• 한국해양학회지
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• v.30 no.2
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• pp.77-90
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• 1995

The sedimentary environments and biostratigrapy of the tidal sediments off the Mankyung-Dongjin River estuary were studied based on sedimentary facies and diatom assemblage analysis. Sediment facies from the five vibracores are mainly clay, silt, and sand facies. The clay and silty sediment facies are more dominant than the sandy facies, and contain diatom frustules. The frequency of the diatom frustules are rate to common, but not found in sandy sediment facies. Bigeneric structures such as burrow and non-bigeneric primary sedimentary structures such as laminated sand and mud or silt and mud couplets, flaser bedding, ripple-cross lamination are found in several stratigraphic levels of the sedimentary sequences. A total of 219 species and varieties, belonging to 61 genera has been identified in the present study. Among them, paralia sulcata is the most abundant species about 30 to 50% of the total diatom frustules. Another predominant species are Cyclotella striata. Thalassionema nitzschioides. Actinoptychus undulatus. Delphineis surirella, Raphoneis amphiceros. Most of the diatoms occurred in this study area are marine, marine-brackish water, and brackish water species, and are benthic and tychopelagic or meroplanktonic species. Also, most of the species are coastal to littoral and littoral to inner neritic species. The occurrences of freshwater species, about 1 to 5% is higher than that of the Namyang Bay tidal sediments. The ecological properties of the diatoms occurred in the study area and primary sedimentary structure such as flaser bedding ripple cross bedding indicate that the deposits are formed under coastal or littoral to subeditorial environments such as tidal zone which was subjected to the influenced of stream water and was more strongly influenced by temperate to warm water than cold water. The sedimentary environments have not been changed distinctively during the time of deposition. The vertical distribution pattern of diatoms in the study area is studied by Q-mode cluster Analysis using spss/pc+ (ver.4.0). The results show that the three cores (GE-3, GE-11, GE-12) are divided into two diatom assemblages, respectively. Biostratigraphic correlation using the data of Q-mode Cluster Analysis are attempt in this study.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.1
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• pp.13-24
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• 2022

The Arctic Ocean is very sensitive to global warming and Arctic Ocean sediments provide a records of terrestrial climate change, analyzing their composition helps clarify global warming. The gravity core sediment ARA07C-St02B was collected at the East Siberian margin during an Arctic expedition in 2016 on the Korean ice-breaking vessel ARAON, and its provenance was estimated through sedimentological, mineralogical and geochemical analysis. The core sediment was divided into four units based on sediment color, sand content and ice-rafted debris content. Units 1 and 3 had higher sand and ice-rafted debris contents than units 2 and 4, and contained a brown layer, whereas units 2 and 4 were mainly composed of a gray layer. Correlation analysis using the adjacent core sediment ARA03B-27 suggested that the sediment units were deposited during marine isotope stage 1 to 4. The bulk mineral, clay mineral, and geochemical compositions of units including a brown layer differed from units including a gray layer. Bulk and clay mineral compositions indicated that coarse and fine sediments had a different origin. Coarse sediments might have been deposited mostly by the East Siberian Coastal Current from the Laptev Sea and the East Siberian Sea or by the Beaufort Gyre from the Chukchi Sea, whereas fine sediments might have been transpoted mostly by currents from the East Siberian Sea, the Chukchi Sea and the Beaufort Sea. Some of the coarse sediments in unit 1 and fine sediments in unit 3 might have been deposited by iceberg ice, sea ice or current from the Beaufort Sea and the Canada Archipelago. Investigating the geochemical composition of the potential origins will elucidate the origin and transportation of the study area's core sediments.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.689-697
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• 2005

Mineralogical composition, $^{137}Cs$ activity, total organic carbon (TOC), and particle size of marine sediments near Wuljin Nuclear Powerplant were analyzed and the relationships among those components were investigated. The particle sizes of sediments were equivalent to sand size and in the range of $-0.48\~3.6\;Md\phi$. TOC contents and $^{137}Cs$ activities were in the range of $0.06\~1.75\%$ and minimum detectable activity (MDA) $\~4.0Bq/kg-dry$ with the average value of $1.15{\pm}0.62$ Bq/kg-dry, respectively. The sediments in study area were characterized by large particle size and small TOC contents, and $^{137}Cs$ activity compared with other marine sediments. The main mineral components were quartz and feldspar (albite, microcline, and small amount of orthoclase) with small amount of pyroxene, calcite, hornblende. Minerals with $10{\AA}$ XRD peak (mainly biotite) and chlorite were also identified. Among those minerals, biotite shows the linear relationship with $^{137}Cs$ content probably due to the frayed edge site (FES) on biotite or small amount of mixed illite. However, TOC content shows most linear relationship with $^{137}Cs$ content because no significant amount of clay minerals, which can adsorb significant amount of Cs, were observed in the study area, indicating that the distribution of $^{137}Cs$ in this study area was more significantly affected by the TOC content than mineral composition.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.175-183
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• 2010

