• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.5 no.3
• /
• pp.208-215
• /
• 2000

The estimated total material transports through the Cheju Strait using all data which investigated in 1997 and 1999 are as follows; A large amount of suspended sediments and dissovted inorganic nutrients are carried tothe South Sea through the Cheju Strait by a persistent eastward flow (Cheju Current) from the Y311ow Sea andthe East China Sea. The annual material Oanspous by the Cheju Current are as follows; 22.9${\times}$10$^6$ ton yr$^{-1}$(SS), 0.52${\times}$10$^{10}$ mol yr$^{-1}$ (NH$_4\;^+$), 6.05${\times}$10$^{10}$ mol yr$^{-1}$ (NO$_3\;^-$), 0.36${\times}$10$^{10}$ mol yr$^{-1}$ (PO$_4\;^{3-}$), 10.27${\times}$10$^{10}$ mol yr$^{-1}$ (Si(OH)$_4$). The annual suspended sediment flux per water transport in the Cheju Strait (44.48${\times}$10$^6$ ton yr$^{-1}$ Sv$^{-1}$) is about 1.7 larger than that in the Korean Strait (26.08${\times}$10$^6$ ton yr$^{-1}$ Sv$^{-1}$). The annual nitrate flux per water transport (11.60${\times}$10$^{10}$ mol yr$^{-1}$ Sv$^{-1}$) is about 1.2 larger than that in the Korean Strait (9.72${\times}$10$^{10}$ mol yr$^{-1}$ Sv$^{-1}$) and 2/3 of that by Kuroshio in the East China Sea (18.55${\times}$10$^{10}$ ton yr$^{-1}$ Sv$^{-1}$). It suggests that chemical rich Cheju Current will play a significant role in the biogeochemical processes in the South Sea where the huge land-based waste are introduced.

• The Korean Journal of Quaternary Research
• /
• v.13 no.1
• /
• pp.35-43
• /
• 1999

Goryeri archaeological site is located in the upstream valley of the Danjang River. The basement rocks of the area are composed of the Cretaceous to Palaeogene biotite granite (KbGr), acidic dyke (Kad), Milyang Andesite (Kma) and Jyunggagsan Formation. Among them Milyang Andesite and Jyunggagsan Formation are prevailed in archaeological site and they are composed of reddish brown tuffaceous shale, sandstone and conglomerate, with intercalations of acidic tuffs and lapilli tuffs. The purpose of this research is not only to compare REE pattern of the soil-sedimentary deposits with those of surrounding rocks, but also to identify vitric tephra in the soil-sedimentary deposits derived from the andesite, acidic tuff and lapilii tuff, in order to illucidate the provenance of the vitric tephra. The rare earth element(REE) of the soils and sedimentary deposits results in the same REE pattern with those analyzed from the surrounding basement rocks. This indicates that the soils and sedimentary deposits are originated from the surrounding basement rocks, most probably from the andesite and lapilli tuff. In addition, vitric tephra were identified both in the Quaternary in-situ weathered soils and sedimentary deposits (PMU-13 and PMU-17), and in the weathered surrounding lapilli tuff. These vitric tephra are considered to be different from those of Japanese AT(Aira Tanzawa) -tephra. The latter is predominant with clean, platty, bubble-walled and Y-shaped vitrics, while the former is conspicuous with those shapes of large and diverse size and devitrified, as well as having secondarily bubbled-surfaces reflecting surface weathering. The size of vitric fragments in the Goryeri site is about 300${\mu}{\textrm}{m}$ and large in size in compasion to 150${\mu}{\textrm}{m}$ of Japanese AT-Tephra. The interim results of the research are contradictary to the explanations based on a series of AT-tephra researches carried by Japanese scholar. In short, the vitric materials of the Goryeri archaeological site are most probably originated from the weathering products of the surrounding basement rocks, and are different from the AT-tephra in their size, shape and devitrification properties. Thus it is highly recommended to have a further comprehensive research which is more emphasized the magmatic genesis of these vitric tephra in addition to the external shape and morphology.

