• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.9 no.1
• /
• pp.30-39
• /
• 2004

In order to understand the environmental impact of marine cage fish farms, we measured the vertical fluxes of particulate to the sediment, the distribution of organic carbon in core samples, sediment oxygen consumption rate (SOD), and macrobenthos with increasing distance from a fish cage in Miruk island located in Tongyong. The experiment was performed in August 2003. Measured values gradually decreased with distance, indicating that the organic matter in the sediment derived from the fish farm. The dominant macrobenthos species were Tharyx mulifilis, Lumbrineris longifolia, Sigambra tentaculata, and Capitella capitata, occupying 88% of the total population. Capirella capirata, an opportunistic polychaete species, were especially abundant between 0 to 5 m radius range. The estimated impact regions of organic matter enrichment based on sediment consilmption rates and compositions of macrobenthos were in good agreement. Most organic matter derived from the fish farm was deposited within a 10 m radius and then dispersed horizontally to nearby (at least 50 m) surface sediment. The vertical organic carbon fluxes to the sediment at the fish farm were higher by a factor of two than those outside the area. The remineralization organic carbon in the upper sediment layer was estimated to be 50% (1.07 g C m$^{-2}$ day$^{-1}$ ) at the fish farm. In contrast, outside the area, 30% (0.30 g C m$^{-2}$ day$^{-1}$ ) of organic carbon was recycled and the remaining 70% was deposited to the deep sediment layer.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.2
• /
• pp.101-106
• /
• 1999

The down-core distribution of chlorophyll a, organic carbon contents and ${\delta}^{13}C$ in the bottom sediments were measured to understand the evolution of eutrophication in Masan Bay. Bottom sediment were collected in January 1994. The chlorophyll a and organic carbon contents in the sediment core decreased with increasing sediment depth, respectively. Bottom sediments (0~20 cm) in Masan Bay was rich in chlorophyll a (avg. 9.6 ${\mu}g\;g^{-1}$ dryweight) and organic C (avg. 2.5%). The down-core distribution of chlorophyll a suggests that the inner part of Masan Bay has experienced the acceleration of chlorophyll a supply since 1960s. Flux of organic carbon to the sea floor is in the range of 10 $gCm^{-2}\;yr^{-1}$ assuming the C:Chl a ratio of 25. It suggests tht approximately 1.3% of the fixed carbon by phytoplankton appears to be deposited in the bottom sediments.

• Geophysics and Geophysical Exploration
• /
• v.26 no.3
• /
• pp.138-149
• /
• 2023

In geoscience and engineering the geological characteristics of sediment strata is crucial and possible if reliable borehole logging and seismic data are available. To investigate the characteristics of the shallow strata in the Korea Strait, laboratory sonic logs were obtained from deep borehole data and seismic section. In this study, we integrated and analyzed the sonic log data obtained from the drilling core (down to a depth of 200 m below the seabed) and multichannel seismic section. The correlation value was increased from 15% to 45% through time-depth conversion. An initial model of P-wave impedance was set, and the results were compared by performing model-based, band-limited, and sparse-spike inversions. The derived P-impedance distributions exhibited differences between sediment-dominant and unconsolidated layers. The P-impedance inversion process can be used as a framework for an integrated analysis of additional core logs and seismic data in the future. Furthermore, the derived P-impedance can be used to detect shallow gas-saturated regions or faults in the shallow sediment. As domestic deep drilling is being performed continuously for identifying the characteristics of carbon dioxide storage candidates and evaluating resources, the applicability of the integrated inversion will increase in the future.

• Ocean and Polar Research
• /
• v.24 no.4
• /
• pp.419-427
• /
• 2002

Meiobenthic community structure near Dokdo was investigated during two survey periods of June, 1999 and October 2000. Meiobenthos were separated from the sediment core samples collected from eight stations. A total of 19 meiobenthic animal groups were identified from those core samples. The most abundant meiobenthic animals belonged to Phylum Nematoda in both seasons and all stations. Sarcomastigophorans, nauplius of crustaceans, and benthic harpactiocoids were the next abundant meiobenthos. Vertical distribution of meiobenthic animals showed the highest individual numbers in the surface sediment layers of 0-1cm depth with a steep decreasing trend with depth for the three sampling stations (A0, A9', A19) located in the continental slope. Horizontal distribution of meiobenthic animals for the study area near Dokdo showed lower density at the sampling stations near Dokdo and the lowest density of meiobenthos in A19 (depth-2261 m). For size distribution, analysis showed that animals which fit onto the mesh size of 0.125mm were abundant. This study suggested that the continental shelf near Dokdo have a more unstable environment fo meiobenthos than the continental slope.

