• Journal of Ecology and Environment
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• v.29 no.3
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• pp.305-321
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• 2006

Atmospheric Acid Deposition: Nitrogen Saturation of Forests: Volume weighted annual average wet deposition of nitroge at 33 sites in Korea during 1999-2004 ranged 7.28 to $21.05kgN{\cdot}ha^{-1}{\cdot}yr^{-1}$ with average $12.78kgN{\cdot}ha^{-1}{\cdot}yr^{-1}$, which values are similar level with nitrogen deposition of Europe and North America. The temperate forests that suffered long-term high atmospheric nitrogen deposition are gradually saturated with nitrogen. Such nitrogen saturated forest watersheds usually leach nitrate ion ($NO_3^-$) in stream water and soil solution. It may be likely that Korean forest ecosystems are saturated by much nitrogen deposition. In leaves with nitrogen saturation ratios of N/P, N/K and N/Mg are so enhanced that mineral nutrient system is disturbed, suffered easily frost damage and blight disease, reduced fine-root vitality and mycorrhizal activity. Consequently nitrogen saturated forests decrease primary productivity and finally become forest decline. Futhermore understory species are replaced the nitrophobous species by the nitrophilous one. In soil with nitrogen saturation uptake of methane ($CH_4$) is reduced and emission of nitrogen monoxide (NO) and nitrous oxide ($N_{2}O$) are increased, which gases are greenhouse gas accelerating global warming.

• Journal of the Korean earth science society
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• v.34 no.2
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• pp.109-119
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• 2013

Duibaejae basalts from Goseong, Gangwon-do, are divided into the lower basalt and the upper basalt depending on the properties, such as occurrence, mineral compositions, and major and trace compositions of the basalts. The lower basalts have characteristics of agglomerate rocks as well as contain, crustal and mantle xenoliths, and olivine, pyroxene, and plagioclase xenocrysts. The upper basalts with columnar joints contain relatively more mantle xenolith and olivine xenocryst than the lower basalts. The major and trace element compositions suggest that the composition of the upper basalts is close to primary magma composition. Enrichment and depletion patterns of the trace and the rare-earth elements of the lower basalts are similar to those of the upper basalts, whereas the lower basalts are more LREE enriched than the upper basalts. The source magmas of the lower and upper basalts from Duibaejae volcanic edifice were generated from about 0.8-1.2% and 3.7-4.0% batch melting of garnet peridotite, respectively. The abundance of granite xenolith, and plagioclase and quartz xenocrysts with reaction rim indicates that the lower basalts, compared with upper basalts, might have been assimilated with the crustal materials during ascending to surface.

• The Journal of the Petrological Society of Korea
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• v.19 no.4
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• pp.255-267
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• 2010

The primary utilization of recently improved (U-Th)/He thermochronometry is to reveal the low-T thermal histories of shallow crustal sections or transient episodes (such as wildfires or meteorite impacts) because of the high sensitivity of He diffusion to temperature in host minerals. In this contribution, we present reviews and perspectives regarding how this method can be used to characterize the ejection-related shock metamorphism of Martian meteorites. The temperature conditions of shock metamorphism can be constrained through shock recovery experiments, paleomagnetism, and $^{40}Ar/^{39}Ar$ and (U-Th)/He dating. The most reliable constraints can be deduced when these independent approaches are combined. However, the thermal history of the ALH84001 Martian meteorite has been under serious debate because the different methods have yielded contrasting results. Recent work has shown how single-grain (U-Th)/He and $^{40}Ar/^{39}Ar$ dating, two noble-gas based thermochronometries with different T sensitivities, can be used to resolve this issue, providing a good example for future research on other meteorites.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.147-156
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• 2001

