Earticle

Florfenicol은 동물용 항생제로 소, 돼지, 닭, 어류 등의 호흡기 및 소화기 질병 치료제로 사용되고 있다. 항생제는 체내에 서 80-90%가 분해되지 않고 환경으로 배출되기 때문에 악영향을 줄 수 있다. 본 연구는 Florfenicol이 수계에 미치는 영향을 연구하기 위하여 예측무영향농도(Predicted No Effect Concentration, PNEC)를 두 가지 방법으로 도출하였다. 급성독성시험 은 OECD test guideline에 따라 진행하였고 조류(Pseudokirchneriella subcapotata)와 물벼룩(Daphnia magna)의 반수영향농 도(EC50)는 각각 2.3 mg/L (72 hr-EC50), 384.3 mg/L (48 hr-EC50)로 산출되었다. 결정론적 방법의 PNECAF는 Florfenicol에 가 장 민감한 조류의 독성자료를 적용하여 2.3×10-3mg/L로 도출되었다. 생물종 10종의 L(E)C50 값들을 이용하여 종민감도분포 (Species Sensitivity Distribution, SSD)를 분석한 결과 HC5는 1.2 mg/L로 산출하였고, 이에 따라 확률론적 방법의 PNECSSD 는 0.2 mg/L로 도출하였다. 두 가지 방법의 PNEC를 비교한 결과 확률론적 방법으로 산출한 PNECSSD의 값이 약 86배 높은 것으로 확인되었다. 따라서 위해성평가 시에는 PNECSSD를 이용한 수질관리 기준치를 제시하는 것이 타당하다고 사료된다.

Florfenicol, animal antibiotic, used in the respiratory and digestive treatment of cows, pigs, chickens, and fish. Antibiotics can have an adverse effect because 80 to 90 percent of antibiotics are released into the environment without decomposing in the body. In this study, we derived Predicted No Effect Concentration (PNEC) in two ways to study the effect of Florfenicol on the water system. Acute toxicity assessment was performed based on the OECD Test Guideline. The halfeffective concentrations (EC50) of algae (Pseudokirchneriella subcapotata) and water flea (Daphnia magna) were calculated as 2.3 mg/L (72 hr-EC50) and 384.3 mg/L (48 hr-EC50). PNECAF was derived as 2.3×10-3 mg/L by applying toxicity data of algae most sensitive to florfenicol. Species Sensitivity Distribution (SSD) was analyzed using L(E)C50 (10 species) values, and HC5 was 1.23 mg/L and PNECSSD was 0.2 mg/L. Comparing the two methods of PNEC, the value of PNECSSD was confirmed to be about 86 times higher than PNECAF. In risk assessment, it seems reasonable to approach the PNECSSD value.

한반도 미세먼지의 연도별 공간분포를 비교 분석하기 위해서 측정소 측정자료를 이용하기에는 대도시 위주로 위치해 있기 때문에 한반도 전체에 대한 미세먼지의 공간분포를 파악하기에는 어려움이 있다. 반면 화학수송모델을 이용하여 공 간분포를 분석하는 방법은 공간분포를 파악하기에는 좋으나 누실된 배출량 자료 등에 의해 미세먼지 농도가 과소 평가 되는 경향이 있다. 본 연구에서는 공간 분포 분석에 측정 자료를 이용한 방법과 화학수송모델의 장점을 결합하여 화학수 송모델에 측정소 측정자료를 자료동화방법으로 재분석하여 분석하였다. 자료동화는 Pun’s Interpolation방법으로 국내 317개소의 대기오염측정소자료를 이용하였다. 자료동화를 통해 재분석한 2006년, 2009년, 2012년에 대해 서울, 부산을 대상으로 자료동화 전·후의 모델 정합도를 분석한 결과 자료동화 전에 비해 자료동화 후에 IOA가 0.39~0.71에서 0.77~0.98로 개선되었고, MBIAS는 -32.7 ~ -17.0 μg/m3에서 -8.1 ~ -0.2 μg/m3로 개선되는 것으로 나타났다. 자료동화를 통해 재분석한 결과를 이용하여 1시간, 24시간 평균의 연간 최대농도와 연평균 지역별 공간분포를 분석하였다. PM-10 농도의 공간분포는 연평균에서는 수도권과 광역시의 미세먼지가 높은 것으로 동일하게 나타났으나 1시간 최대농도와 24 시간 최대농도의 공간분포는 연도별로 차이가 있는 것으로 나타났다. 이는 국내의 고농도 PM-10은 지역의 배출에 의한 것이 아닌 월경성 오염원의 유입으로 나타나는 양상이기 때문에 연도별로 1시간 및 24시간 최대농도 분포가 다른 것으 로 판단된다. 특히 측정소가 없는 강원도의 양양지역에서 인근 측정소 측정자료와는 다른 경향이 나타났다. 이는 자료동 화 방법을 적용한 화학수송모델을 이용한 공간분포 특징으로 본 연구를 통해 자료동화기법으로 재분석 된 화학수송모델 자료는 대기질 현황분석 등에 지역별로 상세한 자료를 제공하는 방안이 될 수 있음을 확인하였다.

