• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.1007-1018
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• 2009

Hydrocyclone is widely used in industry, because of its simplicity in design, high capacity, low maintenance and operational cost. The separation action of a hydrocyclone treating particulate slurry is a consequence of the swirling flow that produces a centrifugal force on the fluid and suspended particles. In spite of hydrocyclone have many advantage, the application for treatment of urban stormwater case study were rare. We conducted a laboratory scale study on treatable potential of micro particles using hydrocyclone filter (HCF) that was a combined modified hydrocyclone with perlite filter cartridge. Since it was not easy to use actual storm water in the scaled-down hydraulic model investigations, it was necessary to reproduce ranges of particles sizes with synthetic materials. The synthesized storm runoff was made with water and addition of particles; ion exchange resin, road sediment, commercial area manhole sediment, and silica gel particles. Experimental studies have been carried out about the particle separation performance of HCF-open system and HCF-closed system. The principal structural differences of these HCFs are underflow zone structure and vortex finder. HCF was made of acryl resin with 120 mm of diameter hydrocyclone and 250 mm of diameter filter chamber and overall height of 800 mm. To determine the removal efficiency for various influent concentrations of suspended solids (SS) and chemical oxygen demand (COD), tests were performed with different operational conditions. The operated maximum of surface loading rate was about 700 $m^3/m^2$/day for HCF-open system, and 1,200 $m^3/m^2$/day for HCF-closed system. It was found that particle removal efficiency for the HCF-closed system is better than the HCF-open system under same surface loading rate. Results showed that SS removal efficiency with the HCF-closed system improved by about 8~20% compared with HCF-open system. The average removal efficiency difference for HCF-closed system between measurement and CFD particle tracking simulation was about 4%.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.83-99
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• 2005

To evaluate environmental charateristics of the South Sea and East China Sea on summer, water and sediment quality were measured in June 2001-2003. Surface layer was affceted by Warm water originated from the high temperature and salinity-Tsushima Warm Current, on the other hand, Yellow Sea Cold Water was spread to the bottom layer in the south-western part of the Jeju island, and salinity at stations near the Yangtze River was decreased below 29psu because of a enormous freshwater discharges. Thermocline-depth was formed at about 10m, and chlorophyll maximum layer was existed in and below the thermocline. COD(Chemical Oxygen Demand), TN(Total Nitrogen), and TP(Total Phosphorus) concentrations showed seawater quality grade II in surface layer of the most area, but concentrations of such as COD, Chl. a, TSS(Total Suspended Solid), and nutrients were greatly increased in the effect area of Yangtze River discharges. Correlations between dissolved inorganic nitrogen, Chl. a and salinity were negative patterns strongly, in contrast, those of inorganic phosphorus, COD and Chl. a were positive, which indicates that phytoplankton biomass and phosphorus are considered as important factors of organic matter distribution and algal growth, respectively. in the study area. The distribution of ignition loss, COD, and $H_2S$ of surface sediment were in the ranges of 2.61-8.81%, $0.64-11.86mgO_2/g-dry$, and ND-0.25 mgS/g-dry, respectively, with relatively high concentration in the eastern part of the study area. Therefore, to effective and sustainable use and management of this area, continuous monitoring and countermeasures about major input sources to the water and sediment, and prediction according to the environmental variation, are necessary.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.103-113
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• 2023

The river confluence is a section in which two rivers with different topographical and hyrodynamic characteristics are combined into one, and it is a section in which rapid flow, inflow of sediments, and hydrological topographic changes occur. In the confluence section, the flow of fluid occurs due to the difference in density due to the type of material or temperature difference, which is called a density flow. It is necessary to accurately measure and observe the confluence section including a certain section of the main stream and tributaries in order to understand the mixing behavior of the water body caused by the density difference. A comprehensive analysis of this water mixture can be obtained by obtaining flow field and flow rate information, but there is a limit to understanding the mixing of water bodies with different physical properties and water quality characteristics of rivers flowing with stratigraphic flow. Therefore, this study attempts to grasp the density flow through the water temperature distribution in the confluence section. Among the extensive data of the river, vertical data and water surface data were acquired, and through this, the stratification phenomenon of the confluence was to be confirmed. It was intended to analyze the mixed pattern of the confluence by analyzing the water mixing pattern according to the water temperature difference using the vertical data obtained by measuring the repair volume by installing the ADCP on the side of the boat and measuring the real-time concentration using YSI. This study can supplement the analysis results of the existing water quality measurement in two dimensions. Based on the comparative analysis, it will be used to investigate the current status of stratified sections in the water layer and identify the mixing characteristics of the downstream section of the river.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.2
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• pp.112-129
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• 2012