To understand the variation of macro benthos community according to the installation of structure and topographic placement in the shellfish farm on tidal flat, the practical example of the tidal shellfish growing area at Namsung-ri Goheung was observed. The results of the research for the field observation were summarized as follows. (1) The ground gradient of the shellfish farm was very flat below about $1^{\circ}$. The shellfish farm ground took the shape of $\sqcup$ from the shoreline to the place of 150 m seawards, and the shape of $\sqcap$ from there to the low tide line. During ebb tide, the $\sqcup$ shape ground stored the sea water, and the $\sqcap$ shape ground was supposed to act as the effect factor to leak slowly or to prevent the outflow. (2) The oyster shell bag or the type of riprap wall as the boundary in the shellfish farm was classified into five types. The air exposure time and flooding time were 181 and 434 minutes, respectively. (3) In the numerical experiment, the deep-sea water wave coming in the study area had 0.5 m of maximum wave height to show the very stable conditions and the wave direction pattern of S-direction was dominant at Naro great ridge, and SE, SSW and S-direction were distributed strongly around the shellfish farm. (4) By the grain size analysis, the sediment around tidal flat consisted of gravel 0.00~5.81(average 1.70)%, sand 14.15~18.39(average 13.23)%, silt 27.59~47.15(average 30.84)% and clay 35.79~55.73(average 36.19)%, and the sediment type was divided into (g)M(lightly gravelly mud), sM(sandy mud) and gM(gravelly mud) by Folk's diagram. (5) The macro benthos community survey conducted in this site in January, 2010 showed that 1 species of Mollusca, 8 species of Polychaeta and 2 species of Crustacea appeared, and 11 species occupying over 1% of total abundance were dominant.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.2
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• pp.87-102
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• 2022

To clarify the spatial distribution pattern of macrozoobenthos in Korean coastal waters in the summer season and investigate the relationship between community structure and benthic environmental factors, field surveys on community structure and benthic environmental factors were conducted at 117 stations in August 2017. A total of 613 macrobenthic species were identified, with the mean density of 1,228 ind./m² and the mean biomass (wet weight) of 110.9 g WW/m². Rich biodiversity was found at stations near Wando and along the coast of the East Sea, and there is a trend that stations with greater biodiversity also showed higher mean density as well. The dominant species in all the coastal areas in Korea was Heteromastus filiformis, which were found at most of the stations during the survey. The relatively deep areas in the East Sea were dominated by Magelona johnsoni and Maldane cristata, which were the third and ninth dominant species in the study areas, respectively. Pseudopolydora kempi and Rhynchospio sp. were observed only at the station located in the Nakdong River estuary. From the cluster analysis the stations could be clustered into three station groups with more similar faunal composition. Group A was located in the eastern coast, characterized with deep water depth and low levels of sand contents, while Group B was located in the southern coast, characterized by shallow depth of water and high content of mud and organic matter. Lastly, Group C was in the western coast, demonstrating low levels of mud content and organic matters. The biodiversity of macrobenthic species in the study area showed high positive correlation coefficients with benthic environmental factors such as sorting, clay, silt, and contents of organic matter in sediments, but negatively correlated with the sand contents. Major dominant species, Theora lata and Eriopisella sechellensis, both showed negative correlation coefficients with the sand contents, but a relatively high positive correlation with the levels of organic contents.It can be concluded that the spatial distribution patterns of macrobenthic organisms in Korean coastal waters are affected by depth, sediment type, and contents of organic matters.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.63-65
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• 2001

