• Korean Journal of Ecology and Environment
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• v.42 no.2
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• pp.242-252
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• 2009

The purpose of this study was to develop a Multi-metric Water Quality Assessment (MWQA) model and apply it to dataset sampled from Paldang and Daechung reservoir in 2008. The various water dataset used to this study included 5 year data sets (2003${\sim}$2007) in Korean reservoirs which were obtained from the Ministry of Environment, Korea. In this study, suggested MWQA model has 4 metrics that were composed of 4 parameters such as chemical, physical, biological, and hydrological variables. And, each of the variables attributed total phosphorus (TP) concentration in water, secchi depth (SD) measure in water, chlorophyll-${\alpha}$(Chl-${\alpha}$) concentration in water and the ratio of inflow of water into lakes and efflux of water from lakes, input/output (I/O). First, we established the criteria for trophic boundaries. The boundary between oligotrophic and mesotrophic categories was defined by the lower third of the cumulative distribution of the values. The mesotrophic-eutrophic boundary was defined by the upper third of the distribution. Second, each metric was given by a point-oligo=1, meso=3, eu=5. And then, obtained total score from each metric was divided 5 grade-Excellent, Good, Fair, Poor, and Very poor. As the results of applying the proposed MWQA model, the Paldang reservoir obtained "Fair" or "Poor" grade and Daechung reservoir obtained "Excellent" or "Good" grade. The suggested MWQA model through these procedures will enable to manage efficiently the reservoir. And, more studies such as metric numbers and attributes should be done for the accurate application of the new model.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.93-100
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• 2024

Pore water freezes in low-temperature compaction, which leads to different compaction characteristics compared to room temperature conditions. In regions like Alberta, Canada, where organic soils are prevalent, compaction performance is influenced by the high water retention and compressibility of organic soils, as well as their sensitivity to freezing and thawing. Alberta's strict environmental regulations demand the reuse of excavated soil for backfill, and the long winter season creates challenging conditions for civil engineering projects. In this study, a laboratory compaction test was conducted to evaluate the low-temperature compaction characteristics of organic soils with varying organic content. The results indicate that the optimum moisture content increases as the organic content increases, and the maximum dry unit weight decreases by up to 21.9%. In addition, under temperature conditions below -4℃, no optimum moisture content was observed, and the dry unit weight decreased as the moisture content increased.

• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.61-71
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• 2007

The photosynthetic characteristics and primary production by phytoplankton in open waters of two wetlands (the Banwol and the Donghwa wetland) of Sihwa Constructed Wetland with different water chemistry were investigated to provide the information for the wetland management considering the water treatment efficiency. During the study period (from March to October, 2005) the primary productivity in open waters ranged from 481 to 11,275 mgC $m^{-2}$ $day^{-1}$, which is very high compared with the eutrophic level of 600mgC $m^{-2}$ $day^{-1}$. From the analysis of the photosynthesis-irradiance (P-I) model parameters, the photosynthetic characteristics may be affected by different concentration and ratio of nutrient (N and P) between two wetlands. Assimilation number (AN) was higher in the Donghwa wetland (average AN: 8.5gC $gChl^{-1}$ $hr^{-1}$) with high P and low N/P ratio than the Banwol wetland (average AN: 5.8gC $gChl^{-1}$ $hr^{-1}$) with high N and high N/P ratio. This result indicates that AN may be concerned with phosphorus than nitrogen and low NIP ratio. Positive correlation (R=0.81) was observed between the initial slope and AN, implying that AN was high in case of phytoplankton having more active photosynthesis ability under low light. On the other hand, maximum photosynthesis (Pmax) was related positively with chlorophyll a concentration showing correlation coefficient of 0.47. In this study, considering the high primary production through phytoplankton photosynthesis in open waters of Sihwa Constructed Wetland, the produced organic matter by phytoplankton may affect the water quality within wetland and its efficiency of water treatment. Also, the photosynthetic characteristics may be affected by different nutrient enrichment (especially phosphorus) of wetlands. This study suggests that the production by phytoplankton and its characteristics in open water of constructed wetland for water treatment should be considered to improve the removal efficiency of organic matter.

