Western Coastal Area Of Korea Research Articles

국내 애멸구 (<em>Laodelphax striatellus Fallen</em>) (노린재목: 멸구과)의 시기별 날개형 및 기생율

The small brown planthopper, Laodelphax striatellus (Falln) (SBPH) is one of the important rice pests in Korea, which transmits rice stripe virus (RSV) to rice. This pest is an indigenous species in Korea and has also known to migrate from China to the western coastal areas of Korea. This study was conducted to investigate the wing morphs of SBPH and its parasitism rate of Haplogonatopus atratus Esaki et Hashimoto in Korea. In 2014, SBPH were collected in April and July from 16 sites throughout South Korea and their wing morphs and parasitism rates were measured under the microscope. Percentage of brachypterous male in July was significantly declined compared to that in April, while that of brachypterous female did not change. A positive relationship was found between latitude and percentage of brachypterous adults in April. Parasitism rate of both nymphs and adults were higher in April than July. In addition, nymphal parasitism rate was generally higher in western coastal areas.

Gmax of Reclaimed Ground on the Western Coast of Korea Using Various Field and Laboratory Measurements

The maximum shear modulus of soil is a principal parameter for the design of earth structures under static and dynamic loads. In this study, the statistical data of the maximum shear moduli of reclaimed ground in the Songdo area on the western coast of Korea were evaluated using various field and laboratory tests, including the standard penetration test (SPT), piezocone penetration test (CPTu), self-boring pressure meter test (SBPT), down-hole seismic test (DHT), seismic piezocone penetration test (SCPTu) and resonant column test (RCT). Soils were classified variously by using a conventional unified soil classification system and classification charts for CPTu data. For the soils containing mostly sand and silt, the soil classifications using the classification charts for CPTu data show good agreement with the unified soil classification. Based on the statistical analysis on various maximum shear moduli, new site-specific empirical correlations between the shear moduli and SPT and CPTu values were proposed. Predictions of the maximum shear moduli using the proposed correlations were compared with the data obtained from the DHT, which is comparatively exact in evaluating the maximum stiffness of soils. The good agreement confirmed that the proposed correlations reasonably predicted the maximum shear moduli of soils in western coastal area of Korea.

Analysis of the Contribution of Wind Drift Factor to Oil Slick Movement under Strong Tidal Condition: Hebei Spirit Oil Spill Case

The purpose of this study is to investigate the effects of the wind drift factor under strong tidal conditions in the western coastal area of Korea on the movement of oil slicks caused by the Hebei Spirit oil spill accident in 2007. The movement of oil slicks was computed using a simple simulation model based on the empirical formula as a function of surface current, wind speed, and the wind drift factor. For the simulation, the Environmental Fluid Dynamics Code (EFDC) model and Automatic Weather System (AWS) were used to generate tidal and wind fields respectively. Simulation results were then compared with 5 sets of spaceborne optical and synthetic aperture radar (SAR) data. From the present study, it was found that highest matching rate between the simulation results and satellite imagery was obtained with different values of the wind drift factor, and to first order, this factor was linearly proportional to the wind speed. Based on the results, a new modified empirical formula was proposed for forecasting the movement of oil slicks on the coastal area.

3차원 전기비저항 모니터링 자료의 시간경과 역산

모델변수의 증감 및 분해능을 고려하는 새로운 교차모델 제한자를 사용한 시간경과 역산 알고리듬을 개발하였다. 증감을 고려한 교차모델 제한자는 같은 변화비를 갖는 모델변수에 같은 제한을 가한다. 이 교차모델 제한자는 모델변수의 증감에 관계없이 의미 있는 변화를 보이는 모델변수들을 강조할 수 있다. 분해능 교차모델 제한자는 분해능이 낮은 모델변수에 작은 제한을 가하는 반면, 분해능이 높은 모델변수에는 큰 제한을 가한다. 따라서 분해능이 낮은 모델변수도 시간 경과에 따라 의미 있는 변화를 보일 경우 효과적으로 식별할 수 있다. 3차원 전기비저항 모니터링 자료의 수치실험을 통하여 이들 두 교차모델 제한자의 타당성을 검증하였다. 최종적으로, 방조제의 안정성 평가를 위하여 서해안에 위치한 방조제에서 얻은 3 차원 전기비저항 모니터링 자료의 처리에 개발된 시간경과 역산법을 적용하였다. 시간경과 역산의 결과 모니터링이 수행된 기간 동안 방조제에 주목할 만한 변화가 없는 것으로 해석되었다. We developed a time-lapse inversion using new cross-model constraints based on change ratio and resolution of model parameters. The cross-model constraint based on change ratio imposes the same penalty on the model parameters with equal change ratio. This constraint can emphasize the model parameters with significant change regardless of their increase or decrease. The resolution cross-model constraint imposes a small penalty on the model parameters with poor resolution, but a large penalty on the model parameters with good resolution. Thus, the model parameter with poor resolution can be effectively identified in the inversion result if they are significantly changed with time. Through the numerical tests for 3D resistivity monitoring data sets, the performance of these two cross-model constraints was confirmed. Finally, for the safety estimation of a sea dyke, we applied the developed time-lapse inversion to the 3D resistivity monitoring data that were acquired at a sea dike located in western coastal area of Korea. The result of time-lapse inversion suggested that there were no significant changes at the sea dike during the monitoring period.

