1. Secondary Organic Aerosol Formation from Gas and Particle Phase Reactions of Aromatic Hydrocarbons Di Hu PhD Committee Meeting March 24, 2004

2. Outline Why aromatics SOA formation potential from aromatics Overall goal of my research

3. Sources of Aromatics Anthropogenic Sources Transportation Solvent use Fuel combustion In the US, transportation sources contribute ~67% to the total aromatic emissions which range from 1.9 x 10 6 to 2.4 x 10 6 tons/year.

4. Why aromatics? Composition, Chemistry, and Climate of the Atmosphere; New York, 1995

5. Why aromatics? Toluene 23.5% m,p-Xylene12.6%1,2,4-Trimetylbenzene8.5% Benzene 7.4% Composition, Chemistry, and Climate of the Atmosphere; New York, 1995

6. Jenkin et al. show that in their model calculations up to 40% of photochemically produced ozone can be attributed to emissions of aromatics in urban areas. (Atmos. Environ. 1996)

7. SOA Formation Potential of Aromatics

10. Recent research has provided strong evidence for polymerization reactions on aromatic aerosols. This results in a much lower volatility SOA material and higher aerosol yields than partitioning can predict.

11. Evidences for Polymer Formation in SOA from the Photo-oxidation of Aromatics/NOx System

12. FTIR Spectra of Toluene and Glyoxal Aerosols Slide from Dr. Myoseon Jang Slide from Dr. Myoseon Jang

13. Kalberer et al. recently have identified polymers as the main constituents of SOA formed from the photo-oxidation of 1,3,5-trimethylbezene, which account for about 50% of the aerosol mass after 30 hours of aging. (Science, 2004)

14. LDI-TOFMS Spectrum of SOA from Photo-oxidation of 1,3,5- Trimethylbezene

15. Time Evolution of Polymer in SOA Measured by LDI-MS

16. Overall Goal of This Project Integrate particle phase heterogeneous processes with gas phase reaction as a unified, multi- phase, chemical reaction mechanism, which will ultimately permit the prediction of amounts of SOA that result from aromatics reacting in the atmosphere.

17. Overall Approach Kinetic mechanism development Outdoor chamber experiments Simulation of chamber experiments

18. Gas Phase Reactions

19. Toluene react with OH

20. Recent research from Mario Molina’s group has shown that the pathway to form epoxide radicals are neglectable.

21. Existing Mechanisms Carbon Bond Carter’s Mechanism Master Chemical Mechanism

22. Toluene react with OH

23. 'C7H8' + OH ----> 0.72*'CH3-C6H5(OH)-OO.' + 0.1*'C6H5CO-H' + 0.18*'CRESOL’ 0.1*'C6H5CO-H' + 0.18*'CRESOL’ +0.28*HO2 + 0.1*XO2 +0.28*HO2 + 0.1*XO2 @ 1.18E-12* EXP(338.0/TK) @ 1.18E-12* EXP(338.0/TK) 'CH3-C6H5(OH)-OO.' + NO ----> 0.55*'H-CO-CH=CH-CO-H‘ + 0.11*'CH3-CO-CH=CH-CO-H' + 0.34*'H-CO-C(CH3)=CH-CO-H' + 0.55*'CH3-CO-CO-H' + + 0.11*'CH3-CO-CH=CH-CO-H' + 0.34*'H-CO-C(CH3)=CH-CO-H' + 0.55*'CH3-CO-CO-H' + 0.45*'H-CO-CO-H'+ NO2 +HO 0.45*'H-CO-CO-H'+ NO2 +HO @ 8.1E-12 @ 8.1E-12