• Korean Journal of Ecology and Environment
• /
• v.46 no.4
• /
• pp.499-506
• /
• 2013

To estimate the effect of algae to particulate organic matter in the upper regions of brackish Lake Sihwa, temporal and spatial variations of particulate organic carbon (POC) and phytoplankton pigments (chlorophyll a; Chl-a, pheophytin-a; Pheo-a), and their relationships were studied at seven sites of the brackish regions from March to October 2005 and 2006. POC concentration varied from 1.0 to $76.6mgL^{-1}$ (mean $7.4mgL^{-1}$), with maximal concentrations occurring in the middle parts of the study area in spring of 2005 and 2006. Concentrations of Chl-a and Pheo-a varied from 1.3 to $942.9{\mu}gL^{-1}$ (mean $71.0{\mu}gL^{-1}$) and $1.4{\sim}1,545.5{\mu}gL^{-1}$ (mean $59.9{\mu}gL^{-1}$), respectively, and corresponded closely with variation in POC. During the study period Pheo-a concentration was 44.2% of total Chl-a, implying that non-living or inactive phytoplankton is also the important part of phytoplankton-derived POC in brackish regions of Lake Sihwa. From the positive linear relationships between POC and phytoplankton pigments (POC with Chl-a (r=0.93), total Chl-a (r=0.88), and Pheo-a (r=0.81)), it is suggested that phytoplankton was a significant component of POC in the upper regions of brackish Lake Sihwa. On the other hand, the ratios of POC/Chl-a and POC/total Chl-a (Chl-a+Pheo-a) were 82.9 and 35.9, respectively. The ratio of POC/total Chl-a is similar to those reported in previous studies, including 40~60 in estuaries. This study suggests that Pheo-a concentration is considered in estimation of POC concentration from phytoplankton pigments in aquatic systems with high content of Pheo-a, like an upper region of blackish Lake Sihwa.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.19 no.4
• /
• pp.302-307
• /
• 2014

To examine the trophic ecology of the ascidian Styela clava in an aquaculture system of Korea, stable carbon and nitrogen isotopes were analyzed monthly in S. clava, coarse ($>20{\mu}m$, CPOM) and fine particulate organic matters ($0.7<<20{\mu}m$, FPOM). CPOM (means: $-18.5{\pm}1.2$‰, $9.3{\pm}0.7$‰) were significantly higher ${\delta}^{13}C$ and ${\delta}^{15}N$ values than those ($-20.5{\pm}1.5$‰, $8.4{\pm}0.5$‰) of FPOM. S. clava had mean ${\delta}^{13}C$ and ${\delta}^{15}N$ values of $-18.9({\pm}1.7)$‰ and $11.6({\pm}0.7)$‰, respectively. S. clava were more similar to seasonal variations in ${\delta}^{13}C$ and ${\delta}^{15}N$ values of FPOM than those of CPOM, suggesting that they rely largely on the FPOM as a dietary source. In addition, our results displayed that the relative importance between CPOM and FPOM as dietary source for the ascidians can be changed according to the availability of each component in ambient environment, probably reflecting their feeding plasticity due to non-selective feeding irrespective of particle size. Finally, our results suggest that dynamics of pico- and nano-size plankton (i.e., FPOM) as an available nutritional source to S. clava should be effectively assessed to maintain and manage their sustainable aquaculture production.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.18 no.4
• /
• pp.206-213
• /
• 2013

Glass eels (Anguilla japonica) are caught in the west coast of Korea on their migratory route from the breeding grounds in the Mariana Trench along the North Equatorial Current and the Kuroshio Current. To identify the food source of natural glass eels, we analyzed the stable C and N isotopes of glass eels caught in April 2012 and investigated possible food sources in the survey area. In particular, with respect to the stable C and N isotopes of particulate organic matter, we extended the surveying area to the northern parts of East China Sea as well as the west coast of Korea. The stable C and N isotope ratios of the glass eels caught in the west coast were found to be $-20.7{\pm}0.1$‰ and $5.0{\pm}0.2$‰, respectively. The stable C and N isotope ratios of the particulate organic matter in the west coast of Korea, in which the glass eels are assumed to eat the particulate organic matter as food source, were estimated to be $-24.0{\pm}0.3$‰ and $2.8{\pm}0.4$‰, respectively. Similar data were obtained from the northern part of the East China Sea, $-24.5{\pm}0.5$‰ and $0.8{\pm}0.3$‰. The stable isotope ratios showed values differing from the stepwise increasing rates up the food web in natural aquatic ecosystem, showing that particulate organic matter in the west coast of Korea and East China Sea was not served as the glass eels food source. This result suggested that the glass eels caught in the west coast might not assimilate nutrition from the marine environment during long migration.

