• Journal of Marine Life Science
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• v.8 no.1
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• pp.87-92
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• 2023

Microplastic particles are ubiquitous in the environment and not standardized particles of size, shape, or type. Therefore, it is very limited to establish a risk assessment framework that accurately evaluated and manage the multi-dimension of marine environment including seawater and sediment based on toxic data. In the study, we review the characteristics and effects of marine environmental microplastic and suggest risk assessment framework (draft) based on the distribution and impact of marine environmental microplastics. Although, the characteristics of environmental microplastic are very widely but the most abundant toxic data are concentrated on unique shape and type, and there are also large gaps of test organism between laboratory-exposed organisms and resident species. Great limitations with respect to toxicity data quality also exist for traditional effect assessment methods, which in reliability of the resulting risk characterizations. However, considering the fact that the international community's movement on microplastics management is gradually strengthening and the pollution level of microplastics in marine environment is increasing, further research on environmental relevant risk assessment technique should be proposed based on the characteristics of microplastics in the marine environment.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.671-687
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• 2022

It has been reported that about 47% of groundwater wells within 10 km from the coastline in the western/southern coastal areas of Korea were affected by seawater. It has been interpreted that the cause of groundwater salinization is seawater intrusion. The Gilsan stream in the Seocheon area was a tidal stream until the Geumgang estuary dam was constructed and operated. Therefore, it is likely that the Gilsan stream catchment was deposited with sediments containing high-saline formation water prior to the use of landfill farmland at this catchment area. The groundwater in this study area showed EC values ranging from 111 to 21,000 µS/cm, and the water quality types were diverse including Ca(or Na)-HCO₃, Ca(or Na)-HCO₃(Cl), Na-Cl(HCO₃), Na-Cl types. It is believed that this diversity of water quality is due to the mixing of seawater and fresh groundwater generated by infiltration of precipitation and surface water through soil and weathered part. In this study, we discussed whether this water quality diversity and the presence of saline groundwater are due to present seawater intrusion or to remnant high-saline pore water in sediments during flushing out process. For this, rain water, surface water, seawater, and groundwater were compared regarding the water quality characteristics, tritium content, oxygen/hydrogen stable isotopic composition, and ⁸⁷Sr/⁸⁶Sr ratio. The oxygen/hydrogen stable isotopic compositions indicated that water composition of saline groundwaters with large EC values are composed of a mixture of those of fresh groundwater and surface water. Also, the young groundwater estimated by tritium content has generally higher NO₃ content. All these characteristics showed that fresh groundwater and surface water have continued to affect the high-saline groundwater quality in the study area. In addition, considering the deviation pattern in the diagrams of Na/Cl ratio versus Cl content and SAR (sodium adsorption ratio) versus Cl content, in which two end members of fresh surface-ground water and seawater are assumed, it is interpreted that the groundwater in the study area is not experiencing present seawater intrusion, but flush out and retreating from ancient saline formation water.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.444-454
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• 2015

Measurements of bottom backscattering strengths in a frequency range of 6-14 kHz were made on the shallow water off the southern Gyeonggi Bay in Yellow Sea in May 2013, as part of the KIOST-HYU joint acoustics experiment. Geological surveys for the experimental area were performed using multi-beam echo sounder, sparker system, and grab sampling to investigate the bottom topography, sub-bottom profile and composition of surficial sediment, respectively. In this paper, the backscattering strengths as a function of grazing angle (in range of $28^{\circ}{\sim}69^{\circ}$) were estimated and compared to the predictions obtained by Lambert's law and APL-UW scattering model. Finally, the effects of geoacoustic parameters corresponding to the experimental area on the backscattering strengths are discussed.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1291-1298
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• 2002

