• Korean Journal of Environmental Biology
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• v.31 no.1
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• pp.19-36
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• 2013

Physiochemical characters of sea waters during summer flood- and winter dry-seasons and their spatial variations were investigated along the coastal area off the eastern South Sea, Korea. Using the hierarchical clustering method, in this study, we present comprehensive analyses of coastal waters masses and their seasonal variations. The results revealed that the coastal water of the study area was classified into six water masses (A to F). During summer season, the surface water was mainly occupied by the coastal pseudo-estuarine water (water mass B) with low salinity and high nutrients and the river-dominated coastal water (water mass C) with low nutrients, respectively. The bottom water was dominated by cold water (water mass D) with very low temperature, high salinity and high nutrients, compared to masses of surface water. Notably, the water mass B, with high concentrations of nutrients (silicate and nitrogen) and low salinity, which is strongly controlled by the water quality of river freshwater, seems to play an important role in controlling the water quality and further regulating physical processes on ecosystem in the eastern coastal area of South Sea. The water mass D (bottom cold water) coupled with a strong thermocline, which exists in near-bottom layer along the western margin of Korea Strait, has a low temperature, pH and DO, but abundant nutrients. This water mass disappears in winter owing to strong vertical mixing, and subsequently may act as a pool for nutrients during winter dry-season. On the other hand, vertically well-mixed water column during the winter season was typically occupied by the Tsushima (water mass E) and the coastal water (water mass F) with a development of coastal front formed in a transition zone between them. These winter water masses were characterized by low nutrient concentration and balance in N/P ratio, compared with summer season with high nutrient concentrations and strong N-limitation. Accordingly, the analysis of water masses will help one to better chemical and biological processes in coastal area. In most of the study area, characteristically, the growth of phytoplankton community is limited by nitrogen, which is clearly different with coastal environment of West Sea of Korea, with a relative lack of phosphorus. It showed the western and the southern coasts in Korea are substantially different from each other in environmental and ecological characteristics.

• Journal of Wetlands Research
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• v.6 no.3
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• pp.71-81
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• 2004

In recent, the heavy rainfall is frequently occurred and the damage tends to be increased. So, more careful hydrologic analysis is required for the designs of the hydraulic or disaster prevention structures. The time distribution of a rainfall is one of the important factors for the estimation of peak flow in hydrologic and hydraulic designs. This study is to suggest a methodology for the estimation of a rainfall time distribution which can reflect the meteorologic and topographical characteristics of Daejeon area. We collect the 34 years' rainfall data recorded in the range of 1969 to 2002 for Daejeon area and we performed the rainfall analysis with the data in between May and October of each year. According to the Huff method, the collected data corresponds to the first quartile which the rainfall is concentrated in the primary stage but the suggested method shows the different rainfall distribution with the Huff method in time. The reason is that the Huff method determines the quartile in each storm event while the suggested one determines it by estimating the dimensionless distribution of rainfall in duration after the accumulation of rainfall in time. The rainfall distributions estimated by two methodologies were applied to the Gabcheon basin in Daejeon area for the estimation of flood flow. Here we use the SCS method for the effective rainfall and unit hydrograph for the flood discharge. As the results, the peak flow for 24-hour of 100-year frequency was estimated as a $3421.20m^3/sec$ by the Huff method and $3493.38m^3/sec$ by the suggested one. We can see the difference of $72.18m^3/sec$ in between two methods and thus we may carefully determine the rainfall time distribution and compute the effective rainfall for the estimation of the peak flow.

• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.47-60
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• 2020

To assess the characteristics of phytoplankton community structures related to environmental factors, seasonal surveys were conducted in the vicinity of Dokdo. In 2019, phytoplankton of four phyla and 69 species were observed. During winter, unidentified nanoflagellates dominated, with an average of 3.19×10⁴ cells L^-1. In spring, unidentified nanoflagellates occupied about 50% of the composition and a variety of dinoflagellates appeared. The summer phytoplankton population showed very low abundance. In autumn, various species of Chaetoceros appeared, along with diatoms, such as Bacteriastrum spp., Guinardia striata, and Pseudo-nitzschia spp. In addition, tropical species Amphisolenia sp. and Ornithocercus sp. were observed in both 2018 and 2019. The diversity was high in the summer of 2018 and the winter of 2019 and the characteristics of each index varied. Cluster analysis was divided into four groups according to species and population characteristics regardless of the season. The stratification of spring was particularly weak. In the autumn of 2018, the water mass was stabilized in the same way as in the summer, which is considered a suitable condition for phytoplankton growth. However, in 2019, the water masses were mixed, resulting in a low population. In a phytoplankton comparison, the dominant group showed seasonal differences, except for summer when the population was low, and the difference was most pronounced in autumn. Therefore, the waters surrounding Dokdo have different environmental and ecological characteristics from the East Sea, but the seasonal characteristics of each year are considered to be different depending on the topography, various currents, the island effect, and other factors.

• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2009.12a
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• pp.297-297
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• 2009

최근 유기농산물에 대한 관심과 요구가 급증하면서 소비자들은 고품질 유기농산물을 선호하고 있어 국내 대부분 유기농가들은 무처리 일반종자를 이용하고 있는 실정이다. 앞으로 국제 기준에 부합하는 채소류 유기재배를 위해서는 유기종자의 이용이 필수적이므로 유기종자 채종체계 확립이 필요한 실정이다. 따라서 본 연구에서는 당근 종자(재래종 heimloom)를 사용하여 유기종자의 채종체계를 확립하고자 하였다. 일반적으로 당근종자 생산은 적어도 2년을 요구한다. Seed to seed 방법과 Root to seed 방법이 이용되고 있는데 본 연구에서는 Root to seed 방법을 사용하였다. Root to seed 방법은 6월에 당근종자를 파종하여 가을에 뿌리를 수확하여 지상부를 5cm 정도 남기고 정지하여 일시 저온저장 하였다가 이듬해 뿌리를 이식하여 새순에서 추대시켜 종자를 수확하는 방법으로 종자 생산성이 높아 종자회사에서 많이 사용하고 있다. 본 연구에서도 Root to seed 방법으로 채종 시험하였다. 2008년도에 파종 및 수확한 뿌리를 저온저장고에 일시 저장 후 1차 이식은 2008년 11월 하순에 노지포장에서 실시하고 이때 월동 중 동해를 막기 위하여 보온덮개로 멀칭 처리하였다. 이듬해 3월 중순에 주간거리 75${\times}$40cm 간격으로 솎음하여 처리당 10주씩 배치하였다. 이식후 뿌리에서 새순 1대를 유도하였고 추대 및 개화 6주후부터 종자가 갈색으로 변하기 시작할 때 채종을 시작하였다. 수확부위는 1차 측지 중 1번째 화지를 대상으로 하였고 화경절단은 화총으로부터 20cm 정도 남겨서 잘랐고 실내에서 1개월 이상 충분히 후숙시킨 후 종자를 정선하여 종자생산성을 조사하였다. 결실율과 발아율 조사는 채종된 종자를 이용하여 종자 충실도와 발아력을 조사하였다. 각 품종별 추대율은 15번 품종과 16번, 24번 품종이 5% 미만으로 매우 부진하였고 그밖에 추대된 묘의 생육 및 발육상은 매우 양호하여 개화에는 커다란 문제가 없었다. 종자 결실율은 23번 품종을 제외한 모든 품종에서 높았고 각 품종별 화총구조를 고려해 볼 때 주간 화총, 1차측지, 2차측지 순으로 결실율이 떨어졌다. 각 품종의 천립중은 1, 11, 12, 14, 20번 품종이 2.02g 이상으로 대립종으로 판단되며 각 품종별 화총의 크기는 비슷하여 대립종은 각 화총당 종자수가 적은 것으로 나타났다. 대분분의 대립종은 만생종으로 생육기간이 소립종 보다 10-20일상 길며 종자 성숙기간도 장기간 소요되며 특히 장마기간을 넘겨야 할 경우에는 비가림 시설 채종재배가 필수적인 것으로 나타났다. 발아율은 10, 11, 14, 18, 19, 26번 품종이 80% 이상으로 가장 높았고 다른 품종에서는 다소 떨어져 품종별 차이가 많았다. 종자 생산성은 장근종과 단근종간에 약간의 차이가 있지만 주간 화총을 포함하여 1차 측지 4-5개에서 채종하는 것이 가장 효율적인 것으로 사료된다. 또한 당근의 개화 기간을 보면 1화륜은 8~10일, 1개체는 40~50일, 채종포장에서는 1화륜에서 측지 6개구까지 채종은 60~70일 소요되어 미숙종자와 과숙종자가 혼재되어 적정 수확시기를 결정하기가 매우 어려운 점이 발생하였다. 본 연구 결과에서 생육특성, 수량성, 품질특성, 종자 생산성, 발아율을 고려해 볼 때 1, 7, 8, 9, 10, 14, 19, 26번 품종이 유기농 재배 및 유기채종에 적합한 것으로 사료되었다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.1
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• pp.1-10
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• 2010

