1. Modeling SOA Formation: New Insights and More Questions ? Department of Environmental Science and Engineering UNC, Chapel Hill

2. Mastery of Fire 400,000 years ago in Europe 400,000 years ago in Europe 100,000 years ago in Africa 100,000 years ago in Africa M. N. Cohne, 1977

3. From a global perspective, fire results in huge emissions of black carbon into the atmosphere Biomass burning6x10 12 g Biomass burning6x10 12 g Fossil fuel burning7x10 12 g Fossil fuel burning7x10 12 g Biogenic aerosols 13-60x10 12 g Biogenic aerosols 13-60x10 12 g ( presentations by: Schnaiter and Jackobson)

4. What are Organic Aerosols? What are Organic Aerosols? organic liquid layer inner solid core inorganic/carbon H2OH2O H 2 SO 4 Semi-volatile organics

5. Fresh wood soot (0.5  m scale)

6. Composition of LA Particulate Matter (adjusted for smoggy days) ( (Rogge &Cass et al, 1993, Turpin et al, 1991) Percent mass

8. PM10 Chemical Characterization in Beijing Xiao-Feng, Min Hua, Ling-Yan Hea, Xiao-Yan Tang, Atmos. Environ. 39 (2005) 2819–2827

9. Characteristics of carbonaceous aerosols in Beijing, China Yele Suna, Guoshun Zhuang, Ying Wang, Lihui Han, Jinghua Guo, Mo Dan, Wenjie Zhang, Zifa Wang, Zhengping Hao, Atmos, Environ. 38 (2004) 5991–6004 coal burning, traffic exhaust, and dust from the long-range transport coal burning, traffic exhaust, and dust from the long-range transport Mineral aerosol from outside Beijing accounted for 79% of the total PM10 minerals and 37% of the PM2.5 in winter. It was 19% and 20% in summer Mineral aerosol from outside Beijing accounted for 79% of the total PM10 minerals and 37% of the PM2.5 in winter. It was 19% and 20% in summer

10. Fengkui Duan, Kebin He, Yongliang Ma, Yingtao Jia, Fumo Yang, Yu Lei, S. Tanaka, T. Okuta, Chemosphere 60 (2005) 355–364 Characteristics of carbonaceous aerosols in Beijing, China Fengkui Duan, Kebin He, Yongliang Ma, Yingtao Jia, Fumo Yang, Yu Lei, S. Tanaka, T. Okuta, Chemosphere 60 (2005) 355–364 OC/EC ratio (on a 1.5 basis showed that SOC accounted more than 50% for the total organic carbon. In winter, the SOC contribution to OC was also significant, and as high as 40%. OC/EC ratio (on a 1.5 basis showed that SOC accounted more than 50% for the total organic carbon. In winter, the SOC contribution to OC was also significant, and as high as 40%.

11. Secondary organic aerosol (SOA) Material as organic compounds that resides in the aerosol phase as a result of atmospheric reactions that occur in either the gas or particle phases.

12. Do we see any chemical evidence for SOA formation? Do we see any chemical evidence for SOA formation?

13. Leonardo Da Vinci describes blue haze and thinks that plant emissions are its source. (F. W. Went, 1959) Da Vinci believes that it was due to water moisture emitted from the plants

14. F.W.Went published papers on biogenic emissions from vegetation over 40 years ago. He posed the question, “what happens to the 17.5x10 7 tons of terpene-like hydrocarbons or slightly oxygenated hydrocarbons once they are in the atmosphere each year?”

15. Went suggests that terpenes are removed from the atmosphere by reaction with ozone attempts to demonstrate “blue haze” formation

16. Went suggests that terpenes are removed from the atmosphere by reaction with ozone attempts to demonstrate “blue haze” formation by adding crushed pine or fir needles to a jar with dilute ozone.

17. Over a eucalyptus forest in Portugal Kavouras et al. (1998,1999) show evidence for terpene reaction products in aerosols Over a eucalyptus forest in Portugal Kavouras et al. (1998,1999) show evidence for terpene reaction products in aerosols

18. Terpenes products Kavouras et al, 1998 ng m -3 pinic acid 0.4 - 85 pinonic acid 9 - 141 norpinonic acid 0.1 - 38 Pinonaldehyde 0.2 - 32 Nopinone 0.0 - 13  -pinene  -pinene

19. Turpin and co-workers In the LA area (estimated on smoggy days from OC / EC ratios ), as much as 50 - 80% of the aerosol organic carbon comes from secondary aerosol formation (1984 and 1987 samples) In the LA area (estimated on smoggy days from OC / EC ratios ), as much as 50 - 80% of the aerosol organic carbon comes from secondary aerosol formation (1984 and 1987 samples) In Atlanta in 1999, SOA averaged 46% of the total OC but with highs of 88% In Atlanta in 1999, SOA averaged 46% of the total OC but with highs of 88%

