• Journal of the Mineralogical Society of Korea
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• v.26 no.3
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• pp.189-196
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• 2013

In this study, we tried to define the origin of fine-grained sediments in Southwestern Cheju Island Mud (SWCIM) using principal component analysis. We used relative clay mineral compositions using 138 marine surface sediments, 4 Huanghe sediments and 3 Changjiang river sediments by the semi-quantitative X-ray diffraction analysis. We made bioplot diagram using R program with principal component 1 and component 2 because they might contain more than 90% of all data. Although the distribution pattern of each clay minerals in SWCIM is so intricate, smectite and kaolinite contents are high in the west region, but illite and chlorite contents are rich in the east region. In the biplot, the east region of SWCIM distribute around Changjiang river, whereas west region of SWCIM disperse around Huanghe. Our results might reveal that west region of SWCIM is mainly originated by Huanghe, but east region of SWCIM by Changjiang River.

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.246-249
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• 2005

• Journal of Soil and Groundwater Environment
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• v.14 no.5
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• pp.1-4
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• 2009

• Economic and Environmental Geology
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• v.41 no.1
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• pp.93-113
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• 2008

This study presents petrochemistry and $^{40}Ar/^{39}Ar$ absolute ages of subsurface volcanic rock cores from twenty(20) boreholes in the eastern lowland (altitude loom below) of Jeju Island, Handeong-Jongdal-Udo-Susan-Samdal-Hacheon areas, and discusses topography and volcanism in the area. The subsurface volcanic rock cores are mainly basalts in composition with minor tholeiitic andesites and basaltic trachyandesites. Sequences of intercalated tholeiitic, transitional and alkalic lavas suggest that tholeiitic and transitional to alkalic lavas must have erupted contemporaneously. Especially, occurrences of trachybasalts and basaltic trachyandesites at the bases in the area imply that the volcanism in the area was initiated with slightly differentiated alkaline magma activity. The $^{40}Ar/^{39}Ar$ absolute ages of the subsurface volcanic rock cores range from $526{\pm}23ka\;to\;38{\pm}4Ka$. The lava-forming Hawaiian volcanic activities of the eastern lowland can be divided into five sequences on the basis of sediment distribution, whole rock geochemistry and $^{40}Ar/^{39}Ar$ absolute ages of the subsurface volcanic rock cores; stage I-U$(550{\sim}400Ka)$, stage II$(400{\sim}300Ka)$ and stage III$(300{\sim}200Ka)$ during syn-depositional stage of Seoguipo Formation, and stage IV$(200{\sim}100Ka)$ and stage V(younger than 100Ka) during post-depositional stage. In the eastern lowland of Jeju Island, compositional variations and local occurrences of the subsurface volcanic rocks as well as existences of various intercalated sediment layers (including hydrovolcanogenic clasts) suggest that the volcanism must have continued for long time intermittently and that the land has been progressively glowed from inland to coast by volcanic activities and sedimentation. It reveals that the subsurface volcanic rocks in the eastern lowland of Jeju Island must have erupted during relatively younger than 200Ka of stages IV and V. The results of this study are partly in contrast with those of previous studies. This study stresses the need that previous reported volcanic activities in Jeju Island based on K-Ar ages of volcanic rocks should be carefully reviewed, and that stratigraphic correlation from boreholes should be conducted by quantitative criteria combined with petrography and petrochemstry as well as radiometric studies of volcanic rock cores.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.257-270
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• 2022

This study evaluated the hydraulic factors contributing to the decreasing groundwater levels across Jeju island. Time-series data for groundwater level, precipitation, and groundwater usage and information on land use were acquired, and the correlations among them were analyzed to evaluate the causes of the decreasing groundwater. The effects of precipitation and groundwater usage on the fluctuations of groundwater level were quantified using response surface analysis and sensitivity analysis, and methods for groundwater quantity management by region were proposed. The results showed that the rate of groundwater decrease in the western region was larger than that in the eastern region. For the eastern region, the influence of precipitation was large and the rate of decrease in the groundwater level was relatively small. The geological formation of this part of the island and continuous seawater intrusion suggest that although the absolute amount of groundwater extracted for use was large, the decrease in the groundwater level was not seen to be great due to an increase in pressure by seawater intrusion. Overall, precipitation and groundwater usage had the greatest effect on the amount of groundwater in the western region, and thus their data would be most useful for informing groundwater management, whereas other factors (e.g., sea level and the location of the freshwater-seawater transition zone) must be considered when understanding Jeju's eastern region. As the characteristics of groundwater level fluctuations in the eastern and western regions are distinct, an optimal management plan for each region should be proposed to ensure the efficient management of groundwater quantity.

