• Economic and Environmental Geology
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• v.34 no.1
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• pp.13-23
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• 2001

Bentonite layers are intercalated within the basal conglomerates in the Tertiary sedimentary basins of Kampo, Janggi and Pohang, southeastern Korea. Eighteen samples of the bentonites went through X-ray diffraction, scanning electron microscopy, heavy mineral analyses, chemical analyses and oxygen, hydrogen stable isotope analyses to define the mineralogical characters of the bentonites. Heavy minerals such as zircons, apatites, amphiboles and biotites separated from bentonites show clean and euhedral surfaces, which are the characteristic features of volcanic origin. But biotites from the Chunbook Conglomerate are found as altered and heavily broken flakes which implies longer transportation of these bentonites. $TiO_{2}/Al_{2}O_{3} ratios of <2 $\mu$m particle fractions (the Chunbook Conglomerate 0.031; Janggi 0.029; Kampo 0.025) suggest that those are originated from volcanic tuffs. That is, the higher the value is, the more mafic in chemical compositions of the original tuffs. Authigenic montmorillonite and zeolite minerals were observed by SEM, which indicates diagenesis origin of bentonites. But the samples from the Chunbook Conglomerate showed only chaotically packed clay flakes in the matrix of sands or conglomerates, which implies detrital influence, not authigenic origin. The structural formulae of montmorillonite from these basins reflects their environment of formation. Fe (Ⅵ) can show the redox condition of its past environment and much lower $Fe^{2+}(Ⅵ)/Fe^{3+}(Ⅵ)$ ratios in montmorillonite of the Chunbook Conglomerate imply the greater oxidizing influence. Calculated burial depths from oxygen stable isotope data of the samples from the Chunbook Conglomerate generally fall to the range of 929~963 m whereas the real burial depth of this area is only 530~580 m. This could be explained as the bentonites of the Chunbook conglomerate had not been formed in situ. Discriminant analyses with the data from chemical analyses and structural formulae of montmorillonites show that bentonites from three different basins could definitely be distinguished with each other. This result arises from the different chemical compositions of original volcanic ashes and the difference of sedimentary environments.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.73-82
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• 2011

X-ray absorption spectroscopy (XAS) study was conducted using arsenite-sorbed two-line ferrihydrite to investigate the mechanism of surface interactions between two-line ferrihydrite and As(III) (arsenite) which are ubiquitous in nature. The two-line ferrihydrite used was synthesized in the laboratory and the study was undertaken at pHs 4 and 10 to compare the difference in mechanisms of surface interaction between acidic and alkaline environments. The effect of arsenite-adsorbed concentrations on surface complexation was investigated at each pH condition as well. From the results of XAS analyses, the structural parameters of arsenite in the EXAFS revealed that the coordination number and distanceof As-O were 3.1~3.3 and 1.74~1.79 ${\AA}$, respectively, which indicate that the unit structure of arsenite complex formed on the surface of two-line ferrihydrite is $AsO_3$. The dominant structures of As(III)-Fe complex were examined to be bidentate binuclear comer-sharing ($^2C$) and the mixture of bidentate mononuclear edge sharing ($^2E$) and $^2C$ appeared as well. At pH 4, arsenite complex showed different structures on the surface of two-line ferrihydrite, depending on the adsorbed concentrations. At pH 10, on the contrary, the surface structures of arsenite complexes were interpreted to be almost identical, irrespective of the adsorbed concentrations of arsenite. Consequently, this microscopic XAS results support the results of macroscopic adsorption experiments in which the surface interaction between arsenite and two-line ferrihydrite is significantly influenced by pH conditions as well as arsenite concentrations.

• The Korean Journal of Pesticide Science
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• v.11 no.2
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• pp.95-105
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• 2007

The aim of this study was to determine the residual amounts of PAHs in environmental samples such as crop, soil and water collected from paddy, upland fields and forestlands near industrial zone and/or a thermal power plant in South Korea. All of the samples were analyzed by GC-mass spectrometer. The average contents of total PAHs in soil samples were 140.2 ${\mu}g\;kg^{-1}$ and the range was from 4.3 to $662.9{\mu}g\;kg^{-1}$. The detection of benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene and dibenzo(a,h) anthracene which have strong carcinogenecity was ranged from 14.2 to 167.8 ${\mu}g\;kg^{-1}$. The residual amounts and detection frequency of PAHs in soil samples from the iron and heavy industrial areas near Pohang and Busan were 3-folds more than those of the other areas. Amounts of PAHs in upland soil samples was 1.5 folds higher than those of paddy soil samples, suggesting that it may be related to the content of organic matter in soil. The average contents of total PAHs in crop samples were 9.7 ${\mu}g\;kg^{-1}$ which ranged from 4.5 to 52.2 ${\mu}g\;kg^{-1}$. However, the residual amounts of PAHs in water samples were not detected. These results showed that soils and crops were slightly contaminated with PAHs. Therefore, the investigation should be continued for evaluating a safety or risk assessment through expansion of regions and crops.