Titanomagnetites, the primary magnetic mineral in submarine basalts, generally has undergone some degree of low temperature oxidation to cation-deficient titanomaghemites. Synthetic analogues of natural titanomaghemite have been prepared by the removal of iron mechanism employing a low-temperature aqueous oxidation method. Along with the low-temperature oxidation of titanomagnetite, magnetic properties of titanomagnetite change sensitively. The results show that as the degree of oxidation increases, the Curie temperature (Tc) increases from $166^{\circ}C$ to $400^{\circ}C$, saturation magnetization (Ms) at room temperature decreases from 126.30 kAlm (25.26 emu/g) to 16.55 kAlrn (3.31 emu/g) monotonously, and coercive force (Hc) and coercivity of remanence (Hcr) increase from 6.13 kAlm (77 Oe) and 23.24 kAlm (292 Oe) to 38.83 kNm (488 Oe) and 47.03 kAlm (591 Oe), respectively. Low field susceptibility (X) decreases from $2023{\times}10^{-6}SI$ to $84{\times}10^{-6}S1$. Based on the results of this study, it is interpreted that the NRM intensity variations of the oceanic crust of presetnt day to 30 Ma is due to the formation of titanomahemites of various degree of oxidation by the low-temperature aqueous oxidation of titanomagnetite, while the magnetic intensity changes of the oceanic crust older than 30 Ma is presumably caused by the combined effect of the formation of titanomaghemites and subsequent inversion of titanomagnemites. DetaileJ causes of the variations of NRM intensity of the oceanic crust may be revealed by systematic studies of the oceanic-floor basalts in the future.

• Economic and Environmental Geology
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• v.40 no.2 s.183
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• pp.141-151
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• 2007

This study was focused on iron removal from illite by L-ascorbic and oxalic acids. Iron has been shown as a secondary mineral such as iron oxides and hydroxides in illite ores. It is also known as a primary agent to degrade brightness index of the ores. Methods such as physical separation and chemical leaching with strong inorganic acids have been widely used to remove the iron from the ores. However, these methods are expensive and give rise to environmental problems. In this study, we examined an alternative method using solutions with different set of combination of sulfuric, hydrochloric, L-ascorbic, and oxalic acids. Compared to chemical treatments with only inorganic acids, our results demonstrate that an addition of L-ascorbic acid in inorganic acids results in decreasing both total concentrations of the inorganic acids and time for the treatments. The treatment with 0.15 M L-ascorbic acid and 0.25 M sulfuric acid in solution for 60 min significantly improved the brightness index from 42.4% to 74.4%. This improvement is similar to that of treatment with only 2.5 M sulfuric acid alone for 150 min. Mineralogical and chemical analyses were performed to compare the effect of acid leaching on illite powders. No obvious differences are observed in the mineralogical characteristics and particle size distributions of the samples. These results suggest that the treatment with the addition of L-ascorbic acid in sulfuric acid could effectively remove iron without modifying the physicochemical properties of illite under conditions used in this study.

• Economic and Environmental Geology
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• v.40 no.2 s.183
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• pp.171-189
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• 2007

A study of anisotropy of magnetic susceptibility (AMS) was undertaken on Cretaceous granitic, volcanic and sedimentary rocks in the eastern region of the Yangsan fault, southeast Korea. A total of 542 independently oriented core samples collected form 77 sites were studied. The main magnetic mineral in granitic rocks is magnetite according to the magnitude of bulk susceptibility, high-temperature susceptibility variation and isothermal remanent magnetization. Both of magnetic lineation and foliation with NE-SW trends are revealed in the granitic rocks, while volcanic rocks show scattered directions and sedimentary rocks show only load foliation parallel to the bedding planes. The following evidences read to the conclusion that both magnetic fabrics in the granitic rocks have been obtained by a tectonic stress before full solidification of the magma: (i) A fully hardened granitic rocks would get hardly any fabric, (ii) Difference of the magnetic fabric trends with those of the geological structures in the granitic rocks themselves formed by brittle deformation after solidification (e.g. patterns of small-faults and joints), (iii) Kinking of biotite and undulose extinction in quartz observed under the polarizing microscope, (iv) Discordance of magnetic fabrics in the granitic rocks with those in the surrounding rocks. The NE-SW trend of the magnetic foliations suggests a NW-SE compressive stress of nearly contemporaneous with the emplacement of the granitic rocks. The compression should have caused a sinistral strike-slip movement of the Yangsan Fault considering the trend of the latter. As the age of the granitic rocks in the study area is reported to be around $60\sim70$ Ma, it is concluded that the Yangsan fault did the sinistral strike-slip movement during this time (L. Cretaceous Maastrichtian - Cenozoic Paleocene).

