Second organic aerosol formation from the ozonolysis of -pinene in thepresence of dry submicron ammonium sulfate aerosol
ZHAO Zhe , HAO Jiming , LI Junhua , WU Shan
DOI:
Received December 13, 2007,Revised February 27, 2008, Accepted , Available online
Volume 20,2008,Pages 1183-1188
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An indoor chamber facility is described for investigation of atmospheric aerosol chemistry. Two sets of -pinene ozonolysis
experiments were conducted in the presence of dry ammonium sulfate seed particle: ozone limited experiments and -pinene limited
experiments. The concentration of gas phase and particle phase species was monitored continuously by on-line instruments and
recorded automatically by data sampling system. The evolution of size distribution was measured by a scanning mobility particle
sizer (SMPS), and -pinene consumed was measured using GC-FID. Secondary organic aerosol (SOA) produced for seed-free system
is 100% organic in content, resulting from a su cient supersaturation of low volatility organics to produce homogeneous nucleation
followed by condensation to the aerosol. Secondary organic aerosol produced in seeded system is a mixture of organic and inorganic
constituents, initially forms via condensation onto the inorganic particles, and subsequent growth occurs via absorption into the organic
surface coating the inorganic core. Although the formation process and the size distribution for seed-free system and seeded system is
di erent, the ultimate mass of SOA formed is equal, and SOA yield for the two system located in the same regression line when using
one-product model, suggesting that the presence of dry ammonium sulfate seed has no measurable e ect on the total aerosol yield, and
the dry seed particle acts solely as a site upon which organic deposition occurs.
