• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.365-373
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• 2020

Biomonitoring Survey and Assessment Manual for lake ecosystem suggest zooplankton collection methods to compare relatively the number of species, population density, and community indices, taking into account the convenience of the field sampling according to the sites' water depth. In this study, the oblique towing and 20 m vertical towing methods presented in the manual were respectively compared with the whole water column-vertical towing and we analyzed the differences and characteristics of zooplankton community information gathered by each collection method. For community indices, there was no difference in the comparison of oblique/vertical towing methods in the shallow lake, but in the deep lake, the diversity and richness indices increased when vertically towing through whole water column rather than when limiting the towing depth to 20 m. In addition, the total zooplankton density collected by the oblique/20 m vertical towing methods was about three times higher than the whole water column-vertical towing method, which means that the density of zooplankton community can be overestimated depending on the collection methods. It appears to be results of differences in the zooplankton density by water layer arising from their vertical distribution and in filtered raw water quantity according to the towing depth/distance. Hence, for zooplankton community information to be used as a functional quantitative indicator representing the entire lake, it would be more appropriate to apply the whole water column-vertical towing method with considering the distribution of zooplankton density by depth and contribution rate of each water layer when converting total zooplankton density.

• Journal of Animal Environmental Science
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• v.18 no.3
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• pp.145-150
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• 2012

This study was conducted to measure methane ($CH_4$) and nitrous oxide ($N_2O$) emissions from the 6 month old litter stockpile used for korean native cattle (Hanwoo) from August 3, 2007 to October 4, 2007. Daily mean $CH_4$ emissions was peaked to 273.013 ${\mu}g\;m^{-2}\;s^{-1}$ (SE : ${\pm}1.047{\mu}g\;m^{-2}\;s^{-1}$) on first day and then gradually decreased to 2.309 ${\mu}g\;m^{-2}\;s^{-1}$ (SE : ${\pm}0.061{\mu}g\;m^{-2}\;s^{-1}$) at the end of this experiment. Daily mean $N_2O$ emissions was as little as 0.269 ${\mu}g\;m^{-2}\;s^{-1}$ (SE : ${\pm}0.018{\mu}g\;m^{-2}\;s^{-1}$) on first day, but exponentially increased up to 3.569 ${\mu}g\;m^{-2}\;s^{-1}$ (SE : ${\pm}0.454{\mu}g\;m^{-2}\;s^{-1}$) on 43rd day and then slowly decreased to 1.888 ${\mu}g\;m^{-2}\;s^{-1}$ (SE : ${\pm}0.012{\mu}g\;m^{-2}\;s^{-1}$) at the end of this experiment. Carbon dioxide equivalent ($CO_2$-eq), calculated by global warming potentials of $CH_4$ or $N_2O$, of $CH_4$ on first day occupied approximately 99% of sum of $CO_2$-eq of $CH_4$ and $N_2O$. Methane emissions decreased and $N_2O$ emissions increased so that $CO_2$-eq ratio of $CH_4$ to $N_2O$ was 50:50 on 34th day. The effect of $N_2O$ on the ratio was increase thereafter. The ratio of daily mean $CH_4$ and $N_2O$ emissions to daily error of the mean was calculated to find daily fluctuation of $CH_4$ and $N_2O$ emissions. The ratio of $CH_4$ was less than 1.0% till 11th day but increased to 10.9% on 57th day. The ratio of $N_2O$ (0.4%~51.0%) was higher than that of $CH_4$, showing high in early stage and then gradually decrease, which was different from the pattern of $CH_4$. The ratio of daily mean emissions to daily error of the mean was little in case of active $CH_4$ or $N_2O$ generation period, which would be caused by the temporal and spatial heterogeneity of composting process. Hence more air supply on early stage to decrease $CH_4$ generation and proper turning to reduce spatial heterogeneity are needed to mitigate greenhouse gas emissions.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.3
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• pp.156-164
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• 2004

