• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.5
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• pp.773-783
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• 2020

In order to evaluate the recovery of fishing ground environment after the cessation of aquaculture farming, we examined the variation in sediment quality over time using different geochemical factors and investigated whether these factors are indicators of sediment quality recovery. The study area was an oyster Crassostrea gigas, farm in Tongyeong, Geyongsangnam-do, South Korea, where aquaculture activities had been carried out for 20 years, and the changes in water and sediment environment were monitored for 14 months after the abandonment of the farm. The mean water depth was 14 m, with a tidal range of 3 m, and seawater current velocity ranged from 4.7 to 7.0 cm/s. After the abandonment of the farm, total organic carbon and total nitrogen concentrations in the surface sediments decreased significantly over time compared to those in the control site; in particular, immediately after farm abandonment, acid-volatile sulfide concentrations decreased relatively rapidly. Carbohydrate and protein concentrations in the sediments showed no significant changes; however, lipid concentrations markedly decreased. Further studies on other aquaculture taxa and various aquaculture areas are needed to establish new policies for environmental management of fishing grounds, such as relocation of fishing grounds and determination of optimal fallowing periods.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.704-715
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• 2012

To examine temporal and spatial variation in salinity and nutrients in the shallow pore water of intertidal sandflats, we measured salinity and nutrient concentrations (dissolved inorganic nitrogen [DIN], phosphorus [DIP], and silicate [DSi]) in pore water of the intertidal zone along the coastline of Jeju Island at two and/or three month intervals from May 2009 to December 2010. Geochemical parameters (grain size, ignition loss [IL], chemical oxygen demand [COD], and acid volatile sulfur [AVS]) in sediment were also investigated. The surface sediments in intertidal sandflats of Jeju Island were mainly composed of sand, slightly gravelly sand and gravelly sand, with a range of mean grain size from 0.5 to 2.5 ${\O}$. Concentrations of IL and COD in sediment were higher along the eastern coast, as compared to the western coast, due to differences in biogenic sediment composition. Salinity and nutrient concentrations in pore water were markedly different across time and space during rainy seasons, whereas concentrations were temporally and spatially more stable during dry seasons. These results suggest that salinity and nutrient concentrations in pore water depend on the advective flow of fresh groundwater. We also observed an imbalance of the DIN/DIP ratio in pore water due to the influence of contaminated sources of DIN. In particular, nutrient concentrations during rainy and dry seasons were characterized by high DIN/DIP ratios (mean-127) and low DIN/DIP ratios (mean-10), respectively, relative to the Redfield ratio (16) in offshore seawater. Such an imbalance of DIN/DIP ratios in pore water can affect the coastal ecosystem and appears to cause outbreaks of benthic seaweed along the coastline of Jeju Island.

• Journal of the Korean earth science society
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• v.32 no.3
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• pp.265-275
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• 2011

The Hamo and Hyeopjae beaches in the western part of Jeju Island were studied in terms of seasonal variations of surface sediment and beach profile. Seasonal drift direction of the beach sands also was investigated. The Hamo beach of $7.3^{\circ}-10.8^{\circ}$ steep is composed of medium sand containing volcanic clasts and shell fragments. The Hyeopjae beach of $2.8^{\circ}-6.5^{\circ}$ steep is composed of coarse shelly sand. Hamo beach deformation is probably caused by the jetties constructed in the western part of the beach. In the Hyeopjae beach, surface sands were drifted into the dune side by the northwestern stormy wind during winter season.

• Ocean and Polar Research
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• v.32 no.2
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• pp.123-135
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• 2010

Around Tongyeong coasts which located in southern coast of Korea composed to the complex coastal line and scattered by small islands. It also has been distributed to a complicated bathymetric structure by several types of channels. This study carried to analyze the spatial characteristics of macrobenthic community and benthic environmental variance on sub-tidal area based on multivariate statistics tools. Sediment composition varied from muddy sand to mud, and along the channels, it composed to a heterogeneous bottoms mixed by shell fragment, cobbles and mud. Organic contents on the surface sediment varied 1.1-3.9%. Total of 272 species, $33,349\;ind./m^2$ of macrobenthos identified in all of sample area. Polychaetes also prevailed among the specimen. L. longifolia, P. pinnata dominated based on density. Considering on the biomass, echinoderm S. lacunosa, A. tricoides listed. Closer to the coastal area, the density and diversity were higher. Community structure based on cluster analysis was discriminated into three groups. Each group was also characterized by geographical state such as depth, sediment composition. In addition, when applied to the bathymetric data, the channel, which composed to the mixed sediment, made a role of limited factor which characterized to benthic community. Because the specimen around the channel have been affected on the diverse sediment mixture. Most of benthic studies in the southern coast of Korea focused to the condition of benthic organic pollution spatially, because along the coast, it also developed a aquaculture ground and industrial complex. But, as results, most of the area, it turn out the less polluted areas nevertheless similar environment situation. It supposed that benthic community affect to the bottom sediment composition by physical characteristics.

• Ocean and Polar Research
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• v.35 no.3
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• pp.229-237
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• 2013

We measured two-dimensional (2-D) oxygen distribution in the surface sediment layer of intertidal sediment using a simple and inexpensive planar oxygen optode, which is based on a color ratiometric image approach. The recorded emission intensity of red color luminophore light significantly changed with oxygen concentration by $O_2$ quenching of platinum(II)octaethylporphyrin (PtOEP). The ratios between the intensity of red and green emissions with oxygen concentration variation demonstrated the Stern-Volmer relationship. The 2-D oxygen distribution image showed microtopographic structure, diffusivity boundary layer and burrow in surface sediment layer. The oxygen penetration depth (OPD) was about 2 mm and the one-dimensional vertical diffusive oxygen uptake (DOU) was 12.6 mmol $m^{-2}d^{-1}$ in the undisturbed surface sediment layer. However, those were enhanced near burrow by benthic fauna, and the OPD was two times deeper and DOU was increased by 34%. The simple and inexpensive oxygen planar optode has great application potential in the study of oxygen dynamics with high spatiotemporal resolution, in benthic boundary layers.