To improve PM-10 spatial distribution predicted by the chemical transport model of CMAQ, re-analysis method using measured PM concentrations was developed and tested its performance. Data assimilation method for the reanalysis was Pun's interpolation method with 28 km radius of influence of measured PM-10 values and measured PM-10 data in 317 air quality monitoring stations in Korea were used in this study. Predicted PM-10 concentrations by CMAQ with the data assimilation method were compared with measured ones for Year 2006, 2009 and 2012. The results showed that CMAQ model performance with data assimilation was significantly improved in predicting PM-10 concentrations; IOA at Seoul and Busan was improved from 0.39~0.71 to 0.77~0.98 and MBIAS was also improved from -32.7~-17.0 μg/m3 to -8.1~ -0.2 μg/m3. To predict PM-10 distribution over Southern Korean Peninsula, PM-10 re-analysis for Year 2006, 2009, and 2012 was carried out. The hourly and daily maximum as well as daily and annual PM-10 concentration distribution maps were obtained using the data assimilation methods developed in this study. The spatial distribution of annual average PM- 10 concentration was relatively high in the urbanized metropolis area such as Seoul metropolitan area, Busan and Ulsan area and those trends were the same for Year 2006, 2009 and 2012. However, the spatial distributions of the hourly and the daily maximum PM-10 concentrations were different in each year. Re-analyzed PM-10 maps showed that the data assimilation method using CMAQ has an advantage in predicting spatial distributions where monitoring stations were sparsely available such as Yangyang area in Kangwon province.

We have performed CFD simulation and analyzed flow and concentration fields for the basic data of the ventilation system for removing pollutants which were produced in a lecture room. The flow patterns indicated differently according to the arrangement of openings and the concentration distribution of pollutants were showed higher and lower because of the effect of that flow patterns. In the case of arranging the openings to the upper and lower side, the stagnation appearance of flow formed in the interested space. In the case of arranging the openings to the right and left side, the stagnation of high concentration pollutants appeared in the middle area of the interested space. On the increasing exhaust velocity, the distribution of pollutants appeared similar to the normal case, but the concentration of pollutants were lower.

A primary air pollutant as an indicator of air quality released from incomplete combustion is Carbon monoxide. A study of the distributions of CO concentration with no heat source in a tunnel model closed at left end side is simulated with a commercial CFD code. The tunnel model is used to investigate the CO concentration distributions at three Reynolds numbers of 990, 1970, and 3290. which are computed by the inlet velocities of 0.3, 0.6 and 1.0 m/s. The CFD predictive approaches can be useful for a better design to analyze the distributions of CO concentrations. In the case of the tunnel model closed at left end side alone, the concentration changes of x/H=-5 and -2.5 have the similar laminar characteristics like the case of the tunnel model closed at both end sides expecially at low values of Reynolds number. Irregular average CO concentration variations at Re=1790 are considered that the transition from laminar to turbulent flow occurs even in three different tunnel models.

