• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.212-223
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• 2014

For the better understanding of long-term and seasonal variations of water quality in Masan Bay, South Sea of Korea, we analyzed the archive data monitored at three stations of the bay during the last 13 years (2000-2012). The average concentrations of the chemical oxygen demand (COD), the dissolved inorganic nitrogen (DIN) and the dissolved inorganic phosphorus (DIP) during the monitoring period are $2.70{\pm}0.09{\mu}/L$, $19.66{\pm}1.84{\mu}m$ and $1.39{\pm}0.13{\mu}m$ in surface water, respectively, and $2.22{\pm}0.07{\mu}/L$, $18.53{\pm}1.36{\mu}m$ and $1.47{\pm}0.12{\mu}m$ in bottom water, respectively. The trophic state of the surface water was the eutrophic level in Masan Bay during the four seasons. The DIN concentrations of both surface and bottom waters increased from August to November and showed the highest average in November. However, The DIN decreased from February to May and showed the lowest average in May. The concentrations of the DIP and the dissolved silicate (DSi) in bottom waters had the highest averages in August because of the high water temperature and oxygen deficient condition. The results of correlation analysis and factor analysis showed that the main factors of surface waters were inflow of nutrients from terrestrial areas and internal production, and the main factors of bottom waters were the variations of the dissolved oxygen (DO), the DIP, and the DSi. The DIN and DIP average concentrations (2007~2012) had decreased in range of 68.1%~76.0% and 66.2~76.6%, respectively from 2007 in which the "Regulation of Total Emission" was established in Masan Bay. Therefore, it could have had positive effects on water quality improvement to take the "Regulation of Total Emission" and other actions such as reducing water pollutions in Masan Bay from 2007.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.83-99
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• 2005

To evaluate environmental charateristics of the South Sea and East China Sea on summer, water and sediment quality were measured in June 2001-2003. Surface layer was affceted by Warm water originated from the high temperature and salinity-Tsushima Warm Current, on the other hand, Yellow Sea Cold Water was spread to the bottom layer in the south-western part of the Jeju island, and salinity at stations near the Yangtze River was decreased below 29psu because of a enormous freshwater discharges. Thermocline-depth was formed at about 10m, and chlorophyll maximum layer was existed in and below the thermocline. COD(Chemical Oxygen Demand), TN(Total Nitrogen), and TP(Total Phosphorus) concentrations showed seawater quality grade II in surface layer of the most area, but concentrations of such as COD, Chl. a, TSS(Total Suspended Solid), and nutrients were greatly increased in the effect area of Yangtze River discharges. Correlations between dissolved inorganic nitrogen, Chl. a and salinity were negative patterns strongly, in contrast, those of inorganic phosphorus, COD and Chl. a were positive, which indicates that phytoplankton biomass and phosphorus are considered as important factors of organic matter distribution and algal growth, respectively. in the study area. The distribution of ignition loss, COD, and $H_2S$ of surface sediment were in the ranges of 2.61-8.81%, $0.64-11.86mgO_2/g-dry$, and ND-0.25 mgS/g-dry, respectively, with relatively high concentration in the eastern part of the study area. Therefore, to effective and sustainable use and management of this area, continuous monitoring and countermeasures about major input sources to the water and sediment, and prediction according to the environmental variation, are necessary.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.3
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• pp.203-218
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• 2011

Long-term trends and distribution patterns of water quality were investigated in the Yeoja Bay of South Sea, Korea from 1976 to 2010. Water samples were collected at 3 stations and physicochemical parameters were analyzed including water temperature, salinity, hydrogen ion concentration (pH), dissolved oxygen (DO), chemical oxygen demand (COD), suspended solids (SS) and nutrients. Spatial distribution patterns of temperature, pH and DO were not clear among stations but the seasonal variations were distinct except ammonium. The trend analysis by principal component analysis (PCA) during 31 years revealed the significant variations in water quality in the study area. Spatial water qualities were discriminated into 2 clusters by PCA; station cluster 1 and 2~3. Annual water qualities were clearly discriminated into 4 clusters by PCA. By this multi-variate analysis, the annual trends were summarized as the followings; water temperature, COD and SS tended to increase from late 1970's, decreased salinity, and increased phosphate from 1991 to 2001 and increased dissolved inorganic nitrogen. Water quality was showed by the input of fresh water same as those of Kyoungin coastal area, Asan coastal area, Choensoo bay, Gunsan coastal and Mokpo coastal area in the Yeoja Bay.

• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.260-269
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• 2009

Hwabuk Dam has been under construction to reduce flood damage in Nakdong River watershed and to supply stable water for middle area of Gyeongbuk Province. Therefore, fish investigation in up and downstream of the dam was conducted from 2004 to 2008 in order to determine any negative effect on fish community due to dam construction and to use as fundamental data for conserving species diversity and maintaining stream health. According to data analysis on water quality, temperature, dissolved oxygen, pH, suspended solids, and total E-coli had seasonal variation, but they did not significantly differ in sites. However, biological and chemical oxygen demand, chlorophyll-a, nitrogen, and phosphorus representing organic matter and nutrient concentration were higher in upper site and decreased to lower site so that they differed by site. Concentration of arsenic among the heavy metals was less than 0.05 mg $L^{-1}$, which is regulated for protection of human health in water quality standard, except for 0.092 mg $L^{-1}$ in June 2005. During the study period, the total number of fish caught from the 6 sites was 10,263 representing 7 families 19 species. Among them, dominant and subdominant species were Korean chub (Zacco koreanus, 62.5%) and Chinese minnow (Rhynchocypris oxycephalus, 10.6%) which inhabit mostly in mid and upper streams, Korea. Among the 19 species, Korean endemic species were 9 species (47.4%) including Korean slender gudgeon (Squalidus gracilis majimae), Korean dark sleeper (Odontobutis platycephala), and Korean shiner (Coreoleuciscus splendidus). There was several individuals of the $1^{st}$-class endangered species, Naktong nose loach (Koreocobitis nahtongensis), caught in 2005${\sim}$2007, and no introduced species of fish was found in entire sampling period. According to result of community analysis, dominance index decreased toward lower site, but diversity and richness indices increased toward lower site. The equation of length-weight relationship on the dominant species was TW=0.000003$(TL)^{3.2603}$. The parameter b in the equation was greater than 3.0 indicating good nutritional condition in the populations. Compared to populations of Korean chub in other streams, the population in Hwabuk Dam watershed had higher mean of condition factor by size indicating better growth rate. With fish fauna and multi-metric health assessment model in each sampling attempt, index of biotic integrity (IBI) was evaluated and it resulted mostly in good (26${\sim}$35) and excellent (36${\sim}$40) condition in all sites, and the mean of IBI was the highest in site 5. The results indicate that it is very important to study not only environmental impact assessment with fish composition but also stream health assessment in order to conserve healthy aquatic ecosystem.

• Journal of Microbiology and Biotechnology
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• v.29 no.10
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• pp.1607-1623
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• 2019

Sediment bioelectrochemical systems (SBESs) can be integrated into brackish aquaculture ponds for in-situ bioremediation of the pond water and sediment. Such an in-situ system offers advantages including reduced treatment cost, reusability and simple handling. In order to realize such an application potential of the SBES, in this laboratory-scale study we investigated the effect of several controllable and uncontrollable operational factors on the in-situ bioremediation performance of a tank model of a brackish aquaculture pond, into which a SBES was integrated, in comparison with a natural degradation control model. The performance was evaluated in terms of electricity generation by the SBES, Chemical oxygen demand (COD) removal and nitrogen removal of both the tank water and the tank sediment. Real-life conditions of the operational parameters were also experimented to understand the most close-to-practice responses of the system to their changes. Predictable effects of controllable parameters including external resistance and electrode spacing, similar to those reported previously for the BESs, were shown by the results but exceptions were observed. Accordingly, while increasing the electrode spacing reduced the current densities but generally improved COD and nitrogen removal, increasing the external resistance could result in decreased COD removal but also increased nitrogen removal and decreased current densities. However, maximum electricity generation and COD removal efficiency difference of the SBES (versus the control) could be reached with an external resistance of $100{\Omega}$, not with the lowest one of $10{\Omega}$. The effects of uncontrollable parameters such as ambient temperature, salinity and pH of the pond (tank) water were rather unpredictable. Temperatures higher than $35^{\circ}C$ seemed to have more accelaration effect on natural degradation than on bioelectrochemical processes. Changing salinity seriously changed the electricity generation but did not clearly affect the bioremediation performance of the SBES, although at 2.5% salinity the SBES displayed a significantly more efficient removal of nitrogen in the water, compared to the control. Variation of pH to practically extreme levels (5.5 and 8.8) led to increased electricity generations but poorer performances of the SBES (vs. the control) in removing COD and nitrogen. Altogether, the results suggest some distinct responses of the SBES under brackish conditions and imply that COD removal and nitrogen removal in the system are not completely linked to bioelectrochemical processes but electrochemically enriched bacteria can still perform non-bioelectrochemical COD and nitrogen removals more efficiently than natural ones. The results confirm the application potential of the SBES in brackish aquaculture bioremediation and help propose efficient practices to warrant the success of such application in real-life scenarios.

