Granitoids in the southern Korean Peninsula range in age from Precambrian to Cenozoic, but were emplaced mostly during the Jurassic and Cretaceous periods. The late Permian–Early Triassic granitoids ...are minor in volume and restricted to the northeastern part of the Cretaceous Gyeongsang Basin (Yeongdeok and Jangsari). Here we report on Permian granites from the Cenozoic Pohang Basin of southeastern Korea. The samples were obtained during the drilling of injection wells in the Pohang enhanced geothermal system (4219 m depth for the drill core; 3658–4174 m for the drill cuttings). We also analyzed outcrop samples from Yeongdeok and Jangsari. We present zircon U-Pb ages and Hf isotope, whole-rock geochemical, and Sr–Nd–Pb isotope data for these Phanerozoic granitoids. The zircons yielded early–late Permian ages (ca. 283–264 Ma) for the Pohang granites, late Permian ages (ca. 261–256 Ma) for the Jangsari granitoids, and late Permian–Early Triassic ages (ca. 253–249 Ma) for the Yeongdeok granitoids. The granitoids are enriched in large-ion lithophile elements and depleted in high-field-strength elements, indicating formation in an arc-related tectonic setting. The Permian Pohang and Jangsari granitoids have a non-adakitic arc-like geochemistry, whereas the Yeongdeok intrusions are adakite-like and show high Sr and low Y-Yb contents. The granitoids have low (87Sr/86Sr)i (0.7038–0.7049) and positive εNd(t) values (+3.7 to +4.7 for the Pohang, +4.4 to +4.9 for the Jangsari, and + 2.4 to +4.1 for the Yeongdeok plutons), and are distinct from the basement of the Yeongnam Massif. The Pb isotope ratios of the studied samples plot in the field for Indian mid-ocean ridge basalts. Zircons from the plutons have positive εHf(t) values: +9.8 to +17.6 for the Pohang, +8.8 to +17.7 for the Jangsari, and + 8.5 to +18.3 for the Yeongdeok plutons. The Permian granitoids were likely the product of extensive fractional crystallization of H2O-rich parental magmas, which were possibly generated in a hydrated mantle wedge. The Yeongdeok adakite-like granitoids were derived from a normal H2O-rich arc magma by amphibole ± garnet fractionation. The juvenile Sr–Nd–Pb–Hf isotope compositions are comparable with those of coeval igneous rocks in the Central Asian Orogenic Belt, rather than intrusive counterparts in the North and South China cratons. We propose two possibilities that Permian–Early Triassic arc-related magmatism in the southeastern Korean Peninsula might have been associated with (1) northward subduction of the Paleo-Asian oceanic plate; or (2) westward subduction of the Paleo-Pacific plate at the eastern margin of the North China Craton.
•We report Permian–Early Triassic (ca. 283–249 Ma) granitoids in SE Korea.•They have positive εNd(t) and εHf(t), and Indian MORB-like Pb isotope ratios.•~30 Ma-long subduction linked to a switch from normal to adakitic compositions.•Adakite-like granites were formed by amphibole(±garnet)-dominated fractionation.
Understanding the relationship between road-deposited sediments (RDS) and total suspended solids (TSS) is essential for managing non-point pollution. Studying the heavy metal concentrations of RDS ...and TSS in rainfall is important to the development of RDS management strategies and to the design of effective stormwater management practices. We investigated the heavy metal (V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Pb) in RDS and TSS in rainfall runoff to assess the metal pollution level and to evaluate the contribution of RDS heavy metal pollution in the TSS. The heavy metal pollution in RDS and TSS in industrial areas was relatively higher in small particles (<125 μm), while TSS had a higher heavy metal concentration than RDS. In addition, the concentration of heavy metals in TSS increased rapidly during the initial rainfall. The amount of particles larger than 125 μm also increased, suggesting that large metal particles accumulated in industrial areas were also discharged in the form of non-point pollution. The amount of RDS per unit of industrial area (g/m2) and the accumulation of heavy metals (Pb, Cu, and Zn) (mg/m2) were 15- and 8–54-fold higher than those of urban areas, respectively. Considering particles <125 μm, which can be easily transported or discharged during rainfall, the contribution rate of RDS to TSS was 41.3%, but the average contribution rate to heavy metals in TSS was 22.1%. The average load of heavy metals from industrial areas in TSS was 77.9%. The load of Cu, Ni, As, Cd, and Sn exceeded 90%, indicating that most of these metals were attributed to industrial activities related to metal processing. Our results suggest the importance of efficient road cleaning and rainfall runoff management strategies to solve the heavy metal pollution problem caused by non-point sources in industrial areas.