• Journal of Korean Society of Forest Science
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• v.96 no.1
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• pp.89-95
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• 2007

This study was carried out to evaluate soil properties by regions from chestnut (Castanea crenata Sieb. et Zucc) stands in Gyeongnam province. Soil physical and chemical properties were measured from soil samples of top 20 em collected from three hillslopes (upper, middle, lower) of the chestnut stands in six regions (Jinjusi, Sacheonsi, Sancheonggun, Hadonggun, Goseonggun, Hapcheongun) where are major chestnut cultivation areas throughout the province. Soil properties were significantly different among regions (p<0.05), while were not significantly different among hillslopes (p>0.05). Soil bulk density, soil pore space, soil pH, organic matter content, total nitrogen, available phosphorus, and CEC were significantly different among regions (p<0.05). Soil bulk density was significantly lower (p<0.05) in Hadonggun ($0.96g/cm^3$ than in other regions ($1.12{\sim}1.22g/cm^3$). Soil pH was below pH 5.03 in most regions and Sancheonggun showed the lowest soil pH value (pH 4.62), followed by Jinjusi, Hadonggun, Hapcheongtm, Goseonggun, and Sacheonsi. Organic matter content was highest in Hadonggun (6.46%), while other regions ranged between 2.93% and 3.47%. Total nitrogen content showed a similar trend like the organic matter content. Available phosphorus was above 100 ppm in Jinjusi, Hadonggun and Sancheonggun, but Sacheonsi showed the lowest concentration (15 ppm) among the regions. Cation Exchange Capacity (CEC) was above 10 cmolc/kg in Goseonggun and Hadonggun, but below 8.6 cmolc/kg in Jinjusi and Hapcheongtm. Potassium content ranged between 0.07 and 0.14 cmolc/kg, and magnesium was above 0.66 cmolc/kg in all regions. The results indicate that soil property in chestnut stands was different among regions in Gyeongnam province. This suggested that the chestnut stands should be managed by the fertilization application reflected in the variability of regional soil property in chestnut stands.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.2
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• pp.147-152
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• 2010

The investigations were conducted to improve the fertilizer use in upland soil on the different topographies, and crops at 163 upland fields located in the parts of Gyengsangbuk-do area. The soil distribution was based on crops, and topographiese. Soils from these fields were analyzed for pH, organic mater, available phosphorus ($P_2O_5$), exchangeable potassium, calcium and magnesium, and found to have pH5.9, organic mater 23.2 g $kg^{-1}$, $P_2O_5$ 549 mg $kg^{-1}$, exchangeable potassium, calcium and magnesium were 0.9, 5.6, and 2.3 $cmol^+\;kg^{-1}$, respectively. The excessive distribution percent of soil samples for crops were higher than the optimum range in $P_2O_5$, and exchangeable potassium. The content of organic matter, $P_2O_5$, exchangeable potassium, calcium, and magnesium were increased with the decreasing slope. The major chemical components in fans topographies were 28.4 g $kg^{-1}$ for organic matter, 700 mg $kg^{-1}$ for $P_2O_5$, and 1.0 $cmol_c\;kg^{-1}$ for exchangeable potassium relatively higher in comparison with other topographies. The content of $P_2O_5$ were lower in diluvium, and hilly areas than other topographies. The soil of red pepper was more influenced by the amount of applied fertility than the slope, and topographies, On the other hand the crops like soybean and sesame, were more affected by the slope, and topographies.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.3
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• pp.152-163
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• 2001

