• 한국농공학회논문집
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• 제52권3호
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• pp.81-88
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• 2010

The purpose of this study is to analyze the spatial characteristics of Namgang-Dam watershed for a Total Maximum Daily Loads (TMDL). Three TMDL target sites, Gyeonghogang1, 2, Namgang-Dam2, are located within Namgang-Dam watershed. Under the current criterion for TMDLs, 3-year arithmetic mean BOD concentration of the target sites should not exceed the target concentration for 2 consecutive years. Two and three times of violation were observed for Gyenghogang2 and Namgang-Dam2 sites while no violation was found for Gyeonghogang1 site. However, no violation was found since 1999 for all three sites. Correlation between each 12 stations within the watershed were analyzed and cluster analysis was conducted to figure out the spatial characteristics of the watershed. Correlation coefficient between Gyonghogang1 and 2 was high (0.758) while the coefficients between lake station (Namgang-Dam2) and stream stations (Gyonghogang1 and 2) were very low. Dendrogram indicated that all of three Namgang-Dam stations were very close and Gyenghogang1, 2 stations were also close.

• 물과 미래
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• 제27권1호
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• pp.53-67
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• 1994

낙동강 중류부에서의 수질해석을 위한 확정론적 수질모형을 개발하였으며 확정론적 수질해석 모형 RQ1은 수리, 수문학적 해석을 위한 RQ1-1과 수질해석을 위한 RQ1-2로 구성되어 있다. 낙동강 중류부의 수질 해석을 위하여 왜관에서 진동에 이르는 이 유역의 월별 평균유량과 최소유량을 산정하였고 하도단면의 기하학적 특성을 기초로 하여 불등유해석을 실시하므로써 수질해석에 필요한 수리학적 특성치를 계산하였다. 확정론적 수질해석모형에 의한 수질해석 결과 BOD의 최대지점은 금호강 합류점 또는 진천천 합류점, DO의 최소 지점은 현풍하류부로 나타났다. 수질모형에 의한 계산결과치는 수개지점에서의 실측지와 합리적인 범위내에서 일치되고 있었으며 이 유역에서 목표수질에 도달하기 위한 금호강에서의 최대 BOD 허용부하량을 산정하여 제시하였다.

• The Korean Journal of Ecology
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• 제26권2호
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• pp.87-89
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• 2003

Although a forest damage of large area due to air pollution has not yet been found in Korea, declines of Korean red pine (Pinus densiflora Sieb. et Zucc.), the most common coniferous species, have been locally reported. To evaluate the effect of air pollution and acid deposition on the forests, SO$_2$ concentration, acid load, soil pH and tree decline were monitored for 13 years from 1988 to 2001 in Namsan, Doowang and Gyebangsan with the gradient of air pollution. During the study period, annual mean SO$_2$ concentration in Namsan, Doowang and Gyebangsan were 14 ppb, 13 ppb and 6 ppb, respectively. Annual mean acid loads in Namsan and Doowang were three to four times more than that in Gyebangsan. As respected, forest surface soils in Namsan and Doowang were acidified to pH 4.1 and 4.3, whereas that in Gyebangsan showed normal value as pH 5.4. On the other hand, decline degrees of Korean red pines in Namsan and Doowang in both 1996 and 2001 were higher than those in Gyebangsan. It is reasonable that the severer tree declines in Namsan and Doowang could be closely related with the higher air pollution, acid load, and the effects (possibly Ca deficit and Al toxicity) of soil acidification.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2010년도 학술발표회
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• pp.1355-1359
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• 2010

The purpose of this study is to analyze the spatial characteristics of Namgang-Dam watershed for a Total Maximum Daily Loads(TMDL). Three TMDL target sites, Gyeonghogang1, 2, Namgang-Dam2, are located within Namgang-Dam watershed. Under the current criterion for TMDLs, 3-year arithmetic mean BOD concentration of the target sites should not exceed the target concentration for 2 consecutive years. Two and three times of violation were observed for Gyenghogang2 and Namgang-Dam2 sites while no violation was found for Gyeonghogang1 site. However, no violation was found since 1999 for all three sites. Correlation between each 12 stations within the watershed were analyzed and cluster analysis was conducted to figure out the spatial characteristics of the watershed. Correlation coefficient between Gyonghogang1 and 2 was high (0.758) while the coefficients between lake station (Namgang-Dam2) and stream stations (Gyonghogang1 and 2) were very low. Dendrogram indicated that all of three Namgang-Dam stations were very close and Gyenghogang1, 2 stations were also close.