24. Reaction of 1 st Generation Product

25. 'CH3-CO-CH=CH-CO-H' + OH ----> 0.2*('CH3-CO-CH=CH-CO-O2.‘ +H2O) + 0.4*'OXOCYL_RAD' + +H2O) + 0.4*'OXOCYL_RAD' + 0.2*'CH3-CO-CH(OH)-CH(OO.)-CO-H' 0.2*'CH3-CO-CH(OH)-CH(OO.)-CO-H' + 0.2*'CH3-CO-CH(OO.)-CH(OH)-CO-H' + 0.2*'CH3-CO-CH(OO.)-CH(OH)-CO-H' @ 5.58E-11 @ 5.58E-11 'OXOCYL_RAD' + NO -O2-> 'Maleic anhydrid' + 'CH3.' + NO2 @ 3.0*k_MEO2_NO @ 3.0*k_MEO2_NO 'CH3-CO-CH(OH)-CH(OO.)-CO-H' + NO ---->0.13*C5OHNO3 + 0.87*('CH3-CO-CH(OH)-CH(O.)-CO-H' + NO2) @ 0.71*k_MEO2_NO 0.87*('CH3-CO-CH(OH)-CH(O.)-CO-H' + NO2) @ 0.71*k_MEO2_NO 'CH3-CO-CH(OH)-CH(O.)-CO-H' + O2 ----> 0.3*(C4OHALD + CO + H2O) + 0.5*('CH3-CO-CO-H'+ 'H-CO-CO-H'+ HO2) + 0.5*('CH3-CO-CO-H'+ 'H-CO-CO-H'+ HO2) + 0.2*(C5OHALD+ HO2) + 0.2*(C5OHALD+ HO2) @ k_DEC @ k_DEC

26. 2 nd Generation Gas Phase Products

27. 3 rd Generation Gas Phase Products

28. Simulation Results of Gas Phase Chemistry

30. Particle Formation Processes G/P Partitioning Particle Phase Reactions

31. G/P Partitioning K p =k on /k off = 7.501RTf om /(10 9 Mwp 0 L ) k off =k b T/h exp(-E a /RT)  k b T/h = 6.2110 12 sec -1 at 298K  Relate E a to log p o L k on =K P k off

32. To Represent These Processes in the Mechanism

33. C4OHALD gas + SEED ----> C4OHALD part + SEED @ kon @ kon C4OHALD gas + TSP ----> C4OHALD part + TSP @ kon @ kon C4OHALD part ----> C4OHALD gas @ koff

34. Particle Phase Reactions

37. GlyP + H2O ----> Gly2OHP @ kpart1 Gly2OHP + H2O ----> Gly4OHP @ kpart2 Gly4OHP + GlyAcidP ----> pre-Poly1 @ kpart3 Pre-Poly1 + C4OHALD ----> Poly1 @ kpart4 Do these reactions well represent what really happens in the particle phase? Particle phase reaction rate coefficients

38. Outdoor Chamber Experiments

39. The Outdoor Chamber Reactor System

40. Hanging Teflon

41. Dual 270m 3 chamber fine particle t 1/2 >17 h

42. Product Analysis

43. Toluene/propylene/NOx/sunlight chamber experiments were carried out with neutral seed and acidic seed.

44. Analytical Methods Derivatization methods to identify the precursors of polymers. LC-ESIMS/MS to identify structure of polymers.

45. PFBHA O-(2,3,4,5,6- pentafluorobenzyl) -hydroxylamine for carbonyl groups

46. PFBBr, Pentafluorobenzyl bromide derivatization for carboxylic and aromatic-OH

47. The three slides are from Prof. Rich Kamens The three slides are from Prof. Rich Kamens BSTFA for hydroxyl, and/or carboxylic groups BSTFA ROH carboxylic acid or alcohol CN Si(CH 3 ) 3 CF 3 O (CH 3 ) 3 Si R O (CH 3 ) 3 Si

48. BF 3 -CH 3 OH + BSTFA Derivatization Method GC-ITMS analysis - electron impact ionization (EI) - methane chemical ionization (CI-methane) - tandem mass spectrometry (MS/MS) Slide from Dr. Mohammed Jaoui Citramalic acid

49. Particle Phase Reaction Rate Coefficients Too ambitious to measure the rate coefficient of each single particle phase reaction. Cross reaction of the multi-functional aldehydes Many products are not commercially available.

50. Simple methyglyoxal experiments (daytime/NOx, nighttime) Do chamber experiment with different toluene and NOx concentrations at different RH and temperature. Measure particle mass, acidity and HNO3 in particle phase. Explore relationships that influence rates of particle formation –particle HNO3 –RH and temperature

51. Overall Approach Kinetic mechanism development Outdoor chamber experiments Simulation of chamber experiments

52. Future Plan Methylglyoxal experiments in this summer Some of the toluene/NO x chamber experiments Proposal at the end of this summer

53. Thank you for your time