To utilize coastal aquaculture ground bottom sediment in which concentrations of harmful pollutants are low and organic content is high as an organic fertilizer alkaline stabilizers such as CaO, Oyster shell, Mg(OH)$_2$ were added to the bottom sediment organic additives of livestock or food wastes. Nutritive qualities of crude fertilizers were measured to examine effects of alkaline stabilizers and organic waste additions. The Mg(OH)$_2$-added crude fertilizer had significantly lower total carbon(T-C) and nitrogen(T-N) content, reflecting the dilution effect due to great amount of Mg(OH)$_2$ addition. However, the addition of oyster shell had no significant effect on the T-C and T-N content of the fertilizer. $P_2O_5$ and $K_2$O content was considerably higher in the mixed sample of aquaculture ground bottom sediments and livestock wastes than in the mixture of the sediments and food wastes, resulting from higher $P_2O_5$ and $K_2$O content in livestock wastes. Addition of Mg(OH)$_2$ increased the content of MgO In the crude fertilizer but significantly reduced the content of other nutritive elements such as $P_2O_5$, $K_2$O and CaO. Addition of oyster shell as an alkaline stabilizer seemed to have the advantage of saving time and expenses far dryness due to its role as a modulator of water content. Moreover, additions of effect Mg(OH)$_2$ decreased the concentrations of heavy metals in the fertilizer by the dilution while additions of oyster shell had no influence on heavy metal concentrations in the fertilizer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.386-392
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• 1996

A numerical method based on genetic algorithms was introduced to characterize the grain-size distribution more effectively. This technique was proved significant particularly for multimodal size distributions, as was verified for samples from Korea Strait continental shelf. Sediment samples collected from the Korea Strait continental shelf revealed that $96\%$ of the grain-size distributions were multimodal. Therefore, the use of grain-size parameters was not the ideal method. As an alternative method, the decomposition of sue curves into elementary normal component curves was used. Means and standard deviations of 593 decomposed normal components were calculated by a numerical method from 268 size curves of Korea Strait sediments. The mean values of decomposed normal components showed peaks at $1\~3\phi\;and\;7\~9\phi$ size classes. The plot of mean and standard deviation values of the coarse fraction normal components on the map showed a characteristic areal distribution. The characteristic distribution was found to derive from underlying Pleistocene sediment on the basis of sea bottom geologic distribution of the area. The method of decomposition into normal components was found to be more effective than the analysis using traditional grain-size parameters in investigation of multimodal size distribution of Korea Strait shelf sediment.

• Journal of Wetlands Research
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• v.20 no.3
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• pp.227-234
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• 2018

This paper was examined the physical characteristics of floc density of suspended fine particles with varying cohesiveness. The analysis of floc density was performed in a small annular flume with a free water surface under different bed shear stresses and ion addition. Fine-grained silica was used as model material, as it is the main mineral components of clay that affects sedimentation. It was concluded that floc density depended on increasing the bed shear stress, the salinity and pH value. Floc density decreased with increasing the salinity in still water and floc size, whereas the opposite was true when increasing the bed shear stress. Also, it increased at pH6.8 more than at pH4.2 when increasing the bed shear stress in the range from 0.0086 to $0.0132N/m^2$.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.3
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• pp.148-154
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• 1998

Gubong gold-mine, previously one of the largest gold mines in Korea, is located at the mid-west of the South Korea. In the areas nearby the mine, the shallow groundwater was the major source for domestic and farming water-supply. Soil contamination by Cd, Cu, Pb and Zn was previously known in this area. This study is objected to identify quality of the shallow groundwater, possibly affected by the mine tailings. Samples were collected from a nearby stream, shallow groundwater and seepage from the tailings. Chemical analysis for the water quality includes major cations such as Na, K, Ca, and Mg, anions as F, Cl, NO$_3$, SO$_4$, HCO$_3$, and trace elements as Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, Se, As, Hg. Water types could be drawn into four groups from the plots of Piper, Stiff diagrams and cluster analysis. SAR-Conductivity plot indicates the water does not pose either alkalinity or salinity hazards for irrigation. Major contaminant in groundwater appeared to be arsenic, released from arsenopyrites in tailings by oxidation. Dredging of buried railing materials could stimulate the release of arsenic from the sediments to the groundwater.