• Korea journal of population studies
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• v.11 no.1
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• pp.204-229
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• 1988

This paper documents and discusses trends and differentials in youth's participation in the labor force and employment. Youth in this study is defined asthe young aged 15-29. Youth passes through a series of life-course transitions,which include school completion own family formation(marriage and childbirth) .mandatory service in the army (by males) , and their economic activities are affectedby those life-course events. Accordingly we show how and to what extent youth'slabor force participation and employment varies with age and how the age patternhas changed over time.Throughout the 1980's and 1990's, youth's labor force participation showeddifferent trends by age group Labor fDrce participation rate of the 15-19 agedsteeply decreased, while that of the 25-29 steadily increased during the twodecades, the rate fsr the 20-24 aged showing not much variation. The former is dueto the increased rate of school enrollment among the age group, while the lattercould be attributed, in part, to the young women s increased and more steadyparticipation in the labor force over time.While labor force participation could be considered as a result of one's choicesand preferences, employment opportunities are more or less restricted by labormarket structure and institutions . This study documents how the structuralconstraints have interacted with individual and group attributes to differentiateemployment opportunities between individuals (educational background) and groups(especially sex diffrences) . One of the most salient feature of youth's em[ploymentstructure is the recent high unemployment rate of the college graduates. We discusshow that is related to the'credential society'in which one's educational credentials and it's social status play major role in determining who gets what in terms of job opportunities. Also is discussed the discordance between school and labor marketsupply and demand system, which is apparent in the prolonged oversupply of thecollege graduates, which is due to the consistently high rate of college entranceobserved since the early 1980's. Theoretically the job market for college graduates isviewed not as the'neoclassical'wage competition market but as job competition market in which one's (good) job opportunity is determined by one s position in thejob queue, which is in turn heavily dependent on from which college one get shis/her college degree as well as one's sex.

• Journal of Climate Change Research
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• v.2 no.2
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• pp.93-106
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• 2011

Republic of Korea officially announced its mid term reduction target which reduce about 30% of BAU GHG emission by 2020 in the 15th meeting of UNFCCC(COP 15) held in Copenhagen, Denmark 2009. To achieve this goal, it is necessary to understand the serious of climate change and take part in GHG reduction not only industry but also the nation. However, such positive participation in green life which may cause inconvenient of the life of the people. It should be accomplished with providing reliable information. This study suggests the scientific potentialities of GHG emission by guideline on low carbon life and green life to form and change a lifestyle suitable for coping with climate change. And also, this study quantitate the GHG reduction which may reduce demand for air conditioning by cool biz and warm biz. In Korea, this campaign has become known as 'CoolMaebsi' by Ministry of Environmental of Korea. 'CoolMaebsi' is a compound word of 'Cool' which means feel refreshed, and 'Maebsi' is a Korean word which means attire. Though this campaign is effective and significant to reduce the GHG emission yet there were no study on quantitative analysis. Therefore this study calculated reduced energy consumption and potential GHG emission by measuring variation of skin temperature. As the result, wearing warm biz and cool biz have an effect of reducing not only the energy consumption but also GHG emission. To achieve the low carbon society, it is necessary to improve the energy saving system and introduce the policy which guide to change a life style.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.526-535
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• 2021

Spatial sampling design plays an important role in GIS-based modeling studies because it increases modeling efficiency while reducing the cost of sampling. In the field of agricultural systems, research demand for high-resolution spatial databased modeling to predict and evaluate climate change impacts is growing rapidly. Accordingly, the need and importance of spatial sampling design are increasing. The purpose of this study was to design spatial sampling of paddy fields (11,386 grids with 1 km spatial resolution) in Korea for use in agricultural spatial modeling. A stratified random sampling design was developed and applied in 2030s, 2050s, and 2080s under two RCP scenarios of 4.5 and 8.5. Twenty-five weather and four soil characteristics were used as stratification variables. Stratification and sample allocation were optimized to ensure minimum sample size under given precision constraints for 16 target variables such as crop yield, greenhouse gas emission, and pest distribution. Precision and accuracy of the sampling were evaluated through sampling simulations based on coefficient of variation (CV) and relative bias, respectively. As a result, the paddy field could be optimized in the range of 5 to 21 strata and 46 to 69 samples. Evaluation results showed that target variables were within precision constraints (CV<0.05 except for crop yield) with low bias values (below 3%). These results can contribute to reducing sampling cost and computation time while having high predictive power. It is expected to be widely used as a representative sample grid in various agriculture spatial modeling studies.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.6
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• pp.511-522
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• 1984

