• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.3
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• pp.295-306
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• 2003

Recently efforts are underway to analyze the impacts of anthropogenic $CO_2$ on the global environments and the amount of oceanic uptake increase. The East Sea is now viewed as a miniature ocean because its circulation pattern is similar to the ocean conveyer belt. The biological pump of the East Sea is a vital component to understand the carbon cycle quantitatively. In this paper, the biological pump is estimated utilizing the stoichiometric ratio between carbon and phosphorus. A simple phosphate budget model is constructed based on the seawater and dissolved oxygen box model that can simulate the recent structural change in deep water circulation of the East Sea. A model run from you 1952 to 2040 shows the steadily intensifying biological pump. Currently it exports about 0.016 Pg C yr$^{-1}$ , which corresponds to 35％ of the carbon introduced into the seawater by the air-sea exchange. An increased oxygen supply to the central water mass as a result of from the transition in the ventilation system might enhance the remineralization of sinking biogenic particles. This should strengthen the upward nutrient flux into the surface layer. Consequently, the biological sequestration of anthropogenic carbon is expected to increase with time. The estimated biological uptake of the anthropogenic carbon in the East Sea since the Industrial Revolution is estimated as 0.025 Pg C.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.401-418
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• 2000

1. Production of the artificial zeolite from coal ash Coal fly ash is mainly composed of several oxides including $SiO_2$ and $Al_2O_3$ derived from inorganic compounds remained after burning. As minor components, $Fe_2O_3$ and oxides of Mg, Ca, P, Ti (trace) are also contained in the ash. These components are presented as glass form resulting from fusion in the process of the combustion of coal. In other word, coal ash may refer to a kind of aluminosilicate glass that is known to easily change to zeolite-like materials by hydrothermal reaction. Lots of hot seawater is disposing near thermal power plants after cooling turbine generator periodically. Using seawater in the hydrothermal reaction caused to produce low price artificial zeolite by reduction of sodium hydroxide consumption, heating energy and water cost. As coal ash were reacted hydrothermally, peaks of quartz and mullite in the ash were weakened and disappeared, and new Na-Pl peaks were appeared strengthily. Si-O-Si bonding of the bituminous coal ash was changed to Si-O-Al (and $Fe^{3+}$) bonding by the reaction. Therefore the produced Na-Pl type zeolite had high CEC of 276.7 $cmol^+{\cdot}kg^{-1}$ and well developed molecular sieve structure with low concentration of heavy metals. 2. Utilization of the artificial zeolite in agro-environment The artificial zeolite(1g) could remove 123.5 mg of zinc, 164.7 mg copper, 184.4 mg cadmium and 350.6 mg lead in the synthetic wastewater. The removability is higher 2.8 times in zinc, 3.3 times in copper, 4.7 times in cadmium and 4.8 times in lead than natural zeolite and charcoal powder. When the heavy metals were treated at the ratio of 150 $kg{\cdot}ha^{-1}$ to the rice plant, various growth inhibition were observed; brownish discoloration and death of leaf sheath, growth inhibition in culm length, number of panicles and grains, grain ripening and rice yield. But these growth inhibition was greatly alleviated by the application of artificial zeolite, therefore, rice yield increased $1.1{\sim}3.2$ times according to the metal kind. In addition, the concentration of heavy metals in the brown rice also lowered by $27{\sim}75%$. Artificial Granular Zeolites (AGZ) was developed for the purification of wastewater. Canon exchange capacity was 126.8 $cmol^+{\cdot}kg^{-1}$. AGZ had Na-Pl peaks mainly with some minor $C_3S$ peaks in X-ray diffractogram. In addition, AGZs had various pore structure that may be adhere the suspended solid and offer microbiological niche to decompose organic pollutants. AGZ could remove ammonium, orthophosphate and heavy metals simultaneously. Mixing ratio of artificial zeolite in AGZs was related positively with removal efficiency of $NH_4\;^+$ and negatively with that of $PO_4\;^{3-}$. Root growth of rice seedling was inhibited severely in the mine wastewater because of strong acidity and high concentration of heavy metals. As AGZ(1 kg) stayed in the wastewater(100L) for 4days, water quality turned into safely for agricultural usage and rice seedlings grew normally.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.1
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• pp.74-89
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• 1999

