-depleted condition from 15 ka (MIS 2) to 60 ka (MIS 3). Core DD09-ST39B, on the other hand, showed oxic bottom-water conditions, possibly due to shallow water depth. These two cores with different redox condition showed opposite trends in terms of CaCO3, TOC, and C37 alkenone concentrations. CaCO3 and C37 concentrations were higher during the LGM in DD09-ST21 while lower contents were observed in DD09-ST39B in the same period. Moreover, consistently low TOC in DD09-ST39B and higher fluctuation of organic matters in DD09-ST21 may suggest difference in primary productivity, preservation capacity, or a potential dissolution effect. During the Holocene, the surface productivity of both cores increased, probably due to renewed ventilation and vertical mixing in the East Sea. Therefore, this study suggests spatial variation in production and preservation of biogenic components in the two cores since last 50 ka for DD09-ST39B and 80 ka for DD09-ST21 due to difference in environmental conditions such as water depth, bottom-water conditions, surface productivity and preservation. © 2013 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Lee H.J.,Marine Environments and Conservation Research Division | Lee S.H.,Marine Environments and Conservation Research Division
Ocean Science Journal | Year: 2012

The Saemangeum Dyke is located in an estuarine setting, regulated in a complicated manner by a macrotidal regime, rivers, and winter monsoon. Accordingly, the constructed dyke resulted in a variety of artificial changes in geological characteristics in the estuary and its vicinity. To investigate those dyke-induced changes, the KORDI (Korea Ocean Research and Development Institute) performed sedimentological and sediment-dynamical observations from 2002 to 2010. On the basis of the KORDI results, the major geological changes and associated dynamical processes are reviewed. Five phenomena, among others, are focused on: depositional-channel creation; gap-related erosion; forced movements of surface sands; tidal-flat growth inside the dyke; and blanketing of mud over the sandy seafloor. These phenomena were unforeseen before the dyke construction, and reflect that the dyke could cause both erosion and deposition on an estuarine scale. The investigations conclude that the sediments in the dyke-influenced region were derived from the two rivers, Mangyeong and Dongjin, of the estuary. This is completely contrary to the offshore origin proposed before the dyke construction. As a result, the review supports the proposal that a thorough geological investigation and rational forecast is necessary prior to dyke construction to avoid economic loss and a fractious environmental debate. © 2012 Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Cho H.Y.,Marine Environments and Conservation Research Division | Oh J.H.,Seoul National University | Kim K.O.,Marine Environments and Conservation Research Division | Shim J.S.,Korea Advanced Institute of Science and Technology
Journal of Coastal Research | Year: 2013

Outlier detection and missing data filling (imputation) processes are essential first step in the statistical analysis of coastal monitoring data. Here, we suggest methods for completing these key processes. An outlier detection method that uses approximate and detailed components is suggested. The decomposition of the time-series data is performed by harmonic analysis. Next, the modified z-score method is applied to the residuals (detailed component) to detect outliers. After removing the outliers in the residuals, the filling process for the missing and removed outlier data is conducted by summing the random and the approximate components. Among the environmental monitoring data, this method is applied to the coastal water temperature data. We used hourly interval coastal water temperature data provided by the NFRDI (National Fisheries Research & Development Institute). In these datasets, the dataset of the Yeong-Deok Geomuyeok (36.58 °N, 129.40 °E) station, Korea, is only used for this method application. This dataset contains some outliers and missing data. To test the model performance, this method is applied to a daily interval modeling dataset from the HYCOM (Hybrid Coordinate Ocean Model). This method provides reasonable results for outlier detection and for filling in missing data in coastal water temperature datasets. © Coastal Education & Research Foundation 2013.

