• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.2
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• pp.3778-3783
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• 1975

The objective of this study is to determine an appropriate cement of soil-cement in which silty soil of salty tidal flat with low plasticity was used. Physical, chemical and mechanical tests were conducted to find out the standard properties of the soil to be used. Various cement contents used in this test were 8%, 10%, 12%, and 14%, and the compressive strength was tested after 7 days and 28 days of standard curing in the above each cement content respectively. The results obtaind are summarized as follows. 1. As the cement content was increased from 8% to 14%, Maximum dry density (M.D.D.) and optimum moisture content (O.M.C.) were not changed remarkably. 2. Density of soil-cement was directly proportional to cement content and inversely proportional to water content. 3. OMC was generally decreased in proportion to the increase of cement content. 4. Compressive stranth was directly proportional to centent and inversely proportional to water content. 5. In freezing and thawing test, maximum loss of 10% in the total Weight was found on the 8% cement mixture. and This loss was rapidly decreased to 2% when the Cement content of the mixture was more than 10%.

• Journal of Life Science
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• v.24 no.10
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• pp.1110-1117
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• 2014

Tidal flats are continuously contaminated by human activities. This study assessed the bioremediation efficiency of tidal flat soil using microcosm reactors and microorganisms originating from the tidal area. We screened 135 bacterial strains that produce extracellular enzymes from the tidal area located in the North port of Incheon bay. Two bacterial strains (Pseudoalteromonas sp. and IC35 Halothiobacillus neapolitanus IC_S22) were selected and used in the microcosm reactors, which were specially designed to functionally mimic the ecological conditions of the tidal flats. Pseudoalteromonas sp. IC35 was selected based on its relatively high activity of the enzymes amylase, cellulose, lipase, and protease. Halothiobacillus neapolitanus IC_S22 was selected for oxidation of sulfur. The M1 and M2 microcosm reactors were operated by continuous feeding of seawater under the same conditions, but M2 was first inoculated with Pseudoalteromonas sp. IC35 before the seawater feeding. The initial COD in both the M1 and M2 microcosm reactors was 320 mg/l. The final COD was 21 mg/l (M1) and 7 mg/l (M2). The M3 and M4 microcosm reactors were operated by continuous feeding of seawater under the same conditions, but M4 was first inoculated with H. neapolitanus IC_S22. The initial sulfate concentration in both the M3 and M4 microcosm reactors was 660 mg/l, and the maximum sulfate concentration was 1,360 mg/l (M3) and 1,600 mg/l (M4).

• Journal of Environmental Science International
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• v.28 no.3
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• pp.341-356
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• 2019

In this study, the impacts of local meteorology caused by tidal changes in the West Sea on ozone distributions in the Seoul Metropolitan Area (SMA) were analyzed using a meteorological model (WRF) and an air quality (CMAQ) model. This study was carried out during the day (1200-1800 LST) between August 3 and 9, 2016. The total area of tidal flats along with the tidal changes was calculated to be approximately $912km^2$, based on data provided by the Environmental Geographic Information Service (EGIS) and the Ministry of Oceans and Fisheries (MOF). Modeling was carried out based on three experiments, and the land cover of the tidal flats for each experiment was designed using the coastal wetlands, water bodies (i.e., high tide), and the barren or sparsely vegetated areas (i.e., low tide). The land cover parameters of the coastal wetlands used in this study were improved in the herbaceous wetland of the WRF using updated albedo, roughness length, and soil heat capacity. The results showed that the land cover variation during high tide caused a decrease in temperature (maximum $4.5^{\circ}C$) and planetary boundary layer (PBL) height (maximum 1200 m), and an increase in humidity (maximum 25%) and wind speed (maximum $1.5ms^{-1}$). These meteorological changes increased the ozone concentration (about 5.0 ppb) in the coastal areas including the tidal flats. The increase in the ozone concentration during high tide may be caused by a weak diffusion to the upper layer due to a decrease in the PBL height. The changes in the meteorological variables and ozone concentration during low tide were lesser than those occurring during high tide. This study suggests that the meteorological variations caused by tidal changes have a meaningful effect on the ozone concentration in the SMA.