20. Turpin Approach for SOA formation The primary aerosol elemental carbon (EC) pri and particle organic content (OC) pri in an un- reacted airshed are measured and a primary ratio of { OC / EC } pri is determined (Turpin et al for 1984 and 1987 aerosol samples) The primary aerosol elemental carbon (EC) pri and particle organic content (OC) pri in an un- reacted airshed are measured and a primary ratio of { OC / EC } pri is determined (Turpin et al for 1984 and 1987 aerosol samples) Under SOA formation OC tot and EC tot are measured Under SOA formation OC tot and EC tot are measured OC sec = OC tot - OC pri OC sec = OC tot - OC pri OC pri = EC {OC /EC} pri OC pri = EC {OC /EC} pri On smoggy days in California ~50 - 80% of the organic carbon comes from secondary aerosol formation On smoggy days in California ~50 - 80% of the organic carbon comes from secondary aerosol formation

21. Spyros Pandis also recently looked at OC/EC ratios (Pittsburgh area) He estimates that SOA formation can account for 35-50% of the organic carbon

22. OC/EC Ratio and Photochemical Activity OC/EC O3O3 Pittsburgh, 2001

23. If we look at the IR spectra of aerosols collected from the smoky mountains, they look like lab aerosols from acid catalyzed particle phase reactions of carbonyls…

24. Heterogeneous reactions as seen in the IR region C-O-C bonds

25. In the 1980s Yamasaki, Bidelman, Pankow began to investigate the equilibrium distribution of PAHs, alkanes, and chlorinated organics between the gas and the particle phases.

26. PAH gas + surface   PAH part

27. log K p = -log P s o + const. Relate solid saturated vapor pressures with K p log P s o log K p naphthaleneBaPPyrene

28. log K p = -log P o L + const.  PAHs,  alkanes  chlorinated organics slope = -1 log P o (L) log K p

29. Problems with the theory many aerosols are composed of 40-100% organics many aerosols are composed of 40-100% organics This gives much more than a mono-layer of coverage This gives much more than a mono-layer of coverage log K p = m log P o (L) + c log K p = m log P o (L) + c

30. In 1994 James Pankow fixes the theory for liquid particles

31. Can we chemically / kinetically model SOA Formation??? Numerical fitting Numerical fitting Semi-explicit Semi-explicit

32. From a modeling perspective Equilibrium Organic Gas-particle partitioning provides a context for addressing SOA formation From a modeling perspective Equilibrium Organic Gas-particle partitioning provides a context for addressing SOA formation

33. Gas/Particle Partitioning particle Particle type CompoundTemperature Humidity gas Thermodynamic Equilibrium? C gas +surf C part K p will vary with 1/P o

34. Odum-Seinfeld Model SOA model Y= M o /  HC Odum theorytheory

35.  - pinene- NOx experiments by Odum Y Mo(  g/m 3 ) 10.012 1 20.028 7 30.059 22 40.067 34 50.078 38 60.122 83 70.125 94 = M o /  HC Y = M o /  HC

36.  -pinene

37. Numerical fitting values for Kom and  for OH, O3, and NO 3 reactions with terpenes and sesquiterpenes were developed by Griffin and Sienfeld et al.  HC ) From the averages for OH, O 3, and NO 3, the amounts of atmospherically reacted terpenes and sesquiterpenes were estimated (  HC ) by Griffin and Sienfeld et al. Y= M o /  HC

38. Globally, biogenic emissions  13-24x10 12 g y -1 of aerosol mass Gives little insight into the chemical nature of products involve in SOA formation

39. From a global perspective, fire results in huge emissions of black carbon into the atmosphere Biomass burning6x10 12 g Biomass burning6x10 12 g Fossil fuel burning7x10 12 g Fossil fuel burning7x10 12 g Biogenic aerosols 13-60x10 12 g Biogenic aerosols 13-60x10 12 g ( presentations by: Schnaiter and Jackobson)

40. Semi explicit models link gas and particle phases C=O O cis-pinonaldhyde particle C=O O Gas phase reactions

41. K p = k on /k off [ i gas] + [part] [ i part] k on k off particle k on k off C=O O

42. K p = k on /k off k off = k b T/h e -Ea /RT

43. Particle formation-self nucleation u Criegee’s can react with aldehydes and carboxylic groups to form secondary ozonides and anhydrides. O=C C=O CH 3 + C C=O. CH 3 oo. C C=O CH 3 C C=O CH 3 O oo

44. Secondary Organic Aerosol (SOA) Formation of Toluene + OH Highly oxygenated gas phase products Sunlight NO x

45. Nucleation Klotz et al. observed a rapid particle formation from the photolysis of hexendiendial. Klotz et al. observed a rapid particle formation from the photolysis of hexendiendial.