The Chosen Supergroup (Cambro-Ordovician), mid-east Korea consists mainly of shallow marine carbonates and contains a variety of limestone conglomerates. These conglomerates largely comprise oligomictic, rounded lime-mudstone clasts of various size and shape (equant, oval, discoidal, tabular, and irregular) and dolomitic shale matrices. Most clasts are characterized by jigsaw-fit (mosaic), disorganized, or edgewise fabric and autoclastic lithology. Each conglomerate layer is commonly interbedded with limestone-dolomitic shale couplets and occasionally underlain by fractured limestone layer, capped by calcareous shale. According to composition, characteristic sedimentary structures, and fabric, limestone conglomerates in the Hwajol, Tumugol, Makkol, and Mungok formations of Chosen Supergroup can be classified into 4 types: (1) disorganized polymictic conglomerate (Cd), (2) horizontally stratified polymictic conglomerate (Cs), (3) mosaic conglomerate (Cm), and (4) disorganized/edgewise oligomictic conglomerate (Cd/e). These conglomerates are either depositional (Cd and Cs) or diagenetic (Cm and Cd/e) in origin. Depositional conglomerates are interpreted as storm deposits, tidal channel fills, or transgressive lag deposits. On the other hand, diagenetic conglomerates are not deposited by normal sedimentary processes, but formed by post-depositional diagenetic processes. Diagenetic conglomerates in the Chosen Supergroup are characterized by autoclastic and oligomictic lithology of lime-mudstone clasts, jigsaw-fit (mosaic) fabric, edgewise fabric, and a gradual transition from the underlying bed (Table 1). Autoclastic and oligomictic lithologies may be indicative of subsurface brecciation (fragmentation). Consolidation of lime-mudstone clasts pre-requisite for brecciation may result from dissolution and reprecipitation of CaCO3 by degradation of organic matter during burial. Jigsaw-fit fabric has been considered as evidence for in situ fragmentation. The edgewise fabric is most likely formed by expulsion of pore fluid during compaction. The lower boundary of intraformational conglomerates of depositional origin is commonly sharp and erosional. In contrast, diagenetic conglomerate layers mostly show a gradual transition from the underlying unit, which is indicative of progressive fragmentation upward (Fig. 1). The underlying fractured limestone layer also shows evidence for in situ fragmentation such as jigsaw-fit fabric and the same lithology as the overlying conglomerate layer (Fig, 1). Evidence from the conglomerate beds in the Chosen Supergroup suggests that diagenetic conglomerates are formed by in situ subsurface fragmentation of limestone layers and rounding of the fragments. In situ subsurface fragmentation may be primarily due to compaction, dewatering (upward-moving pore fluids), and dissolution, accompanying volume reduction. This process commonly occurs under the conditions of (1) alternating layers of carbonate-rich and carbonate-poor sediments and (B) early differential cementation of carbonate-rich layers. Differential cementation commonly takes place between alternating beds of carbonate-rich and clay-rich layers, because high carbonate content promotes cementation, whereas clay inhibits cementation. After deposition of alternating beds and differential cementation, with progressive burial, upward-moving pore fluid may raise pore-pressure in the upper part of limestone layers, due to commonly overlying impermeable shale layers (or beds). The high pore-pressure may reinforce propagation of fragmentation and cause upward-expulsion of pore fluid which probably produces edgewise fabric of tabular clasts. The fluidized flow then extends laterally, causing reorientation and further rounding of clasts. This process is analogous to that of autobrecciation, which can be analogously termed autoconglomeration. This is a fragmentation and rounding process whereby earlier semiconsolidated portions of limestone are incorporated into still fluid portions. The rounding may be due mainly to immiscibility and surface tension of lime-mud. The progressive rounding of the fragmented clasts probably results from grain attrition by fluidized flow. A synthetic study of limestone conglomerate beds in the Chosen Supergroup suggests that very small percent of the conglomerate layers are of depositional origin, whereas the rest, more than $80\%$, are of diagenetic origin. The common occurrence of diagenetic conglomerates warrants further study on limestone conglomerates elsewhere in the world.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.399-403
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• 2012

The management of heavy metals in soil is important for environmental-friendly agriculture and keeping an ecosystem healthy. In this study, we examined the concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn, and As) in 260 paddy soils sampled from Gyeongnam Province. The concentrations of the heavy metals were 0.143 mg $kg^{-1}$ (ranged 0.003-0.537) for Cd, 0.322 (0.002-0.986) mg $kg^{-1}$ for Cr, 25.41 (6.03-76.19) mg $kg^{-1}$ for Cu, 16.36 (2.63-32.94) mg $kg^{-1}$ for Ni, 18.67 (4.16-87.02) mg $kg^{-1}$ for Pb, 71.76 (22.99-153.58) mg $kg^{-1}$ for Zn, and 3.516 (0.002-19.481) mg $kg^{-1}$ for As, respectively. In addition, the concentration of Cd was highest in mountain foot-slope, Ni and As were highest in diluvial terrace, and Zn was highest in marine plains. Higher concentrations of Cd, Cu, and Zn were found in silty clay loam soils compared to silt loam, sandy loam, and loam soils.