The aim of this study was to provide basic data in managing the project that was carried out on Bulgwangcheon in a nature-friendly way to improve the conditions around the areas, which was brought to completion in 2002, based on changes in ecological characteristics. For this propose, this study examined documents related to the project, compared physical and enviromnental changes before and after the project was conducted and analyzed changes in the stream ecosystem. The result showed that in areas that effluent water was often observed, especially when it rained, the river wall was washed away and vegetation was found damaged. As for actual vegetation, this study compared planting coverage of each section of the research area and actual vegetation charts. The results indicated that Lespedeza spp., Aster koraiensis among mixed seeds that were planted in the reservoir path were almost swept away while Festuca arundinacea dominated the areas. Phragmites communis, Miscanthus sacchariflorns and Salix gracilistyla which had been planted in a small number were also almost washed out though a small number of them were left to form a colony. After examining the topography and structure of the plant community, this study found that areas where mixed seed were planted had changed into two types of vegetation: First type of area is dominated by P and R which are usually raised in apron with abundant floating particles. The second type of area is dominated by dry gramineous plant such as F and A. Areas around low flow channel where Phragmites communis, Miscanthus sacchariflorus and Salix gracilistyla planting construction method is applied was washed away with the width of low flow channel reduced. Though P, M and S formed a small community in some areas around the low flow area, they were in small number and in composition of simple plant species. Two ways were suggested in this study to manage the stream in an ecological way. First, adequate revetment construction methods should be applied by monitoring the flow of the stream as well as considering the flood control of urban streams. Second, target vegetation communities that are suitable for the environment of the stream should be chosen and be plantedconstantly with high density. At the same time, ornamental native plants shouldn't be planted as they have been and disturbing vegetation should be removed.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.469-483
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• 2020

The results of long-term groundwater level and quality monitoring can be used not only as the basic data for evaluating the impact of various disasters including climate change and establishing responses, but also as key data for predicting and managing geological disasters such as earthquakes. Some countries use groundwater level and quality monitoring for researches to predict earthquakes and to assess the impacts of the earthquake disaster. However, a few cases in Korea report on individual groundwater quality factors (i.e., dissolved ions) observed before and after the earthquakes, being different from other countries. To establish the abnormality criteria for groundwater quality in Pohang, groundwater samples were collected and analyzed five times from 14 agricultural or private wells existing in Shingwang-myeon and Heunghae-eup. As a result of the analysis, it was found that Ca2+ was the dominant cation in Shingwang-myeon, while Na+ was the dominant cation in Heunghae-eup. The elevated NO3- concentration in Shingwang-myeon is contributed to the agricultural activity in the area. A high concentration of Fe was detected in a well on Heunghae-eup; the concentration exceeded the drinking water standard by nearly 100 times. Relatively higher dissolved ions were observed in the groundwater of Heunghae-eup, and it is considered as the result of the flow velocity difference and water-rock reaction accompanying the difference in bedrock and sediment characteristics. The groundwater of Shingwang-myeon appeared to be most affected by the weathering of granite and silicates, while that of Heunghae-eup was mainly affected by the weathering of silicates and carbonate. The background concentrations (baselines) of groundwater Shingwang-myeon and Heunghae-eup was identified through the survey; however, the continuous monitoring is required to monitor the possible changes and the repeatability of seasonal variation.