Based upon the sedimentological, geochemical and micropaleontological analyses of two sediment cores from the Antarctic Peninsula (AP), three distinct lithological units can be recognized: (1) ice-proximal an/or ice-distal diamictons in the lower part of the cores, accumulated just seaward of the grounding line of the ice shlef until 11,000 yrs BP; (2) diatomaceous mud between 6,000 and 2,500 yrs BP in the middle part, resulted from a large influx of organic materials by enhanced production of open marine condition; (3) diatomaceous sandy mud since 2,500 yrs BP, characterized by an increase in sand content and decrease in TOC and diatom abundance in the lower layers, which reflects the formation of more extensive and seasonally persistent sea ice. Based on the C-14 radiocarbon dating, the sub-ice shlef deposition of the diamicton on the AP western shelf completed around 11,000 yrs BP. Colder condition was reinstated between 12,800 and 11,600 BP with a dropin TOC content and diatom abundance, which is coincident with the Younger Dryas event in the North Atlanticregion. At this time, the ice shelf, that is now absent in the study area, appears to advance as evidenced by an abrupt increase in sea-ice taxa. A climatic optimum is recognized between 9,000 and 2,500 BP, coincide witha mid-Holocene climatic optimum 'Hypsithermal Warm Period' from the other Antarctic sites. During this time, diatomaceous mud accumulated by a large influx of organic materials by enhanced production occurred in openmarine condition. Around 2,500 BP, diatomaceous sandy mud reflects the formation of more extensive and seasonally persistent sea ice, coincident with the onset of the Neoglacial in the Antarctic. Our results provide evidence of climatic change from the Antarctic Peninsula`s western shelf that helps in determining the existence and timing of Holocene milennial-scale climatic events in the Southern Hemisphere.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.1
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• pp.47-58
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• 2002

Much of the plastic film house soils in the southern part of the Korean peninsula are managed using a upland-paddy rotation culture system (hereafter, RS) to prevent salt accumulation in soil. However, information on the effects of RS on soil properties and environmental conservation is limited. In order to determine the effects of RS on soil properties, 22 fields under RS and 20 fields under a non-rotation system (hereafter, NRS) in plastic film houses were selected in Chinju, in southern Korea, and the P distribution characteristics were investigated, including the chemical properties. The RS contributed to the removal of water-soluble salts in the surface layer and to the redistribution of organic matter evenly in the soil profile. In the AP horizon, available phosphorus levels were $1,611mg\;kg^{-1}$ in RS and $1,789mg\;kg^{-1}$ in NRS, which markedly exceeds the optimum range for plant cultivation. Total P was lower in RS (average $4,593mg\;kg^{-1}$) than in NRS (average $5,440mg\;kg^{-1}$) and this decrease was taken to be an effect of RS. Inorganic P was the predominant form of P in both systems, followed by organic P and residual P. A soil profile showed that total and inorganic P concentrations decreased with depth in both systems. However, organic P increased withdepth in RS, which was in contrast to that noted in NRS. The increase in organic P with depth in RS implied that organically rather than inorganically derived phosphate moved through the soil. The concentrations of water-soluble P, Ca-P and Al-P were higher in NRS than in RS soil profiles, but the Fe-P concentration was higher in RS than in NRS, which might be affected by the anaerobic conditions found in paddy soils. In both systems, the Al-P form of extractable P predominated in the surface layer, followed by Ca-P, Fe-P and water-soluble P. With increasing depth, the composition rate of Ca-P to extractable P decreased to less than 10% in the 60-70cm depth, as Fe-P dominated at this level. The content of water-soluble P, potentially the main source of eutrophication, was higher in NRS than in RS. These results indicated that the RS used in plastic film houses contributed to the removal of water-soluble salts but only slightly decreased the phosphate concentration.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.227.1-227.1
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• 2015

산업이 발달하면서 다양한 화학물질이 배출되고 이로 인하여 환경이 오염되고 있으며, 특히, 대부분의 유기 화합물은 대기오염에 많은 영향을 주는 물질로 알려져 있다. 최근 유기 화합물을 제거하기 위해서 UV와 가시광에서 반응하는 광촉매 연구가 진행되고 있다. 본 연구에서는 밴드갭에 변화를 주는 doped $TiO_2$와 가시광에서 반응하는 조촉매를 이용하여 광촉매의 특성을 향상시키는 coupled $TiO_2$를 제조하였다. Doped $TiO_2$를 제조하기 위해서 비금속 물질인 질소(nitrogen)을 사용하였고, coupled $TiO_2$는 graphine oxide(GO)를 환원하여 $TiO_2$-RGO 촉매를 제조하였다. N-$TiO_2$와 $TiO_2$-RGO의 광학 특성을 평가하기 위해서 UV/Vis 분광광도계를 사용하였다. Methylene blue(MB)와 methyl orange(MO)가 분해되는 반응을 통해서 N-$TiO_2$와 $TiO_2$-RGO의 광촉매 특성을 평가하였다. 또한, MB와 MO 분해 테스트에 395 nm long pass filter를 이용하여 가시광에서의 광촉매 활성을 평가하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.292-292
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• 2009