• Journal of Korea Port Economic Association
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• v.25 no.1
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• pp.15-28
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• 2009

The purpose of this paper is to show the empirical extraction way of benchmarking ports for overcoming the shortcoming which the traditional DEA method has by using 20 Korean ports in 2003 for 2 inputs (birthing capacity, cargo handling capacity) and 2 outputs(Export and Import Quantity, Number of Ship Calls). Because DEA method has produced the limited set of efficient units which are reference to inefficient units respective of their differences in efficiency scores, it is necessary to adopt the more feasible benchmarking information according to the path analysis(tier or stratification). The core empirical results of this paper are as follows. Benchmarking ports against inefficient ports according to the tier analysis are that Masan Port(Janghang$\rightarrow$Jeju$\rightarrow$Seogoipo$\rightarrow$Yeosu), Jinhae Port(Janghang$\rightarrow$Mogpo$\rightarrow$Seogoipo$\rightarrow$Wando), Pohang&DonghaePort(Janghang$\rightarrow$Samcheonpo$\rightarrow$Pyungtag$\rightarrow$Samcheog), and Sogcho Port(Janghang$\rightarrow$Mogpo$\rightarrow$Seogoipo$\rightarrow$Wando). The policy implication to the Korean seaports and planners is that Korean seaports should introduce the new methods like Tier analysis of this paper for evaluating the port performance and enhancing the efficiency in short term, mid term, and long term according to the tier 3 stage, the tier 2 stage, and the tier 1 stage with original DEA stage.

• Journal of Korean Society of Forest Science
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• v.98 no.1
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• pp.94-105
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• 2009

Black locust (Robinia pseudoacacia) stand is representative lowland exotic plantation with low ecological quality and arrested succession in South Korea. To facilitate succession and restore natural vegetation, small canopy gaps (${\sim}57m^2$), which can modify minimally structural variables and reduce restoration related disturbances on stand, was established in the black locust stand, and oak (Quercus serrata) seedlings were introduced in the gap. Two types of varying levels were introduced for gap creation; cutting (C) and girdling (G) on canopies. Understory removal (CU and GU) treatment was applied as subtypes of structural modification. Growth (diameter, height and leaf area) of target species and responses (species composition, diversity and coverage) of understory community were monitored during study years (2007~2008). Canopy openness was different significantly among treatments but not for light availability. Based on the result of logistic regression, growth of height and leaf area of seedlings were significant variables on seedling survival. Height and leaf area of seedlings were increased during study years, although radial growth was reduced. During study years, there were no significant differences in species composition and diversity, and total coverage increased about 20%. Increase of resources by gap creation and understory removal likely affect growth of target species. Small gap creation was effective to reduce understory responses in composition and diverstiy. Synthesized, growth of target species and responses of understory community to small canopy gap creation exhibited, in short term, possibility of utilization in alternative forest restoration and management option. Long-term monitoring is necessary to certificate effect of artificial gap creation on forest restoration.

• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.4
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• pp.218-234
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• 2004

Recent warm winters were evaluated for a possible shifting of the northern limit for winter barley cultivation in Korea. Therefore, safe zones for winter barley cultivation were reclassified based on the average and minimum January air temperature in recent years. The results are as follows: By analysis of mean values of January average air temperatures for 30 years (1971-2000), the northern limits for safe cultivation of hulled, naked, and malting barley were Ganghwa - Icheon - Chungju - Chunyang - Goseong, Cheonan - Geumsan - Mungyeong - Andong - Sokcho, and Gwangju - Jangheung - Sancheong - Pohang - Uljin lines, respectively. Meanwhile, based on the January average air temperature of 14 years (1987-2000) with warmer winters, the safe cultivation zone of winter barley shifted northward of the normal (1971-2000). So, the northern limits for hulled, naked, and malting barley were Pocheon - Chuncheon - Wonju - Yangpyeong - Chunyang, Ganghwa - Icheon - Chungju - Uiseong - Goseong, and Gunsan - Suncheon - Jinju - Miryang - Yeongdeok - Uljin lines, respectively. Winter barley cultivars with the strongest tolerance to low temperature can be grown up to the adjacent areas of Taebaek Mountains (that is, Inje, Hongcheon, Jecheon, and Taebaek areas). Based on January mean air temperatures of 10-year return period for 30 years (1971-2000), the northern limits for hulled and naked barley were Boryeong - Namwon - Geochang - Gumi - Goseong and Seocheon - Jeongeup - Hapcheon - Yeongdeok - Sokcho lines, respectively. It ~ppears that malting barley can be cultivated only at southern coastal areas (that is, Busan, Tongyeong, Yeosu, and Wando areas). On the other hand, based on the weather conditions of 14 years (1987-2000) with warmer winters, the northern limits for hulled, naked, and malting barley were Ganghwa - Icheon - Yeongju - Goseong, Seosan - Namwon - Mungyeong - Andong - Sokcho, and Gwangju - Jangheung - Sacheon - Ulsan - Uljin lines, respectively. The northern limit for winter barley cultivars including Olbori with the strongest tolerance to low temperature was the Ganghwa - Wonju - Chungju - Chunyang - Goseong line.