This study was conducted to evaluate the effect of the application of green manure in the form of either green barley and Chinese milkvetch in reducing the amounts of N fertilizers and conventional fertilizers needed for paddy rice. Prior to rice transplanting, the green barley and Chinese milkvetch as a green manure produced respectively $668kg\;10a^{-1}$ and 3,492kg\;$10a^{-1}$ in fresh shoot weight basis. Calculated nitrogen content from harvested green manures was 3.9 and $17.8kg\;10a^{-1}$, respectively. Plant height and tiller number of rice increased when two kinds of green manure incorporated into soil. Above mentioned parameters also increased with increasing amounts of N fertilizers at both ear formation and heading stage of rice. Rice grain number was not affected by green manures treatment but increased when N fertilizers were applied. Although rice panicle and grain number increased with green manure treatments and fertilizer applications, whereas the percentage of ripened grain decreased. Chinese milkvetch with additional N fertilizer applications increased brown rice yield from 1 to 5% compared to rice yields in plots where non-green manure with the conventional amount of fertilizer application was applied. Rice treated with Chinese milkvetch and 30% of the conventional N fertilizer rate yielded the same as rice fertilized conventionally. During the rice growing season, $NH_4-N$ content of paddy soil was higher in green manures treatment than non-green manure one. Average $NH_4-N$ content in paddy soil drastically decreased after heading stage below $5.7mg\;kg^{-1}$ in non-green manure treated plots. While on the other, $NH_4-N$ content in soil slowly decreased in plots those were treated with green manures at harvesting stage, average $NH_4-N$ content was still greater than $5.5mg\;kg^{-1}$. Nitrogen content of rice shoot and brown rice seed was higher in green manure treatment.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.303-314
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• 2021

To understand how to efficiently observe the biomass and community of phytoplankton, phytoplankton sampling was carried out from June to October 2019 at the Yeongju dam sediment control reservoir(YJ) and Bohyeonsan dam reservoir(BH1 and BH2). The results derived from microscopic observation, such as the conventional phytoplankton qualitative/quantitative analysis, and from the CHEMTAX method based on the pigments, were compared. The relative contribution of phytoplankton, calculated by the microscopy and CHEMTAX methods, showed a significant difference in all four classes: cryptophyta, chlorophyta, cyanobacteria, and diatoms. In addition, the correlation between the two observation methods was poor. This might be caused by methodological differences in microscopy that do not consider the varying cell sizes among phytoplankton species. In this study, by converting the cells into carbon, the slope between both carbon biomasses based on microscopy and CHEMTAX was improved close to the 1 : 1 line, and the y-intercept was closer to 0 for cryptophyta and diatoms. For cyanobacteria, the slope increased, the y-intercept decreased, and the plot approached 1 : 1 although the correlation coefficients were not improved in all classes. The present study suggests that application of CHEMTAX based on pigment analysis could be a possible approach to efficiently determine the relative carbon proportions of individual classes of phytoplankton community composition.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.41-51
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• 2008

As the local bus service diagram after the bus route reform is studied by variable analysis based on traffic card data and income adjustment data, the characteristic of the local bus system is revealed in Busan Metropolitan city. The relationship between traveling length and traveling time is influenced by traveling velocity. In order to keep a headway within 10 minutes, bus service number per minute should be over 0.1013 vehicles. The traveling time of afternoon is generally longer than that of forenoon. Compared with the bus used by a lot people, the deviation of that used by a few people is larger in the all cases of length, headway, time and velocity. According to the analysis of the relationship among card trip number, average income and transfer rate, the relationship between card trip number and average income is expressed as linear function in the general bus and as exponential function in the high-grade & rapid bus. The 1% increase of transfer rate is equal to 6.3 trip/vehicle/day decrease and 4.9 trip/vehicle/day decrease in two bus types respectively. The four effective variables are defined by the discriminant analysis between the profitable routes and the unprofitable; According to discriminant size, bus service number per km, bus via suburb, subway meeting number, bus via university. In order to increase the income when the minibus will be included among public transit transfer system in 2008, it should be necessary to settle the bus network and revitalize the public transit better. In order to decrease the cost, it should be necessary to reorganize the hierarchy between the local bus and the minibus better.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.54-61
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• 2001

