• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.2
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• pp.95-100
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• 2012

This study was determined to analysis marine environmental and phytoplankton monitoring in Wando coastal waters in August during the period of 2009-2010 and provided the basic environmental data against Southwest Sea of Korea. In August, 2009, the distribution of water temperature and salinity showed an unique characteristics for all of stations, which was associated with a long duration of rainfall after July, 2009 and a lack of sunshine. In the lower of August, 2010, the stratification of water temperature and salinity was shown, which was caused by an intensive sunshine after the middle of August, 2010. Gangjin Bay and Gogeundo waters showed a highly different water temperature and transparency. It is thought that two regions have a distinct water mass and characteristics. In dissolved oxygen and oxygen saturation were higher according to higher water depth regardless of stations. In August, 2009, different dominant species occurred that Gangjin Bay showed a higher cell density of diatom, but Gonyaulax polygramma played an important role in dominant species in Gogeundo waters. It is associated with the introduction red tide water of G. polygramma occurring to southern coastal water in August, 2009. In August, 2010, diatom was extremely higher cell density compared with that of dinoflagellate that regarded as adaptive microrganism against higher quantity of suspended solid in Wando waters. Although Wando has a record of Cochlodinium red tide, this species may be difficult to grow and persist. Dominant species, diatom, play an important role in food organism for shellfish and forming a ecological lineage.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1219-1230
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• 2008

Stream inflows induced by flood runoffs have a higher density than the ambient reservoir water because of a lower water temperature and elevated suspended sediment(SS) concentration. As the propagation of density currents that formed by density difference between inflow and ambient water affects reservoir water quality and ecosystem, an understanding of reservoir density current is essential for an optimization of filed monitoring, analysis and forecast of SS and nutrient transport, and their proper management and control. This study was aimed to quantify the characteristics of inflow density current including plunge depth($d_p$) and distance($X_p$), separation depth($d_s$), interflow thickness($h_i$), arrival time to dam($t_a$), reduction ratio(${\beta}$) of SS contained stream inflow for different flood magnitude in Daecheong Reservoir with a validated two-dimensional(2D) numerical model. 10 different flood scenarios corresponding to inflow densimetric Froude number($Fr_i$) range from 0.920 to 9.205 were set up based on the hydrograph obtained from June 13 to July 3, 2004. A fully developed stratification condition was assumed as an initial water temperature profile. Higher $Fr_i$(inertia-to-buoyancy ratio) resulted in a greater $d_p,\;X_p,\;d_s,\;h_i$, and faster propagation of interflow, while the effect of reservoir geometry on these characteristics was significant. The Hebbert equation that estimates $d_p$ assuming steady-state flow condition with triangular cross section substantially over-estimated the $d_p$ because it does not consider the spatial variation of reservoir geometry and water surface changes during flood events. The ${\beta}$ values between inflow and dam sites were decreased as $Fr_i$ increased, but reversed after $Fr_i$>9.0 because of turbulent mixing effect. The results provides a practical and effective prediction measures for reservoir operators to first capture the behavior of turbidity inflow.

• Journal of Korea Water Resources Association
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• v.46 no.12
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• pp.1181-1191
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• 2013

This study have implemented finding the optimal water temperature parameter set for Hapcheon dam reservoir using CE-QUAL-W2 model. In particular the sensitivity analysis was carried out for four water temperature parameters of wind sheltering coefficient (WSC), radiation heat coefficient (BETA), light extinction coefficient (EXH2O), heat exchange coefficient at the channel bed (CBHE). Firstly, WSC, BETA, EXH2O shows relatively high sensitivity in common during April to September, and CBHE does during August to November. Secondly, as a result of identifying depth range of parameter influence, BETA and EXH2O show 0~9 m and 8~14 m which is thermocline layer close to water surface, CBHE is deep layer 12 m away from bottom. Finally, applying annual or monthly optimal parameter sets indicates that the bias between two sets does not show much differences for WSC and CBHE parameters, but BETA and EXH2O parameters show $0.20^{\circ}C$ and $0.51^{\circ}C$ of monthly average biases for two parameter sets. In particular the bias reveals to be $0.4^{\circ}C$ and $1.09^{\circ}C$ during May and August that confirms the necessity of use of monthly parameters during that season. It is claimed that the current operational custom use of annual parameters in calibration of reservoir water quality model requires the improvement of using monthly parameters.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.11
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• pp.613-625
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• 2017