OLED(Organic Light Emitting Device)는 LCD(Liquid Crystal Display)의 뒤를 잇는 차세대 디스플레이의 선두주자로서 자체발광형이기 때문에 백라이트 등의 보조광원이 불필요하며, 구동전압이 낮고 넓은 시야각과 빠른 응답속도 등의 특징을 가지고 있다. 또한 플렉서블 기판을 사용할 수 있어 차세대 디스플레이인 플렉서블 디스플레이에 적합하다. 플렉서블한 디스플레이를 만들기 위해서 플라스틱 기판에 OLED 물질을 사용하여 기존에 무겁고, 깨지기 쉬우며, 변형이 불가능한 유리로 만든 소자 보다 더 가볍고 깨지지 않고 변형이 가능한 플렉서블 디스플레이를 제작 할 수 있다. 그러나 플라스틱 기판은 매우 큰 투습율을 가지고 있어 OLED소자에 적용시키면 공기 중의 수분이나 산소와 접촉이 많아져 쉽게 산화되어 소자의 효율 및 수명이 짧아진다. 또한 OLED에 사용되는 유기물도 산소나 수분에 의해 특성이 급격히 저하되기 때문에 산소 및 수분의 차단은 필수적이다. 이러한 단점을 최소화하기 위해서 PECVD(Plasma Enhanced Chemical Vapor Deposition)로 만든 SiON(Silicon Oxynitride) 박막을 차단막(Passivation layer)으로 사용하였다. PECVD를 이용하여 SiON 박막을 증착시킬 때 RF Power, 공정압력, Distance의 변화에 따른 박막의 결정화도, 수분투습도, 광투과도 등의 특성을 FT-IR(Fourier Transform Infrared Spectroscopy), Ellipsometer, UV-visible Spectrophotometer, MOCON를 이용하여 SiON 박막의 특성을 고찰하였다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.05a
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• pp.414-417
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• 2003

유역의 경사가 비교적 급하고, 소규모 축산농가의 미처리된 축산폐수 및 농경지 배수, 산재된 마을하수 등 비점오염원의 유출이 강우시 집중적으로 이루어지는 중산간 농업용 저수지의 수질개선을 위한 공법으로 부영양화된 충남 아산 마산저수지의 유입부에 조성한 저류지를 이용한 수질개선효과 및 물질분해자로서 미생물학적 특성을 2000년부터 2002년까지 3년간 연구함으로서 향후 유사한 농업용저수지의 수질개선 방안으로 실용화 가능성을 모색하고자 하였다. 그 결과 수질정화효과는 총질소와 총인 등 영양염류의 정화효과가 비교적 우수하게 나타났으며, 유기오염물질로서 BOD, COD, SS 등은 평균 수질정화효과는 (-)의 값을 보여주었으나, 강우기에는 정화효율이 높게 나타났다 또한, 저류지의 물질 침전기능 외 오염물질의 활발한 분해작용을 살펴보고자 세균 분포 특성을 조사한 결과 유입수와 저류지, 저수지 각각의 수체에서 조사된 총세균수 및 총세균수에 대한 진정세균수의 비율이 유입수<저류지<유출수의 순으로 나타나 저류지의 유기물질 분해 활성이 높음을 보여주고 있다. 따라서 저수지 유입부에 조성한 저류지의 수질개선효과는 강우시 입자성 유기물질의 효과적 제거 뿐만아니라 영양염류의 제거효과, 특히 질소의 제거효과가 높은 정화기구로서 설치비용이 적고, 유지관리가 간단한 특성을 살려 유사한 중규모 농업용저수지의 수질개선 기법으로 널리 활용할 가치가 있음으로 사료된다.