Changes in methanogenic pathway at low temperature were studied by incubation experiments of sediment slurries from the littoral zone of Reservoir Paldang. Methane production rates in sediment slurries increased exponentially between $5＾{\circ}C$and $45＾{\circ}C$, reached a maximum rate of $7.4\;nmol\;{\cdot}\;g^{-1}\;{\cdot}\;h^{-1}$ at $45＾{\circ}C$, and then declined to low rate. The shift of incubation temperature from high temperature ($30＾{\circ}C$) to lowtemperature ($15＾{\circ}C$) resulted in a decrease of methane production rate and of hydrogen accumulation rate, and the transient accumulation of acetate concentration. Chlorofarm inhibited perfectly methanogenesis and resulted in the accumulation of hydrogen and acetate as immediate precursors for metltane formation at both incubation temperatures of $15＾{\circ}C$ and $30＾{\circ}C$. In terms of equivalent methane which was calculated from the two intermediary metabolites accumulated in absence of methanogenesis, methane production from acetate was accounted for 14% of total methanogenesis at $30＾{\circ}C$ and 75% at $15＾{\circ}C$, respectively. When the high acetate concentrations above 19 mM were added to sediment slurries, methane production was inhibited at the low temperature ($15＾{\circ}C$) . Our results demonstrate that contribution of acetate on methanogenesis increases at low temperature, but this pathway is inhibited by high concentration of acetate. Therefore acetate-utilizing methanogensis appears to be a key reaction at low temperature, and seems to be one of bottlenecks of the low temperature anaerobic degradation of organic matter in littoral sediments of the reservoir.

• Korean journal of applied entomology
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• v.12 no.1
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• pp.33-39
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• 1973

The yield of rice is increased to amounts of fertilizer applied in paddy field but excessive application of fertilizer stimulates outbreaks of disease and insect pest. If, therefore, diseases and pests stimulated by excessive application of fertilizer would be effectively controlled, increaseed yield of rice would be possible. This experiment was conducted to determine the fertilizer application rate that would produce maximum yields when diseases and pests are controlled. 1. The fertilizer application rates and the incidence of leaf and apanicle blast were positively correlated at the $1\%$ level. 2, Without disease and pest control the maximum yield of hulled rice was 347-378kg/10a, which occurred at nitorgen application levels of 8.0-8.5 kg/10a. with effective control of diseases and pests the maximum yield of hulled was 453-462 kg/10a, which occurred at nitrogen application levels of 18.5-19.0 kg/10a. Yield increase at appropriate nitrogen levels by disease and pest control resulted in more than 100 kg/10a. 3. There was no significant yield difference between the NPK experimental plots with fixed PK levels and with varying PK levels. 4. The maximum effect of disease and pest .control as expressed biy yield index of hulled rice was $65\%$, the minimum effect was $30\%$, the average effects were $42-45\%$.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1991-1994
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• 2008

