2004 Fiscal Year Final Research Report Summary
Chemical composition and hygroscopic properties of secondary organic aerosol : Their impact on the atmospheric environment
| Project/Area Number |
14204055
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
地球化学
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| Research Institution | Hokkaido University |
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Principal Investigator |
KAWAMURA Kimitaka Hokkaido University, Inst.Low Tem.Science, Professor, 低温科学研究所, 教授 (70201449)
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| Co-Investigator(Kenkyū-buntansha) |
MOCHIDA Michihiro Hokkaido University, Inst.Low Tem.Science, Instructor, 低温科学研究所, 助手 (10333642)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Secondary organic aerosols / Hygroscopic property of aerosols / Particle generator / Aerosol size distribution / Aitken particle / Hygroscopicity Tandem Differential Mobility Analyzer / Atmospheric observation in Tokyo / Stable carbon isotopic composition |
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| Research Abstract |
Tandem differential mobility analyzer (TDMA) system was assembled and modified to hygroscopic TDMA, by which hygroscopic properties of atmospheric particles were measured. This system was first used to determine the growth factors of cellulose pyrolysis products such as levoglucosan and D-glucose, and lignin-pyrolysis products such as 4-hydroxybenzoic acid, syringic acid. We found that levoglucosan and glucose are very hygroscopic compounds and thus can act as cloud condensation nuclei in the atmosphere.
TDMA and H-TDMA system has been used for size distributions and hygroscopic properties of aerosols during the IMPACT campaign conducted in urban Tokyo together with many instruments including High-volume air samples, PM1 impactor, annular denuder sampling system, etc. The samples were analyzed for low molecular weight dicarboxylic acids, ketocarboxylic acids and dicarborryls, as well as semi-volatile aldehydes, water-soluble organic carbon (WSOC), elemental carbon (EC) and organic carbo
… More
n (OC).
1.Concentrations of oxalic acid and other water-soluble dicarboxylic acids as well as related compounds increased from early morning to noon and then decreased toward to the evening. The amplitudes of the peaks for individual species were 3-15 times relative lo nighttime concentrations, suggesting photochemical production of secondary organic aerosols.
2.OC and WSOC also showed diurnal variation with maxima around noontime. The relative abundances of diacids over OC and WSOC also showed maxima in daytime. This suggests that polar organic compounds are selectively produced in urban atmosphere during photochemical episode.
3.Hygroscopic properties of aerosols were measured in Tokyo at particle size mode of 100 nm and 200 nm. Hygroscopic growth factors for fine particles were found to increase from the morning to noontime and further increase toward the evening. This finding is consistent with the increased concentrations of water-soluble dicarboxylic acids and WSOC in daytime. We also found that this hygroscopic growth is more significant for 200 nm size particles than that for 100 nm particles. These physical properties of particles may be associated with the chemical composition of the aerosols. Photochemical production of water-soluble organic aerosols seemed to be followed by the photochemical evolution of organic aerosols, namely, photochemically aged aerosols may be more enriched in larger particles. Less
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