• Journal of the Korean earth science society
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• v.36 no.3
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• pp.222-235
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• 2015

Samples were collected from both places including the coastal area within the height of 5 m above the mean sea level (msl) (DH) and the top of the coastal terrace of 10-15 m msl (KS) high in Gwangseungri, Gochanggun, Korea. To find the origin of the deposit in the coastal area, granulometric analysis and geochemical analysis were performed. The result showed that the DH samples were originated from the reddish soils overlaying weathered bedrock which presented gradual change of chemical composition from the bottom toward the top. Clay minerals were found from the DH samples. These results concluded that the DH samples were found as in-situ weathered materials. The KS samples were originated from the soil layer covering gravel layer at the foot slope of the hill along the coast. The KS samples contained different chemical compositions from the DH. It is inferred that some of this layer was disturbed or experienced the influx of foreign material. The particle size of the KS samples was different from those found on the beach. The particle size of lower parts of KS site was finer than that on the beach, but the particle size of middle part of the site was coarser than that on the beach. The sorting of the KS site was poorer than that on the beach. Thus, it is inferred that some parts of the layer were formed by short-lived high energy event rather than sustained and continuous action of tidal currents and/or waves. Analysis using an optically stimulated luminescence (OSL) method showed that the burial age of samples from KS site were found 0.65-0.71 ka. Though the characteristics of the sediment layer and forming event in this area should be further studied, it can be inferred that this sedimentary layer formed by coastal flooding with storm.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.3
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• pp.15-26
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• 2020

To recover phosphorus from incinerated sewage sludge ash(ISSA), ISSA were extracted with sulfuric acid solution, and the optimal phosphorus recovery conditions were experimented by comparing the recovered phosphorus contents and heavy metals by raising pH. Also the phosphorus recovery efficiency was compared when acid extract was reused or classified by particle size of ISSA. The optimal conditions for recovering phosphorus from ISSA were 1N sulfuric acid solution with an L/S ratio of 10, and an extraction time of 30 minutes. Considering the addition of alkali substances and the content of heavy metals in the recovered sediment, it is concluded to recover phosphorus under pH 5. Reuse of the ISSA extract increased the recovery rate of phosphorus by 14~21% depending on the reuse rate (100 and 50%), but it also increased zinc contents to 33 and 21%, and copper contents to 35 and 20%, respectively. The experiment of ISSA divided into four sections by particle size showed that there was no distinct advantage of phosphorous recovery by classification of certain particle size of ISSA. The removal of heavy metals from extracts through EDTA and cation exchange resin showed no definite effect.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.5
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• pp.639-650
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• 2022

In areas where large-scale sediment transport occurs, it is important to apply appropriate countermeasure method because the phenomenon tends to accelerate by time duration. Among the various countermeasure methods applied so far, beach nourishment needs to be reviewed as an erosion prevention measure because the erosion pattern is mitigated and environmentally friendly depending on the particle size. In the case of beach nourishment. a detailed review is required to determine the size, range, etc., of an appropriate particle diameter. In this study, we investigated the characteristics of the related topographic change using the change in the particle size of nourishment materials, the application of partial area, and the condition under the coexistence of waves and wind as variables because those factors are hard to be analyzed and interpreted within results and limitation of that the existing numerical models are not able to calculate and result out so that it is required that phenomenon or efforts are reviewed at the same time through physical model experiments, field monitoring and etc. So we attempt to reproduce the tendency of beach erosion and deposition and predict possible phenomena in the future using machine learning techniques for phenomena that it is not able to be interpreted by numerical models. we used the hydraulic experiment results for the training data, and the accuracy of the prediction results according to the change in the training method was simultaneously analyzed. As a result of the study it was found that topographic changes using machine learning tended to be similar to those of previous studies in short-term predictions, but we also found differences in the formation of scour and sandbars.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.25 no.2
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• pp.9-25
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• 2020

