1. The Role of Isoprene in Secondary Organic Aerosol Formation
Alfonso Castellanos
Evan Jones
Jenny Wei
Paul Fang
Summer Research Connection Seminar
Oak Crest Institute of Science
8/12/2011

2. Aerosols are Everywhere
What are aerosols?
Small, particulate matter suspended in the atmosphere.
Where do they come from?
Volcanic eruptions
Deserts
Biological activity
Saltwater bodies
Human activities (e.g. burning coal, oil, tropical forests)

3. Why are Aerosols Important?
Climate Change:
Scatter and absorb sunlight
Change the size of cloud particles
Components of acid rain
Health Effects:
Harmful to cardiopulmonary health
Chemical Effects:
Sites for chemical reactions

4. Secondary Organic Aerosols (SOAs)
Aerosols are produced from the atmospheric oxidation of volatile organic compounds (VOCs), which are emitted by plants, household products, and combustion of hydrocarbons.

5. Isoprene Contributes to SOA Formation
VOC emitted by plants
SOA precursor
Why study isoprene?
SOAs containing carbon skeletons similar to that of isoprene were found over forest regions
Contribution to SOA formation is of greater significance than previously assumed
Aside from methane, isoprene is the highest globally emitted VOC from biogenic sources
Mechanisms of isoprene photooxidation are not well understood
Isoprene

6. What reactants or catalysts are necessary for isoprene to form SOAs or SOA intermediates?
Secondary Organic Aerosols

7. ? Secondary Organic Aerosols Isoprene
Possible Reactants/Conditions to Test:
pH (4-7)
First generation isoprene oxidation products
Methyl Vinyl Ketone (MVK)
Methacrolein
Metal oxide
TiO2
ZnO
Dust (sieved)
Methacrolein
Methyl Vinyl Ketone

8. Reaction Procedure
1. Combine isoprene in aqueous buffer with metal/dust and/or first generation products (Methyl Vinyl Ketone/Methacrolein)
2. Place stir bar inside the vial
3. Expose vials to light source on a stir plate
4. Analyze reaction products using Gas Chromatography-Mass Spectrometry (GC-MS)

9. What would the results mean?
What results do we anticipate?
We anticipate a reaction will occur and we will detect new compounds in our reaction mixture that are not our starting materials
What would the results mean?
If the new compounds we discover are SOAs, this will indicate that isoprene can, in fact, form SOAs through photocatalysis on dust or metal oxide surfaces

10. GC-MS Sample Preparation
1. Mix EtOAc with our sample
2. Vortex samples to mix
3. Centrifuge for 10 minutes
4. Pipet 100 μL EtOAc layer into GC-MS vials
5. Run through the GC-MS instrument

11. How GC-MS Can Be Used to Identify Compounds
??? 1
Abundance 2
Time (t) 2 2
Gas Chromatography separates compounds
Mass Spectrometry fragments compounds
m/z
Abundance
m/z
Abundance
m/z
Abundance

12. Previous Isoprene Research at Oak Crest
Undergraduate Researchers: Howard Yan and Natalie De Vries
Howard & Natalie
Energy Source
UV Lamp
Time
3 hours
Rationale
Concentrated light source likely to cause reaction

13. Results From Previous Research+ +
Dust
Isoprene
Methacrolein
Methacrolein dimer + +
Dust
Isoprene
MVK
???
Howard Yan, Natalie De Vries

14. New Experiments To Simulate Atmospheric Conditions
Howard & Natalie
Our Group
Energy Source
UV Lamp
Sunlight
Time
3 hours
6-7 hours
Rationale
Concentrated light source likely to cause reaction
Simulate atmospheric conditions

15. hν ?? TiO2 +/- + Isoprene pH 6 MVK Isoprene + TiO2 + MVK
Retention time = 7.4 min

16. hν dust + + Isoprene pH 5 or 6 MVK MVK dimer
Isoprene pH 6 + MVK + dust
Isoprene pH 5 + MVK + dust
Retention time = 8.0 min

17. Preliminary Results Summary
Reactions with MVK and dust/TiO2 seem to form new products
=> Conduct control experiments:
are results repeatable?
does product formation require light?
does product formation require metal or dust?
As we started our second round of experiments, we discovered MVK dimer in our MVK solution

18. Control Experiments No light No metal catalyst Reaction A Isoprene +
MVK
Dust or TiO2
Reaction B Isoprene +
MVK
Dust or TiO2
Reaction C Isoprene +
MVK

19. Controlling Light Intensity For Each Reaction
First Round of Experiments
Control Experiments

20. hν + +/- dust Isoprene pH 6 MVK MVK dimer Isoprene + MVK (no light)*
Isoprene + MVK + dust (no light)
Isoprene + MVK + dust (light)
Isoprene + MVK (light)
*Sample not exposed to heat or light

21. hν ?? + +/- TiO2 Isoprene pH 4 MVK Isoprene + MVK + TiO2 (light)
Isoprene + MVK +TiO2 (no light)
Isoprene + MVK (light)
Isoprene + MVK (no light)*
*Sample not exposed to heat or light

22. Isoprene Control Reaction
MVK
Isoprene hν ??
TiO2 +
+/-
MVK + TiO2
MVK +TiO2 + Isoprene
Isoprene Control Reaction

23. Conclusions
In the MVK and dust reactions, light and dust seem to have an opposite effect on the degradation of MVK dimer
In the MVK and TiO2 reactions, the following compound formed with or without isoprene
MVK dimer ??

24. Future Directions
Identify the product from the MVK and TiO2 reaction and investigate as candidate for SOA intermediate
Analyze the contents of the dust particles
Experiment with other variables
Different dust particles (volcanic, desert, etc.)
Longer periods of time (e.g. 2 days, 3 days, etc.) ??

25. Acknowledgements Mentor: Marc Baum Oak Crest Institute of Science
Howard Yan
Natalie De Vries
Sean Kennedy
John Moss
Summer Research Connection
Sherry Tsai
James Maloney
Family
Sponsors
National Science Foundation
Howard Hughes Medical Institute
Siemens Foundation