The Nagdong is one of the biggest rivers in Korea, which is very important water source not only for tap water of Pusan city but also for the industrial water. Therefore, authors tried to check the water quality year by year. In this experiment one hundred and twenty water samples collected from August 1983 to July 1984 were analyzed bacteriologically and physiologically. Fifteen sampling stations were established between near Samrangjin and estuary of the river. To evaluate the water quality, temperature, pH, chloride ion, salinity, chemical oxygen demand (COD), electrical conductivity, nutrients, total coliform, fecal coliform, fecal streptococcus, viable cell count and bacterial flora were observed. The variation of water temperature was ranged $-1.5{\sim}29.0^{\circ}C$ (Mean value $13.9{\sim}16.5^{\circ}C$), it in spring was higher as $10{\sim}15^{\circ}C$ about $10^{\circ}C$ than in winter and it in autumm was very stabilized as about $20^{\circ}C$ at each station. The pH variation of the samples was ranged $6.68{\sim}9.15$. The range of concentration of chloride ion and salinity varied $7.4{\sim}l,020.5$ mg/l and $1.05{\sim}33.0\%0$, respectively. Especially, salinity of the 3rd water war was the higher than others as $25.76{\sim}31.58\%0$. COD was ranged $1.45{\sim}14.94$ mg/l and the lower part of the Nagdong River was heavily contaminated by domesitc sewage and waste water from the adjacent factor area. The range of electrical conductivity was $1.360{\times}10^2{\sim}5.650{\times}10^4{\mu}{\mho}/cm$ and that was by far higher the estuary than the upper. Concentration of nutrients were $0.008{\sim}0.040$ mg/l (Mean value $0.019{\sim}0.068$ mg/l) for $NO_2-N,\;0.038{\sim}5.253$ mg/l ($0.351{\sim}2.347$ mg/l) for $NO_3-N,\;0.100{\sim}2.685$ mg/l($0.117{\sim}1.380$ mg/l) for $NH_4-N,\;0.003{\sim}0.084$ mg/l($0.014{\sim}0.065$ mg/l) for $PO_4-P$ and $0.154{\sim}6.123$ mg/l ($1.165{\sim}3.972$ mg/l) for $SiO_2-Si$, respectively. Usually nutrients contents of the water in the upper part(included station 1 to 5) were higher than those of the estuarine area. The bacterial density of the samples ranged 7.3 to 460,000/100 ml for total coliforms, 3.6 to 460,000/100 ml for fecal coliform, $0{\sim}46,000/100ml$ for fecal streptococcus and $<30{\sim}1.2{\times}10^5/ml$ for viable cell count. Composition of coliform was $28\%$ Escherichia coli group, $18\%$ Citrobacter freundii group, $31\%$ Enterobacter aerogenes group and $22\%$ others. Predominant species among the 659 strains isolated from the samples were Pseudomonas spp. ($42\%$), Flavobacterium spp. ($20\%$) and Moraxella spp. ($12\%$).

• Korean Journal of Agricultural Science
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• v.7 no.1
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• pp.12-26
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• 1980

A new, improved maize varieties are greatly needed to meet the national demand for the maize, and a new germplasm should be investigated to supply necessary breeding materials for the required maize breeding. The Korean local maize lines, which has never been wholly studied for the purpose of breeding should be enough to supply such breeding materials at least in Korea. The objectives of this study were to maintain useful Korean local lines, to investigate good plant characters and to analyze the Korean local maize lines in the respect of genetic make-up. A total of 820 lines and 200 lines were used for the present study. Lines to maintain were planted at experimental farm of the Crop Experiment Station, Office of Rural Development, Suwon and the lines to study genetic make-up were planted in Dae-jon. The summarized results are as follows : 1. A total of 1200 lines from 820 collections were sibbed for future use. 2. Two hundred collection were sibbed, selfed and testcrossed for genetic study in 1980. 3. Ten lines were surely confirmed as resistant lines to virus disease epidemic in most introduced maize varieties. 4. A dozen Lines were having three to four ears per plant. 5. Five lines were showing three to four tillers per plant. 6. One of the most significant and important finding through the study was to obtain the lines with three to four tillers bearing all together eight to nine ears. The lines of multi-ears and multi-tillers must have great breeding potential for the future use. 7. A great variation was observed in the tasselling days, 100 kernel weight and protein content. 8. From the genetic study of local maize lines for plant height and 100 kernel weight, the following findings were obtained. a. On the average six percent of inbreeding depression expressed in percent decrease over sibbed counterpart were found for the plant height. b. Fourty percent of heterosis expressed in percent increase over sibbed counterpart were observed in the plant height. c. The homogeneity or degree of homozygosity calculated from heterosis minus inbreeding depression was on the average 34 percent for plant height. d. The average inbreeding depression expressed in percent decrease over sibbed counterpart was 15 percent for 100 kernel weight. e. The average heterosis expressed in percent increase over sibbed counterpart was 43 percent for 100 kernel weight. f. The degree of homozygosity calculated from the heterosis minus inbreeding depression was 28 percent for 100 kernel weight.