Regional climate-driven C 3 and C 4 plant variation in the Cheollipo area, Korea, during the late Pleistocene

Marine isotope stage 3 (MIS3), spanning from 25 to 60 ka BP, was a time of substantial environmental change that included changes in the global ice volume and atmospheric composition, with resultant regional climate changes. To understand past vegetation responses to such environmental changes in Korea, we estimated the abundance of C 3 and C 4 plants using the C/N and carbon isotope ratios of sedimentary organic matter. The MIS3 sedimentary unit at the Cheollipo site, located in a western coastal area of Korea, is characterized by a dark to light gray colored sedimentary unit (3.05 to 5.05 m in elevation, MIS3), which is between an underlain oxidized yellowish sedimentary unit (< 3.05 m in elevation) and an overlain oxidized yellowish sedimentary unit (> 5.05 m in elevation). The estimated abundance of C 4 plants varied between 60 and 10% during the MIS3. The suborbital-scale variation in the estimated percentage of C 4 plants was similar to those reported in continental ice volume and the East Asian monsoon intensity, suggesting that C 4 plants prevailed under colder and drier conditions (intensified winter monsoon), whereas C 3 plants have favored a warmer and wetter climate (intensified summer monsoon). Compared with high latitude regions (e.g., Chinese Loess Plateau and Lake Baikal) where low summer temperature suppressed aridity and pCO 2 influences during the last glacial period, vegetation change in Cheollipo area may have more sensitively responded to aridity change which had been affected by the summer/winter monsoon intensity. The climate change in the western coastal area (Yellow Sea side) of Korea during the late Pleistocene may have been controlled by regional climate change coupled with continental ice volume change.

액상화 가능 지수를 이용한 국내 서해안 지역의 액상화 평가

느슨한 포화 사질토 층에 위치한 구조물은 지진 시 액상화로 인해 막대한 인적 경제적 피해가 발생하기 때문에 액상화 발생 가능 지반으로 분류된 지역은 구조물의 설계 및 운영 시 액상화 발생 가능성에 주의를 기울어야 한다. 한반도의 경우 중진 지역에 해당되고 역사 문헌의 발생 기록을 제외한 어떤 액상화 피해도 보고되지 않음에 따라 오랫동안 액상화에 대해서는 안전지대로 여겨져 왔다. 하지만, 최근 해외 지진 사례에 의하면 국내 서해안 지역 지반과 유사한 비소성 실트질 흙에서의 액상화 발생과 이로 인한 피해 사례가 종종 보고되고 있다. 본 연구에서는 국내에서의 액상화 가능성 평가 기법 합리화의 일환으로 서해안 두 부지를 대상으로 피에조콘 관입시험(CPTu)과 표준관입시험(SPT) 결과를 이용하여 액상화가능지수(LPI)를 산정하였다. LPI는 심도 20m까지의 액상화 가능성을 통합 적분하여 액상화로 인한 지표면 피해 발생 정도를 지수로 제시한다. 먼저 대상 현장에 대해 시나리오별 액상화 발생 가능성을 평가한 후, CPTu와 SPT로부터 산정된 LPI 값을 비교하였다. 액상화 저항 강도를 의미하는 진동저항응력비(CRR) 값에 의하면, CPTu로부터 구한 보정 콘 선단저항력 (qc1N)CS가 40에서 120 사이인 경우 또는 CRR이 0.23 이하인 경우에 SPT로부터의 산정된 값보다 작게 평가되었다. 또한 CRR 차이는 세립질 함유량이 큰 흙에서 두 방법 간의 차이가 더 크게 나타났다. Liquefaction is a significant threat to structures on loose saturated sandy soil deposits in the event of an earthquake, and can often cause catastrophic damage, economic loss, and loss of life. Nevertheless, the Korean peninsula has for a long time been recognized as a safe region with respect to the hazard of liquefaction, as the peninsula is located in a moderate seismicity region, and there have been no reports of liquefaction, with the exception of references in some historical documents. However, some earthquakes that have recently occurred in different parts of the world have led to liquefaction in non-plastic silty soils, a soil type that can be found in many of the western coastal areas of Korea. In this study, we first present procedures for evaluating the liquefaction potential, and calculate the liquefaction potential index (LPI) distribution at two western coastal sites using both piezocone penetration test (CPTu) data and standard penetration test (SPT) data. The LPI is computed by integrating liquefaction potential over a depth of 20m, and provides an estimate of liquefaction-related surface damage. In addition, we compared the LPI values obtained from CPTu and SPT, respectively. Our research found that the CRR values from CPTu were lower than those from the SPT, particularly in the range between 40 and 120 for the corrected tip resistance, (qc1N)CS, from the CPTu, or in the range of CRR less than 0.23, resulting in relatively high LPI values. Moreover, it was observed that the differences in the CRR between the two methods were relatively higher for soils with high fine contents.