• Journal of the Korean Electrochemical Society
• /
• v.11 no.2
• /
• pp.109-114
• /
• 2008

Though ethanol can theoretically generate 12 electrons during oxidation to carbon dioxide, the complete oxidation of ethanol is hard to achieve due to the strong bond between the two carbons in its molecular structure. Therefore, development of high activity catalyst for ethanol oxidation is necessary for the commercialization of direct ethanol fuel cell. In this study, some binary and ternary electrocatalysts of PtSn/C and PtSnAu/C have been synthesized and characterized. The catalysts were fabricated with modified polyol method with the amounts of 20 wt%, where the Pt : Sn ratios in the PtSn/C were 1 : 0, 4 : 1, 3 : 1, 2 : 1, 1.5 : 1, 1 : 1, 1 : 1.5 and Pt:Sn:Au ratios in the PtSnAu/C were 5 : 5 : 0, 5 : 4 : 1, 5 : 3 : 2, 5 : 2 : 3. From the XRD and TEM analysis results, the catalysts were found to have face centered cubic structure with particle size of around $1.9{\sim}2.4\;nm$. The activity in the ethanol oxidation was examined with cyclic voltammetry and the results indicated that PtSn(1.5 : 1)/C and PtSnAu(5 : 2 : 3)/C had the highest activity in each catalyst system. Further tests with single cell were performed with those catalysts. It was found that PtSn/C(1.5 : 1) exhibited the best performance while the long term stability of PtSnAu/C(5 : 2 : 3) is better than PtSn/C(1.5 : 1).

• KSBB Journal
• /
• v.11 no.2
• /
• pp.238-245
• /
• 1996

Microbial desulfurization characterlstics of a bituminous coal have been determined by using Thiobacillus ferrooxidans. The effects of process variables (such as coal pulp density, particle size and addition of surfactants) on pyrite removal have been investigated in both shake and airlift-bioreactor culture experiments. In shake experiments, pyrite could be removed over 78% for pulp densifies below 20% (w/v) and removed below 40% for pulp densities over 30% (w/v) in 8 days. Pyrite removal decreased with increasing pulp densities, and it also decreased sharply with increasing particle sizes. In airlift bioreactor experiments, pyrite at 50% (w/v) pulp density could be removed about 50%. Its value is much higher than 15% at the same pulp density in a shake experiment. With addition of surfactants, pyrite removal was enhanced in shake experiments significantly, whereas it was slightly decreased in an airlift bioreactor experiment.

• Resources Recycling
• /
• v.7 no.5
• /
• pp.19-25
• /
• 1998

High temperature thermal behaviors of EAF dust by coke at initial reaction stage were studied to obtain the fundamental data of EAF dust treatment process, that is Extended Arc Plasma Furnace System called RAPID system. In this study thermal behaviors including calcination of limestone, devolatilization of EAF dust itself, and reduction & devolatilization of mixture(EAF dust : coke : limestone = 80 : 10 : 10 wt.%) were investigated as functions of reaction temperature (1000~1300$^{\circ}C$) and reaction time (3~12 min), considering the 180% equivalence of carbon reduction and 1.7 bacisity for optimum reduction and melting of EAF dust in the RAPID system. Size of sample was about below 0.1 mm for these experiments. Limestone was completely calcined at above 1100$^{\circ}C$ within 1 minutes. In the case of devolatilization of EAF dust itself, weight loss of EAF dust was about 14% at 1300$^{\circ}C$ and 12 minutes, and partial sintering and melting were found in part of sample. Weight loss of mixtures increased with increasing reaction temperature and time, about 46% weight loss in it was occurred at 1300$^{\circ}C$ and 12 minutes. From these weight losses showing devolatilization and reduction of EAF dust, the treatment time of EAF dust inside.

