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Shuichi Hasegawa 한국대기환경학회 2022 Asian Journal of Atmospheric Environment (AJAE) Vol.16 No.2
Organic aerosols (OA) in the atmosphere have complex emission sources and formation processes that must be determined to understand the OA composition and behavior. The thermal optical method is generally used to analyze organic carbon (OC) in OAs, and the resulting thermally fractionated OC profiles can be considered to be a synthesis of the organic materials contained in OAs. In this study, carbon-fraction profiles of 43 organic materials were determined and categorized into five types on the basis of their profile patterns. Then a chemical mass balance (CMB) analysis using the five types and the measured carbon-fraction profiles of particulate OC from various emission sources was conducted. The major sources thus determined were generally reasonable considering the known chemical properties of emission source particles. In addition, the seasonal organic matter composition in ambient particulate OC measured at a suburban site of Tokyo was experimentally estimated by a CMB analysis using the five types, and the potential of making good use of thermally fractionated OC data to understand the characteristics of OAs was discussed.
Spatiotemporal Variations of Fine Particulate Organic and Elemental Carbons in Greater Tokyo
Hiroshi Hayami,Shinji Saito,Shuichi Hasegawa 한국대기환경학회 2019 Asian Journal of Atmospheric Environment (AJAE) Vol.13 No.3
Hourly concentrations of fine particulate OC and EC are monitored for more than one year by optical monitors at three sites in and out of Tokyo, Japan. Distances between the sites are 20 to 50 km. SOC concentrations are estimated from the OC and EC concentrations by an EC tracer method. Site A in an industrial site shows higher EC concentrations than site B in a residential area, but differences between the sites are much reduced for OC. Site C in a rural area, where measurements are available in colder months, shows pronounced seasonal variations with high peaks in October and December and characteristic diurnal variations in OC with the highest in the evening in October, due probably to open field burning. Photochemical formation of SOC is suggested but does not rise up so much OC concentrations in summer, which are quite lower than other seasons. A comparison between relative concentrations of EC among the sites and local emissions amounts indicates missing or considerable underestimation of EC emissions near the rural site C. Time lag correlations suggest transport of OC produced by open field burning around site C to site A. These findings would be useful for improving model performances in OC/EC predictions.
( Ranjan Kumar Dahal ),( Shuichi Hasegawa ),( Manita Timilsina ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2
The Himalaya is the highest mountain range of the globe which has been formed by the collision of India and Eurasia plates. The Nepal Himalaya is well defined in various geological zones from the beginning, but the engineering geological significance of each geological zone is not well understood. As a result, engineering geological issues in the Nepal Himalaya during infrastructure development are prime concerns for planners. Convergence and shear zones in tunnels of hydropower projects, cut slopes failures in highways and canal embankment failures are recent hot news in local newspapers. Likewise, various thrust systems in the Nepal Himalaya are always considered as critical zones for infrastructure construction and many projects are abandoned only due to the presence of Main Central Thrust (MCT), or Main Boundary Thrust (MBT) or Main Frontal Thrust (MFT) in the project site. However, on the other hand, it is confirmed that movements in MCT and MBT were ceased nearly 6 and 1 Ma ago respectively. Movement frequency along MFT is also believed to be more than few hundred years and seismic activities along MFT are also not the same in whole Nepal. Similarly, the largescale landslide on the Midland and Lesser Himalayan regions has produced crushed rock mass and slope can be excavated easily without blasting which cannot be a common scenario in hard rock geology. This presentation will describe all these issues with field data and case histories.