• Journal of the korean society of oceanography
• /
• v.35 no.2
• /
• pp.98-108
• /
• 2000

A geochemical study on a hemipelagic core sediment taken from the northwest Pacific Ocean (eastern edge of the Shikoku Basin) was conducted to use of excess barium (Ba(ex)) for evaluate the paleoceano-graphic changes. Also, the excursion of sedimentary Ba(ex) was compared with those of biogenic opal, carbonate and organic carbon content in the sediment during the last glacial and interglacial periods. The calculated Ba(ex) derived from the major and minor element shows a distinctive glacial-interglacial variations, and the mass accumulation rate (MAR) of Ba(ex) shows coincident variations with the MARs of biogenic fractions. Especially, strong positive correlation (r$^2$=0.85) between the MAR of Ba(ex) and the MAR of biogenic carbonate is recognized. Based on the strong positive correlation(r$^2$=0.85) between the MAR of Ba(ex) and the MAR of carbonate content, we estimated the degree of carbonate dissolution rate during the glacial and interglacial periods. Assuming the proportional variation and the refractory nature of barium exist between two factors, the variation of index Ca/Ba ratio in sediment indicates the degree of carbonate dissolution. Sedimentary Ca/Ba ratios index clearly show a striking fluctuation between the glacial and interglacial periods with higher positive correlation during glacial and lower correlation during interglacial. This fact indicates enhanced carbonate dissolution during interglacial period. Thus, the sedimentary Ca/Ba ratio in sedimentary records can be used as one of the useful tools for estimation of the relative degree of carbonate dissolution. The excursion of Ba(ex) and the sedimentary Ca/Ba ratio follows the typical pacific carbonate dissolution type(enhanced dissolution during interglacial and reduced dissolution during glacial time) as suggested by previous work (e.g., Wu et al., 1990). Variation in sedimentary Ca/Ba ratio thus strongly supports that glacial-interglacial fluctuation in carbonate dissolution has been prevailed in the northwest Pacific Ocean.

• Fisheries and Aquatic Sciences
• /
• v.11 no.2
• /
• pp.103-112
• /
• 2008

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

• Journal of Environmental Science International
• /
• v.11 no.3
• /
• pp.215-225
• /
• 2002

In order to evaluate the relationship between geochemical characteristics and benthic facies of the sediments from the Oenaro Island where red tide proliferation is first observed every year including this year, surface and short multiple core sediment samples were analyzed in terms of geochemical and benthic facies variation. The contents of organic carbon, carbonate, and sulfide gas were relatively low. The variation in C/N ratios, which indicate nature of organic carbon, suggested that the organic carbon recorded in the study area is composed of mixtures of marine and terrigenous organic matters. The concentration of minor elements found at the surface and multiple core sediment samples were also low as well as the enrichment factors(Ef) for the seven heavy metals indicated that the sediment of this area is not polluted significantly. The macrobenthic faunal community comprised 61 species, and their mean density was 708 ind./m2. Polychaete worms were major taxa of this benthic community. A crustacean amphipod, Melita sp. was the most abundant species accounted for 20.7% of total abundance, and the small polychaetes such as Heteromastus filiformis, Paralacydonia poradoxa, Magelona japonica and Sigambra tentaculata were the next dominant species. The macrobenthos around the Oenaro Island were more diverse and abundant than that in Gamak Bay. The benthic communities in the study area sustained somewhat different species composition based on the cluster analysis and the MDS ordination. The benthic community health condition at three stations seemed to be unbalanced, and slightly polluted based on the biological index such as BPI and BC. There was no clear relationship between the geochemistry characteristic and the benthic faunal facies attributed by the micro-algal blooms in this coastal area.