46. C7KETENE + C14KETENE C14KETNE + C14KETENE SEED1 2+2 Cycloadditon P o L ~ 10 -21 torr

47. Particle Growth from Toluene Reaction with Background OH bkg 6 min 10 min 3 min

48. CHO O O CH 3 O O O Criegee2 Criegee1 O O O  -pinene O 3 COOH pinic acid + other products O pinonic acid CHO O COOH + CO, HO 2, OH COOH O norpinonaldehyde norpinonic acid Mechanism

49. pinonaldehyde

50. Overall kinetic Mechanism linked gas and particle phase rate expressions linked gas and particle phase rate expressions

52. Particle Phase reactions particle C=O O cis-pinonaldhyde C=O O polymers Gas phase reactions

53. Particle Phase reactions particle C=O O cis-pinonaldhyde C=O O polymers Gas phase reactions

54. Particle Phase reactions C=O O cis-pinonaldhyde C=O O polymers Gas phase reactions

55. pinonaldehyde 2 x Pinonaldehyde dimerization

56. ESI-QTOF mass spectrum of SOA from reaction of  -pinene + O 3 + acid seed aerosol (Tolocka et. al., 2004 )

57. M Na + (ESI-QTOF Tolocka et al, 2003) Particle phase pinonaldehyde dimers from  -pinene +O 3 on acid particles Similar results were obtained by Hartmut Herrmann’s group (Atmos Envir, 2004)

58. Chemical System  -pinene + NOx+ sunlight + ozone----> aerosols

59. 0.95 ppm  -pinene + 0. 44ppm NO x O3O3 NO NO 2 model data Time in hours EST ppmV

60. Gas phase pinonaldehdye O O mg/m 3 Time in hours EST

61. Particle phase model TSP mg/m 3 Particle phase model TSP mg/m 3 Measured particle mass vs. model data Time in hours EST

62. Much lower terpene concentrations Different background aerosols which have different chemical and physical properties Low volatility gas phase products will have different interactions with different pre-existing particles The Real Atmosphere

63. New UNC aerosol smog chamber

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

65. 0.1 ppmV Toluene + 0.1 ppm NOx

66.  -pinene SOA formation in the presence of dilute diesel and woods soot particles different solubilities of gas phase products in the different soot matrices 

67.  s of  -pinene products in diesel and woods soot particles(UNIFAC) CompoundsDieselWood cis-pinonaldehyde~5~1 pinalic-4-acid~8~1 cis-pinonic acid~8~1 10-hydroxypinonaldehyde~25~1 cis-pinic acid~11~2 * Jang et al. 1997. Envr.Sci.Tech. 31, 2805-2811 Activity Coefficients were estimated at 298 K and 50 RH% by UNIFAC.

68. [ i gas] + [part] [ i part] [ i gas] + [part] [ i part] K p = k on /k off k on k off k on = k off 7.5 RTf om / {   p o L Mw10 9 }

69. The bottom line??? We could not even come close to predicting  -pinene SOA in the presence of background diesel seed aerosol We could not even come close to predicting  -pinene SOA in the presence of background diesel seed aerosol Our model was consistently under predicting observed SOA formation by a factor of 5 to 10 Our model was consistently under predicting observed SOA formation by a factor of 5 to 10

70. 50  g/m 3 of Diesel Soot Particles Inject diesel

71. 250  g/m 3 of Diesel Soot Particles Inject diesel

72. Is the polarity of diesel exhaust particles changing as it ages  SOA?? Sangdon Lee (Atmos. Envirn 2004) a dded deuterated alkanes to the chamber atmosphere followed by the addition of diesel exhaust Sangdon Lee (Atmos. Envirn 2004) a dded deuterated alkanes to the chamber atmosphere followed by the addition of diesel exhaust Measured gas and particle phase concentrations and calculated a measured K p : K p = d 42 part / {d 42 gas xTSP} Measured gas and particle phase concentrations and calculated a measured K p : K p = d 42 part / {d 42 gas xTSP} Compared to theory Compared to theory

73. Predicted K p Observed K p

74.  When  - pinene is present the effect is even greater

75. Diesel particle polarity increases as it ages and reacts in the presence of  -pinene predicted observed

76. 50  g/m 3 diesel exhaust + 0.13 ppm  -pinene in sunlight Add 0.13 ppmV  -pinene model data

77. Where do we go from here? Begin integrating single compound mechanisms Expand mechanisms to take into account longer atmospheric aging times Build better nucleation representations Build a particle size model which shows the distribution of products with size

78. Where do we go from here? Investigate the compounds that are resulting in SOA formation from diesel exhaust

79. Acknowledgements Grants from National Science Foundation Grants from National Science Foundation USEPA STAR RESEARCH GRANT program USEPA STAR RESEARCH GRANT program Gifts of a GC-FTIR-MS system (HP 5890 GC & HP 5965B FT-Infrared Detector) from the Hewlett Packard Corporation and the Saturn GC-ITMS from the Varian Corp. Gifts of a GC-FTIR-MS system (HP 5890 GC & HP 5965B FT-Infrared Detector) from the Hewlett Packard Corporation and the Saturn GC-ITMS from the Varian Corp.

80. Dept. Eviron Sci and Eng, NC Chapel Hill NORTH CAROLINA kamens@unc.edu http://airsite.sph.unc.edu/~kamens http://airsite.sph.unc.edu/~kamens