In 2010 and 2015, total 77 surface sediment samples were collected to assess the anthropogenic effects of trace metals in surface sediments of Garolim Bay, and the physical characteristics (particle size and specific surface area) and geochemical components (major (Al, Ca, Fe, K, Ba) and trace metals (Mn, Cs, Cr, Co, Ni, Cu, Zn, Pb), organic carbon and calcium carbonate) were analyzed. Mean grain size of Garolim Bay surface sediments ranged from 0.51-5.58 Ø (mean 3.98 Ø) and increased from the inlet of bay to the inner bay, and from the waterway to the land. Most of the metal concentrations except for some elements showed the similar distribution to those of mean grain size and specific surface area. As the particle size decreased and the specific surface area increased, the metal concentration increased. In order to estimate the factors controlling the concentration of trace metals, factor analysis was performed, and three factors were extracted (92.7% of the total variation). Factor 1 accounted for 71.3% of the total variation, which was a grain size factor. Factor 2 accounted for 14.2% of the total variation, Factor 3 accounted for 7.2% of the total variance. Enrichment factor was calculated using the particle size corrected background concentration. Metals with a enrichment factor of 1.5 or higher and the number of samples were 4 for Cr (St. 1, 16, 27, 39) and 1 for Pb (St. 39), but there were little differences in the concentrations of 1M HCl leached metals for these metals. The percentage of 1M HCl leached fraction to total metal concentration decreased in the order of Pb~Co>Cu>Zn~Mn>Ni>Cr. Comparing this value with contaminated and clean sediments in other coastal areas, the percentages for each metal were similar regardless of the trace metal levels in all regions. This fact might be resulted from the reaction between the 1M HCl solution and the different sediment constituents, indicating that there is a limit to apply this percentage of leached metal to the estimation of the contamination extent.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.30-36
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• 2017

SS(Suspended Solid) concentration by soil erosion into river at normal and flood season should be measured. However, to present the variation of SS due to various development project such as EIA(Environmental Impact Assessment), River Master Plan, and so on, it is necessary to estimate not measure SS, but there are not exist how to estimate SS. In the present study, therefore, we propose the hydrologic method of estimating SS concentration using the results of particular frequency flood discharge and sediment discharge by RUSLE method. SS consists of silty and clay soil and colloid particle etc. However, in the present study, silty and clay soils of sediment discharge except send set up SS standards. The flow discharge to estimate SS concentration are 1~2 years for normal season, 30~100 years for flood season. Meanwhile, analysis software for probable rainfall uses Fard2006, probable rainfalls under 2-year frequency are estimated using rainfall data and frequency factor of Gumbel distribution. The results of estimating SS concentration using runoff volume by sediment and flow discharges of silty and cray soils as above method show that reliable level of SS concentration is considered in predevelopment of natural condition and under development of barren condition. Especially, SS concentration takes notice that the value of sediment discharge makes a huge difference according to channel slope, it was confirmed that the value obtained by dividing the SS concentration by the channel slope is relatively constant even though the topographical factors are different. Therefore, if the present study will be proceeded for various watersheds, it will be developed as estimation method of SS concentration.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.6
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• pp.771-781
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• 1994

Monthly measurements made at 15 stations along the axis of the upper Neuse River estuary show a highly variable degree of correlation between concentration of suspended particulate material (SPM) and attenuation coefficient (c) of light as measured by transmissometer. Coefficients of determination along transect lines ranged from $0.12{\sim}0.93$ and calibration slopes ranged from $0.50{\sim}5.63$. When examined on a station-by-station basis, coefficients of determination ranged from $0.21{\sim}0.96$ and calibration slopes ranged from $1.04{\sim}4.94$. Surface calibrations made at individual stations over the full 13-month period were the most consistent of all observations and were considerably better than calibrations made using all of the stations on a given day. Organic content, which can dominate the suspended sediment load during some months, does not appear to explain the variations in reliability of the calibrations. However, an abundance of large aggregates with time-varying size and shape distributions may be partly responsible for variations in optical properties of the sediments, and thus may confound the relationship between SPM and c in the Neuse River estuary Time-varying calibrations to account for non-negligible changes in optical properties may not suffice in complex estuarine environments where the in situ particle dynamics are poorly understood. However, the best use of Beam Transmissometer will continue to be for applications such as detecting water-column events or for use in situations where wide error bars in establishing SPM concentrations are acceptable.

• Journal of the Korean Geographical Society
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• v.42 no.4
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• pp.506-525
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• 2007

Incision into bedrock channel is the primary control of landform evolution, but research into bedrock incision process stagnated for long time. Due to the scaling problem of the application of results from flume studies to bedrock channel, there is a strong need to simulate the bedrock incision process with more realistic models. As a part of investigation into controls of bedrock channel incision, three-dimensional changes of rock surface with abrasion was investigated with physical modelling. 18 rock plates were abraded with various sediment particle size and sediment load and abraded surfaces of the plates were scanned with high resolution 3-D scanner. To identify the spatial pattern of erosion of the rock plates, various methods were used. There was no synthetic or holistic method that showed all features of bedrock plate produced by abrasion, so each plate was analyzed using some available methods. Contour maps, shaded relief maps and profiles show that abrasion concentrated on the centre of plate (cross profile) and upstream and downstream edges (longitudinal profile) and eroded area extended inwards. It also found that the cracks and boundaries of forming materials easily eroded than other parts. Changing patterns of surface roughness were investigated with profiles, regression analysis and spectral analysis. Majority of plates showed decrease in small-scale roughness, but it depends on microstructures of the plates rather than general hardness or other factors. SEM inspection results supported this idea.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.56-68
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• 2005

