Modeling SOA Formation: New Insights and More Questions ?

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 • 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 burning 6x1012 g • Fossil fuel burning 7x1012 g • Biogenic aerosols 13-60x1012g (presentations by: Schnaiter and Jackobson)

4. H2SO4 Semi-volatile organics H2O What are Organic Aerosols? organic liquid layer inner solid core inorganic/carbon

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 BeijingXiao-Feng, Min Hua, Ling-Yan Hea, Xiao-Yan Tang, Atmos. Environ. 39 (2005) 2819–2827

9. Characteristics of carbonaceous aerosols in Beijing, ChinaYele 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 • 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. Characteristics of carbonaceous aerosols in Beijing, ChinaFengkui 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%.

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?

13. Leonardo Da Vincidescribes 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.Wentpublished papers on biogenic emissions from vegetation over 40 years ago. He posed the question, “what happens to the17.5x107 tonsof 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

18. a-pinene b-pinene 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

19. Turpin and co-workers • In the LA area (estimated on smoggy days from OC /EC ratios), as much as 50 - 80% of the aerosolorganic 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%

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) • Under SOA formation OCtot and ECtot are measured • OCsec= OCtot- OCpri • OCpri = EC {OC/EC} pri • 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 O3 Pittsburgh, 2001

23. If we look at the IR spectraof aerosols collected from the smoky mountains, they look likelab 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, Pankowbegan to investigate the equilibrium distribution ofPAHs, alkanes, and chlorinated organicsbetween the gas and the particle phases.

26. PAHgas + surface  PAHpart

27. BaP Pyrene log Kp naphthalene log Pso Relate solid saturated vapor pressures with Kp log Kp = -log Pso + const.

28. slope = -1 log Kp log Po(L) log Kp = -log PoL + const. • PAHs, • alkanes • chlorinated organics

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

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

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

32. From a modelingperspective Equilibrium Organic Gas-particle partitioningprovides a context for addressing SOA formation

33. Thermodynamic Equilibrium? Cgas +surf Cpart Temperature Compound Humidity Particle type Gas/Particle Partitioning gas particle Kp will vary with 1/Po

34. Odum-Seinfeld Model SOA model Y= Mo / D HC Odum theory

35. a- pinene- NOx experiments by Odum Y Mo(mg/m3) 1 0.012 1 2 0.028 7 3 0.059 22 4 0.067 34 5 0.078 38 6 0.122 83 7 0.125 94 Y= Mo / D HC

36. a-pinene

37. Numerical fitting values for Kom and a for OH, O3, and NO3 reactions with terpenes and sesquiterpenes were developed by Griffin and Sienfeld et al. From the averages for OH, O3, and NO3 , the amounts of atmospherically reacted terpenes and sesquiterpenes were estimated (D HC ) by Griffin and Sienfeld et al. Y= Mo / D HC

38. Globally, biogenic emissions13-24x1012g 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 burning 6x1012 g • Fossil fuel burning 7x1012 g • Biogenic aerosols 13-60x1012g (presentations by: Schnaiter and Jackobson)

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

41. kon koff particle C=O O kon [ igas] + [part] [ipart] koff Kp = kon/koff

42. Kp = kon/koff koff = kbT/h e -Ea/RT

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

44. Secondary Organic Aerosol (SOA) Formation of Toluene Sunlight Highly oxygenated gas phase products + OH NOx

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

46. C7KETENE 2+2 + Cycloadditon C14KETENE C14KETNE + C14KETENE SEED1 PoL ~ 10-21 torr

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

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

49. pinonaldehyde

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