• Journal of Power System Engineering
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• v.21 no.2
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• pp.48-56
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• 2017

The steady-state, incompressible and three-dimensional numerical analysis was carried out to evaluate the velocity fields around the seabed tiller used for the improvement of the seabed soil and the pulling force and buoyancy generated by driving the seabed tiller. The turbulence model used in this study is a realizable $k-{\varepsilon}$ well known to be excellent for predicting the performance of the flow separation and recirculation flow as well as the boundary layer with rotation and strong back pressure gradient. As a results, a typical vortex pair appears near the adjacent rotor vane tip. When the current is stopped, there is no force when pulling the seabed tiller, but when the current flows at 1.2 knots, the force acts on the downstream side and the pulling force is much greater. In stationary currents, the buoyancy of the seabed tiller acts more strongly towards the seabed as the number of rotations of the rotor increases, but acts more strongly toward the sea surface at 1.2 knots of current.

• Korean Journal of Remote Sensing
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• v.28 no.1
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• pp.121-128
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• 2012

High resolution intertidal DEM is a basic material for science research like sedimentation/erosion by ocean current, and is invaluable in a monitoring of environmental changes and practical management of coastal wetland. Since the intertidal zone changes rapidly by the inflow of fluvial debris and tide condition, remote sensing is an effective tool for observing large areas in short time. Although radar interferometry is one of the well-known techniques for generating high resolution DEM, conventional repeat-pass interferometry has difficulty on acquiring enough coherence over tidal flat due to the limited exposure time and the rapid changes in surface condition. In order to overcome these constraints, we tested the feasibility of radar interferometry using Cosmo-SkyMed tandem-like one-day data and ERS-ENVISAT cross tandem data with very short revisit period compared to the conventional repeat pass data. Small temporal baseline combined with long perpendicular baseline allowed high coherence over most of the exposed tidal flat surface in both observations. However the interferometric phases acquired from Cosmo-SkyMed data suffer from atmospheric delay and changes in soil moisture contents. The ERS-ENVISAT pair, on the other hand, provides nice phase which agree well with the real topography, because the atmospheric effect in 30-minute gap is almost same to both images so that they are cancelled out in the interferometric process. Thus, the cross interferometry with very small temporal baseline and large perpendicular baseline is one of the most reliable solutions for the intertidal DEM construction which requires very accurate mapping of the elevation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.161-168
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• 2008

The ecological environmental zones in coastal area, like tidal flat and salt marsh, were gradually decreased due to large scale of coastal development projects, reclamation and so on. Therefore, the development of artificial tidal flat and salt marsh has been emphasized in coastal area as mitigation concept and studies on related this background has performed. But studies on the quantitative evaluation for degree of restoration were insufficient. In this paper, as a fundamental study for evaluation of restoration on the creation of ecological environmental zones in coastal area, it was conducted that the monitoring and experiment for bio-chemical factors (bio-diversity, population and biomass of macro-benthos, survival ratio of reed, the number of heterotrophic bacteria and physico-chemical characteristics such as COD, IL, TN, TP and pH) using a in-situ pilot plant of tidal flat (Zone. P1) and salt marsh (Zone. P2), which was distinguished by content of dredged soil, in Jinudo, Nakdong estuary. From results of this study, the restoration index (RI), for evaluation concerning degree of restoration on the creation of ecological environmental zones in coastal area, was suggested and quantitative evaluation was performed using a restoration index (RI).

• Journal of Ecology and Environment
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• v.45 no.4
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• pp.264-276
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• 2021

Background: Salt marshes provide a variety of ecosystem services; however, they are vulnerable to human activity, water level fluctuations, and climate change. Analyses of the relationships between plant communities and environmental conditions in salt marshes are expected to provide useful information for the prediction of changes during climate change. In this study, relationships between the current vegetation structure and environmental factors were evaluated in the tidal flat at the southern tip of Ganghwa, Korea, where salt marshes are well-developed. Results: The vegetation structure in Ganghwa salt marshes was divided into three groups by cluster analysis: group A, dominated by Phragmites communis; group B, dominated by Suaeda japonica; and group C, dominated by other taxa. As determined by PERMANOVA, the groups showed significant differences with respect to altitude, soil moisture, soil organic matter, salinity, sand, clay, and silt ratios. A canonical correspondence analysis based on the percent cover of each species in the quadrats showed that the proportion of sand increased as the altitude increased and S. japonica appeared in soil with a relatively high silt proportion, while P. communis was distributed in soil with low salinity. Conclusions: The distributions of three halophyte groups differed depending on the altitude, soil moisture, salinity, and soil organic matter, sand, silt, and clay contents. Pioneer species, such as S. japonica, appeared in soil with a relatively high silt content. The P. communis community survived under a wider range of soil textures than previously reported in the literature; the species was distributed in soils with relatively low salinity, with a range expansion toward the sea in areas with freshwater influx. The observed spatial distribution patterns may provide a basis for conservation under declining salt marshes.