For two agricultural reservoirs that are rented for fishing spots, benthic nutrient fluxes experiment were performed two times with two sediments from fishing-effective zone and one sediment from fishing-ineffective zone using laboratory core incubation in oxic and anoxic conditions. During benthic nutrient fluxes experiment, the changes in DO, EC, pH, and ORP in the supernatant were not significantly different between fishing-effective zone and fishing-ineffective zone, and were similar to the sediment-hypolimnetic diffused boundary layer in agricultural reservoir. Except for $NO_3{^-}-N$, more benthic nutrient fluxes of $NH_4{^+}-N$, T-P, and $PO{_4}^{3-}-P$ from sediment to hypolimnetic was measured in anoxic than in oxic conditions (p<0.05). As the DO concentration in hypolimnetic decreases, the microorganism-mediated ammonification is promoted, the nitrification is suppressed, and finally the $NH_4{^+}-N$ diffuses out from sediment to hypolimnetic. Also, the diffusion of T-P and $PO{_4}^{3-}-P$ from sediments to hypolimnetic is accelerated through the dissociation of the phosphorus bound to both organic matters and metal hydroxides. The difference in the benthic nutrient diffusive fluxes between fishing-effective zone and fishing-ineffective zone was not statistically significant (p>0.05). Therefore, it was found that fishing activities did not increase the benthic nutrient diffusive fluxes to a statistically significant level. Due to the short fishing activities of 10 years and the rate-limited diffusion of the laboratory core incubation, the contribution of fishing activities on sediment pollution is estimated to be low. No significant correlation was found between the total amount of nutrients in sediment and the benthic nutrient diffusive fluxes in both aerobic and anaerobic conditions. Therefore, nutrients input from various nonpoint sources of watersheds are considered to be a more dominant factor rather than fishing activities in water quality deterioration, and both aeration and water circulation in hypolimnetic were required to suppress the anoxic environment in agricultural reservoirs.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.3
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• pp.442-450
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• 1997

The chemical properties of water masses were investigated at 33 stations of the southeastern last Sea in February, 1995 on board R/V Tam-Yang. The water masses were not clearly distinguished due to the vortical mixing in winter. However, on the basis of the T-S and $T-O_2$ diagrams, water masses in the study area were divided into five groups (Type I, Type II, Type III, Type IV, Type V). (1) $>9.0^{\circ}C,\;>34.35\;psu,\;5.08\~5.60m\ell/\ell$ at Type I, (2) $6.0\~9.0^{\circ}C,\;34.15\~34.35\;psu,\;5.60\~5.90\;m\ell/\ell$ at Type II, (3) $4.0\~6.0^{\circ}C,\;34.00\~34.15\;psu,\;>5.90m\ell/\ell$ at Type III, (4) $1.5\~4.0^{\circ}C,\;34.00\~34.05\;psu,\;5.40\~5.90\;m\ell/\ell$ at Type IV, (5) $<1.5^{\circ}C,\;34.05\~34.07\;psu,\;4.80\~5.40\;m\ell/\ell$ at Type V. In the vertical profiles of nutrients, the concentrations were very low in the surface layer and increased rapidly with depth. The highest concentrations occurred in Type IV, while the concentrations in Type I were the lowest. The N/P ratios were less than Redfield ratio, indicating that nitrogenous nutrients were the limiting factor tor phytoplankton growth. The concentrations of POC and PON were in the range of $0.49\~20.03\;{\mu}g-at/\ell\;and\;0.09\~5.34\;{\mu}g-at/\ell$, respectively. The relatively high concentration occured in the surface layer of inner shore, showing that the concentration at each water mass followed the order Type I > Type II > Type III > Type IV > Type V, respectively. The C:N ratio in particulate organic matter was lower than the values reported in other region due to relatively high concentrations of PON in the study area. Relatively high ratios of POC to chlorophyll $\alpha$ during the study periods indicate that non-living detritus comparised most of the POC in the study area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.203-213
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• 1991

