A Paleozoic subduction complex in Korea: SHRIMP zircon U–Pb ages and tectonic implications     

Sung Won Kim  Sanghoon Kwon  M. Santosh  Ian S. Williams  Keewook Yi 《Gondwana Research》2011,20(4):890-903

The Wolhyeonri complex in the southwestern margin of the Korean Peninsula is divided into three lithotectonic units: Late Paleozoic Zone I to the west, Middle Paleozoic Zone II in the middle and Early Paleozoic Zone III to the east. Zones II and III display characteristics of continental arc magmatic sequence. Zone II is dominated by mafic metavolcanics, whereas zone III is characterized by the presence of dismembered serpentinite bodies including chaotic mélange. These zones are proposed to have been formed in a convergent margin setting associated with subduction. Here we present zircon SHRIMP U–Pb ages from the various units within the Wolhyeonri complex which reveal the Paleozoic tectonic history of the region. The Late Carboniferous ages obtained from the main shear zone between the Wolhyeonri complex and the Paleoproterozoic Gyeonggi massif are thought to mark the timing of continental arc magmatism associated with the subduction process. In contrast, Zone I with Neoproterozoic arc magmatic remnants might indicate deposition in a forearc basin. The Wolhyeonri complex also preserves strong imprints of the Triassic collisional event, including the presence of Middle Triassic high-pressure metabasites and eclogites near the eastern boundary of the Zone III. These range of radiogenic ages derived from the Wolhyeonri complex correlate well with subduction and accretion history between the North and South China cratons. Similar geochronological features have also been indentified from the Qinling, Tongbai–Xinxian, and northern Dabie areas in east-central China. The existence of Paleozoic coeval subduction in East Asia prior to the Triassic collision is broadly consistent with a regional tectonic linkage to Gondwana.  相似文献   

Boundary currents in a meridional channel subject to seasonally varying buoyancy forcing: application to the Tsushima Current     

Young Ho Seung  Kuk Jin Kim 《Journal of Oceanography》2011,67(5):563-575

The theoretical problem of formation of boundary currents in an idealized basin subject to seasonally varying buoyancy forcing is considered in an attempt to apply it to the seasonally varying Tsushima Current. Until now, all the theories intended to explain the branching of the Tsushima Current have been for the annual mean Tsushima Current—the seasonally varying Tsushima Current has never been properly explained. A simple numerical experiment shows that eastern and western boundary currents change in time, concurrently, when local buoyancy forcing is sufficient, as it is in the Tsushima Current. However, this is not true for ineffective local buoyancy forcing. The importance of the role played by local buoyancy forcing is further supported by simple theoretical considerations. Overall, this study suggests that effective local buoyancy forcing is probably essential to the formation of seasonally varying eastern and western boundary currents of the Tsushima Current.  相似文献   

Temporal and geographical trends in the genotoxic effects of marine sediments after accidental oil spill on the blood cells of striped beakperch (Oplegnathus fasciatus)   总被引：1，自引：0，他引：1  

Lee HJ  Shim WJ  Lee J  Kim GB 《Marine pollution bulletin》2011,62(10):2264-2268

To determine the impact of genetic toxicity caused by the Hebei Spirit oil spill on December 7, 2007, we measured DNA damage in the blood cells of striped beakperch in vitro after exposure to extracts from sediments in the Taean area. The objective of this study was to investigate temporal changes of toxic effects caused by residual PAHs in the sediments up to 18 months after an oil spill. In conclusion, DNA damage had reduced over this 18-month period; that is, the sediments recovered quickly from the oil pollution. In addition, statistically significant correlations between PAHs and DNA damage were observed. Because the comet assay is sensitive to DNA damage induced by genotoxic substances from the polluted sediments, the comet assay can be considered a useful tool as a biomarker in investigating genetic toxicity in environmental monitoring and elucidating the recovery of oil pollution after oil spill as well.  相似文献   

Relationship between value of open space and distance from housing locations within a community     

