전창표 Chang Pyo Jun , 김창환 Chang Hwan Kim , 이성주 Seong Joo Lee

DOI: Vol.26(No.2) 65-80, 2013

Sediment transport mechanism and distribution of organic sediments are elucidated by the study of particle size, mineralogy, organic matters and microfossils of the surface samples collected from seafloor adjacent Dokdo island. Shallow marine sediments are dominated by coarse- grained sediments including gravel and sand, and their sedimentation has mainly been controlled by traction. While the samples collected from oceanic zone are characterized by high contents of fine- grained sediments such as silt and mud in bulk sediments, and the changes of mineral compositions including clay minerals and feldspar, and the fine sediments have been deposited mainly by suspension. The change of organic sedimentary communities is detected between neritic and oceanic zone. Although marine organic matter is predominant in neritic zone terrestrial organic matter is monopolized according to increasing water depth. This trend is associated with grain size of sediments. The results also suggest that high pollen concentrations in whole organic matters may played an important role in excessive organic carbon in sediment.

독도, 퇴적 기작, 유기 탄소, 퇴적물, 화분, Dokdo, sediment transport mechanism, organic carbon, palynomorph, pollen

박수오 Soo Oh Park , 김영재 Young Jae Kim , 이영재 Young Jae Lee

DOI: Vol.26(No.2) 81-86, 2013

A series of birnessite was synthesized at 25, 40, 60, and 80℃, respectively. Intensities of XRD and the ratio of signal to noise of the peaks for samples increases with increasing temperature up to 60℃, whereas the intensity and ratio for a sample synthesized at 80℃ decrease, showing that crystal-linity of the birnessite synthesized at 60℃ is better than that of the synthesized at 80℃.However, BET surface areas for these two samples show that the surface area increases 39.4 to 89.7m²/g with increasing synthesizing temperature from 60 up to 80℃,indicating that a small surface area is shown in a well-crystallized birnessite rather than that of a poorly crystallized birnessite. SEM images show that morphologies for samples, are seriously influenced by temperature. The morphology of the synthe-sized at 25 shows a round-shape, while a plate-like morphology is shown in the synthesized birnessite at 80℃. In addition, aporous layered structure is also shown in the synthesized birnessite at 80℃.These results suggest tha physicochemical properties of the synthesized birnessite are sensitively affected by mechanical changes of parameters such as temperature during the synthesization.

버네사이트, 망간산화물, 결정도, BET 비표면적, 다공성 층상구조, birnessite, manganese oxide, crystallinity, BET surface area, porous layered structure

황진연 Jin Yeon Hwang , 최진범 Jin Beom Choi , 정기영 Gi Young Jeong , 오지호 Ji Ho Oh , 최영훈 Young Hun Choi , 이진현 Jin Hyun Lee

DOI: Vol.26(No.2) 87-99, 2013

The occurrence, mineralogical characteristics, and origin of the dolomite ores were inve-stigated from major dolomite mines in South Korea. Mineralogical and textural properties of the ores and associated minerals were analyzed using X-ray diffraction, thin section petrography, and scanning electron microscopy. Dolomite ores were light to dark gray in color and mainly composed of dolomite in varying particle size with minor amounts of calcite, quartz and micas. Calcite, quartz, illite, feldspar, kaolin minerals, and chlorite occurred in local veins, dikes and alteration zones. Sepiolite and wolla-stonite occurred in the altered part of some mine. Asbestos minerals such as chrysotile and tremolite, however, were not identified in the present study. Reddish brown to yellow clay materials were mainly compesed of illite, occasionally associated with kaolin minerals and smectite. These clay minerals might be a product of the local hydrothermal alteration related to the dyke intrusion and subsequent weathering. As well indicated in the previous studies, mineral composition, texture, and occurrence of the dolostone beds suggest their formation through the diagenesis of carbonate sediments deposited in the shallow sea during the Precambrian to Paleozoic period.

백운석, 백운암, 산출상태, 성인, 석면, dolomite, dolostone, occurrence, genesis, asbestos

이승열 Seung Yeol Lee , 강정천 Jung Chun Kang , 박민지 Min Ji Park , 양경희 Kyoung Hee Yang , 정훈영 Hoon Young Jeong