Zooplankton samples were collected vertically from different layers with a closing net at 14 stations in the middle East Sea of Korea in February, August and September to study distribution of biological indicators for analysis of water masses. Horizontal and vertical distributions of important species of copepods and chaetognathas known as indicator species were closely related to distributions of different water masses and oceanic fronts. Pleuromamma gracilis, Calanus tenuicornis, Sagitta enflata and Sagitta minima were found to be reliable indicator species to determine warm water mass with warm core, and Calanus cristatus, Calanus tonsus and Sagitta elegans could be used as cold water species for evaluating the movement of cold current from North Korea, and Gaetanus armiger was deep sea water species. Therefore, it was found that North Korean Cold Current down to the south along the coast appeared to be significant in the surface around Chumunjin area, and from here towards the south the cold water containing S. elegans submerged under warm water with S. enflata which were about $2{\~}4^{\circ}C$ higher than that of the vicinity and reappeared near Chukpeon area in surface layer. In the layer between loom and 300m depths, distribution of Pleuromamma gracilis and Sagitta bedoti indicated that warm water mass and front zone influenced by the different water systems were formed in northwestern area off Ulreung-do. In $300{\~}500m$ layer, the proper cold water could be estimated to be present in the northwestern area off Ulreung-do throughout the survey period by the high abundance of Gaetanus armiger. In August, distributions of S. bedoti, S. enflata and S. minima were valuable index to find oceanic fronts and warm core.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.177-184
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• 1991

We have investigated geographical distribution and physico-chemical properties of water masses or water types at mid-bottom depth in the neighbouring sea of Cheju Island in August 1986. In 50m layer the Yellow Sea Bottom Cold Water(YSBCW) below $12^{\circ}C$ was observed in the northwestern area of Cheju Island, while the Tsushima Warm Water(TWW) with relatively high temperature$(>16^{\circ}C)$ and salinity more than 34.0 in its southeastern area extended as far as the coast of about 15km. Also, 50m layer at the outside stations of its southwestern area indicated relatively cold water temperature$(11-30^{\circ}C)$, probably due to southward transport of the Yellow Sea Bottom Cold Water(YSBCW . The Yellow Sea Warm Water(YSWW), the mixed water of the YSBCW and the TWW, ranged $13^{\circ}C$ to $16^{\circ}C$ in water temperature and was appeared mainly in the coastal and intermediate area of Cheju Island. And the relatively cold water in the southwestern area and the Tsushima Warm Water were more extensively distributed in 50m layer than the deeper layer. Horizontal distributions of nitrate and phosphate showed a pattern similar to that of water temperature. As it were, the Yellow Sea Bottom Cold Water had the highest concentration of nutrients, while southwestern outside stations had the lowest nutrient contents. Especially, the concentration of nitrate in the latter was remarkably low compared with the value at the other stations. It may be attributed to intensive vertical mixing by collision of the northward driven Tn with the southward driven YSBCW. Also, it was particular that the Tsushima Warm Water indicated relatively high silicate content corresponding to that of the Yellow Sea Bottom Cold Water. Based on the data of $\Delta Si/\Delta P$ ratio, it seems that the mid-bottom waters in this study area are younger than the surface or intermediate water in the Korean East Sea.

• Journal of Radiation Protection and Research
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• v.40 no.4
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• pp.223-230
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• 2015

The objective of this study is to identify the radionuclide distribution in public water by carrying out the analysis of artificial radionuclides($^{134}Cs$, $^{137}Cs$, $^{239+240}Pu$), natural radionuclide($^{210}Pb$) and TOC in the lake Euiam sediment in Chuncheon, South Korea. The $^{134}Cs$ concentration in all lake sediments showed below MDA values, and the $^{137}Cs$ concentration in lake sediment were ranged from MDA to $8.79Bq{\cdot}kg^{-1}-dry$. The $^{137}Cs$ concentrations in surface sediment were reported to be 2.4 to $4.2Bq{\cdot}kg^{-1}-dry$. The lowest concentration of $^{137}Cs$ was reported at St. 4 and the highest concentration was reported at St. 3, respectively. The $^{239+240}Pu$ concentration in lake sediment were ranged from 0.049 to $0.47Bq{\cdot}kg^{-1}-dry$. The lowest concentration was reported at St. 2 and the highest concentration was reported at St. 3. The correlation(r) between the $^{239+240}Pu$ concentration and $^{137}Cs$ concentration in lake sediment presented higher values (0.54 to 0.97) and this suggests the behavior and origin of $^{137}Cs$ is identical to the $^{239+240}Pu$ in the sediment. The $^{134}Cs$ concentration below MDA value and the $^{239+240}Pu/^{137}Cs$ ratio(mean value of 0.041) indicated that the artificial radionuclides in the sediment were originated from global fallout by the atmospheric testing of nuclear weapons conducted by former USSR and U.S.A, but not from the Fukushima Daiichi NPP accident. The sedimentation rate derived from $^{210}Pb$ age-dating method at St. 2 is calculated to be $0.31{\pm}0.06cm{\cdot}y^{-1}$. This value is similar to the value ($0.41{\pm}0.05cm{\cdot}y^{-1}$) estimated from the $^{137}Cs$ maximum peak produced from early 1960's. The content of TOC in lake Euiam sediments varied from 0.20 to 13.01%. While the highest correlation between TOC and $^{137}Cs$ concentration in the sediment were found at St. 1, the others presented the low correlation.