• Journal of Periodontal and Implant Science
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• v.47 no.6
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• pp.372-380
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• 2017

Purpose: The aim of this prospective pilot study was to compare alveolar ridge preservation (ARP) procedures with open-healing approach using a single-layer and a double-layer coverage with collagen membranes using radiographic and clinical analyses. Methods: Eleven molars from 9 healthy patients requiring extraction of the maxillary or mandibular posterior teeth were included and allocated into 2 groups. After tooth extraction, deproteinized bovine bone mineral mixed with 10% collagen was grafted into the socket and covered either with a double-layer of resorbable non-cross-linked collagen membranes (DL group, n=6) or with a single-layer (SL group, n=5). Primary closure was not obtained. Cone-beam computed tomography images were taken immediately after the ARP procedure and after a healing period of 4 months before implant placement. Radiographic measurements were made of the width and height changes of the alveolar ridge. Results: All sites healed without any complications, and dental implants were placed at all operated sites with acceptable initial stability. The measurements showed that the reductions in width at the level 1 mm apical from the alveolar crest (including the bone graft) were $-1.7{\pm}0.5mm$ in the SL group and $-1.8{\pm}0.4mm$ in the DL group, and the horizontal changes in the other areas were also similar in the DL and SL groups. The reductions in height were also comparable between groups. Conclusions: Within the limitations of this study, single-layer and double-layer coverage with collagen membranes after ARP failed to show substantial differences in the preservation of horizontal or vertical dimensions or in clinical healing. Thus, both approaches seem to be suitable for open-healing ridge preservation procedures.

• Journal of the Mineralogical Society of Korea
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• v.5 no.1
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• pp.22-31
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• 1992

The Sancheong kaolin was fractionated into 9 size fractions by wet sieving, sedimentation, and centrifugation. The systematic X-ray diffraction combined with electron microscopy shows that the clay mineral composition of each size fraction is related to the original fabric of kaolin. Minerals such as halloysite (10${\AA}$), kaolinite, illite, and goethite which were formed by procipitation from solution are generally concentrated in the finer fractions, whereas verniculite which was formed by pseudomorphic transformation from other primary minerals are concentrated in the coarser factions. Kaolinits of various types which were formed by precipitation or transformation show a wide size range but they are generally concentrated in the coarser fractions. Halloysite or halloysite-kaolinite clusters in coarse fractions are the fragmentation products of the walls of original boxwork clusters in coarse fractions are the fragmentation products of the walls of original boxwork kaolin which escaped the complete dispersion even through the grinding, ultrasonic agitation, and chemical treatment. Separation of fully hydrated halloysite and kaolinite was possible by systematic wet size fractionation. The coarse-grained minerals such as vermiculite and kaolinite are usually removed during the preparation of clay fraction smaller than 2${\mu}m$, whereas the fine-grained minerals such as illite and goethite are overlooked in X-ray diffraction of the bulk samples because of their minor contents. The systematic wet size fractionation is needed for understanding of the exact mineralogy of kaolin of weathering origin.

• Economic and Environmental Geology
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• v.26 no.2
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• pp.145-154
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• 1993