• Environmental Engineering Research
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• 제10권6호
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• pp.306-315
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• 2005

Total gas phase mercury (TGM) concentrations and event wet-only precipitation for Hg were collected for nine months (from April, 2002 to Dec., 2002) at Sterling, NY on the shoreline of Lake Ontario. TGM concentrations measured in this study ($3.02{\pm}2.14\;ng/m^3$) were in somewhat high range compared to other background sites. Using simplified quantitative transport bias analysis (SQTBA) possible sources affecting high Hg concentration in Sterling was identified, and they are coal-fired power plants located in southern NY and Pennsylvania. Wet deposition measured at Mercury Deposition Network (MDN) sites including Pt. Petre and Egbert, ON were compared with data obtained at the Sterling to estimate the total mercury wet deposition flux to Lake Ontario. The wet deposition flux was calculated to be the highest at the Sterling site ($7.94\;{\mu}g/m^2$ from April, 2002 to Dec. 2002) and the lowest at the Egbert ($3.92\;{\mu}g/m^2$), due to the both the difference in precipitation depth and Hg concentration in the precipitation. The deposition measured at the Sterling site is similar to Lake Michigan deposition of $6-14\;{\mu}g/m^2$ (converted for ninth months) measured for Lake Michigan Mass Balance Study (LMMBS).

• Environmental Engineering Research
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• 제19권3호
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• pp.223-228
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• 2014

We investigated seasonal algae variability and its influence on water quality in an agricultural reservoir. We observed that maximal total phosphorus (TP) loads were 1,715 kg from farmland in September, which changed the ecosystem in the reservoir. At this time, Dictyosphaerium pulchellum as green algae dominated. Aulacoseira ambigua as diatom became the most dominant from November 2010 to May 2011. The diatom was sensitive to water temperature. Microcystis spp. and Oscillatoria spp. as cyanobacteria were dominant during summer and fall, and sank down to the sediment during winter and spring. Increasing water temperature during summer causes anaerobic conditions in the sediment, leading to regrowth of cyanobacteria. With regard to the ratio of total nitrogen (TN) to TP, green algae and cyanobacteria were dominant at TN:TP ratios less than 20-30. Diatoms were dominant at TN:TP ratios greater than 30-40. Statistical analysis indicated that diatom growth was dependent on water temperature and TN concentration. TP concentration and water temperature were the key factors for the growth of cyanobacteria and green algae. From these results of this study, the management of land-use was an important parameter for improving water quality in the agricultural reservoir.

• 한국물환경학회지
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• 제23권2호
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• pp.266-273
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• 2007

In this study, discharge of the pollutants from the rice paddies during cultivation and its pattern were investigated. The pH in the returned and rainfall water from ten different paddies was between 6.9 and 7.4, which is not associated with the cultivation time and farming style of individual paddy. TN and TP concentrations were highest in the beginning of first top dressing (fertilization), which indicates that proper top dressing and returned water management is crucial to reduce their discharge loads. In particular, TN concentration was more or less constant until tillering stage. This is thought to be due to the runoff of soil-adsorbed nitrogen and compost. Average SS concentration in the returned and rainfall water was 28 mg/L, and organics was predominantly soluble form, and highest COD 25 mg/L during transplanting, lowest 11.3 mg/L and average 11.3 mg/L. Density of TC (total coliform bacteria) was from 1000/100 mL to 114,000/100 mL and FC (fecal coliform) was 5 to 16% of TC density.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2960-2973
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• 2022

Since Fukushima nuclear power plant (NPP) accident in 2011, the importance of research on various severe accident phenomena has been emphasized. Particularly, detailed analysis of combustion risk is necessary following the containment damage caused by combustion in the Fukushima accident. Many studies have been conducted to evaluate the risk of local hydrogen concentration increases and flame propagation using computational code. In particular, the potential for combustion by local hydrogen concentration in specific areas within the containment has been emphasized. In this study, the process of flame propagation generated inside a reactor core to containment during a loss of coolant accident (LOCA) was analyzed using MELCOR 2.1 code. Later in the LOCA scenario, it was expected that hydrogen combustion occurred inside the reactor core owing to oxygen inflow through the cold leg break area. The main driving force of the oxygen intrusion is the elevated containment pressure due to the molten corium-concrete interaction. The thermal and mechanical loads caused by the flame threaten the integrity of the containment. Additionally, the containment spray system effectiveness in this situation was evaluated because changes in pressure gradient and concentrations of flammable gases greatly affect the overall behavior of ignition and subsequent containment integrity.