A regional climate model (RCM) can be a powerful tool to enhance spatial resolution of climate and weather information (IPCC, 2001). In this study we conducted dynamical downscaling using Weather Research and Forecasting Model (WRF) as a RCM in order to obtain high resolution regional agroclimate indices over the Korean Peninsula. For the purpose of obtaining detailed high resolution agroclimate indices, we first reproduced regional weather for the period of March to June, 2002-2008 with dynamic downscaling method under given lateral boundary conditions from NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data. Normally, numerical model results have shown biases against observational results due to the uncertainties in the modelis initial conditions, physical parameterizations and our physical understanding on nature. Hence in this study, by employing a statistical method, the systematic bias in the modelis results was estimated and corrected for better reproduction of climate on high resolution. As a result of the correction, the systematic bias of the model was properly corrected and the overall spatial patterns in the simulation were well reproduced, resulting in more fine-resolution climatic structures. Based on these results, the fine-resolution agro-climate indices were estimated and presented. Compared with the indices derived from observation, the simulated indices reproduced the major and detailed spatial distributions. Our research shows a possibility to simulate regional climate on high resolution and agro-climate indices by using a proper downscaling method with a dynamical weather forecast model and a statistical correction method to minimize the model bias.

• Korean Journal of Ecology and Environment
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• v.44 no.1
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• pp.75-84
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• 2011

We examined the effect of the turbid water on the periphytic diatom community in an artificial stream system. The artificial stream was constructed with transparent acryl and composed of four channels. Each channel ($20\;cm{\times}200\;cm{\times}40\;cm$) was supplied continuously with eutrophic lake water. In order to the freely colonize and grow diatoms, artificial substrate was installed with commercial slide glass soaked in 1% agar. Prior to introducing turbid water, the artificial stream was operated with lake water for 6 days to permit the propagation of diatom community on the substrates. The turbid water prepared with sediment sieved with ${\varphi}$ $64\;{\mu}m$ at $2\;g\;L^{-1}$ (final concentration, 300 NTU) was provided daily for 50 minute duration. The experiment was conducted for 7 days with manipulated experimental condition of light ($50{\sim}80\;{\mu}mol\;m^{-2}s^{-1}$, light:dark=24:0), temperature ($10{\pm}1^{\circ}C$), and flow rate ($0.31\;cm\;s^{-1}$). Sampling and analysis were conducted daily for water quality and diatom. Turbidity of the water varied 162.2~173.2 NTU during the experiment. After introduction of turbid water, DO, pH and TN were decreased, while SS and TP increased significantly. A total of 14 genera and 47 species of diatoms was observed on the artificial substrates during the experimental period. Of these, Navicula appeared to be a most dominant genus with 10 species, followed by Cymbella (6 species), Fragilaria (6 species) and Gomphonema (5 species). Achnanthes minutissima was the most dominant species (>70% of total frequency) in both control and treatment experiments. Increase in diatom abundance lasted for three days since turbid water introduction, after that they gradually decreased by the termination of the experiment. These results suggest that frequent supply of highly-concentrated turbid water significantly decreases the periphytic diatom community, and retard the recovery of the stable food-web within the stream.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.29-45
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• 2017

This study explored spatiotemporal variability of water quality in correspondence with hydro-meteorological factors in the four stations of Euiam Reservoir located in the upstream region of the North-Han River from May 2012 to December 2015. Seasonal effect was apparent in the variation of water temperature, DO, electric conductivity and TSS during the study period. Stratification in the water column was observed in the near dam site every year and vanished between August and October. Increase of nitrogen nutrients was observed when inflowing discharge was low, while phosphorus increase was distinct both during the early season with increase of inflowing discharge and the period of severe draught persistent. Duration persisting high concentration of Chl-a (>$25mg\;m^{-3}$: the eutrophic status criterion, OECD, 1982) was 1~2 months of the whole year in 2014~2015, while it was almost 4 months in 2013. Water quality of Euiam Reservoir appeared to be affected basically by geomorphology and source of pollutants, such as longitudinally linked instream islands and Aggregate Island, inflowing urban stream, and wastewater treatment plant discharge. While inflowing discharge from the dams upstream and outflow pattern causing water level change seem to largely govern the variability of water quality in this particular system. In the process of spatiotemporal water quality change, factors related to climate (e.g. flood, typhoon, abruptly high rainfall, scorching heat of summer), hydrology (amount of flow and water level) might be attributed to water pulse, dilution, backflow, uptake, and sedimentation. This study showed that change of water quality in Euiam Reservoir was very dynamic and suggested that its effect could be delivered to downstream (Cheongpyeong and Paldang Reservoirs) through year-round discharge for hydropower generation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.3
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• pp.149-158
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• 2015