Application of a streamer resistivity survey in a shallow brackish-water reservoir

To delineate the resistivity structure of sub-bottom sediments in a shallow brackish-water reservoir in the western coastal area of Korea, we carried out a streamer resistivity survey using a dipole–dipole array. First, through numerical testing, we confirmed that the resistivity method with a dipole–dipole array could be applied in a shallow marine environment, when the resistivity contrast between water and the underlying sediments ranges from a factor of 3 to 5. Also, inversion with a water layer explicitly included is more effective than the conventional inversion method in resolving power, which we confirmed by observing that the inversion results for synthetic datasets matched better when a water layer was included in the inversion procedure.After constructing a data acquisition system composed of a resistivity meter, GPS, and echo sounder, and developing data processing software, we conducted a streamer resistivity survey and inverted the data obtained to identify the hydrogeological sequences and sediment characteristics at the bottom of the shallow brackish-water reservoir. Drill logs identified three sediment layers, including silty sand, fine sand, and mixed sand. The resistivity distributions from inversion matched the resistivity ranges measured on materials obtained by sampling near the drilling points. We constructed a contour map of the top of the mixed-sand layer, using semivariogram analysis. Comparing these results with the drilling results, the depth to each layer, and the measured and estimated resistivity range of the materials, also corresponded to resistivity profile. From this study, we are assured that the streamer resistivity method would be a useful tool for surveying shallow brackish-water reservoirs.

Reproduction and Population Dynamics of Acetes Chinensis (Decapoda: Sergestidae) on the Western Coast of Korea, Yellow Sea

Reproduction and population dynamics of Acetes chinensis were studied on the western coastal areas of Korea, Yellow Sea, between May 2000 and October 2001. Female maturity was determined from the ratios of females with maturing ovaries by size. The size at which 50% of females are mature is estimated as 8.96 mm carapace length. The mature females first appeared in April, reached a peak in July, and then did not appear after September. The main breeding season (percentage of females with mature ovaries greater than 50%) was from July to September. Similar pattern could be found in monthly changes of gonad index (GI), showing relatively higher GI during the annual breeding season. Mean gonad index examined weekly during the breeding season (June–September) peaked both in the middle of June and early September. Parameters of growth were estimated using the modified von Bertalanffy growth function (VBGF) model incorporating seasonal variation in growth. Females grew faster and reached a larger size at age than males (L∞ = 13.51 mm CL and K = 0.69 yr−1 for females, and L∞ = 10.48 mm CL and K = 0.84 yr−1 for males). The mortality rate (Z) (± 95% confidence limit) calculated by length-converted catch curves was estimated as 3.93 (± 2.00) yr−1. The structure of the recruitment patterns obtained by the ELEFAN program indicated two normally distributed groups. The estimated longevity was 0.75–1.0 yr for the summer generation and 0.58–0.83 yr for the winter generation.

The concentrations and fluxes of total gaseous mercury in a western coastal area of Korea during late March 2001

Factors affecting the distribution and exchange of total gaseous mercury (Hg) were investigated over a bare paddy field at Hari, a relatively clean district at Kang Hwa Island, Korea in late March 2001. The Hg concentrations were quantified at two heights (1 and 5 m above the ground), and then combined with micrometeorological measurements of turbulent exchange coefficients for flux computation. During the 8-day period of measurements, mean concentrations of Hg (3.72 ng m −3, N=164) were lower than those reported from urbanized/industrialized areas but higher than the background concentration (i.e., 1–2 ng m −3). The Hg fluxes, however, were comparable to those reported in the literature for polluted environments and showed clear diurnal pattern with maximum (∼600 ng m −2 h −1) during midday and the minimum (∼100 ng m −2 h −1) at nighttime. Occasionally, at nighttime when the turbulent mixing was weak under stable conditions, a deposition of Hg was observed at much lower rates (about −32.3 ng m −2 h −1). The rate of Hg emission tended to increase with increasing air/soil temperatures and pollutant levels under enhanced turbulent mixing. By contrast, dry deposition of Hg seemed to be related to the increase of certain pollutants such as fine particles (PM 2.5) and CO. Overall, the bare paddy field was a strong source of Hg with the daily net Hg emission of 4.4 μg m −2 during the measurement period.

