The effect of relative humidity (RH) on the composition and concentrations of gas-phase products and secondary organic aerosol (SOA) generated from the photooxidation of isoprene under high-NOx conditions was investigated. Experiments were performed with hydrogen peroxide as the OH precursor and in the absence of seed aerosol. The relative yields of most gas-phase products were the same regardless of initial water vapor concentration with exception of hydroxyacetone and glycolaldehyde, which were considerably affected by RH. A significant change was observed in the SOA composition, with many unique condensed-phase products formed under humid (90% RH) vs. dry (< 2% RH) conditions, without any detectable effect on the rate and extent of the SOA mass growth. There is a 40% reduction in the number and relative abundance of distinct particle-phase nitrogen-containing organic compounds (NOC) detected by high resolution mass spectrometry. The suppression of condensation reactions, which produce water as a product, is the most important chemical effect of the increased RH. For example, the total signal from oligomeric esters of 2-methylglyceric acid was reduced by about 60% under humid conditions and the maximum oligomer chain lengths were reduced by 7-11 carbons. Oligomers formed by addition mechanisms, without direct involvement of water, also decreased at elevated RH but to a much smaller extent. The observed reduction in the extent of condensation-type oligomerization at high RH may have substantial impact on the phase characteristics and hygroscopicity of the isoprene aerosol. The reduction in the amount of organic nitrates in the particle phase has implications for understanding the budget of NOC compounds.
机构:
CALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Paulot, F.
;
Crounse, J. D.
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机构:
CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Crounse, J. D.
;
Kjaergaard, H. G.
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机构:
Univ Otago, Dept Chem, Dunedin, New ZealandCALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Kjaergaard, H. G.
;
Kroll, J. H.
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机构:
CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA
Aerodyne Res Inc, Ctr Aerosol & Cloud Chem, Billerica, MA 01821 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Kroll, J. H.
;
Seinfeld, J. H.
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机构:
CALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Seinfeld, J. H.
;
Wennberg, P. O.
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机构:
CALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
CALTECH, Div Geophys & Planetary Sci, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
机构:
CALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Paulot, F.
;
Crounse, J. D.
论文数: 0引用数: 0
h-index: 0
机构:
CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Crounse, J. D.
;
Kjaergaard, H. G.
论文数: 0引用数: 0
h-index: 0
机构:
Univ Otago, Dept Chem, Dunedin, New ZealandCALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Kjaergaard, H. G.
;
Kroll, J. H.
论文数: 0引用数: 0
h-index: 0
机构:
CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA
Aerodyne Res Inc, Ctr Aerosol & Cloud Chem, Billerica, MA 01821 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Kroll, J. H.
;
Seinfeld, J. H.
论文数: 0引用数: 0
h-index: 0
机构:
CALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
Seinfeld, J. H.
;
Wennberg, P. O.
论文数: 0引用数: 0
h-index: 0
机构:
CALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA
CALTECH, Div Geophys & Planetary Sci, Pasadena, CA 91125 USACALTECH, Dept Environm Sci & Engn, Pasadena, CA 91125 USA