• Korean Journal of Plant Resources
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• v.21 no.1
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• pp.73-82
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• 2008

The resource plants of the Mt. Geonji was listed 354 taxa; 92 families, 242 genera, 303 species, 48 varieties and 3 forms. 354 taxa listed consists of 205 taxa of edible plants(57.1%),234 taxa of medicinal plants(65.2%), 167 taxa of ornamental plants(46.5%) and 218 taxa of the others(60.7%). Specific plant species by floral region were total 22 taxa; Trapella sinensis var. antennifera in class IV, Iris ensata var. spontanea in Class II, 16 taxa(Salix glandulosa, Alnus hirsuta, Chrysosplenium flagelliferum, Mallotus japonicus, Ilex macropoda, Grewia biloba var. parviflora, Vaccinium oldhami, Lysimachia barystachys, Fraxinus mandshurica, etc.) in class I. The naturalized plants in this site were 12 families, 23 genera, 28 species, 2 varieties, 30 taxa(Bromus unioloides, Phytolacca americana, Oenothera erythrosepala, Ipomoea hederacea var. hederacea, Aster pilosus, Erechtites hieracifolia) and naturalization rate was 8.5% of all 354 taxa vascular plants. Wild plants disturbing ecosystem like Solanum carolinense and Ambrosia artemisiifolia var. elatior have been increasing. So, it needs continuing control and conservation measures on the plant ecosystem.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.3
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• pp.137-144
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• 2002

To obtain the basic information about pedo-genetic properties and origin of the parent materials of "Yongil" series in Korea, this study was conducted. The soil characteristics such as chemical and sand particles of typifying pedon, and distributional patterns in the area were analysed. The typifying pedon of "Yongil" series was distributed on the top of rolling area in the eastern coastal area of Korea, Yonggan-ri, Heunghae-eup, Pohang-si, Gyongbuk province. The results are as follows; The "Yongil" series in Korea was distributed on the rolling hill under altituede of 50m, and was used for cultivated upland, and the total acreage about 376ha. The content of sand was more than 50%, however the clay content in the depth of 40~100cm of the soil profile rapidly increased. The medium sand (0.5~0.1mm in size) are dominant among sand fraction, but coarse one are rare. So the rate of medium to total sand was higher in IIB horizon as 0.62~0.76 than A and C horizons. The content of heavy minerals in medium sand was low as 1.0~6.6% and the ratio of quartz to feldspars was higher in Ap2 and B1 horizon as 1.7 than IIB horizon which had less than 1.39. The cumulative curves of sand particles in Yeongil series showed the well sorted and differ from residuum soils derived from sand stone, but similar to dune soils(Haeri series). So it could be deducted from this study that "Yeongil" series are aeolian deposits derived from aeolian materials and have bisequum profile; the upper part depth of 40cm was recent cover sand, the horizon of 40~100cm depth was developed in Pleistocene epoch from the same materials.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.194-205
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• 2022

Sandbars formed by sediment transportation and sedimentation are some of the most important habitats for specific wildlife and they provide an aesthetic landscape in streams. The purpose of this study was to understand the successional process of the colonization and development of early vegetation over time on sandbars exposed by the opening of a gate at a downstream weir. We selected the following four study sites in the Geumgang River, South Korea: three weir-upstream sites with different gate-opening times and a control site that was not affected by weir operation. Changes in the structural characteristics and spatial distribution of the riparian vegetation on the sandbars exposed after opening the gate at the weir were surveyed according to the different exposure periods of the sandbars at the study sites. The newly formed sandbars accounted for more than 33% of the area of the existing floodplain in the three weir-upstream sites of the Geumgang River after opening the gate at the weir. Nine main plant communities were distributed on the exposed sandbars. These communities were classified as annual mesophytic, perennial hydrophytic, perennial hygrophytic, subtree, and tree vegetation based on their species traits. As the duration of exposure of the sandbar increased, the area of the bare sandbar and the annual herbaceous and perennial hydrophytic communities decreased, and the areas occupied by perennial hygrophytic, subtree, and tree communities increased. Changes in vegetation on the sandbar were classified into three types of succession according to the condition of the aquatic habitat before the gate-opening and the degree of physical disturbance caused by the water flow after the gate-opening. The types of succession were: 1) succession starting from hydrophytes in the lentic aquatic zone, 2) succession starting from annual herbaceous hygrophytes in the lotic aquatic zone, and 3) willow-dominated succession in the disturbed channel side. Our results suggested that the dynamics of successional changes in vegetation should be considered during weir operation to ecologically manage the habitats and landscape of the fluvial landforms, including sandbars in streams.