Southwest Of Korea Research Articles

The Implications of Seeping Hydrocarbon Gases in the Gunsan Basin, Central Yellow Sea, off the Southwest of Korea

A detailed analysis of high-resolution (3.5 kHz) chirp seismic profiles acquired in the Gunsan Basin of the central Yellow Sea revealed that hydrocarbon gases are actively seeping via the formation of many plumes. The uppermost sedimentary layer was acoustically confirmed to be fully or partially charged with gases. Somewhat favored by the low-tide period, episodic gas seepage is mainly associated with the underlying fault systems of Cretaceous-Cenozoic sedimentary strata in the southwestern part of the basin. Catastrophic gas expulsion seems to have formed a crater at the sidewall of a sedimentary ridge and two diapirs. Here, methane is poorly concentrated but rich in the heavy carbon isotope (δ13C, −52.6‰ to −44.7‰ The Vienna Peedee Belemnite [VPDB]), indicating that methane formed mainly through biodegradation of heavy oils at depth remains in the shallow sediments following its expulsion. Episodic rapid upward advection of porewater is also manifest by unmixed heavy methane trapped in the upper part of the primary biogenic methane (δ13C, about −90‰ VPDB)-filled sediment core. These findings imply that the Gunsan Basin fulfills the requirements for possible generation and preservation of oil and gas, like the petroliferous basins of eastern China and the Yellow Sea.

Monitoring of Positive List System on Residual Pesticides Analysis of Agricultural Products in Southwest of Korea

Pesticide residues must be managed for food safety and regulations are being strengthened worldwide. In Korea, the Positive List System (PLS) was introduced to prevent the misuse and manage unregistered pesticides. The PLS is a system that applies 0.01 mg/kg to crops for which maximum residue limits is not set. A more stringent regulatory system could lead to an increase in agricultural products that exceed standards. Therefore it is necessary to confirm the change in the determination rate of agricultural products exceeding the previous pesticide residue standards. In terms of climate change, temperature increase and changes in precipitation patterns are the main pest and pathogen infection determinants. Complex interactions and climate variability will lead to more frequent spraying of pesticides and eventually affect consumer exposure at the end of the food chain. Therefore, we confirmed the relationship between temperature and precipitation, which are climate factors and pesticide residues. Agricultural products (n=5,560) distributed at wholesale market (SeoBu, GakHwa) in the southwest Korea were collected and 311 kind of residual pesticides were analyzed using GC-MS/MS and LC-MS/MS. This study could serve as basic data for pesticide residue prevention, management, control and monitoring in countries seeking to tighten pesticide standards.

Spatial structuring of silver pomfret Pampus candidus in Northern Indian Ocean using microsatellite DNA

Silver pomfrets are spread along the Indo-West Pacific: from the Persian Gulf to Indonesia, Japan, West and Southwest of Korea and Eastern parts of China and forms a commercial fishery in all these countries. For formulating fishery management strategy of the silver pomfret, accurate population information is necessary. The genetic stock structure of silver pomfret in the Northern Indian Ocean was explored using 12 polymorphic microsatellite markers. Morphological and molecular studies confirmed that the silver pomfrets along the Northern Indian Ocean is Pampus candidus. Pampus candidus populations along Arabian Sea and Bay of Bengal region (FST = 0.049, P < 0.05) using microsatellite data revealed significant genetic differentiation which was further supported by multi-locus distance matrix testing (Principal Co-ordinate Analysis) and model-based clustering. The results indicate that there are three distinct genetic stocks of silver pomfret within the study area.

Wintertime Large Temperature Inversions in the Yellow Sea Associated With the Cheju and Yellow Sea Warm Currents

AbstractLarge temperature inversions in the Yellow Sea during winter were investigated by analyzing conductivity‐temperature‐depth data collected in January and February 1986, April 1996, and February 1997. Large inversions with temperature differences across inversion layers greater than 2 °C were observed at three places: southwest of Korea, southeast of the Shantung Peninsula, and on the northeastern flank of the Changjiang Banks. Pronounced thermohaline fronts were commonly established where warm offshore waters with high salinity were found below cold coastal waters with low salinity. In the southwestern area of Korea, where the front develops in an east‐to‐west direction, the Cheju Warm Current water flows eastward to the south of the front, while north of the front, cold Korean coastal water flows westward. In the southeastern area of Shantung Peninsula, where the front forms in northeast to southwest, the Yellow Sea Warm Current flows northeastward on the offshore side, while cold Chinese coastal water flows southwestward. Moderate temperature inversions were observed midwest of Korea and on Changjiang Banks when warm offshore waters extended into cold coastal areas. In the inversion areas, warm waters are heavier than cold waters, reflecting a stronger contribution of salinity to density than that of temperature. Consequently, isotherms and isohalines in the inversion areas commonly decline downward toward cold water areas. We concluded that the occurrence of large inversions is closely related to the advection of the Cheju Warm Current and Yellow Sea Warm Current waters to the thermohaline frontal zones where the warm offshore waters underlay lighter cold coastal waters.