We measured nitrate and other nutrients in sediment pore waters retrieved from three sites at the southern upper-tidal flats of the Ganghwa Island. Denitrification rate is estimated by applying a simple 1-D model to the nitrate profiles. Results from Jangwha and Dongmak sites are $7.8{\sim}9.4{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, and $1.4{\sim}3.6{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, respectively. Rates are comparable to those reported around the world in an order of magnitude. Denitrification was lower in summer. The rates were about 1.5 times higher at site where the surface sediments consist of relatively coarser particles. This implies that particle size would control the reactant supply to the subsurface sediment. One may claim the denitrification as an evidence of the biogeochemical purification function of tidal flat. However, the purification seems not a general attribute of a tidal flat when whole system is scrutinized by a thermodynamic criterion. Currently the term 'tidal flat' is used when describing the diverse coastal wetlands such as salt marshes, sandy tidal flats and muddy tidal flats, which exhibit quite different ecological functions. Thus it is worthy of mentioning that the classification of coastal wetlands on the basis of sedimentological characteristics and biogeochemical functions should facilitate our understanding.

• Korean Journal of Remote Sensing
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• v.27 no.3
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• pp.235-258
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• 2011

The purpose of this study is to investigate climatological variations from the temporal and spatial surface particulate organic carbon (POC) estimates based on SeaWiFS spectral radiance, and to determine the physical mechanisms that affect the distribution of pac in the Gulf of Mexico. 7-year monthly mean values of surface pac concentration (Sept. 1997 - Dec. 2004) were estimated from Maximum Normalized Difference Carbon Index (MNDCI) algorithm using SeaWiFS data. Synchronous 7-year monthly mean values of remote sensing data (sea surface temperature (SST), sea surface wind (SSW), sea surface height anomaly (SSHA), precipitation rate (PR)) and recorded river discharge data were used to determine physical forcing factors. The spatial pattern of POC was related to one or more factors such as river runoff, wind-derived current, and stratification of the water column, the energetic Loop Current/Eddies, and buoyancy forcing. The observed seasonal change in the POC plume's response to wind speed in the western delta region resulted from seasonal changes in the upper ocean stratification. During late spring and summer, the low-density river water is heated rapidly at the surface by incoming solar radiation. This lowers the density of the fresh-water plume and increases the near-surface stratification of the water column. In the absence of significant wind forcing, the plume undergoes buoyant spreading and the sediment is maintained at the surface by the shallow pycnocline. However, when the wind speed increases substantially, wind-wave action increases vertical motion, reducing stratification, and the sediment were mixed downward rather than spreading laterally. Maximum particle concentrations over the outer shelf and the upper slope during lower runoff seasons were related to the Loop Current/eddies and buoyancy forcing. Inter-annual differences of POC concentration were related to ENSO cycles. During the El Nino events (1997-1998 and 2002-2004), the higher pac concentrations existed and were related to high runoffs in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico. During La Nina conditions (1999-2001), low Poe concentration was related to normal or low river discharge, and low PM/nutrient waters in the eastern Gulf of Mexico, but the opposite conditions in the western Gulf of Mexico.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.484-491
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• 2015

The productivity of Manila clam(Ruditapes philippinarum) aquaculture farm is closely related to suitable site selection, so it is essential to assess the habitat suitable for aquaculture species in order to manage yield. This study evaluated the habitat suitable index(HSI) with 9 sites for tidal flat farm, Gochang(Hajun) on May 2014. The suitability index was selected Growth(hydrodynamics, chlorophyll a), Survival(sediment-sand, silt-clay) and Water Environment(dissolved oxygen, salinity). Both Weight and No weight were tried for objective judgment as HSI scoring method. As a result, it shows lower tidal flat(HSI; No weight: 0.60~0.76, Weight: 0.47~0.70) is higher than upper(HSI; No weight: 0.25~0.27, Weight: 0.09~0.10), hydrodynamics and sediment particle size are the most effective. This research can consider the potential suitable site for Manila clam through scientific approach, and provide the basis for optimal management practices in tidal flat farm.