Song K.-M.,Marine Environments and Conservation Research Division
Ocean and Polar Research | Year: 2013

The vertical structure of sediment temperatures in the tidal flats of Geunso Bay and Seonyu Island in western Korea were measured for more than a year and analyzed. Mean temperature decreased with depth in spring and summer. On the contrary, it increased with depth in fall and winter, faithfully reflecting the seasonal variation resulting from the heating and cooling of the surface sediment. The surface sediment temperatures are shown to be strongly dependent on solar radiation, M2, and M4 tidal components. They are also weakly affected by precipitation. Thermal diffusivity of sediment is estimated at each depth and in each of the four seasons by applying the amplitude equation method. In Geunso Bay, the estimated seasonal-mean values decreased with depth, while they showed little change in Seonyu Island. Depth-averaged thermal diffusivity in Geunso Bay (1.94 × 10-7 m2/s) was smaller than Seonyu Island (2.20 × 10-7m2/s). The variability of thermal diffusivity is shown to corelate with sediment composition and sorting from the grain-size analysis of intertidal sediments in Geunso Bay and Seonyu-do.

Park J.S.,Marine Environments and Conservation Research Division | Kang K.,National Institute of Meteorological Research | Lee S.,Marine Environments and Conservation Research Division | Lee S.-R.,Pusan National University
Ocean and Polar Research | Year: 2013

A GPS-drifter was newly designed to observe the sea surface skin current and to estimate the direct wind effect on the sea surface. After conducting a test to establish and verify the accuracy of the GPS itself in the laboratory, in-situ experimental campaigns at Saemangeum in Gunsan city and Haeundae in Busan city, Korea, were carried out to ascertain the drifter track and to estimate the velocity data set on Oct. 3, 15, 23, 27 and Nov. 25, 2011. The current meters, RCM9 and ADCP, were moored together to remove the background current field, and the wind data were obtained from several marine stations such as towers and buoys in these areas. The drifter-observed velocity show good agreement with the flow obtained by the HF radar in the Saemangeum area. The direction of the wind-driven current extracted from the drifterobserved velocity was completely deflected to the right, however the degree of the angle was different according to the drift types. The average speed of the wind-driven current matched with 2.19~2.81% of the wind speed and the deflection angle was about 8.0~10.9° without adjustment for the land-sea effect, and about 2.19~2.84% and 4.1~6.0° with the adjustment for the land-sea effect.

Park J.,Pusan National University | Khim B.-K.,Pusan National University | Lee H.J.,Marine Environments and Conservation Research Division | Lee S.R.,Pusan National University
Ocean and Polar Research | Year: 2014

Recently, more attention has been paid to the geomorphological changes in the Nakdong River Estuary, because those changes are caused by artificial activities including weirs, reclamation and construction. In order to analyze quantitatively the recent geomorphological variability in the Nakdong River Estuary, we surveyed the depth and elevation of submarine topography near Jinwoodo and Sinjado from March 2007 to February 2012. A statistical method (based on Digital Shoreline Analysis System) and an Empirical Orthogonal Functions method were used to evaluate the morphological changes. According to the statistical variables (DCE, NDC, EPR, LRR), the highest amount and rate of accumulation were recorded around the Gadeokdo whereas the greatest amount of erosion appeared around the coast off the eastern part of Sinjado. In particular, a dynamic variation of morphology was clearly observed in the vicinity of the sub-tidal channel located between Jinwoodo and Sinjado, which seems to be attributable to channel migration. As a result of the EOF method, the first mode (48.7%) is most closely related to the pattern of morphological variability that might be associated with the westerly movement of sediment by longshore current. The spatial variability of the second mode (16.6%) was high in the shoreface of Sinjado, showing a 4-year periodicity of temporal variability. The strong correlation (coefficient 0.73) between the time coefficient and suspended sediment discharge from Nakdong River emphasizes the role of sediment discharge to deposition in this area. The spatial variability of the third mode (11.3%) was distributed mainly around the coast off the eastern part of Sinjado, which is related to the movement of the coastline of Sinjado. Based on the last 5 year's data, our results suggest that the study area is characterized on the whole by a depositional pattern, but the extent of sedimentation is different locally.

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