The volatile organic compounds exposure is governed by the source distance and dispersion of the pollutant into air and groundwater. The purpose of this study was to validate suggested models for the prediction of concentration distributions. The study design was organized into different methods to simulate industry site. The distribution models generally showed a fair agreement with measured data. For graphical representation of concentration of volatile hydrocarbon, it has to obtain a continuous representation of the contamination of the site. Therefore, the used interpolative methods examined for this project are the IDW(inverse Distance Weighting) and kriging method. In the results, in summary, all two different methods can be used to quantify exposures at a particular source area, and thus provide, a solid foundation for making risk-based decisions. All the calculations can be performed using Excel's built-in functions, and the capabilities of geospatial analysis allow the results to be displayed visually. However, anyone who uses these methods should understand all of the assumptions and limitation.

Prandtl's mixing length theory was modified to obtain a power velocity distribution in which the coefficient and the exponent are variable over a range from : $$ A simple suspended-sediment concentration distribution was developed from the modified velocity distribytion : $ With nominal values of $\beta$=1.0, $\kappa$=0.4 and visual accumulation tube values of the fall velocity, the comparison between the theory and field measurements by the USGS on the Rio Grande is fair. Doubling the value of the exponent results in a good comparison. Further researches are needed for choosing the values of $\beta$, $\kappa$, and fall velocity values, and consideration on the effects of large-scale turbulence and secondary flows are necessary for them. In a pragmatic sense, on any gaging sites the close analysis of very detailed measurements can establish its specific coefficient and exponent.

멱 유속 분포를 구하기 위해 개정 Prandtl 혼합 거리 이론이 이용되었으며, 여기에서 사용된 지수값의 범위는 1/4~1/7이었다. 이 개정된 유속분포를 이용하여 간단한 부유사 농도 분포식을 개발하였다. 미국 지질조사국이 리오그란데강에서 실측한 자료와 명목값인 $\beta$=1.0, $textsc{k}$=0.4, 그리고 가시관에 의해 얻어진 침강속도를 이용한 개정 농도식 계산결과와 실측지와의 비교는 양호한 편이었으며, 지수에 임의로 두배를 해주었을 경우에는 좋은 결과를 보였다. 적당한 $\beta$, $textsc{k}$, 그리고 침강속도를 선택하기 위해 더 많은 연구가 필요하지만 이러한 연구가 대규모 난류와 이차류 영향에 대한 설명을 할 수는 없을 것이다. 하지만 실용적인 측면에서 보면 어느 관측지점에 대한 매우 자세하고 특별하게 측정된 자료는 그 지점에 맞는 지수나 계수를 찾아낼 수도 있다.

Modifications of Prandtl's mixing length theory were used to obtain a power velocity distribution in which the coefficient and exponent are variable over a range from 1/4 to 1/7. A simple suspended-sediment concentration distribution was developed which can be associated with this modified velocity distribution. Using nominal values of ${\beta}$=1.0, $\kappa$=0.4 and visual accumulation tube values of fall velocity, the comparison between theory and field measurements by the USGS on the Rio Grande is fair. Doubling the value of the exponent results in a good comparison. Further research is needed to be able to better choose ${\beta}$, $\kappa$, and fall velocity values, but such research will not be able to account for the effects of large-scale turbulence and secondary flows. In a pragmatic sense, a special set of fairly detailed measurements can establish coefficients and exponents for any gaging site.

Selective catalytic reduction (SCR) is a successful technique to reduce $NO_x$emissions in diesel exhaust gases. The aim of current study is to develop a SCR catalytic filter device for reducing $NO_x$ and soot emissions simultaneously in diesel combustors. SCR catalysts are used to reduce $NO_x$ emissions, and the novel catalytic filters inside SCR system are especially designed and manufactured to reduce soot particles. $NH_3$ or urea (which is converted to ammonia) is injected into exhaust stream then reacts with $NO_x$ emissions over the catalyst surface of SCR device, so that a uniform distribution of $NH_3$ is one of the challenges in the novel design of SCR device in order to attain $NO_x$ conversion and reduce NH3 slip optimally. In this study, three catalytic filters with $120^{\circ}$ interval are vertically mounted under the horizontal plate. Ammonia is injected radially perpendicular into the inlet main flow. The ammonia concentration in the SCR catalytic filter device is investigated by numerical simulation. Gaseous flow in SCR catalytic filter device is modeled as laminar and turbulent flow by varying the Reynolds numbers. The results show that there is the small influence of circulations on the ammonia concentration near the inlet domain at the low Reynolds number. On the contrary, the high influence of circulations on the ammonia concentration is observed at high Reynolds number.