• Journal of Korea Water Resources Association
• /
• v.47 no.8
• /
• pp.729-742
• /
• 2014

This study predicted long-term sediment distribution for 76 years by using RMA-2 which is two-dimensional numerical model and SED2D which is the sediment transport model to quantitatively analyze sediment distribution in the reservoir based on sediment intrusion and efficiently manage the reservoir. For water level-discharge-sediment data required in boundary conditions of the model, real-time data measured by the Korea Water Resources Corporation were used. The sediment input data was calculated using K-DRUM model. Sedimentation depth was compared with results of model by collecting cross-section core in the reservoir during the dry season. As the result of validation, the sediment depth in the reservoir was similar to actually measured value. For prediction of long-term sediment distribution, terrain data measured in 2012 was used as starting crosssection and simulations for 76 years until 2088 were made. As the results of simulations, sediment distributions of 1.63~1.26 m and 1.45~0.007 m were shown in upstream and downstream of Hapcheon Dam, respectively.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.11
• /
• pp.613-625
• /
• 2017

For two agricultural reservoirs that are rented for fishing spots, benthic nutrient fluxes experiment were performed two times with two sediments from fishing-effective zone and one sediment from fishing-ineffective zone using laboratory core incubation in oxic and anoxic conditions. During benthic nutrient fluxes experiment, the changes in DO, EC, pH, and ORP in the supernatant were not significantly different between fishing-effective zone and fishing-ineffective zone, and were similar to the sediment-hypolimnetic diffused boundary layer in agricultural reservoir. Except for $NO_3{^-}-N$, more benthic nutrient fluxes of $NH_4{^+}-N$, T-P, and $PO{_4}^{3-}-P$ from sediment to hypolimnetic was measured in anoxic than in oxic conditions (p<0.05). As the DO concentration in hypolimnetic decreases, the microorganism-mediated ammonification is promoted, the nitrification is suppressed, and finally the $NH_4{^+}-N$ diffuses out from sediment to hypolimnetic. Also, the diffusion of T-P and $PO{_4}^{3-}-P$ from sediments to hypolimnetic is accelerated through the dissociation of the phosphorus bound to both organic matters and metal hydroxides. The difference in the benthic nutrient diffusive fluxes between fishing-effective zone and fishing-ineffective zone was not statistically significant (p>0.05). Therefore, it was found that fishing activities did not increase the benthic nutrient diffusive fluxes to a statistically significant level. Due to the short fishing activities of 10 years and the rate-limited diffusion of the laboratory core incubation, the contribution of fishing activities on sediment pollution is estimated to be low. No significant correlation was found between the total amount of nutrients in sediment and the benthic nutrient diffusive fluxes in both aerobic and anaerobic conditions. Therefore, nutrients input from various nonpoint sources of watersheds are considered to be a more dominant factor rather than fishing activities in water quality deterioration, and both aeration and water circulation in hypolimnetic were required to suppress the anoxic environment in agricultural reservoirs.

• Journal of the Mineralogical Society of Korea
• /
• v.24 no.3
• /
• pp.179-188
• /
• 2011

In order to investigate absolute age of marine sediment in the KR5 region, northeastern Pacific, we measured the Be isotope ($^{10}Be$ and $^{9}Be$) of box core (BC08-02-13) sediment with depth. Core sediment is divided into three sedimentary facies (Facies I, Facies II, FaciesIII). Facies I mainly consists of brown to dark brown (10YR4/3) homogeneous mud with high water content. Facies II shows brownish yellow (10YR6/6) color. The unconformity is recognized at the boundary between Facies I and Facies II, Facies III consists of very dark brown (10YR2/2) mud. Many bioturbated burrows are observed at FaciesII and FaciesIII. Based on Be dating results, FaciesIII and Facies II had been deposited before 3.7 Ma and 2.3 Ma, respectively. After 2.3 Ma, the upper part of Facies II was eroded due to the change of sedimenary environment. Facies I has been deposited since 1.8 Ma. The unconformity located at the boundary between Facies I and Facies II may be driven by the envrionmental change due to the migration of Intertropical Convergence Zone.