• Korean Journal of Environmental Agriculture
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• v.11 no.1
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• pp.26-40
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• 1992

Cheju Island formed by Quarternary volcanism provides highly permeable hydrogeological environment. To meet the increasing demand of water in the island, many groundwater wells have been developed. The environmental isotopes(oxygen-18, deuterium, tritium) and chemical analysis of water samples from the eastern part of the island were carried out to ascertain whether groundwater in the eastern part of the island was contaminated by sea water. The result of tritium analysis indicated fast infiltration of meteoric water into underground and rapid mixing process between rain water and groundwater. The results of oxygen-18 and deuterium analysis demonstrated that most of the wells in the eastern part of the island were influenced by sea water intrusion. Chemical analysis of water samples revealed that most groundwater in study area were classified into Na-Cl type and showed high chloride/bicarbonate ratios. Sea water intrusion in the northeastern part of the island has proceeded at least 3 km within the coastaline, and in the south eastern part about 700m.

• The Korean Journal of Mycology
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• v.46 no.2
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• pp.105-113
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• 2018

In this study, we report the occurrence of four domestic mushrooms (among 317 samples) that were previously undocumented in the eastern part of Jeju Island in Korea. To identify the mushrooms, DNA sequences of the mushrooms were analyzed by comparing them with the data available in NCBI GenBank. Mushrooms were identified as Agaricus flocculosipes, Amanita concentrica, Coprinopsis strossmayeri, and Favolus acervatus, none of which have been previously documented in Korea. Furthermore, microscopic observations revealed that the morphology of the four mushrooms was consistent with the features of the species matched by the DNA sequences analysis.

• Journal of Life Science
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• v.18 no.3
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• pp.395-402
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• 2008

Level of microbial contamination was examined in four fish farms of Jeju east coast for sanitary indication of bacterial contamination such as heterotrophic bacteria, Escherichia coli O157:H7, Salmonella spp., Vibrio parahaemolyticus, Staphylococcus aureus, Bacillus cereus and total coliforms. The samples were collected and investigated from June to October in 2007. Bacterial species of S. aureus, B. cereus and Salmonella spp. were frequently detected from the seawater of above fish farms. Salmonella spp., S. aureus, B. cereus were detected in the range of $0{\sim}4.3{\times}l0^3,\;0{\sim}2.7{\times}l0^4,\;0{\sim}7.6{\times}l0^3$ CFU/ml, respectively, from the fish feed used in all four selected farms. Additionally, Salmonella spp., S. aureus, B. cereus were detected in oliver flounder (Paralichthys olivaceus) of these farms, however total coliforms and E. coli O157:H7 were not detected during our experimental period. For the production of microbiologically safe and healthy oliver flounder, proper quality control of feed, sanitation programs, and continuous monitoring of microorganism are essential practices, which required to include in the farm management system.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.79-89
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• 2005

Groundwater level changes in coastal aquifers occur due to oceanic tides, where the properties of oceanic tides can be applied to estimate hyadraulic parameters. Hydraulic parameters of coastal aquifers located in eastern part of Jeju island were estimated using the tidal response technique. Groundwater level data from a saltwater intrusion monitoring well system was used which showed tidal effects from 3 to 5 km. The hydraulic gradient was assessed by utilizing the filtering method from 71 consecutive hourly water-level observations. Calculated hydraulic diffusivity ranged from 2.94${\times}10^7m^2d^{-1}$ to 4.36${\times}10^7m^2d^{-1}$ . The hydraulic gradient of the coastal aquifer area was found to be ~$10^{-4}$, whereas the gradient of the area between wells Handong-1 and 2 was found to be ~$10^{-6}$, which is very low comparatively. Analysis of groundwater monitoring data showed that groundwater levels are periodically higher near coastal areas compared to that of inner land areas due to oceanic tide influences. When assessing groundwater flow direction in coastal aquifers it is important to consider tidal fluctuation.

• Korean Journal of Food Science and Technology
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• v.4 no.4
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• pp.285-290
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• 1972

Oranges (Citrus unshiu var.) from local orchards at Seogwi, Daejeong, Hanrim, Cheju and Seongsan where are in the southern, southwestern, northwestern, northern and eastern parts of Cheju island respectively were stored in a semi-underground room and an air-circulating refrigerated store. To compare the storage qualities between the growing districts, changes in freshness, acidity and sugar content of oranges were investigated during storage. 1) Oranges from Seogwi and Cheju districts showed remarkably lower Percentage of rot fruits with no relation of storage temperature than those of Hanrim, Daejeong and Seongsan. 2) Browning of oil gland was severe on oranges of northern and southern districts while it was little developed in case of the other districts. 3) Water soluble total sugar content was gradually increased and titratable acidity and reducing sugar content of pulp tissues was decreased during storage. 4) Oranges from the western part showed the higher ratio of sugar content to acidity and better taste as compared with the east oranges.