A photocatalytic process was carried out with two types of TiO₂: commercial (C-TiO₂) and in-house synthesized (S-TiO₂). Parameters, such as, initial particle concentration and the nanoparticle (NPs) agglomerations effect on hydroxyl radical (●OH) concentration were investigated using electron spin resonance (ESR) spectroscopy with a spin trapping technique. The experimental results demonstrate that generation of ●OH and DMPO/●OH (5,5-dimethyl-1-pyrolline-N-oxide/hydroxyl radical) adduct formation is controlled by a shorter time-scale of the chemical reaction on particle surfaces and longer timescale particle agglomerations in the bulk dynamics. It was found that S-TiO₂ has a smaller particle size than C-TiO₂ NPs. As a consequence, S-TiO₂ NPs yield a higher concentration of ●OH compared to that of C-TiO₂NPs of the same concentration. These findings reveal an agreement between the ESR signals, agglomeration size analysis, and transmission electron microscopy (TEM) data. Detail explanations are presented mainly on the drive of dynamic time scales and the limitation of the number of NPs governed by their associated distributions. With the kinetic studies, we propose the mechanism for the generation of ●OH via a study of ESR DMPO/●OH spin trap technique. The mechanism accounts for the active surface area as the agglomeration process occurred throughout the suspension and the possibility of DMPO/●OH recombination as the surface of TiO₂ became dense with DMPO/●OH adduct.

The purpose of this study was to investigate the concentration and distribution characteristics of $PM_{10}$ at high schools classrooms in Ulsan and its surroundings. This study evaluated $PM_{10}$ levels in classrooms at 79 high schools in Ulsan from May 2008 to May 2009. The average $PM_{10}$ level was 63.8 ${\mu}g/m^3$, and the rate of exceeding the statutory maintenance limit was 16.0%. The average $PM_{10}$ level was higher in general schools (64.9 ${\mu}g/m^3$) compared to professional schools (59.2 ${\mu}g/m^3$), and private schools (66.6 ${\mu}g/m^3$) was higher than that of public schools (62.5 ${\mu}g/m^3$). The average $PM_{10}$ level (68.4 ${\mu}g/m^3$) in general classrooms was significantly (p < 0.01) higher than that in multi-purpose ones (54.6 ${\mu}g/m^3$), and first-year student classrooms (73.3 ${\mu}g/m^3$) was significantly (p < 0.05) higher than that in second or third grade ones (67.6 ${\mu}g/m^3$, 51.5 ${\mu}g/m^3$, respectively). The $PM_{10}$ level in schools in Dong-Gu in the vicinity of assorted industrial complexes was higher than that of schools located in other districts around the Ulsan Metropolitan Area. The regression model showed that $PM_{10}$ level was positively associated with number of students and relative humidity.

Organic dye-doped glasses, viz., ruthenium (II) tris(4,7'-diphenyl-1,10'-phenanthroline) $[Ru(dpp)_3]^{2+}$ incorporated into thin silica xerogel films produced by the sol-gel method, were prepared and their $O_2$ quenching properties investigated as a function of the $[Ru(dpp)_3]^{2+}$ concentration (3-400 ${\mu}M$) within the xerogel. The ratio of the luminescence from the $[Ru(dpp)_3]^{2+}$-doped films in the presence of $N_2$ and $O_2$ ($I_{N2}/I_{O2}$) was used to describe the film sensitivity to $O_2$ quenching. ($I_{N2}/I_{O2}$ changed three-fold over the $[Ru(dpp)_3]^{2+}$ concentration range. Time-resolved intensity decay studies showed that there are two discrete $[Ru(dpp)_3]^{2+}$ populations within the xerogels (${\tau}_1$ ~ 300 ns; ${\tau}_2$ ~ 3000 ns) whose relative fraction changes as the $[Ru(dpp)_3]^{2+}$ concentration changes. The increased $O_2$ sensitivity that is observed at the higher $[Ru(dpp)_3]^{2+}$ concentrations is a manifestation of a greater fraction of the 3000 ns $[Ru(dpp)_3]^{2+}$ species (more susceptible to $O_2$ quenching). A model is presented to describe the observed response characteristics resulting from $[Ru(dpp)_3]^{2+}$ distribution within the xerogel.

