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RISS 인기검색어
- 검색키워드
- 저자 : Oohashi, Kiyokazu (검색결과 4 건)
- 무료
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Carbon-forming reactions under a reducing atmosphere during seismic fault slip
Oohashi, Kiyokazu,Han, Raehee,Hirose, Takehiro,Shimamoto, Toshihiko,Omura, Kentaro,Matsuda, Tatsuo Geological Society of America 2014 Geology Vol.42 No.9
<P>Graphite is a well-known solid lubricant and can be as important as clay minerals in reducing the frictional strength of faults. Some natural fault zones contain carbonaceous material (CM) even where host rocks do not contain it, and seismic fault motion can promote the graphitization of low-grade CM. Thus, the origin of CM in fault zones is an important issue in fault mechanics. Previous high-velocity friction experiments have revealed various chemical reactions in fault zones during seismic fault motion, but most experiments have been conducted in an atmosphere under oxic conditions. Here we report experimental results on Carrara marble (free of CM), conducted under N<SUB>2</SUB> or H<SUB>2</SUB> atmospheres at a slip rate of 1.3 m/s and normal stresses of 2.0–3.1 MPa. A small amount of blackish material formed in generated gouge only under reducing conditions with the H<SUB>2</SUB> atmosphere, and Raman spectroscopic analysis revealed the presence of CM (amorphous carbon) in the material. The CM is attributable to (1) the generation and pyrolitic dissociation of CH<SUB>4</SUB>, and/or (2) a reduction reaction of emitted CO<SUB>2</SUB> due to calcite decomposition. We confirmed the formation of CH<SUB>4</SUB> using gas chromatography. The CM produced in experiments resembles CM in the Nojima fault (Japan) gouge in terms of Raman spectra. The granitic host rock of this fault is free of CM, and calcite is precipitated close to the CM; therefore, the CM probably formed through processes similar to those simulated in our experiments. Future research should investigate the amount and origin of CM in natural fault zones.</P>
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Seasonal Variation of PM2.5 Components Observed in an Industrial Area of Chiba Prefecture, Japan
Yujiro Ichikawa,Suekazu Naito,Katsumi Ishii,Hideaki Oohashi 한국대기환경학회 2015 Asian Journal of Atmospheric Environment (AJAE) Vol.9 No.1
In order to survey the seasonal variation of the chemicalcomposition of particulate matter of 2.5 μm orless (PM2.5), PM2.5 was sampled from 8 February 2013to 31 March 2014 in an industrial area of Chiba Prefecture,Japan. Chemical measurements of the sampleincluded: ionic components (Na+, NH4+, Ca2+,Mg2+, K+, Cl-, NO3- and SO42-), carbonaceous components- organic carbon (OC) and elemental carbon(EC), and water-soluble organic carbon (WSOC). Also, secondary organic carbon (SOC) was measuredbased using the EC tracer method, and char-EC andsoot-EC were calculated from the analytical results. The data obtained were interpreted in terms of temporalvariation. Of the overall mean value of PM2.5mass concentration obtained during the study period,ionic components, OC and EC accounted for 45.3%,19.7%, and 8.0%, respectively. NO3- showed a uniqueseasonal distribution pattern due to a dependenceon temperature and absolute humidity. It wasestimated that an approximate temperature of 14℃,and absolute humidity of 7 g/m3 were critical for thereversible reaction of NH4NO3 (p) ⇋ NH3 (g)+HNO3(g). The amount of OC and EC contributing to themonthly PM2.5 mass concentration was higher in autumnand winter compared to spring and summer. This result could be attributed to the impact of burningbiomass, since WSOC and the ratio of char-EC/soot-EC showed a similar pattern during the correspondingperiod. From the comparison of monthlyWSOC/OC values, a maximum ratio of 83% was obtainedin August (summer). The WSOC and estimatedSOC levels derived from the EC tracer methodcorrelated (R=0.77) in summer. The high occurrenceof WSOC during summer was mainly due to the formationof SOC by photochemical reactions. Throughlong-term observation of PM2.5 chemical components,we established that the degree to which the abovementionedfactors influence PM2.5 composition, fluctuateswith seasonal changes.
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