Molecular detection of viruses causing hemorrhagic fevers in rodents in the south-west of Korea.

Many pathogens causing hemorrhagic fevers of medical and veterinary importance have been identified and isolated from rodents in the Republic of Korea (ROK). We investigated the occurrence of emerging viruses causing hemorrhagic fevers, such as hemorrhagic fever with renal syndrome (HFRS), severe fever with thrombocytopenia syndrome (SFTS), and flaviviruses, from wild rodents. Striped field mice, Apodemus agrarius (n = 39), were captured during 2014-2015 in the south-west of ROK. Using molecular methods, lung samples were evaluated for SFTS virus, hantavirus, and flavivirus, and seropositivity was evaluated in the blood. A high positive rate of hantavirus (46.2%) was detected in A. agrarius lungs by reverse transcription-nested polymerase chain reaction (RT-N-PCR). The monthly occurrence of hantavirus was 16.7% in October, 86.7% in November, and 25% in August of the following year (p < 0.001). Moreover, 17.9% of blood samples were serologically positive for hantavirus antibodies. The most prevalent strain in A. agrarius was Hantaan virus. All samples were positive for neither SFTS virus nor flavivirus. Hantaan virus was detected in 86.7% of A. agrarius in November (autumn), and thus, virus shedding from A. agrarius can increase the risk of humans contracting HFRS. These findings may help to predict and prevent disease outbreaks in ROK.

Factors controlling mud accumulation in the Heuksan mud belt off southwestern Korea

The Heuksan mud belt (hereafter HMB) is 20~50 km wide, ~200 km long, and ~50 m thick, having accumulated in the course of the Holocene transgression on the tide-dominated epicontinental shelf southwest of Korea. The internal architecture of the HMB is characterized by offshore prograding clinoforms. Of particular interest are the depositional processes responsible for this anomalously thick mud accumulation within a relatively short period of time. Tidal currents are important in the dispersal of mud in the HMB, although these alone cannot explain such an enormous mud deposit. In order to understand the formative processes of the HMB, a detailed sedimentary facies analysis, including high-resolution grain-size measurements, has been conducted on more than 30 short cores and three long drill cores recovered from the mud belt. Five major mud facies were identified. Of these, mud sequences showing a thickening–thinning trend of alternating silt and clay laminae suggestive of a tidal origin occur dominantly at inner to mid shelf locations. By contrast, internally structureless muds with sharp bases and no bioturbation, which are interpreted of representing fluid-mud deposits, are widespread at mid to outer shelf locations. Wave-generated mud ripples and storm beds on the inner shelf suggest that storm waves in winter resuspend previously deposited mud to form near-bed fluid-mud suspensions with resulting gravity-driven mud transport across the low-gradient outer shelf. This previously not recognized process is probably a major factor controlling depositional processes on the giant mud belt, enabling rapid accumulation and offshore progradation even during transgression, i.e., at times of sea-level rise.

Blade design and performance analysis on the horizontal axis tidal current turbine for low water level channel

Most tidal current turbine design are focused on middle and large scale for deep sea, less attention was paid in low water level channel, such as the region around the islands, coastal seas and rivers. This study aims to develop a horizontal axis tidal current turbine rotor blade which is applicable to low water level island region in southwest of Korea. The blade design is made by using BEMT(blade element momentum theory). The section airfoil profile of NACA63-415 is used, which shows good performance of lift coefficient and drag coefficient. Power coefficient, pressure and velocity distributions are investigated according to TSR by CFD analysis.

Two New Records of Ennominae Species (Lepidoptera: Geometridae) from Korea

Two ennomine species, Amblychia angeronaria Guenee and Peratostega deletaria (Moore), are reported for the first time from Korea. Amblychia angeronaria was collected from Isl. Gageo-do, in the south west of Korea. The species is distinguished by the large wingspan, the ochreous forewing with a row of large white dots on the postmedian and a grayish apical dot, and the grayish or dark ochreous hindwing with undulating postmedial line and dark grayish subterminal line. Peratostega deleraia was collected from Isl. Jeju-do, and can be distinguished by the dark brown forewing with a blackish dentate postmedian and a light brown apical dot, and the dark brown hindwing with the light brown subtermen and angulate termen. Diagnosis and description of the species are given along with figures of the male and female genitalia.