Seong-Hoon Cho  Dayton M. Lambert  Seung Gyu Kim  Roland K. Roberts  William M. Park 《Journal of Geographical Systems》2011,13(4):393-414

This research uses a sequence of hedonic spatial regressions for a metropolitan housing market in the Southeastern United States to explore a new procedure that establishes the relationship between the value attributable to open space and distance from housing locations (a “distance-decay function”) within a given community. A distance-decay function allows identification of the range of distance over which open space affects housing values and the estimation of a proxy for the value added to nearby houses resulting from hypothetical open space preservation. Ex post analyses of the open-space regression coefficients suggest marginal implicit price functions for three types of open space that decay as open space area increases with respect to house location. After controlling for other factors in the spatial hedonic model, simple distance-decay functional relationships were established between the implicit prices of developed open space, forest-land open space, and agriculture-wetland open space and the buffer radius of the open-space areas surrounding a given housing location. The proposed method may be useful for identifying the range over which preferences for different types of open space are exhibited.  相似文献   

Integrative assessment of sediment quality in terms of chemical contamination in Jinhae Bay,South Korea     

Sang Hee Hong  Gi Myung Han  Un Hyuk Yim  Dhong-il Lim  Sung Yong Ha  Nam Sook Kim  Won Joon Shim 《Ocean Science Journal》2014,49(3):265-278

The assessment of sediment quality by considering chemical contaminants is required for the effective management of coastal environments. In this study, complex data sets of heavy metals and organic pollutants were integrated to evaluate sediment quality. Thirty-two target pollutants were quantitatively determined in surface sediments from 80 stations in Jinhae Bay, South Korea. A sediment quality index (SQI) was derived by combining the functions of “scope” (the number of variables that do not meet guideline objectives) and “amplitude” (the magnitude by which these variables exceed the guideline objective). The SQI reflects the spatial gradient and differences in the contamination status with regard to heavy metals and organic pollutants in Jinhae Bay. Fifty-nine out of eighty stations surveyed (74%) were classified as being in “excellent” or “good” condition according to the SQI, and no stations were in a “poor” condition. The mean sediment quality guideline quotient (mSGQq) ranged from 0.06 to 0.31 (from nontoxic to marginally toxic). Acute sediment toxicity leading to amphipod mortality was recorded at 17 stations (21%) of the 80 surveyed, where the mortality rate was slightly over 20%. No significant relationship was observed between sediment toxicity and the concentration of each toxicant or mSQGq.  相似文献   

Biochemical responses of juvenile rockfish (Sebastes schlegeli) to low levels of dissolved oxygen in Gamak Bay     

Jee-Hyun Jung  Ha Na Kim  Young Sun Chae  Won Joon Shim 《Ocean Science Journal》2014,49(3):241-247

Gamak Bay is one of the largest aquaculture areas in the South Sea of Korea and exhibits hypoxia conditions during the summer. The harmful effects of hypoxia on aquaculture fish stock have not been elucidated. This study describes the biochemical effects of low levels of dissolved oxygen (DO) on cultivated juvenile Sebastes schlegeli in Gamak Bay. The hypoxia-inducible factor 1α (HIF1α) gene was induced significantly in S. schlegeli collected from low oxygen level areas, which suggests that fluctuations in the DO induces the expression of HIF1α. The level of antioxidant enzyme exhibited significantly higher activities in fish obtained from station F2 in which low levels of DO were shown in 2010 and 2011. The results of this study demonstrate that cultivated S. schlegeli are affected by the low levels of DO in Gamak Bay and superoxide dismutase enzymes operate dependently with HIF1α. The plasma glucose level did not exhibit significant difference in the fish among the sampling stations. We noted that HIF1α and the superoxide dismutase enzymes are useful biomarkers that might enable the detection of otherwise unnoticed hypoxic stress.  相似文献   

Ocean Science Journal indexed in the Science Citation Index Expanded     

Won Joon Shim 《Ocean Science Journal》2014,49(2):83-83

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The effect of grain size on the viscosity and yield stress of fine-grained sediments   总被引：1，自引：1，他引：0  