Gold-silver deposits in the Kwangyang-Seungju area are emplaced along $N4^{\circ}{\sim}10^{\circ}W$ to $N40^{\circ}{\sim}60^{\circ}W$ trending fissures and fault in Pre-cambrian Jirisan gneiss complex or Cretaceous diorite. Mineral constituents of the ore from above deposits are composed mainly of pyrite, arsenopyrite, pyrrhotite, magnetite, sphalerite, chalcopyrite, galena and minor amount of electrum, tetrahedrite, miargyrite, stannite, covellite and goethite. The gangue minerals are predominantly quartz and calcite. Gold minerals consist mostly of electrum with a 56.19~79.24 wt% Au and closely associated with pyrite, chalcopyrite, miargyrite and galena. K-Ar analysis of the altered sericite from the Beonjeong mine yielded a date of $94.2{\pm}2.4\;Ma$ (Lee, 1992). This indicates a likely genetic tie between ore mineralization and intrusion of the middle Cretaceous diorite ($108{\pm}4\;Ma$). The ${\delta}^{34}S$ values ranged from +1.0 to 8.3‰ with an average of +4.4‰ suggest that the sulfur in the sulfides may be magmatic origin. The temperatures of mineralization by the sulfur isotopic composition with coexisting pyrite-galena and pyrite-chalcopyrite from Beonjeong and Jeungheung mines were $343^{\circ}C$ and $375^{\circ}C$ respectively. This temperature is in reasonable agreement with the homogenization temperature of primary fluid inclusion quartz ($330^{\circ}C$ to $390^{\circ}C$; Park.1989). Four samples of quartz from ore veins have ${\delta}^{18}O$ values of +6.9~+10.6‰ (mean=8.9‰) and three whole rock samples have ${\delta}^{18}O$ values of +7.4~+10.2‰ with an average of 7.4‰. These values are similar with those of the Cretaceous Bulgugsa granite in South Korea (mean=8.3‰; Kim et al. 1991). The calculated ${\delta}^{18}O_{water}$ in the ore-forming fluid using fractionation factors of Bulgugsa et al. (1973) range from -1.3 to -2.3‰. These values suggest that the fluid was dominated by progressive meteoric water inundation through mineralization.

• Journal of the East Asian Society of Dietary Life
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• v.18 no.3
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• pp.391-396
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• 2008

This study was carried out to help restore and spread broaden the consumption of Chungtaejeon, a our traditional tea, Chungtaejeon in Korea, and as well as to gather the basic data on Chutaejeon tea. We have also compared the various ingredients components and physiological activities of Chungtaejeon tea extracts with that of green tea extracts. According to the results, the total phenol contents in of the Chungtaejeon and green tea extracts were 90.56 and 98.70 mg/100 mL, respectively, and their tannin contents levels in Chungtaejeon and green tea extracts were 214.14 mg/100 mL and 259.60 mg/100 mL, respectively, showing a difference in content. The catechin contents of the Chetaejeon and green tea extracts were in the order of EGC($15.80{\sim}16.50\;mg/100mL$), EGCG($10.40{\sim}10.60\;mg/100 mL$), and ECG($9.55{\sim}9.88\;mg/100 mL$), however, with the exception of EC(7.86 mg/100 mL) in the green tea extracts, there were not significant differences between that in them Chetaejeon and green tea extracts. Quercetin was the main flavonoid ingredient component in those both the Chungtaejeon and green tea extracts was quercetin, at levels of 0.08 mg/100 mL and 0.06 mg/100 mL and its contents in Chungtaejeon and green tea extracts were 0.08 mg/100 mL and 0.06 mg/100 mL, respectively. The primary amino acid in both tea extracts was theanine main amino acid at levels of, theanine contents were most increased in 8.02 mg/100mL and 10.80 mg/100 mL, respectively, Chungtaejeon tea extracts by 8.02 mg/100 mL and green tea extracts by 10.80 mg/100 mL. And the arginine contents of the Chungtaejeon and green tea extracts in Chungtaejeon and green tea extracts were 1.78 mg/100 mL and 1.86 mg/100 mL, respectively. In terms of mineral composition, potassium content was highest contents in the Chungtaejeon and green tea extracts by 19.80 and 18.04 mg/100 mL, respectively. Finally, the Chungtaejeon tea extracts offered the greatest anti-oxidation and ACE inhibition activities were most increased in the Chungtaejeon tea extracts, and the green tea extracts showed the highest level of nitrite radical scavenging activity at 90% was extremely much increased in the green tea extracts by 90%.