• 한국의학물리학회지:의학물리
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• 제33권4호
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• pp.88-100
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• 2022

Purpose: Cerebral microbleeds are more susceptible than surrounding tissues and have been associated with a variety of neurological and neurodegenerative disorders that are indicative of an underlying vascular pathology. We investigated relaxivity changes and microvascular indices in the presence of microbleeds in an imaging voxel by evaluating those before and after contrast agent injection. Methods: Monte Carlo simulations were run with a variety of conditions, including different magnetic field strengths (B₀), different echo times, and different contrast agents. ΔR2^* and ΔR2 and microvascular indices were calculated with varying microvascular vessel sizes and microbleed loads. Results: As B₀ and the concentration of microbleeds increased, 𝜟R2^* and 𝜟R2 increased. 𝜟R2^* increased, but 𝜟R2 decreased slightly as the vessel radius increased. When the vessel radius was increased, the vessel size index (VSI) and mean vessel diameter (mVD) increased, and all other microvascular indices except mean vessel density (Q) increased when the concentration of microbleeds was increased. Conclusions: Because patients with neurodegenerative diseases often have microbleeds in their brains and VSI and mVD increase with increasing microbleeds, microbleeds can be altered microvascular signals in a voxel in the brain of a neurodegenerative disease at 3T magnetic resonance imaging.

• 한국수산과학회지
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• 제28권3호
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• pp.279-293
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• 1995

강우시 유출되는 비점원오염물질의 유출특성을 조사하고, 수영만에 있어서 하천오염물질이 만내로 유입되어 미치는 영향을 4가지 경우인 점원오염부하가 미치는 영향(Case 1), 연간 비점원오염부하가 미치는 영향(Case 2), 우기시 오염부하가 미치는 영향(Case 3)과 실측강우 조사기간동안 비점원오염부하가 미치는 영향(Case 4)으로 나누어 예측 및 평가하였다. 이상의 연구 결과를 요약하면 다음과 같다. 비점원오염물질의 특성을 보면 강우시 하천의 수질변동은 강우강도와 유량의 증감과 매우 밀접한 관계를 가지고 증감한다 COD, TSS와 VSS의 경우는 2차 강우 후 유량이 최대인 $65.736m^3/s$가 될 때 오염물질의 최대치가 나타났는데 최대치는 각각 121.4mg/l, 1148.0mg/l와 262.0mg/l를 보여주었다. 그리고 영양염류인 경우는 1차 강우가 시작되어 유량이 1차 최대치인 $4.686m^3/s$로 증가할 패 최대치를 보여주는데 $TIN,\;NH_4\;^+-\;N,\;NO_2\;^--N$과 $PO_4\;^{3-}-P)$는 각각 20.306mg/l, 14.154mg/l, 9.571mg/l와 1.785mg/l를 나타내며 2차 강우가 시작된 후 약간 증가하다가 감소하였다. 해수유동모델에 의한 결과를 보면 만내 유향은 낙조시에 시계방향으로 창조시에 반시계방향으로 북동-남서방향이다. 만내 조류속은 최대 0.3m/s이고 만외 유속은 0.4m/s 정도이며 계산치는 관측치와 매우 유사하게 재현되고 있다. 확산모델의 보정은 점원오염부하량이 만내에 미치는 영향을 수영만내 관측치를 이용해 반복 시뮬레이션하여 보정하였고 보정결과 COD, SS의 계산 결과는 관측치와 잘 일치하였다. 확산모델의 적용결과 수영강의 오염부하는 낙조시에는 해운대 해수욕장으로 창조시는 광안리 해수욕장으로 수질을 악화시켰다. 비점원오염부하가 만내에 미치는 영향을 재현시킨 결과 연간 강우로 인한 비점원오염부하(Case 2)와 우기시 강우로 인한 오염부하(Case 3)가 미치는 영향은 점원오염부하(Case 1)가 만내 수질이 미치는 영향과 비교해 광안리 해수욕장의 오염부하를 약간 증가시키며 큰 차이는 보이지 않았다. 강우 조사시 비점원오염부하가 미치는 영향(Case 4)은 수영만내에 매우 심각한 오염현상을 보여준다. 낙조시에는 COD와 SS의 만내의 농도 분포는 각각 2.0-30.0mg/l와 7.0-200.0mg/l를 보여준다. 낙조시에는 창조시보다 낮은 오염정도를 나타내나 해운대 해수욕장으로는 높은 오염을 가중시키는 것을 볼 수 있다. 그러나 강우가 멈춘 후 24시간이 경과하여 실측한 수영만의 오염분포를 보면 건기시 해역농도에 비해 약간 높은 농도분포를 보여 주는 것으로 보아 입자가 큰 침강성 고형물질의 빠른 침강과 수영만내 해수유동으로 인해 빠르게 확산되어 농도가 감소되는 것으로 보인다. 그러나 강우가 시작한 후 매우 높은 오염물질을 함유하는 강우유출수가 만내로 유입될 때의 충격부하는 수영만의 해양생태계에 심각한 영향을 미치리라 예상되며 만약 이들 강우유출수를 처리하여 만내로 유출시키면 만내 수질은 개선되리라 사료된다.