1. © University of Reading 2006www.reading.ac. uk Secondary Organic Aerosol Formation: Ozonolysis of Terpenes George Marston, Yan Ma and Rachel Porter Department of Chemistry

2. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 Ronald Reagan "Trees cause more pollution than automobiles do.” ‘88 "A tree is a tree. How many more do you have to look at?" '66 "The American Petroleum Institute filed suit against the EPA [and] charged that the agency was suppressing a scientific study for fear it might be misinterpreted. The suppressed study reveals that 80 percent of air pollution comes not from chimneys and auto exhaust pipes, but from plants and trees." ‘79

3. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 3 Background The ozonolysis of alkenes is important for atmospheric chemistry:  Oxidation of VOCs  Generation of radicals  Generation of oxygenated products Secondary Organic Aerosol (SOA)

4. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 4 SOA Formation Acid products from the ozonolysis of terpenes are components of SOA and may lead to particle formation Health implications SOA can have direct and indirect effects on climate change

5. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 5 Alkene Ozonolysis Criegee Intermediate

6. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 6 OH Formation

7. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 7 Terpenes  - pinene  - pinene 3- carene terpinol ene

8. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 8  -Pinene Ozonolysis Products Pinonic acidPinic acid Norpinonic acid Norpinic acid Pinalic acidNorpinalic acid OH-pinonic acid OH-pinalic acid

9. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 9 First step k1k1 (1   )k 1

10. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 10 Aims To develop mechanisms for acid formation in terpene ozonolysis To model results to provide input of rate constants and branching ratios for the Master Chemical mechanism  To determine which channel (CI) gives rise to which product  To determine branching ratios for decomposition of primary ozonides  To compare product yields from different terpenes

11. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 11 Methodology Enone Enal

12. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 12 Experimental Static reaction chamber coupled to gas chromatography / mass spectrometry / flame ionisation detection Acid products trapped on filters and derivatised to methyl esters (BF 3 /Methanol) Enal and enone synthesised from ozonolysis of a suitable terpene

13. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 13  -Pinene Results

14. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 14 Enal Results

15. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 15 Enone Results Only Pinonic Acid and Norpinonic Acid are observed

16. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 16 Enone Results

17. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 17 Branching Ratio

18. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 18 Pinonic Acid Formation

19. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 19  -Pinene Summary

20. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 20 3-Carene Yields

21. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 21 3-Carene, Enone and Enal 3-carene Enal Enone

22. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 22 3-Carene and Enone

23. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 23 3-Caronic Acid Mechanism

24. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 24 3-Carene Summary

25. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 25  -pinene

26. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 26 Mechanism  -pinene  -pinene +RO 2 -H 2 CO +O 2

27. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 27 Pinalic-4-acid + 92 %8 % Pinalic-3-acid Pinalic-4-acid

28. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 28 Terpinolene 93 %7 % + Terpinolalic Acid (a) Terpinolalic Acid (b)

29. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 29 Hydroperoxide Formation 80 % 20 %

30. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 30 Hydroperoxide Formation favoured over ? ? Formation of hydroperoxide directly from quenching of nascent Criegee Intermediates? 

31. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 31 Summary  Ring opening in  - pinene and terpinolene  Intramolecular reactions  Hydroperoxide formation Improvements in mechanisms Uncertainties: Some quantitative data, but more needed

32. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 32 Acknowledgements Natural Environment Research Council University of Reading Dr Yan Ma Dr David Johnson Rachel Porter Dr Andy Russell Dr David Chappell Tim Wilcox Thomas Luciani

33. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 33

34. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 34 Mechanisms

35. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 35 Mechanisms

36. Uncertaintues in Ozone Terpene Mechanisms: UC, Davis, 2008 36 Mechanisms