Sueng Won JEONG 《山地科学学报》2014,11(1):31-40

In debris flow modelling,the viscosity and yield stress of fine-grained sediments should be determined in order to better characterize sediment flow.In particular,it is important to understand the effect of grain size on the rheology of fine-grained sediments associated with yielding.When looking at the relationship between shear stress and shear rate before yielding,a high-viscosity zone（called pseudoNewtonian viscosity） towards the apparent yield stress exists.After yielding,plastic viscosity（called Bingham viscosity） governs the flow.To examine the effect of grain size on the rheological characteristics of fine-grained sediments,clay-rich materials（from the Adriatic Sea,Italy; Cambridge Fjord,Canada; and the Mediterranean Sea,Spain）,silt-rich debris flow materials（from La Valette,France） and silt-rich materials（iron tailings from Canada） were compared.Rheological characteristics were examined using a modified Bingham model.The materials examined,including the Canadian inorganic and sensitive clays,exhibit typical shear thinning behavior and strong thixotropy.In the relationships between the liquidity index and rheological values（viscosity and apparent yield stress）,the effect of grain size on viscosity and yield stress is significant at a given liquidity index.The viscosity and yield stress of debris flow materials are higher than those of low-activity clays at the same liquid state.However the viscosity and yield stress of the tailings,which are mainly composed of silt-sized particles,are slightly lower than those of low-activity clays.  相似文献   

Historical record of metal accumulation and lead source in the southeastern coastal region of Korea     

Dhong-il Lim  Seung Woon Jung  Man Sik Choi  Sun Mee Kang  Hoi Soo Jung  Jin Yong Choi 《Marine pollution bulletin》2013

Concentrations of heavy metals and Pb isotopes were measured in the 1-M HCl leaching fraction of core sediments spanning the last 400 years. This sedimentary record of pollution history in metal concentrations shows a good correlation with the increases in industrialization, urbanization, and energy consumption since 1901s. Notably, the Pb concentration and the ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios were constant before the 1910s (16.7 μg/g, 0.844, and 2.098, respectively), whereas they increased steadily up to 21.9 μg/g, 0.848, and 2.101 after the 1910s. The correlations between Pb isotope ratios (²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) showed different linear regression trends for core sediments before and after the 1910s, indicating differences in Pb sources. Our interpretation suggests that the source of anthropogenic Pb in Korean coastal region and the Yellow Sea shelf was presumed to be Chinese coals or ores, which have also played a major role as sources of atmospheric particulate Pb.  相似文献   

Three‐dimensional responses of buried corrugated pipes and ANN‐based method for predicting pipe deflections     

Moon Kyum Kim  Seok Ho Cho  Ik Jung Yun  Jong Hwa Won 《国际地质力学数值与分析法杂志》2012,36(1):1-16

This study investigated localized responses, such as circumferential stresses, on corrugation and pipe deflections. Also, this study examined the effect of corrugation geometry on the overall and localized response of corrugated pipes with refined three‐dimensional modeling of the entire soil–pipe interaction system, including corrugation. To investigate the availability of the traditional two‐dimensional method, the results from the three‐dimensional finite element method (FEM) were compared with those from the two‐dimensional FEM. The soil–pipe modeling techniques of this study were verified by comparing the FEM results by Utah State University and analytical results. An artificial neural network (ANN)‐based model to predict vertical deflections of buried corrugated pipes was developed to overcome the shortcomings of existing methods and obtain results that are close to the level of accuracy of FEM results. In order to train an ANN, analyses on a large amount of data were executed with various standardized pipe geometries and burial depths regulated by the Korea Highway Corporation using the two‐dimensional FEM verified in this study. The widely used back propagation algorithm was adopted. The ANN‐based model developed in this study was shown to be an effective tool by comparing the results with test data and sensitivity analyses were executed based on the data from the developed ANN. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献