• Journal of Environmental Science International
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• v.23 no.2
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• pp.181-192
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• 2014

In Korea, the chemical oxygen demand($COD_{sed}$) in freshwater sediments has been measured by the potassium permanganate method used for marine sediment because of the absence of authorized analytical method. However, this method has not been fully verified for the freshwater sediment. Therefore, the use or modification of the potassium permanganate method or the development of the new $COD_{sed}$ analytical method may be necessary. In this study, two modified $COD_{sed}$ analytical methods such as the modified potassium permanganate method for $COD_{Mn}$ and the modified closed reflux method using potassium dichromate for $COD_{Cr}$ were compared. In the preliminary experiment to estimate the capability of the two oxidants for glucose oxidation, $COD_{Mn}$ and $COD_{Cr}$ were about 70% and 100% of theoretical oxygen demand(ThOD), respectively, indicating that $COD_{Cr}$ was very close to the ThOD. The effective titration ranges in $COD_{Mn}$ and $COD_{Cr}$ were 3.2 to 7.5 mL and 1.0 to 5.0 mL for glucose, 4.3 to 7.5 mL and 1.4 to 4.3 mL for lake sediment, and 2.5 to 5.8 mL and 3.6 to 4.5 mL for river sediment, respectively, within 10% errors. For estimating $COD_{sed}$ recovery(%) in glucose-spiked sediment after aging for 1 day, the mass balances of the $COD_{Mn}$ and $COD_{Cr}$ among glucose, sediments and glucose-spiked sediments were compared. The recoveries of $COD_{Mn}$ and $COD_{Cr}$ were 78% and 78% in glucose-spiked river sediments, 91% and 86% in glucose-spiked lake sediments, 97% and 104% in glucose-spiked sand, and 134% and 107% in glucose-spiked clay, respectively. In conclusion, both methods have high confidence levels in terms of analytical methodology but show significant different $COD_{sed}$ concentrations due to difference in the oxidation powers of the oxidants.

• The Korean Journal of Malacology
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• v.32 no.3
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• pp.149-155
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• 2016

To assess the effects of environmental factors on the sustainability of cultured ark shell Scapharca broughtonii production, we investigated the habitat characteristics of shellfish-farming bays (Gangjin Bay, Yeoja Bay, Keoje Bay and Deukryang Bay). We measured the physiochemical parameters (temperature, salinity, dissolved oxygen, nutrients, chemical oxygen demand and Chlorophyll a) and the geochemical characteristics (chemical oxygen demand, ignition loss, C/N ratio and C/S ratio). Surface sediments were collected from several shellfish-farming bays to examine the geochemical characteristics of both the benthic environment and heavy metal pollution. The grain sizes for Gangjin Bay, Yeoja Bay and Keoje Bay were similar, at the ratio of silt and clay in comparison with Deukryang bay of it. The C/N ratio was more than 5.9, reflecting the range arising from the mix of marine organisms and organic matter. The C/S ratio (more than 4.2) showed that the survey area had anoxic or sub-anoxic bottom conditions. The index of accumulation rate (Igeo) of the metals showed that those research areas can be classified as heavily polluted, heavily to moderately polluted, or more or less unpolluted, respectively. We suggested that the growth of ark shell Scapharca broughtonii in the shellfish-farming bay was effected by the various environmental conditions.

• Journal of the Korean Geotechnical Society
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• v.32 no.7
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• pp.25-34
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• 2016

Recently, in Korea, problems related with unstability of slope or sinkhole in urban area due to erosion of compacted granite soil which was used as a backfill or embankment material have been treated as important issues. Small hole might develop inside of backfill area due to erosion of not only weathered granite soil but also clay, silt, fine sand size particles when underground water flows. Once erosion starts in a soil mass, erosion rate increases gradually to cause rapid destruction. In this study, a rotating cylinder test (RCT) was performed to evaluate the hydraulic resistance characteristics of compacted weathered granite soil under various relative densities and preconsolidation pressures. Meanwhile, an image analysis method was introduced to analyze radius of irregularly eroded sample. It was found that image analysis is an effective means of minimizing the error in calculating a critical shear stress and threshold shear stress on the irregularly eroded sample. Furthermore, in general, hydraulic resistance capacity increases with the increase of relative density and preconsolidation pressure.