Reproduction and population dynamics of Penaeus chinensis (Decapoda: Penaeidae) on the western coast of Korea, Yellow Sea

This paper describes reproduction, population structure, growth, and size at sexual maturity of a penaeid shrimp ( Penaeus chinensis) in the western coastal areas of Korea, Yellow Sea. The reproductive season was April–June, with peaks in June. Insemination took place from October to July, and larvae form during April–June. Recruitment to the fished population takes place in August, and is compatible with a 1 year life cycle and a single breeding season. Size at 50% sexual maturity (CL 50), determined from both mature females and inseminated females, was 39.19 mm CL and 38.71 mm CL, respectively. Fecundity was related to body size, ranging from 315,620 ova in the smallest female to 642,140 ova in the largest. Diameter of ova ranged from 250 to 370 μm. Size distribution of the population was similar in the 2 years of the study. Specimens were not found within the studied area during winter (January–March), indicating that the shrimp had moved outside the range of the fishery, probably to deeper water. Growth was estimated by the modified von Bertalanffy growth function incorporating seasonal variation in growth. In both years females ( K=0.96 yr −1 and L ∞=58.6 mm CL ) grew faster, reaching a larger size at age than males ( K=0.45 yr −1 , L ∞=54.9 mm CL ). This is indicated by differences in growth performance indices ( ϕ′) between females (1.75) and males (1.39).

Determination of Atmospheric Perfluorocarbon Background Concentrations of fL/L Range at the Western Coastal Area of Korea

As part of perfluorocarbon (PFC) tracer release experiment conducted at the western coastal area of Korea in February 2001, the background concentration level of perfluorocarbons (PFCs) in the atmosphere was determined by gas chromatography with electron capture detector. Prior to the PFC tracer release experiment in the field, air samples were collected using active samplers and the background concentrations of PFCs were determined. The concentrations of perfluoromethylcyclohexane (<TEX>$C_7F_{14}$</TEX>, PMCH) in the western coastal area of Korea were in the range of 5.8-8.7 fL/L. The mean concentration of the PMCH in the region exhibited no significant spatial and temporal variations. This concentration level is somewhat higher and has larger standard deviation than those of studies previously conducted in USA and Europe on the background concentration levels of PFCs. Because the background concentration of PMCH in Korea is still very low and consistent temporally and spatially, the PMCH tracer can be used suitably for the studies of long-range atmospheric transport.

Two endemic foci of heterophyids and other intestinal fluke infections in southern and western coastal areas in Korea.

Two endemic foci of heterophyid infections were discovered in coastal villages of Puan-gun, Chollabuk-do, and Sachon-gun. Kyongsangnam-do, Korea. Fecal examinations were performed on 153 inhabitants of Puan-gun and 138 of Sachon-gun, using cellophane thick smear and formalin-ether sedimentation technique. The helminth egg and/or protozoan cyst positive rate was 21.5% (33/153) in Puan-gun and 39.1% (54/138) in Sachon-gun. In Puan-gun, the egg positive rate of heterophyids was the highest, 17.6%, and that of other parasites was 0.7-2.6% by parasite species. In Sachon-gun, that of heterophyids was 18.8%, followed by Clonorchis sinensis (12.3%), and other parasites (0.7-5.0%). Twenth-two (Puan-gun) and six (Sachon-gun) heterophyid egg positive cases were treated with praziquantel, and adult flukes were collected from their diarrheic stools. A total of 3,284 adult flukes of Heterophyes nocens was collected from all of the 22 patients treated in Puan-gun (3-778 individually), and other trematodes were also collected from 2-15 patients: Pygidiopsis summa, Stellantchasmus falcalus. Metagonimus yokogawai, M. miyatai, Stictodora fuscata. Heterophyopsis continua, Acanthoparyphium kurogamo, and Gymnophalloides seoi. In Sachon-gun, M. yokogawai (3,007 specimens), H. nocens (120), and S. falcatus (46) were collected from 5 of 6 treated patients, and H. continua and S. lari each from one patient. The present study revealed that heterophyid flukes, especially H. nocens and M. yokogawai, are prevalent in the southern and western coastal areas of Korea where fresh and/or brackish water fishes are popularly eaten raw.

The loes-like red yellow soil of the south western coastal area of Korea in comparison with the loess of China and Japan

The analyses of the physical and chemical properties including X ray diffraction analysis of the red yellow soil of the Hwangsan-Myun, Kimje County and Gamgok-Myun, Chungeup County, in the SW coastal area of Korea were carried out and the results were compared with those of the loess in China and Japan and the red soil of Korea.