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•Heavy metals in road-deposited sediments (RDS) increases with decreasing size.•Heavy metals of total suspended solids (TSS) in runoff was higher that RDS.•Metal pollution in TSS has a greater influence on the industrial activities than RDS.•In industrial area, efficient runoff managements to control pollution is important.
The aims of this study were to apply and validate a logistic regression model for landslide hazard, considering rainfall probability and using a geographic information system. The study focused on ...the Deokeokri and Karisanri areas of Inje, South Korea. We chose logistic regression for its mathematical rigor and its use of implementation in GIS software. Rainfall probability is analyzed for a quantitative prediction of rainfall changes in the study area. The rainfall probability was calculated using the Gumbel distribution. Then, the probabilities of landslides in the study area in target years (1, 3, 10, 50, and 100 years in the future) were calculated assuming that landslides are triggered by daily rainfall of 202 mm or 3-day cumulative rainfall of 449 mm. Landslide hazard maps were developed for the two study areas, and the logistic regression coefficients for one area were applied to the other area to validate the method. In Karisanri, all recorded landslides were used for validation. Validation results for the 202-mm daily precipitation threshold in Karisanri showed an average accuracy of 79.14 %, whereas those for the 449-mm 3-day cumulative precipitation threshold showed an average accuracy of 81.31 %. A combination of rainfall probability and logistic regression with a GIS is an effective method for analyzing the possibility of future landslides.
Fractures (including faults and joints) are important pathways for magma in the upper crust. Two theories of dyke intrusion are generally accepted: dykes open pre-existing fractures or dykes inject ...propagating new fractures at their tips. Thus, there is a close interrelationship between dyke intrusion and fractures. We present a field-based study focused on geometric patterns of intrusions, because detailed descriptions and analyses of exposed dykes can provide useful complementary information regarding the roles of fractures as dyke formation pathways. Most non-planar dyke examples that we analyzed are from four areas (Geoje Island, Kori, Uljin, and Suncheon) of Korea. Some dykes show morphological similarities to fractures, such as branching, bending, and splaying. Therefore, we classified the intrusion patterns based on the equivalent terminology for fractures (e.g., tip, wall, and linkage), which is useful for describing dykes at the outcrop scale and for research into inter-relationships between dykes and fractures. This study improves our understanding for the role of fractures in guiding dyke emplacement.
We assessed landslide susceptibility using Chi-square Automatic Interaction Detection (CHAID), exhaustive CHAID, and Quick, Unbiased, and Efficient Statistical Tree (QUEST) decision tree models in ...Jumunjin-eup, Gangneung-si, Korea. A total of 548 landslides were identified based on interpretation of aerial photographs. Half of the 548 landslides were selected for modeling, and the remaining half were used for verification. We used 20 landslide control factors that were classified into five categories, namely topographic elements, hydrological elements, soil maps, forest maps, and geological maps, to determine landslide susceptibility. The relationships of landslide occurrence with landslide-inducing factors were analyzed using CHAID, exhaustive CHAID, and QUEST models. The three models were then verified using the area under the curve (AUC) method. The results showed that the CHAID model (AUC = 87.1%) was more accurate than the exhaustive CHAID (AUC = 86.9%) and QUEST models (AUC = 82.8%). The verification results showed that the CHAID model had the highest accuracy. There was high susceptibility to landslides in mountainous areas and low susceptibility in coastal areas. Analyzing the characteristics of the landslide control factors in advance will enable us to obtain more accurate results.
From the 1960s to the 2000s, the Republic of Korea (ROK) witnessed the rapid development of its shipbuilding industry, establishing itself as one of the world’s largest shipbuilders. This article ...seeks to answer the question of what drove the rapid development of South Korea’s shipbuilding industry. It accomplishes this by examining both classical sea power theory and the unique South Korean shipbuilding development model of the 1960s to the 2000s. Drawing from primary sources obtained from the ROK Presidential Archive and secondary sources, including newspapers and scholarly articles, this paper concludes that a combination of classic drivers of sea power development – including maritime commerce and threats – and the unique South Korean model, characterised by government subsidies and investments in both commercial shipbuilding and warship construction, contributed significantly to the development of South Korea’s shipbuilding industry. Finally, by learning from South Korea’s experience, developing and middle power countries looking to establish their shipbuilding industry should consider subsidising the industry in its early stages and contributing to a healthy ecosystem by investing in both commercial and warship construction.