• Ocean and Polar Research
• /
• v.33 no.1
• /
• pp.55-68
• /
• 2011

The distribution and inter-annual variation of nutrients (N, P, Si) and dissolved/particulate organic carbon were investigated in the equatorial thermocline ridge ($7^{\circ}{\sim}11.5^{\circ}N$, $131.5^{\circ}W$) of the northeast Pacific. From the Oceanic Nino Index and Multivariate ENSO Index provided by NOAA, normal condition was observed in July 2003 and August 2005 on the aspect of global climate/ocean change. However, La Ni$\~{n}$a and El Ni$\~{n}$o episodes occurred in July 2007 and August 2009, respectively. Thermocline ridge in the study area was located at $9^{\circ}N$ in July 2003, $8^{\circ}N$ in August 2005, $10^{\circ}N$ in July 2007, and $10.5^{\circ}N$ in August 2009 under the influence of global climate/ocean change and surface current system (North Equatorial Counter Current and North Equatorial Current) of the northeast Pacific. Maximum depth integrated values (DIV) of nutrients in the upper layer (0~100 m depth range) were shown in July 2007 (mean 21.12 gN/$m^2$, 4.27 gP/$m^2$, 33.72 gSi/$m^2$) and higher variability of DIV in the equatorial thermocline ridge was observed at $10^{\circ}N$ during the study periods. Also, maximum concentration of dissolved organic carbon (DOC) in the upper 50 m depth layer was observed in July 2007 (mean $107.48{\pm}14.58\;{\mu}M$), and particulate organic carbon (POC, mean $9.42{\pm}3.02\;{\mu}M$) was similar to that of DOC. Nutrient concentration in the surface layer increased with effect of upwelling phenomenon in the equatorial thermocline ridge and La Ni$\~{n}$a episode, which had formed in the central Pacific. This process also resulted in the increasing of organic carbon concentration (DOC and POC) in the surface layer. From these results, it is suggested that spatial and temporal variation of chemical and biological factors were generated by physical processes in the equatorial thermocline ridge.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.30 no.1
• /
• pp.1-9
• /
• 2020

Objectives: The purpose of this case study is to assess workers' exposure to carbon nanotubes(CNTs) and characterize particles aerosolized during the process of producing CNT-enabled polytetrafuoroethylene(PTFE) composites at a worksite in Korea. Methods: Personal breathing zone and area samples were collected for determining respirable concentrations of elemental carbon(EC) using NIOSH(National Institute for Occupational Safety and Health) Method 5040. Personal exposure to nano-sized particles was measured as the number concentration and mean diameter using personal ultrafine particle monitors. The number concentration by particle size was measured using optical particle sizers(OPS) and scanning mobility particle sizers(SMPS). Transmission electron microscopy (TEM) area samples were collected on TEM grids and analyzed to characterize the size, morphology, and chemistry of the particles. Results: Respirable EC concentrations ranged from 0.04 to 0.24 ㎍/㎥, which were below 23% of the exposure limit recommended by NIOSH and lower than background concentrations. Number concentrations by particle size measured using OPS and SMPS were not noticeably elevated during CNT-PTFE composite work. Instant increase of number concentrations of nano-sized particles was observed during manual sanding of CNT-PTFE composites. Both number concentrations and mean diameters did not show a statistically significant difference between workers handing CNT-added and not-added materials. TEM analyses revealed the emission of free-standing CNTs and CNT-PTFE aggregate particles from the powder supply task and composite particles embedded with CNTs from the computer numerical control(CNC) machining task with more than tens of micrometers in diameter. No free-standing CNT particles were observed from the CNC machining task. Conclusions: Significant worker exposure to respirable CNTs was not found, but the aerosolization of CNTs and CNT-embedded composite particles were observed during handing of CNT-PTFE powders and CNC machining of CNT-PTFE composites. Considering the limited knowledge on the toxicity of CNTs and CNT composite particles to date, it seems prudent to take a precautionary approach for the protection of workers' health.