• Korean Journal of Remote Sensing
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• v.14 no.1
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• pp.53-68
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• 1998

Observation of hydrometeors' behavior in the atmosphere is important to understand weather and climate. By conventional observations, we can get the distribution of water vapor at limited number of points on the earth. In this study, the precipitable water has been estimated from the split window channel data on GMS-5 based upon the technique developed by Chesters et al.(1983). To retrieve the precipitable water, water vapor absorption parameter depending on filter function of sensor has been derived using the regression analysis between the split window channel data and the radiosonde data observed at Osan, Pohang, Kwangiu and Cheju staions for 4 months. The air temperature of 700 hPa from the Global Spectral Model of Korea Meteorological Administration (GSM/KMA) has been used as mean air temperature for single layer radiation model. The retrieved precipitable water for the period from August 1996 through December 1996 are compared to radiosonde data. It is shown that the root mean square differences between radiosonde observations and the GMS-5 retrievals range from 0.65 g/$cm^2$ to 1.09 g/$cm^2$ with correlation coefficient of 0.46 on hourly basis. The monthly distribution of precipitable water from GMS-5 shows almost good representation in large scale. Precipitable water is produced 4 times a day at Korea Meteorological Administration in the form of grid point data with 0.5 degree lat./lon. resolution. The data can be used in the objective analysis for numerical weather prediction and to increase the accuracy of humidity analysis especially under clear sky condition. And also, the data is a useful complement to existing data set for climatological research. But it is necessary to get higher correlation between radiosonde observations and the GMS-5 retrievals for operational applications.

• Journal of The Korean Astronomical Society
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• v.52 no.1
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• pp.11-21
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• 2019

Intensive Monitoring Survey of Nearby Galaxies (IMSNG) is a high cadence observation program monitoring nearby galaxies with high probabilities of hosting supernovae (SNe). IMSNG aims to constrain the SN explosion mechanism by inferring sizes of SN progenitor systems through the detection of the shock-heated emission that lasts less than a few days after the SN explosion. To catch the signal, IMSNG utilizes a network of 0.5-m to 1-m class telescopes around the world and monitors the images of 60 nearby galaxies at distances D < 50 Mpc to a cadence as short as a few hours. The target galaxies are bright in near-ultraviolet (NUV) with $M_{NUV}$ < -18.4 AB mag and have high probabilities of hosting SNe ($0.06SN\;yr^{-1}$ per galaxy). With this strategy, we expect to detect the early light curves of 3.4 SNe per year to a depth of R ~ 19.5 mag, enabling us to detect the shock-heated emission from a progenitor star with a radius as small as $0.1R_{\odot}$. The accumulated data will be also useful for studying faint features around the target galaxies and other science projects. So far, 18 SNe have occurred in our target fields (16 in IMSNG galaxies) over 5 years, confirming our SN rate estimate of $0.06SN\;yr^{-1}$ per galaxy.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.685-690
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• 2011

In this study, a solvothermal reaction to prepare nanocrystalline titania was carried out using $TiCl_4$ and mixed solvents of alcohol and water. The effects of the type and the composition of alcohol on the crystal structure and agglomeration of final $TiO_2$ products were investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM). In the solvothermal reaction using the n-butanol solutions with different volume ratios of n-butanol/water (100/0, 75/25, 50/50, 25/75, 0/100), the extent of agglomeration of obtained rutile $TiO_2$ was found to change with the volume ratio of n-butanol/water, and the n-butanol/water ratio of 75/25 revealed the best result for the preparation of well-dispersed nanocrystalline $TiO_2$ powders. The crystal phase of $TiO_2$ prepared through the solvothermal reaction changed with the type of alcohol in solvent (alcohol/water = 75/25). $TiO_2$ products obtained with the aqueous solutions of methanol, ethanol and isopropanol have an anatase phase, while that with n-butanol has a rutile phase. The results showed that, in the solvothermal reaction using both $TiCl_4$ as a starting material and the alcohol-water mixed solvents without any other additive, the enhancement of dispersion and control of crystal structure of $TiO_2$ products can be feasible by simply varying the composition and type of alcohol in the mixed solvents.

• Atmosphere
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• v.33 no.2
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• pp.223-246
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• 2023

This paper summarized the research papers on weather extremes that occurred in the Republic of Korea, which were published in the domestic and foreign journals during 1963~2022. Weather extreme is defined as a weather phenomenon that causes serious casualty and property loss; here, it includes typhoon, heavy rain, drought, heat wave, cold surge, heavy snow, and strong gust. Based on the 2011~2020 statistics in Korea, above 80% of property loss due to all natural disasters were caused by typhoons and heavy rainfalls. However, the impact of the other weather extremes can be underestimated rather than we have actually experienced; the property loss caused by the other extremes is hard to be quantitatively counted. Particularly, as global warming becomes serious, the influence of drought and heat wave has been increasing. The damages caused by cold surges, heavy snow, and strong gust occurred over relatively local areas on short-term time scales compared to other weather hazards. In particularly, strong gust accompanied with drought may result in severe forest fires over mountainous regions. We hope that the present review paper may remind us of the importance of weather extremes that directly affect our lives.