Title: Paul Ziemann, Roger Atkinson, Janet Arey
1Laboratory Studies of Processing of Carbonaceous
Aerosols by Atmospheric Oxidants
Paul Ziemann, Roger Atkinson, Janet Arey Air
Pollution Research Center and Department of
Environmental Sciences
DOE/Atmospheric Science Program
2Objectives
Investigate reactions of OH and NO3 radicals and
O3 with organic particles characteristic of
primary emissions to determine the following gt
Rates gt Products gt Mechanisms gt Effects of
oxidation on hygroscopic properties
2
3Aerosol Oxidation Reactions
Products -CO, -CHOH, -CHOOH, -C(O)OH, -CHONO2
Oxidants
Particle properties Composition, phase,
structure, size
Oxidants OH, O3, NO3
3
4Experimental Approach Reaction Conditions
Environmental chambers gt 7000 L Teflon
chambers filled with clean air gt RH 0.5 to
50 gt blacklights for photolysis Organic
aerosol particles next figure Oxidants gt OH
radicals formed by CH3ONO blacklight photolysis
gt O3 obtained from O3 generator gt NO3 radicals
formed by N2O5 decomposition gt Cl radicals
formed by Cl2 blacklight photolysis Volatile
organic compound appropriate compound for
quantifying oxidant in relative rate measurements
4
5Experimental Approach Particle Properties
Composition model compounds and combustion
tracers gt pure or multicomponent gt
acyclic, cyclic saturated, unsaturated
hydrocarbons, oxygenated compounds with
carbonyl, hydroxyl, carboxyl, peroxyl,
and nitrooxy groups gt octacosane,
cholesterol, cholestane, levoglucosan,
stearic acid, oleic acid, dioctyl sebacate,
adipic acid () Phase liquid, solid, multiphase
(including coated) Size 0.1-0.5 µm
diameter Generation evaporation-condensation,
atomization, or gas-phase reactions
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6Experimental Approach Gas and Particle Analysis
Particle size distributions scanning mobility
particle sizer Gas composition gt O3, NOx
monitors gt Carbonyls collected on Tenax or SPME
fibers with on- fiber derivatization and
GC-MS analysis Particle composition and phases
gt Thermal desorption particle beam mass
spectrometer (real-time and
temperature-programmed desorption) gt Filter or
impactor sampling with derivatization and GC-
MS analysis Particle hygroscopicity tandem
differential mobility analyzer
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7 Experimental Apparatus
8Products/Deliverables
gt Rate constants for reactions of OH, NO3, O3
with various particulate organic compounds
(oxidative lifetimes) gt Gas-phase and
particle-phase reaction products and reaction
mechanism (isomerization, decomposition, etc.) gt
Effects of particle phase(s) on reaction kinetics
and products gt Effects of oxidation reactions
on molecular tracers gt Effects of oxidation on
hygroscopic growth factors/CCN activity gt
Source of m/z 44 for AMS POA vs. SOA
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9Requirements
gt TexAQS 2006 and MCMA 2006 gt Aerosol organic
composition (speciation, functional groups,
saturated and unsaturated compounds) for
primary particle emissions and ambient
particles gt Important source tracers
8