Distributions and budgets of nitrogen and phosphorus in inner and central areas of Hiroshima bay were investigated for three years from January 1991 to December 1993. The mean loadings of nitrogen and phosphorus Stowed into the entire bay were 870 tonN/month and 129 tonP/month, respectively. About 79 % of nitrogen and 84 % of phosphorus loadings were flowed into the inner area. The TN:TP and DIN:DIP atomic ratios of the discharged freshwater were about 15 and 21, respectively. The PON:POP and DIN:DIP atomic ratios of seawater in the bay varied from 8 to 14 with a mean value of 11, and from 8 to 18 with a mean value of 12, respectively. Estimated fluxes of nitrogen and phosphorus based on the exchange of seawater were 585 tonN/month and 106 tonP/month, respectively, from the inner area to the central area, whereas those fluxes were 62 tonN/month and 107 tonP/month, respectively, from the central area to Akinada. When the remainders of nitrogen and phosphorus substracted outflows from inflows should be sunk, sink fluxes of nitrogen and phosphorus per surface area of the entire bay would be about 9.83 gN/m²ㆍyr and 0.27 gP/m²ㆍyr, respectively. In the central area, the remainders of nitrogen and phosphorus were greater than those in inner area. The residence times of nitrogen and phosphorus were estimated to be about 112 days, respectively, in the entire of Hiroshima Bay.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.45-50
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• 2001

Open rack vaporizer (ORV) has been used in liquefied natural gas (LNG) receiving terminal in order to vaporize LNG into natural gas (NG) by heat exchange with seawater The U-type ORV which had been operated with seawater for 14 years is one of the important utilities of the gas production and the weld part of tube connected with header_ pipe had experienced many corrosion problems. To elucidate the cause of corrosion at weld part of vaporizer tube, corrosion potentials were compared by parts. This study concerns on the measurement of corrosion pit depth using non-destructive method and the evaluation of stress distribution in an aspect of safety with finite element analysis. In order to confirm the reliability of galvanic corrosion between weld parts and base metal, the measurement of corrosion potential by parts was conducted for 20 minutes in 3.5$\%$(wt.) NaCl solution. Many non-destructive methods were tried to measure the remaining thickness of vaporizer tube at fields. For general corrosion, tangential radiography test was confirmed as an effective method. In case of a fine corrosion pit, the shape of corrosion pit was reproduced using surface replication method. From collected data, stress distributions were quantitatively evaluated with 2-dimensional finite element method and the diagnostic evaluation on internal pressure of the U-type vaporizer could be made.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.209-218
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• 2021

First principle-based modeling studies have been performed to improve the heat exchange efficiency of ORV and optimize operation, but the heat transfer coefficient of ORV is an irregular system according to time and location, and it undergoes a complex modeling process. In this study, FNN, LSTM, and AutoML-based modeling were performed to confirm the effectiveness of data-based modeling for complex systems. The prediction accuracy indicated high performance in the order of LSTM > AutoML > FNN in MSE. The performance of AutoML, an automatic design method for machine learning models, was superior to developed FNN, and the total time required for model development was 1/15 compared to LSTM, showing the possibility of using AutoML. The prediction of NG and seawater discharged temperatures using LSTM and AutoML showed an error of less than 0.5K. Using the predictive model, real-time optimization of the amount of LNG vaporized that can be processed using ORV in winter is performed, confirming that up to 23.5% of LNG can be additionally processed, and an ORV optimal operation guideline based on the developed dynamic prediction model was presented.

• The Korean Journal of Pesticide Science
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• v.4 no.1
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• pp.19-25
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• 2000

The adsorption and leaching of organophosphorus pesticide, EPN (O-ethyl-O-4 -nitrophenyl phenyl phosphonothioate) were investigated in Namwon soil(black volcanic soil), Aewol soil(very dark brown volcanic soil) and Mureung soil(dark brown nonvolcanic soil) in Cheju Island. The residue of EPN was surveyed on coastal environment of Cheju in Aug. 1996. The organic matter of Namwon soil, Aewol soil and Mureung soil was 19.8, 6.2 and 2.4%, respectively. The cation exchange capacity of Namwon soil, Aewol soil and Mureung soil was 24.8, 13.0 and 9.5 meq/100 g, respectively. The Freundlich constant, k value, was 89.4, 26.9 and 9.25 for Namwon soil, Aewol soil and Mureung soil, respectively. The k value of Namwon soil with very high organic matter content and cation exchange capacity was the highest for Aewol soil and Mureung soil. The Freundlich constant, 1/n, show a high correlation with organic matter content, i.e. it is less than unity for organic matter rich soil of Namwon soil and greater than unity for organic matter poor soil of Mureung soil. The leaching of EPN was slower for Namwon soil with high k values, and faster for Mureung soil with low k values. The results of the study was demonstrated the potential of pollution for EPN have little leached into soil environment. EPN was not detected in seawater and sediment in the coastal environment in Cheju Island. EPN used in the farm on tile Cheju island were not residued in the coastal environment.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.4
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• pp.297-306
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• 2008