DOI: Vol.26(No.2) 101-110, 2013

Due to the large specifie surface area and great reactivity toward environmental contami-nants sanocrystalline mackinawite, FeS, has been widely applied for the remediation of contaminated groundwater and soil. Furthermore, nanocrystalline FeS is rather thermodynamically stable against anoxic corrosion, and its reactivity can be regeneraled continuously by the activity of sulfate-readucing bacteria, However, nanocrystalline mackinawite is prone to either spread out along the groundwater flow or cause pore clogging in aquifers by particle aggregation. Accordingly. This mineral should be modified for the application of permeable reactive barriers, PRBs, In this study, coating methods were investigated by which mackinawite nanoparticles were deposited on the surface of alumina or activated alumina. The amount of FeS coating was found to significantly vary with PH with the highest amount occurring at PH∼6.9 for both minerals. At this PH, the surfaces of mackinawite and alumina, or activated alumina, were oppositely charged, with the resultant electrostatic attraction making the coating highly effective. At this PH, the coating amounts by alumina and activated alumina were 0.038and 0.114 mmol.FeS/g respectively. Under anoxic conditions, arsenite sorption experiments were conducted with uncoated alumina uncoated actovated alumina, and both minerals coated with FeS at the optimal PH for comparison of their reactivity. Uncoated activated alumina showed the higher arsenite removal compared to uncoated alumina. Notably, the arsenite sorption capacity of activated alumina was little changed by the coating with FeS. This might be attributed to the abundance of highly reactive hydroxyl functional groups, AIOH, on the surface of activated alumina, making the arsenite sorption by the coated FeS unnoticeable. In contrast, the arsenite sorption capacity of alumina was found to increase substantially by the FeS coating This was due to the consumption of the surface hydroxyl functional groups on the alumina surface and the subsequent occurrence of As, III, sorption by the coated FeS. Alumina on the surface area basis, has about 8times higher FeS coating amount and higher As sorption capacity than silica. This study indicates that alumina is a better candidate than silica for the coating of nanocrystalline mackinawite.

매킨나와이트, 알루미나, 코팅, 투과반응벽, 아비산염, mackinawite, alumina, permeable reactive barrier, arsenite

정기영 Gi Young Jeong , 최진범 Jin Beom Choi

DOI: Vol.26(No.2) 111-118, 2013

Diagenetic black chert nodules occur in the Paleozoic dolostone in Susan, Jecheon,Korea, They reacted with dolomite to form alteration rim around the nodules during the contact metamorphism probably related to the intrusion of biotite granite. In the earlier stage of alteration, talc and calcite replaced both the chert and dolomite, which were subsequently replaced by tremolite.Significant mass of tremolite occurs along the horizon enriched with chert nodules. Scanning electron microscopy and optical microscopy of the tremolite specimens revealed the elongated morphology of diverse as pect ratios coexisting in several mm scale. Non-asbestiform tremolite columns were also common as well as asbestiform fibrous bundles. Quantitative estimation of asbestos should be more cautious for naturally occurring materials because all the tremolite particles in the outcrop are not asbestiform. The occurrence of asbestiform tremolite in the susan area indicates that a combination of chert-bearing dolostone, heat source, and aqueous fluids is one of the geological environments for the formation of asbestiform tremolite.

백운석, 처트, 투각섬석, 석면, 전자현미경, 형태, Dolomite, chert, tremolite, asbestos, electos, electron microscopy, morphology

권기덕 Ki Deok Kwon , Louise J. Criscenti

DOI: Vol.26(No.2) 119-127, 2013

Borosilicate glass dissolution is an important chemical process that impacts the glass durability as nuclear waste form that may be used for high-level radioactive waste disposal. Experi-ments reported that the glass dissolution rates are strongly dependent on the bulk composition. Because some relationship exists between glass composition and molecular-structure distribution, eg, non-brid-ging oxygen content of SiO4 unit and averaged coordination number of B), the composition-dependent dissolution rates are attributed to the bulk structural changes corresponding to the compesitional variation, We examined Na borosilicate glass structures by performing classical molecular dynamics, MD, simulations for four different chemical compositions, xNa2O.B2O3.ySiO2, Our MD simulations de-monstrate that glass surfaces have significantly different chemical compositions and structures from the bulk glasses. Because glass surfaces forming an interface with solution are most likely the first dissolution-reaction occurring areas, the current MD result simply that composition-dependent glass dissolution behaviors should be understood by surface structural change upon the chemical composition change.

붕규산염 유리, 방사성 폐기물 처리, 분자 동역학 시뮬레이션, 유리 용해도, 유리 표면구조, borosilicate glass, nuclear waste management, molecular dynamics simulations, glass surface structure, composition-dependent glass dissolution

현성필 Sung Pil Hyun , 문희선 Hee Sun Moon , 윤필선 Pil Sun Yoon , 김보아 Bo A Kim , 하규철 Kyoo Chui Ha

DOI: Vol.26(No.2) 129-138, 2013

River bank filtration has been considered as a promising alternative water management scheme, in which groundwater is extracted from an aquifer near a river after infiltration of the river water in to the aquifer, thereby improving and maintaining the quality of water recovered. Iron, Fe, associated with sediment in contact with groundwater and infiltrating surface water is an important factor in determining the quality of water recovered from the pumping wells in river bank filtration. This study reports the results of Fe speciation in the aquifer sediment samples collected from different depths at the river bank filtration site in Changwon, studied using four different chemical extraction methods, namely, ferrozine, oxalate, HCI, and DCB methods. Overall, the results show that Fe, II, as well as the total Fe content decreases with depth down to ∼20 m and then increases further below. This trend is consistent with the redox characteristics suggested by visual observation. The silt/clay size fraction, 0<62.5㎛ has up to 2∼10times more Fe compared with the sand size fraction, 62.5㎛<0<2mm, depending on the extraction method. Of the four extraction methods, DCB solution. extracted the most Fe from the sediment samples. The amounts of Fe extracted by the different extraction methods can be a good indicator of the redox conditions along the depth of the aquifer.

강변 여과, 퇴적물, 철 광물, 화학적 추출, 지하수, river bank filtration, sediment, iron mineralogy, chemical extraction, groundwater