우리나라는 도시화, 산업화에 따른 수질저하 및 용수확보 문제를 해결하기 위하여 각종 환경기초시설의 증설과 수질개선을 위한 대책을 수립하여 왔다. 그러나 점오염원에 국한한 수질개선은 한계가 있었으며, 1995년 환경부는 전국 비점오염원 조사를 통해 비점오염원이 수질오염에 기여하는 비율이 T-N, SS는 50% 이상을 점유하고 기타 BOD, T-P도 $20{\sim}30%$ 수준임을 밝힌 바 있다. 이에 정부는 오염총량관리제를 도입하여 비점오염원의 관리를 시작하였으나, 강우시 정확한 유량자료를 바탕으로한 수질 측정자료의 부족으로 비점오염원 관리에 있어 어려움이 따르고 있다. 따라서 본 연구에서는 비점오염원 관리 및 연구를 위한 기초자료로 활용될 수 있도록 수도권 및 인근지역 주민의 식수원인 팔당호로 직유입되고, 정확한 수질자료 확보가 필요한 경안 수위관측소 지점에서 2007년 6월${\sim}$9월에 일어난 강우 중 4개의 강우사상에 대하여, 수질측정을 실시하였다. 본 연구에서 이용한 유량자료는 2007년 수위-유량관계곡선식으로 산정한 환산 유량이며, 실측한 수질자료를 바탕으로한 유량과 부하량의 관계는 통계학적으로 분석하였다. 수질측정 항목은 수온, DO, pH, EC, SS, BOD, CODMn, CODCr, T-N, T-P 등이며, BOD의 농도는 2개의 강우사상에서만 분석하였다. 현장에서 휴대용미터를 이용하여 수온, DO, pH, EC를 측정하였고, 나머지 항목은 한국건설기술연구원내 환경정밀분석 센타에 의뢰하였다. 각 항목별 유량-부하량 관계식은 기존의 지수식이 아닌 선형이나 다항식으로 산정하였다. 다항식으로 산정된 식의 결정계수($R^2$)는 BOD, T-N 항목을 제외한 각 항목에서 0.6 이상의 값을 가졌다. 항목별로 보면 SS는 0.90, $COD_{Mn}$은 0.87, $COD_{Cr}$은 0.84, T-P는 0.62의 값을 가졌다. 또한, T-N은 0.53, BOD는 0.32의 값을 가져 유량과 부하량의 관계가 거의 상관성이 없는 것으로 나타났다. BOD의 경우는 4개의 강우사상 중 2개의 강우사상에서만 분석되어 다른 항목에 비해 실측자료가 부족한 관계로 그 특성을 판단하기 어려웠다. 본 연구가 주로 홍수기에 이루어져 실측자료가 많지 않았기 때문에 본 연구의 대상지점을 대표할 수 있는 유량-부하량 관계식으로는 미흡한 한 것으로 분석되었다. 본 연구자료를 기초로 장기간 많은 자료를 확보하여 유량-부하량 관계식을 수정 보완한다면, 차후 비점오염원 관리의 기초자료로 활용될 수 있을 것으로 판단된다.

• Journal of Aquaculture
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• v.9 no.4
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• pp.377-384
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• 1996

A 15-week of growth trial was conducted to evaluate practical diets for growing Korean rockfish (Sebastes schlegeli). Two replicate groups of the fish average weighing 125 g were fed one of four experimental diets containing $41\~45\%$ protein and $6\~8\%$ lipid. A control diet with $58\%$ fish meal as protein source was included and practical form diets with $40\%$ fish meal and various practical ingredients such as meat meal, blood meal, soybean meal, and corn gluten meal were included. These experimental dry pellet diets were compared with commercial diets containing $51\~53\%$ protein and $5\~13\%$ lipid for marine fish or raw fish-based moist pellet (RMP) diet containing $58\%$ protein and $9\%$ lipid consisted of $50\%$ frozen horse mackerel and $50\%$ commercial binder meal. Weight gain, feed efficiency, daily feed intake and protein efficiency ratio in the fish fed the experimental diets and commercial diets were not significantly different to those in the fish fed the control diet. However weight gain, feed efficiency and protein efficiency ratio in the fish fed the RMP diet were significantly higher than those in the fish fed the experimental diets and commercial diets. These differences of growth performance between experimental diets and RMP diet may be reason for different dietary protein and energy levels. The experimental diet can save up to $20\%$ cost of fish production compare with control diet, whereas RMP diet is more expensive than other diets in the fish production.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.102-115
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• 2015

Several emergy researches have been carried out to estimate the value of marine ecosystem services in Korea over the last decade. Their results cannot be compared mainly due to inconsistency in emergy-money ratios used to convert emergy unit into monetary unit. This study aimed at providing a standardized format for the emergy evaluation of the Korean economy and environment for different emergy evaluations to be compatible. Even though the area of the continental shelf increased in this study compared to those of previous studies, areaweighted average tidal range for the entire continental shelf of Korea resulted in smaller tidal range, decreasing the final emergy input from tide. However, emergy inputs from nonrenewable resources and purchased goods and services increased with new categorization and use of more detailed data, combined with updated unit emergy values. This led to higher emergy-money ratio for the Korean economy, indicating that previous emergy valuations might have overestimated the contributions of marine ecosystem to the real wealth of the Korean society. The base year for gross domestic product used in the emergy evaluation needs to be clearly indicated due to its impact on the calculation of the emergy-money ratio. A standardized emergy table for the Korean economy will contribute to ensuring consistency among future emergy researches on the valuation of marine ecosystem services.