Pb concentrations and isotopic compositions in the soil and sediments around the abandoned mine in southwest of Korea

This study was undertaken to investigate the influence of Pb contaminant dispersal from an abandoned mine. For the study, 23 samples of sediment and soil were collected around the abandoned mine located in southwest of Korea. Pb concentrations and isotope ratios of sediment samples were analyzed through ICP-OES (Optima 5300 DV, Perkin Elmer) and MC-ICP-MS (Plasma II, Nu), respectively. The sediment samples collected in the main stream from the mine entrance showed high Pb concentrations of 139 - 1079 mg/kg, while Pb concentrations of the other sites were 19 - 29 mg/kg. Pb isotope ratios of the main stream sediments were 2.4854 - 2.4883 for 208Pb/207Pb and 1.1693 - 1.1740 for 206Pb/207Pb. On the other hand, the Pb isotopic compositions of sediments collected from the other sites were clearly different from those of ore deposits. The Pb isotope ratios versus inverse concentrations plot showed high linear correlation between the main stream, the tributary stream and one of the downstream sites representing the two end member mixing system between these sites. According to the binary mixing equation, the relative contribution of Pb pollutants from the abandoned mine to the downstream area were approximately 33% - 36%.

한국에서 발생한 청천난류 사례들에 대한 수치연구

Generation mechanisms of the three moderate-or-greater (MOG)-level clear-air turbulence (CAT) encounters over South Korea are investigated using the Weather Research and Forecasting (WRF) model. The cases are selected among the MOG-level CAT events occurred in Korea during 2002-2008 that are categorized into three different generation mechanisms (upper-level front and jet stream, anticyclonic flow, and mountain waves) in the previous study by Min et al. For the case at 0127 UTC 18 Jun 2003, strong vertical wind shear (0.025 <TEX>$s^{-1}$</TEX>) generates shearing instabilities below the enhanced upper-level jet core of the maximum wind speed exceeding 50 m <TEX>$s^{-1}$</TEX>, and it induces turbulence near the observed CAT event over mid Korea. For the case at 2330 UTC 22 Nov 2006, areas of the inertia instability represented by the negative absolute vorticity are formed in the anticyclonically sheared side of the jet stream, and turbulence is activated near the observed CAT event over southwest of Korea. For the case at 0450 UTC 16 Feb 2003, vertically propagating mountain waves locally trigger shearing instability (Ri < 0.25) near the area where the background Richardson number is sufficiently small (0.25 < Ri < 1), and it induces turbulence near the observed CAT over the Eastern mountainous region of South Korea.

Effects of temperature and irradiance on photosynthesis and growth of a green-tide-forming species (Ulva linza) in the Yellow Sea

Samples of the massive drifting green alga, Ulva linza, were collected from the coastal waters of the Yellow Sea, southwest of Korea, in early July 2009, and cultured under laboratory conditions. The effects of various temperature (10–30°C) and irradiance levels (0–1,000 μmol photons m−2 s−1) on photosynthesis, growth, and tissue nutrient content of U. linza were investigated in laboratory for both individuals of the late-stage vegetation (LSV) and the early-stage vegetation (ESV). After 1 h acclimation to various irradiance and temperature conditions, maximum gross photosynthetic rate of ESV was significantly higher than those of LSV. In the long-term (7-d) acclimation experiments to various irradiance and temperature levels, gross photosynthetic rates of ESV individuals were also significantly higher than those of LSV individuals. High photosynthetic rate of ESV individuals induced increase in mass of about 60% over the growth saturation irradiance (136 μmol photons m−2 s−1) and about 20% under low temperature conditions (10–15°C) during 7-d. The gross photosynthesis of LSV individuals was low when examined under temperature and irradiance conditions that were optimum for ESV growth. Consequently, free-floating U. linza exhibits cellular senescence beginning in early July in the Yellow Sea, and green tides formed by this species cannot be maintained beyond this time in the open sea. However, we expect that U. linza can proliferate quickly after settlement on new coastal habitats of the Yellow Sea because of the high tissue nitrogen utilization for photosynthesis in ESV, which is formed by germination of reproductive cells.