Vagal nerve activity has been known to play a crucial role in the induction and maintenance of atrial fibrillation (AF). However, it is unclear how the distribution and concentration of local acetylcholine (ACh) promotes AF. In this study, we investigated the effect of the spatial distribution and concentration of ACh on fibrillation patterns in an in silico human atrial model. A human atrial action potential model with an ACh-dependent $K^+$ current ($I_{KAch}$) was used to examine the effect of vagal activation. A simulation of cardiac wave dynamics was performed in a realistic 3D model of the atrium. A model of the ganglionated plexus (GP) and nerve was developed based on the "octopus hypothesis". The pattern of cardiac wave dynamics was examined by applying vagal activation to the GP areas or randomly. AF inducibility in the octopus hypothesis-based GP and nerve model was tested. The effect of the ACh concentration level was also examined. In the single cell simulation, an increase in the ACh concentration shortened $APD_{90}$ and increased the maximal slope of the restitution curve. In the 3D simulation, a random distribution of vagal activation promoted wavebreaks while ACh secretion limited to the GP areas did not induce a noticeable change in wave dynamics. The octopus hypothesis-based model of the GP and nerve exhibited AF inducibility at higher ACh concentrations. In conclusion, a 3D in silico model of the GP and parasympathetic nerve based on the octopus model exhibited higher AF inducibility with higher ACh concentrations.

Carbon monoxide (CO) is a primary air pollutant as an indicator of air quality released from motor vehicle combustion. A comparative study of the distributions of CO concentration with no heat source in two tunnel models open and closed at both end sides is simulated with a commercial CFD code. The tunnel models are used to investigate the CO concentration distributions at three Reynolds numbers, which are computed by the inlet velocities of 0.3, 0.6 and 1.0 m/s. For a better tunnel design, the CFD predictive approaches are available in qualitatively studying the distributions of CO concentration. In the case of the tunnel open at both end sides in sixty seconds, the total CO concentrations are approximately twenty eight percent higher than those in the closed case.

Spatial distribution of phytoplankton pigment concentration (PPC) and sea surface temperature (SST) around the East Korean Warm Current (EKWC) was described, using both ocean color images and advanced very high resolution radiometer (AVHRR) images. Water mass in this region can be classified into five categories in the horizontal profile of PPC and SST, nLw(normalized water-leaving radiance) images: (1) coastal cold water region associated with concentrations of dissolved organic material or yellow colored substances and suspended sediments, (2) cold water region of thermal frontal occurred by a combination of phytoplankton absorption and suspended materials, (3) warm water overlay region by the phytoplankton absorption than the suspended materials; (4) warm water region occurred by the low phytoplankton absorption, and (5) offshore region occurred by the high phytoplankton absorption. In particular, the highest PPC area appeared in the ocean color and SST images with a band shaped distribution of the thermal front and ocean color front region, which is located the coastal cold waters along western thermal front of the warm streamer of the EKWC.

Total primary production resulting from the photosynthetic process can be defined as the amount of organic matter produced in a given period of time. It is proportional to the chlorophyll-a (chl-a) values in the surface layer of the ocean. The MODIS board on Aqua satellite measures visible and infrared radiation in 36 wavebands, providing simultaneous images of chl-a concentration and sea surface temperature (SST) in the upper layer of the sea. The seasonal distribution of chl-a concentration during one year from April 2005 to March 2006 was examined. Light has a role of starting the seasonal cycle. The Kuroshio Current in this area induces many oceanographical features affecting to the change of seasonal control. The chl-a concentration is also seasonal, which is low in summer and high in winter. In summer, the meandering of Kuroshio Current induces strong eddies and increases the chl-a concentration. In autumn, the delayed small autumn bloom occurred until last December due to the Kuroshio Current. When the Kuroshio axis moves far from the coast, the coastal water dominates and increases the concentration even in the winter. The spring bloom starts early at the beginning of March and decreases during the spring.