# Presentation: 187997

## Laboratory Studies of Processing of Carbonaceous Aerosols by 

- Air Pollution Research Center and  Department of Environmental Sciences

- Laboratory Studies of Processing of Carbonaceous Aerosols by
- Atmospheric Oxidants

- DOE/Atmospheric Science Program

## Investigate reactions of OH and NO3 radicals and O3 with organic particles characteristic of primary emissions to determine the following:

- > Rates
- > Products
- > Mechanisms
- > Effects of oxidation on hygroscopic properties

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- Objectives

## Aerosol Oxidation Reactions 

- Aerosol Oxidation Reactions

- Oxidants

- Products:
- -C=O, -CHOH,
- -CHOOH, -C(O)OH, -CHONO2

- Particle properties:
- Composition, phase, structure, size

- Oxidants:
- OH, O3, NO3

## Experimental Approach: Reaction Conditions

- Environmental chambers:
-   > ~7000 L Teflon chambers filled with clean air
-   > RH ~0.5 to ~50%
-   > blacklights for photolysis
- Organic aerosol particles: next figure
- Oxidants:
-   > OH radicals formed by CH3ONO blacklight photolysis
-   > O3 obtained from O3 generator
-   > NO3 radicals formed by N2O5 decomposition
-   > Cl radicals formed by Cl2 blacklight photolysis
- Volatile organic compound: appropriate compound for
-   quantifying oxidant in relative rate measurements

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## Experimental Approach: Particle Properties

- Composition: model compounds and combustion tracers
-     > pure or multicomponent
-     >  acyclic, cyclic; saturated, unsaturated; hydrocarbons,
-         oxygenated compounds with carbonyl, hydroxyl,
-         carboxyl, peroxyl, and nitrooxy groups
-     >  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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## Experimental Approach: Gas and Particle Analysis

- Particle size distributions: scanning mobility particle sizer
- Gas composition:
-   > O3, NOx monitors
-   > Carbonyls collected on Tenax or SPME fibers with on-
-      fiber derivatization and GC-MS analysis
- Particle composition and phases:
-   > Thermal desorption particle beam mass spectrometer
-      (real-time and temperature-programmed desorption)
-   > Filter or impactor sampling with derivatization and GC-
-      MS analysis
- Particle hygroscopicity: tandem differential mobility analyzer

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## Experimental Apparatus

## Products/Deliverables 

- > Rate constants for reactions of OH, NO3, O3 with various
-    particulate organic compounds (oxidative lifetimes)
- > Gas-phase and particle-phase reaction products and
-    reaction mechanism (isomerization, decomposition, etc.)
- > Effects of particle phase(s) on reaction kinetics and
-    products
- > Effects of oxidation reactions on molecular tracers
- > Effects of oxidation on hygroscopic growth factors/CCN
-    activity
- > Source of *m/z* 44 for AMS: POA vs. SOA

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## Requirements 

- > TexAQS 2006 and MCMA 2006
- > Aerosol organic composition (speciation, functional
-    groups, saturated and unsaturated compounds) for
-    primary particle emissions and ambient particles
- > Important source tracers

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