Patrinia monandra (Valerianaceae): an unrecorded species in Korea

We report an unrecorded species of Patrinia in Korea, P. monandra C. B. Clarke. This species was found from Neasosa, Buan-gun, Prov. Jeollabuk-do, Sanghwangbong and Bogildo, Wando-gun, Prov. Jeollanam-do in the southwest of Korea. We named 'Gin-dook-gal' as a common name of this species. It is easily distinguishable from Patrlnia villosa (Thunb.) Juss. by the characteristics such as lemon yellow corolla, one (sometimes three) stamen(s) and fruit fused with large bracteole-wing orbiculate.

Influence of stratification on residual tidal currents in the Yellow Sea

The M2 tide and residual current generation in the Yellow Sea are examined using the Blumberg and Mellor [1987] numerical coastal ocean circulation model. With no stratification the model tide and tidal currents show good agreement with the observed tide and tidal currents. Coherent residual currents are predicted around the southwest of Korea, flowing northward as a strong jet with a maximum speed of 8 cm s−1, and around Yangtze Bank, flowing southeastward as a weak broad current. With initial stratification, tidal mixing occurs in the bottom boundary layer, which leads to surface tidal fronts around Yangtze Bank and the southwest of Korea, and our model experiments reproduce successfully the basic water property structure in these regions. The resulting stratified tidal rectification intensifies the residual currents at the front and at the top of the bottom boundary layer over the sloping bottom, so that the vertical structure of the residual currents is modified. The strong residual currents in the top of the bottom mixed layer around Yangtze Bank support the interpretation of Kim et al. [1991] for the southeastward movement of Yellow Sea Bottom Cold Water in summer. The residual currents in the surface layer reach ∼40% of the mean currents observed by Beardsley et al. [1992] using satellite‐tracked drifters deployed in the Yellow Sea in summer. These results suggest that stratified tidal rectification is an important process in driving the summertime subtidal flow in the Yellow Sea.

Deux fêtes de village en Corée

The Korean village as a basic sociological unit is held together by religious festivals (tongje) celebrated at regular, mostly annual, intervals. Two villages in the south-west of Korea are presented as typical examples. The first, Kuryong, is an agricultural community located at the foot of a mountain. The second village, Suri, is situated on an island off the west coast of the Korean peninsula. Its inhabitants live mostly on fishing and the gathering of seaweed. Both villages hold an annual festival at the beginning of the lunar year. The protective deity feasted in the agricultural village is at the same time the deity of a mountain east of the village — a feature not uncommon in Korea. The festival is conducted by six officiants who are male representatives of the community selected a few days prior to the ceremony. The central rite consists in the offering of incense, wine and food to the deity, accompanied by numerous prostrations and prayers for protection of the village. Ritual purity is strictly observed and women are excluded from the ceremony. The community participates only in a final reunion. A very similar ceremony is found in the village on the island. However, in Suri, the ceremony of offerings and prayer to the protective deity — residing on top of the island hill — is only one part, called sangdangje, of a larger festival. The other part, hadangje, takes place on the beach. Women play an active role, all villagers participate and a large part of the ceremony consists of improvisation and merry-making. The deity being feasted is the dragon king present in the form of a puppet. The villagers approach him with offerings of wine and money and the deity, through a spokesman, gives words of praise or admonition in an improvised dialogue with the fishermen. A strong sexual symbolism and much spontaneity characterize the festival in which no taboos of purity are observed. At the end, the dragon king is sent off into the sea in a small boat bearing impurities and misfortune away. Comparing these two village festivals, it appears that they belong to two entirely different types. The first, with its strong emphasis on ritual purity and fixed ritual procedure, is related to Confucian ancestor worship and was introduced in the villages by the educated elite. In contrast to this, the second festival seems to be much older and to have a popular and indigenous origin. Traces of similar festivals held in the same region during the first centuries A.D. can already be found in the San-kuo chih. What Christian Deschamps describes here for Korea is of great interest to historians of Chinese religion. The ceremony of sending off the Dragon King's boat, as practiced in the Suri village, resembles the Chinese Pestilence King Exorcism still practiced in Taiwan as well as in mainland China (see Kenneth Dean's report in this issue of the Cahiers d'Extrême-Asie, p. 203). The tension between indigenous cults and the Confucian administrators who try to replace these festivals with their official rites is a phenomenon well known throughout Chinese history. Jean Lévi's study (in this issue, p. 81) throws new light on these perennial efforts of the Chinese government to "civilise" local customs.