In this study, we investigate tidal wave propagation characteristics, and classify regional tidal regime using tidal form number considered distribution of astronomical tide, overtides, and compound tides in the Han River Estuary, Gyeonggi Bay. The characteristics of the tidal wave propagation in main channels show dominance of major tidal constituents (e.g., $M_2$, $S_2$, $N_2$, $K_1$ and $O_1$) contributing to the astronomical tide however, distinct increasing of shallow water (e.g., $M_4$) and long period (e.g., $MS_f$) components toward up-estuary. Using the characteristics of tidal form number to astronomical tide, overtides, and compound tides, the regional tidal regime could be assorted into three regions. Firstly, a dominance area of astronomical tide was presented from open sea to a front of Incheon Harbor (Yeomha channel) and to north entrance of Seokmo channel. The area between south and north entrance of Yeomha channel and Ganghaw north channel classified into zone of showing strong shallow water components. It could be separated into upper estuary, upstream the Singok underwater dam, showed dominance of shallow overtides (e.g., $M_4$ and $MS_4$) water and long-term compound tides (e.g., $MS_f$) larger magnitude than astronomical tide. The shallow water components was earlier generated in lower part (south entrance) of Yeomha channel have strong bottom by effect of shallower and narrower compared with Seokmo channel. Tidal asymmetries of upper estuary cause by a development of overtides and compound tides are mainly controlled by influence of man-made structure.

• Economic and Environmental Geology
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• v.36 no.4
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• pp.305-312
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• 2003

This study was performed to delineate the subsurface geology, geologic structure, and distribution pattern of the Palgongsan granitic body, and to reveal the relationship between the Kyeongsang basin and Yongnam massif by gravity survey. The study area is located between the latitude of 35$^{\circ}$45'-36$^{\circ}$21'N and longitude of 128$^{\circ}$15'-129$^{\circ}$00'E. Total of 966 gravity data measured by Seoul National University, KlGAM(Korea Institute of Geology, Mining ＆ Materials), Pusan National University and Yonsei University were used. The Bouguer gravity anomaly in the study area ranges from -12.88 to 26.01 mgal with a mean value of 11.27 mgal. A very low anomaly zone is located in the Yongnam massif in west of the study area. The anomaly value increases going from west to east. A low anomaly distribution in Palgongsan granite and Yongnam massif is interpreted as the effect of their lower density than that of Kyeongsang Super Group. Power spectrum analysis is applied to evaluate the average depth of basement the Kyeongsang Basin and Conrad discontinuity from gravity anomaly. The average depths of density discontinuities are calculated 10.45 km and 4.9 km, and these are interpreted as Conrad discontinuity and depth of basement of the Kyeongsang Basin, respectively. The depth of Palgongsan granite is derived by means of 2-dimensional modeling and it decreases gradually toward the east. The gravity anomaly east of the study area decreases abruptly due to Shingryeong fault and Nogosan ring fault. Two deepest and sharp roots of Palgongsan granite are recognized by 2-dimensional modeling of each profiles. The depths of those roots are 5.3 km on a profile AA' and 7 km on a profile BB' which is the maximum depth of Palgongsan granite. Small granitic bodies are also seen to be intruded around the Palgongsan granite. The root of Palgongsan granite is shown by 3-dimensional analysis based on the interpolation of 2-dimensional modeling along each profiles to exist in the southwest vicinity of Palgongsan granite. The total volume of Palgongsan granite is approximately 31.211 $Km^3$.

• Journal of Environmental Impact Assessment
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• v.24 no.2
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• pp.134-153
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• 2015

When making urban planning, it is important to understand climate effect caused by urban structural changes. Seoul city applies UPIS(Urban Plan Information System) which provides information on urban planning scenario. Technology for analyzing climate effect resulted from urban planning needs to developed by linking urban planning scenario provided by UPIS and climate analysis model, CAS(Climate Analysis Seoul). CAS develops for analyzing urban climate conditions to provide realistic information considering local air temperature and wind flows. Quantitative analyses conducted by CAS for the production, transportation, and stagnation of cold air, wind flow and thermal conditions by incorporating GIS analysis on land cover and elevation and meteorological analysis from MetPhoMod(Meteorology and atmospheric Photochemistry Meso-scale model). In order to reflect land cover and elevation of the latest information, CAS used to highly accurate raster data (1m) sourced from LiDAR survey and KOMPSAT-2(KOrea Multi-Purpose SATellite) satellite image(4m). For more realistic representation of land surface characteristic, DSM(Digital Surface Model) and DTM(Digital Terrain Model) data used as an input data for CFD(Computational Fluid Dynamics) model. Eight inflow directions considered to investigate the change of flow pattern, wind speed according to reconstruction and change of thermal environment by connecting green area formation. Also, MetPhoMod in CAS data used to consider realistic weather condition. The result show that wind corridors change due to reconstruction. As a whole surface temperature around target area decreases due to connecting green area formation. CFD model coupled with CAS is possible to evaluate the wind corridor and heat environment before/after reconstruction and connecting green area formation. In This study, analysis of climate impact before and after created the green area, which is part of 'Connecting green network across the north and south in Seoul' plan, one of the '2020 Seoul master plan'.