• The Korean Journal of Petroleum Geology
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• v.6 no.1_2 s.7
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• pp.37-43
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• 1998

Chemical components of water, chemical and isotopic compositions of extractable gases were analyzed to characterize the properties of the natural gases which are dissolved in ground water in the Pohang area. Amount of total extracted gases ranges from 27 ml/l to 50.1 ml/l. Hydrocarbon gases are composed of methane ($27{\~}376,420 ppm$) and ethane ($19{\~}127 ppm$). Amount of total hydrocarbon gases is related to the lithology and geological factors around the reservoir. Quantity of hydrocarbon gases tends to increase in the Tertiary reservoirs and in the reservoirs where the Tertiary formations are thick enough. According to the relationship between hydrocarbon gases and total solids in the ground water, it is believed that the hydrocarbon gases were dissolved in the Tertiary formation water. Based on the methane content ($>99.9\%$) and isotopic composition (${\delta}C^{13};-73.1\%_{\circ}{\~}-43.22\%_{\circ}$), we interpret the gases to be of predominantly biogenic origin which were generated by the methanogenic bacterial processes under the low temperature and anoxic conditions.

• Journal of the Mineralogical Society of Korea
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• v.30 no.4
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• pp.149-159
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• 2017

We investigated the mineralogical and chemical characteristics of oyster shell as the possible substitute for the limestone used as an absorbent of $SO_2$ gas. The oyster shells from Taean and Tongyeong were used for the comparison with limestone and those from Boyreong and Yeosu were additionally investigated. XRD results show that all shells are composed of calcite with the exception of the myostracum layer attached to adductor muscle and ligament, which is composed of aragonite. The marine sediments as impurities exist on the surface of shells or as inclusions in the shells. Calcite is the main mineral composition of the shell of barnacle which is also one of the impurities. The oyster shell is composed of three main layers; prismatic, foliated, and chalk. The oyster shell from Tongyeong with the largest shell size, has the smallest thickness of prismatic and foliated layers which contain protein called conchiolin, whereas that from Taean with the smallest shell size has the largest prismatic and foliated layers. The sizes of those two layers of the shells from Boryeong and Yeosu are larger than that from Tongyeong but smaller than Taean. Those differences are supposed to be due to the different growth environments because the oysters from Tongyeong are cultured under the sea while those from Taean are in the tidal zone. The oyster shells generally show higher amount of sulfur and phosphorus than limestone, mainly due to the composition of protein. Some elements such as Mg show significant variations in different layers. As for trace elements, Li shows much higher amount in oyster shells than limestone, suggesting the influence of the composition of the sea water on the formation of the oyster shells.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.1
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• pp.15-26
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• 2003

Ultrasonic inspection methods are widely used for detecting flaws in materials. The signal analysis step plays a crucial part in the data interpretation process. A number of signal processing methods have been proposed to classify ultrasonic flaw signals. One of the more popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature space. This paper describes an alternative approach which uses the least mean square (LMS) method and expectation maximization (EM) algorithm with the model based deconvolution which is employed for classifying nondestructive evaluation (NDE) signals from steam generator tubes in a nuclear power plant. The signals due to cracks and deposits are not significantly different. These signals must be discriminated to prevent from happening a huge disaster such as contamination of water or explosion. A model based deconvolution has been described to facilitate comparison of classification results. The method uses the space alternating generalized expectation maximization (SAGE) algorithm In conjunction with the Newton-Raphson method which uses the Hessian parameter resulting in fast convergence to estimate the time of flight and the distance between the tube wall and the ultrasonic sensor Results using these schemes for the classification of ultrasonic signals from cracks and deposits within steam generator tubes are presented and showed a reasonable performances.