• The Korean Journal of Malacology
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• v.20 no.2
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• pp.125-130
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• 2004

Arkshell, Scapharca broughtonii spats were placed in natural environmental condition for 30 days from July 28 to August 27, 2004, in order to estabilish intermediate culture technique. Growth and survival of the spats in different intermediate culture areas with various culture methods were measured. Water temperature of studied area ranged from 24.1 to 28.5$^{\circ}C$, salinity was 15.4 to 33.3 psu, dissolved oxygen was 3.92 to 12.6 mg/l. Scapharca broughtonii spats cultured in Yeosu developed the best, 10.15 ${\pm}$ 1.12 mm in average shell length, and the highest survival was recorded as 77% in Namhae. Shell lengths of the Scapharca broughtonii spats cultured in the water depths of 2, 5, and 10 m were 7.14 ${\pm}$ 1.14 mm, 6.98 ${\pm}$ 1.74 mm and 6.27 ${\pm}$ 1.33 mm, and the survivals showed 75.5%, 77.0% and 76.5%, respectively. When 1 mm, 2 mm, and 3 mm-sized spats were cultured for 30 days in water depth of 5 m, the shell length increased to 6.73 ${\pm}$ 1.46 mm, 6.98 ${\pm}$ 1.74 mm and 7.04 ${\pm}$ 1.19 mm, and survivals were 67.0%, 77.0% and 58.5%, respectively. The shell lengths of spat cultured for 30 days in mesh sizes of 1 ${\times}$ 1 mm, 2 ${\times}$ 2 mm and 3 ${\times}$ 3 mm, 5 m below the surface were 8.14 ${\pm}$1.23 mm, 8.26 ${\pm}$ 1.19 mm and 8.78 ${\pm}$ 1.16 mm, and survivals were 41.5%, 43.0% and 44.5%, respectively.

• Journal of the Korean association of regional geographers
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• v.4 no.2
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• pp.49-64
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• 1998

Bing-gye valley(Kyongbuk Province, South Korea) is well known as a tourist attraction because of its meteorologic characteristics that show subzero temperature during midsummer. Also, there are some interesting geomorphic features in the valley area. Therefore, the valley is worth researching in geomorphology field. The aim of this paper is to achieve two purposes. These are to clarify geomorphic features on talus within Bing-gye valley area, and to infer the origin of Bing-gye valley. The main results are summarized as follows. 1) The formation of Bing-gye valley It would be possible to infer the following two ideas regarding the formation of Bing-gye valley. One is that the valley was formed by differential erosion of stream along fault line, and the other is that the rate of upheaval comparatively exceeded the rate of stream erosion. Especially, the latter may be associated with the fact that the width of the valley is much narrow. Judging that the fact the width of the valley is much narrow, compared with one of its upper or lower valley, it is inferred that Bing-gye valley is transverse valley. 2) The geomorphic features of talus (1) Pattern It seems to be true that the removal of matrix(finer materials) by the running water beneath the surface can result in partly collapse hollows. Taluses are tongue-shaped or cone-shaped in appearance. They are $120{\sim}200m$ in length, $30{\sim}40m$ in maximum width. and $32{\sim}33^{\circ}$ in mean slope gradient. The component blocks are mostly homogeneous in size and shape(angular), which reflect highly jointed free face produced by frost action under periglacial environment. (2) Origin On the basis of previous studies, the type of the talus is classified into rock fall talus. When considered in conjunction with the degrees of both weathering of blocks and hardness of blocks, it can be explained that the talus was formed under periglacial environment in pleistocene time. (3) The inner structure of block accumulation I recognize a three-layered structure in the talus as follows: (a) superficial layer; debris with openwork texture at the surface, 1.3m thick. (b) intermediate layer: small debris(about 5cm in diameter) with fine matrix(including humic soil), 70cm thick. (c) basal layer: over 2m beneath surface, almost pure soil horizon without debris (4) The stage of landform development Most of the blocks are now covered with lichen, and/or a mantle of weathering. It is believed that downslope movement by talus creep well explains the formation of concave slope of the talus. There is no evidence of present motion in the deposit. Judging from above-mentioned facts, the talus of this study area appears to be inactive and fossil landform.