• Proceedings of KOSOMES biannual meeting
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• 2008.05a
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• pp.129-132
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• 2008

This study was performed to characterize the seasonal variation of water quality and sediment environment from May, 2007 to February, 2008 in 20 stations of Kamak bay. $4.83\sim11.07mg/L$ on surface and $4.70\sim11.19mg/L$ on bottom in DO, $0.16\sim2.03mg/L$ on surface and $0.10\sim1.55mg/L$ on bottom in COD, $0\sim3.04{\mu}g$-at/L on surface and $0\sim15.21{\mu}g$-at/L on bottom in DIN, $0\sim3.04{\mu}g$-at/L on surface and $0\sim2.01{\mu}g$-at/L on bottom in DIP. IN sediment the ranges were 3.80 to 9.78% in IL, $0\sim5.37mg/g$-dry in AVS and $3.09\sim41.01mg/g$-dry in COD.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.1-12
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• 2007

Mooring survey for measurement of tidal current and suspended sediments was carried out at 4 inlets of Yeoja Bay in April, 2000 in order to understand the source of sediment supply. Net suspended sediment transport load during 2 tidal cycles through the M-1(West Inlet) was $133.88\;kg{\cdot}m^{-1}$ toward the Yeoja Bay, whereas the flux through the M-2(Jabal Inlet) was outward the Bay with the amount of $146.43\;kg{\cdot}m^{-1}$. The influx through the M-3 and 4(Bulgyo and Dong Isa Stream) was $23.25\;kg{\cdot}m^{-1}$ and $4,312.31\;kg{\cdot}m^{-1}$ toward the Yeoja Bay, respectively. Influx of suspended sediment on Yeoja Bay mainly occurred in the Dong Isa Stream. In the wet season the composition of surface was coarser-grained than dry season, possibly due to the influx of silty sediment from Dong Isa Stream In the wet season.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.161-168
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• 2010

We conducted a field survey of the generation and development of the delta area of the Nakdong River estuary, Korea. To examine deposition and erosion of the barrier islands, we observed the spatiotemporal variations of sediment transport and quantitatively estimated the settling velocity of coastal sediment. For the field survey, we established two survey sites off the coasts of Jinu Island and Doyodeung, which had shown rapid variations in deposition and erosion. At these sites, we measured the net surface elevation change of the bottom level at approximately 1-month intervals. Main findings were summarized as follows. (1) Calculated daily deposition and erosion velocity during the observation period ranged from -1.39 to 3.56cm/day at Jinu Island and from -4.0 to 3.07cm/day at Doyodeung, respectively. (2) Although two typhoons passed by the study area during the observation period, the maximum net surface elevation was larger in October than during the passage of those typhoons.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.541-547
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• 2013

It is important to establish water treatment technologies for drinking water because Korea belongs to water-stressed country. Leachate from recent incident of foot-and-mouth disease has become an opportunity to be aware of the need to manage water quality. Water purifiers are adopted to four or five steps of filtration process. Each steps are composed of a sediment filter, a pre-carbon filter, an UF or a RO membrane filter and a post-carbon filter. And additionally a ceramic filter can be used as a final stage. In this study, operational conditions in each steps are examined and characteristics of each filters are investigated. SEM analysis is used for filter surface and shape investigation using 6 commercial samples. Pore sizes of the sediment filter, the UF membrane filter, and the RO membrane filter are 30~47 ${\mu}m$, 0.005~0.5 ${\mu}m$, and 0.025~0.25 ${\mu}m$, respectively. Specific surface areas of activated carbons are ranged from 622 to 1,308 $m^2/g$.

• Journal of Environmental Science International
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• v.22 no.7
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• pp.787-799
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• 2013

The aim of this study was to investigate the accumulation of metallic elements and the control effect of marine pollution caused by ocean dumping in the sediments at a waste disposal area in the Yellow Sea. In July 2009, concentrations of organic matter and metallic elements (Al, Fe, As, Cd, Cr, Co, Hg, Ni, Mn, Pb, and Zn) were measured in surface sediments at the site. The ignition loss (IL) in the surface sediments showed a mean value of 15.4%, about 1.5 times higher than the mean value of the sediments in the coastal areas of Korea. The chemical oxygen demand (COD) at some disposal sites exceeded 20 mg $O_2/g{\cdot}dry$, which signifies the initial concentration of marine sediment pollutants in Japan. The disposal sites contain higher concentrations of Cr, Cu and Zn than the sediments of bays and estuaries that might be contaminated. The magnitude of both metal enrichment factors (EF) and adverse biological effects suggest that pollution with Cr and Ni occurred due to the dumping of waste in the study area. In addition, the geoaccumulation index (Igeo) showed that the surface sediments were moderately contaminated. By the mid-2000s, when the amount of waste dumped at this site was the highest, the concentration of metallic elements was higher than ever recorded. On the other hand, in 2008-09, the need for environmental management was relatively low compare with the peak. As a result, the quality of marine sediment has been enhanced, considering the effect of waste reduction and natural dilution in the disposal area.