This study was carried out to identify the characteristics of hydrochemistry controlling groundwater chemical condition in a repository site of Gyeongju. For this study, 12 bore holes of all monitoring bore holes in the study area were selected and total 46 groundwater samples were collected with depth. In addition, 3 surfacewater samples and 1 seawater sample were collected. For water samples, cations and anions were analyzed. The environmental isotopes(${\delta}^{18}O-{\delta}D$, Tritium, ${\delta}^{13}C,\;{\cdot}{\delta}^{34}S$) were also analyzed to trace the origin of water and solutes. The result of ${\delta}^{18}O\;and\;{\delta}D$ analysis showed that surface water and groundwater were originated from precipitation. Tritium concentrations of groundwater decreased with depth but high concentrations of tritium indicated that groundwater was recharged recently. The results of ion and correlation analysis showed that groundwater types of the study area were represented by Ca-Na-$HCO_3$ and Na-Cl-$SO_4$, which was caused by sea spray and water-rock interaction. Especially, high ratio of Na content in groundwater resulted from ion exchange. For redox condition of groundwater, the values of DO and Eh decreased with depth, which indicated that reducing condition was formed in deeper groundwater. In addtion, high concentration of Fe and Mn showed that redox condition of groundwater was controlled by the reduction of Fe and Mn oxides.

• Journal of Life Science
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• v.18 no.1
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• pp.103-108
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• 2008

An agar-degrading marine bacterium, strain AS-1 was isolated from the seawater. The strain AS-1 was identified as Sphingomonas paucimobilis (90% probability) by VITEK. The optimum medium for agarase activity of the isolated strain was determined to be marine medium, marine broth 2216 containing 0.1% agar as carbon source. An extracellular agarase was purified 104-fold from the culture supernatant by ammonium sulfate precipitation, ion exchange chromatography and gel filtration methods. The molecular weight of the purified enzyme was estimated to be 80 kDa by SDS-PAGE. The optimum pH and temperature for activity were 7.0 and $40^{\circ}C$, respectively. Antioxidative activity of the strain AS- was 72% in the supernatant cultured for 12 h. The culture supernatant of the strain AS-1 showed antibacterial activity against bacteria causing putrefaction and food poisoning such as Escherichia coli, Staphylococcus aureus and Proteus vulgaris. However, the cell growth of the lactic aicd forming strain, Lactobacillus plantarium was promoted by the treatment of 10% culture supernatant of an agar-degrading strain.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.60-67
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• 2010

Recently, there has been an increase in the construction of various types of coastal structures for efficient wave dissipation, seawater exchange, and so on. Among these, a perforated slit caisson has been widely used to reduce the reflected wave energy and the wave pressure on the structure. Therefore, many studies on the wave force on a caisson, as well as the wave reflection from it, have been carried out with laboratory experiments and numerical analyses, considering it as a 2-D problem. However, because a structure like a perforated slit caisson has a variable 3-D shape, waves forces should be considered as a 3-D problem. Therefore, in this paper, a fully-nonlinear 3-D numerical model (LES-WASS-3D) is proposed to examine the reflection characteristics of a perforated slit caisson with two chambers. The numerical model, LES-WASS-3D, was verified in a 3-D wave field by a comparison with existing experimental data for wave reflection coefficients. Then, using the numerical results, the reflection from a perforated slit caisson with two chambers was examined in relation to wave steepness, chamber width, and the shape/porosity of perforated slit.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.640-645
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• 2014

This study aimed to determine the swimming suitability of sea and to suggest methods to address the problems on sea water color and green plants growing on sediment in the artificial created swimming in the beach of southwestern Korea. Sea water samples were collected from January to December of 2010 and analysis for SS, COD, $NH_4{^+}-N$, TP, MPN, sediment IL, ORP and plants on sediment. The results showed that the sea water under the swimming suitability "level of management" based on the relating high levels of SS and TP, but still suitable for swimming on the basis of MPN. Improving exchange seawater flow, dredging, coating and chemical treatment of polluted sediments in addition to removal of point sources and restriction of non point sources in the study area could improve the sea water quality and swimming suitability of the sea.