Crude oil and its derivatives are considered as one group of the most pervasive environmental pollutants in marine environments. Bioremediation using oil-degrading bacteria has emerged as a promising ...green cleanup alternative in more recent years. The employment of biosurfactant-producing and hydrocarbon-utilizing indigenous bacteria enhances the effectiveness of bioremediation by making hydrocarbons bioavailable for degradation. In this study, the best candidates of biosurfactant-producing indigenous bacteria were selected by screening of biochemical tests. The selected bacteria include Bacillus algicola (003-Phe1), Rhodococcus soli (102-Na5), Isoptericola chiayiensis (103-Na4), and Pseudoalteromonas agarivorans (SDRB-Py1). In general, these isolated species caused low surface tension values (33.9–41.3 mN m−1), high oil spreading (1.2–2.4 cm), and hydrocarbon emulsification (up to 65%) warranting active degradation of hydrocarbons. FT-IR and LC-MS analyses indicated that the monorhamnolipid (Rha-C16:1) and dirhamnolipid (Rha-Rha-C6-C6:1) were commonly produced by the bacteria as potent biosurfactants. The residual crude oil after the biodegradation test was quantitated using GC-MS analysis. The bacteria utilized crude oil as their sole carbon source while the amount of residual crude oil significantly decreased. In addition the cell-free broth containing biosurfactants produced by bacterial strains significantly desorbed crude oil in oil-polluted marine sediment. The selected bacteria might hold additional capacity in crude oil degradation. Biosurfactant-producing indigenous bacteria therefore degrade crude oil hydrocarbon compounds, produce biosurfactants that can increase the emulsification of crude oil and are thus more conducive to the degradation of crude oil.
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•Bioremediation using oil-degrading bacteria is a promising green cleanup alternative.•BS-producing indigenous bacteria were selected by screening of biochemical tests.•Various rhamnolipids were produced by the bacteria as potent biosurfactants.•The production of BSs (rhamnolipids) by the bacteria may affect the degradation of crude oil.•Biosurfactants significantly desorbed crude oil in oil-polluted marine sediment.
Biosurfactant-producing indigenous bacteria can effectively expedite the bioremediation of crude oil contaminated environments.
This article elucidates the reasons behind South Korea’s diminished security cooperation with Japan during the Moon Jae-in administration (2017–2022). The author discovered that President Moon halted ...ongoing security cooperation activities initiated by his predecessor, even though the North Korean nuclear threat became exponential. In particular, this article argues that not the national-level factors, such as South Koreans’ negative perception of Japan on the basis of their collective memory, but the leader factor was the main reason for the worsening of South Korea–Japan’s security cooperation during the Moon administration, contrary to most people’s expectations. The Moon administration’s progressive political leaders, who had acquired anti-United States/anti-Japan and pro-North Korea/pro-China perspectives during their anti-government protests in the 1970s and 1980s, decided to be confrontational towards Japan to their political benefit. The reality that the security cooperation between South Korea and Japan jumpstarted once the conservative Yoon Suk-yeol administration leaders replaced them supports this finding.
Climate change may alter the frequency and intensity of rainfall, and thereby significantly affect the frequency and magnitude of shallow landslides. To accurately evaluate the temporal probability ...of landslide initiation, it is therefore important to consider the effect of climate variation. Although various approaches have been proposed to estimate the temporal probability of landslides to date, most of them were based on the stationary assumption, i.e., that the statistical properties of the historical rainfall data are time-invariant. However, if historical rainfall data show nonstationary characteristics such as a trend or an abrupt change, the stationary assumption is no longer valid and induces a miscalculation. In this study, we propose a new approach that can estimate the temporal probability of future rainfall-induced landslide occurrence while incorporating the nonstationary characteristics of the rainfall data. In assessing such data, a nonstationary generalized extreme value distribution was used to evaluate the temporal probability. Then, by combining the derived nonstationary temporal probability with landslide susceptibility results obtained from the random forest model, probabilities of landslide occurrence were calculated for future periods, from 1 to 50 years, and compared with the results based on a stationary model. The results showed that the stationary model underestimated the landslide probability compared with the nonstationary approach. This is because an increasing trend in local rainfall, taken from a gauge in the study area, was not considered in the stationary analysis. Thus, climate change has ongoing consequences for landslide occurrence. To reflect the impacts of climate change, a nonstationary approach capable of coping with climate variation should therefore be considered in any landslide hazard analysis.
•A process for evaluating landslide probability considering nonstationarity is developed.•Multiple statistical tests are used to assess nonstationarity in extreme rainfalls.•Nonstationary EVA is used to estimate temporal probability of landslide occurrence.•Landslide probability is estimated by combining temporal probability with susceptibility.•Future landslide probability from nonstationary model is greater than from stationary model.
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