• Journal of the Korean association of regional geographers
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• v.17 no.5
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• pp.521-535
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• 2011

This study intended to explain the relationship between climate change and magnetic susceptibility of estuarine sediment. Data of OSL dating and magnetic susceptibility from estuarine tidal sediment were compared with various climate change data. During the last Holocene, the intense of magnetic susceptibility related with weaker Siberian High and stronger Asian Summer Monsoon. It is explained that high precipitation and runoff made much fluvial sediment input to the estuary. From the early to mid Holocene, there is no clear relationship between climate change and MS because of the much coastal sediment input caused by rapid sea level rise and the formation of upland soil and coastal marsh. These results contribute to reconstruct paleo-environmental changes of west coast of Korea, in the way of using benefit of ubiquitous estuarine tidal flats and relatively useful magnetic susceptibility methodoloy.

• Journal of Korea Soil Environment Society
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• v.5 no.3
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• pp.25-33
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• 2001

The study was performed to examine the influence of sea tide on a tideland composition by Saemankeum reclamation and to evaluate a correlation between the characteristics of physical and the pollution level of heavy metals. Also, it was investigated the characteristics of heavy metal adsorption through a batch experiment and applied to adsorption isotherm equations. In the results, the flow of sea tide occurred to accumulation action and had an effect on the content of heavy metals. It suggests that influence factors for the content of heavy metals in the tidal flat be grain size, cation exchange capacity and organic matter content. Adsorption capacity of heavy metals occurs to 90% adsorption rate for injection concentration within 30 minutes. The flow patterns in Saemankeum area will undergo a change for soil size distribution. In result, this soil size changed will effect the adsorption capacity of heavy metals.

• Korean Journal of Environment and Ecology
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• v.20 no.1
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• pp.52-69
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• 2006

The flora of vascular plants and the vegetation on the tidal flat was investigated in Jebudo located at Hwaseong city of Gyeonggi-do province from 2004 to 2005. Jebudo has been considered to show difference from the flora which is peculiar to island as it became semi-land by free traffic to mainland with the installation of a road which had enabled entry into the Jebudo in 1991 due to sea-splitting phenomenon. The result of the vascular plants in Jebudo were consissted of 305 taxa; 264 species, 38 varieties and 3 forms of 202 genera of 74 families. As a result of examination by distinctive survey areas within Jebudo, a tidal flat(I) region where the halophyte was being spread has been researched as 7 taxa; 7 species of 6 genera of 5 families. The taxa in Godo-Island(II) was reseached as 50 taxa; 39 species, 11 varieties and 42 genera of 24 families. The taxa in Sand dune area(III) was reseached as 61 taxa; 52 species and 9 varieties of 53 genera of 25 families. The most plant species was reseached in Mt. Tapjae (IV) reaseach area among the reseach areaes 136 taxa; 118 species, 17 varieties and 1 form of 108 genera of 55 families. The taxa in Dangje Mt.(V) was reseached as 119 taxa; 105 species, 13 varieties and 1 form of 95 genera of 45 familes. The taxa in Dongmi Mt. (VI) was reseached as 100 taxa; 85 species and 15 varieties of 83 enera of 43 families. The taxa in Paddy field(VII) was reseached as 120 taxa; 106 species, 13 varieties and 1 form of 86 genera 31 families. Especially, a Crypsinus hastatus community which is a rare plant designated by Korea forest service and a preservation plant designated by the natural environment preservation law (1998) has been discovered at a cliff of Topjae mountain near the ferry located at the northeast side. According to the result of researching halophyte communities which make up the zonation according to the environmental gradient, the communities were being formed in the order of Limonium tetragonum community, Phragmites communis community, Carex scabrifolia community, Triglochin maritimum community and Carex scabrifolia community in accordance with the order of soil particle size with breakwater as their standard.