Secondary Aerosol Formation from Gas and Particle Phase Reactions of Aromatic Hydrocarbons - PowerPoint PPT Presentation

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Secondary Aerosol Formation from Gas and Particle Phase Reactions of Aromatic Hydrocarbons

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  1. Secondary Aerosol Formation from Gas and Particle Phase Reactions of Aromatic Hydrocarbons Di Hu and Richard Kamens Funded by the USEPA STAR program July 30, 2003 to July 29, 2006 Department of Environmental Science and Engineering UNC, Chapel Hill

  2. The objective of this project is to develop a simple “efficient” multi-phase chemical mechanism that will predict secondary organic aerosol formation from aromatic atmospheric reactions

  3. Volatile aromatic compounds comprise a significant part of the urban hydrocarbon mixture in the atmosphere, up to 45% in urban US and European locations

  4. Toluene, m- & p-xylenes,benzene and 1,2,4-trimethyl benzene, o-xylene and ethylbenzene make up 60-75% of this load. In the US, transportation sources contributed ~67% to the total aromatic emissions which range from 2.4 x 106 to 1.9 x 106 tons/year.

  5. Laboratory studies show that gas phase reactions ofaromaticsform a host of oxygenates   secondary organic aerosol material (SOA) • hydroxy unsaturated dicarbonyls • di and tri carboxylic acids • Nitrated hydroxy carbonyls


  6. Edney and Keindienst et al, 2001

  7. Historically “lumped” aromatickinetic models have focused on Ozone formation: illustrate how these fit smog chamber data; solid lines = data, dashed lines = model) look at a mechanism

  8. CB4 fit to 4 ppmC Tolueneand 0.4 ppm NOxUNC outdoor aerosol chamber

  9. { TOLUENE CHEMISTRY… CB4 } OH + TOL = 0.08 XO2 + 0.36 CRES + 0.44 HO2 + 0.56TO2 TO2 + NO = 0.90*NO2 + 0.90*HO2 + 0.90*OPEN TO2 = CRES + HO2 OH + CRES = 0.4 CRO + 0.60 XO2 + 0.60 HO2 + 0.30 OPEN OPEN = C2O3 + HO2 + CO, OPEN + O3 = 0.03*RCHO + 0.62 C2O3 + 0.70 HCHO+ 0.03 XO2 + 0.69 CO + 0.08 OH + 0.76 HO2 + 0.2MGLY

  10. Jang and Kamens, 2001

  11. O=CH CH 3 CH OH 3 + H O 2 O + HO 2 benzaldehyde NO NO o-cresol 2 +O CH 2 * 3 CH . CH 2 3 OH OH OH H . H CH toluene CH CH 3 3 3 OH + . OH NO . O 2 O O2 +O H H 2 H H O NO oxygen bridge rearrangement OH H +O . O 2 H + HO 2 H ring cleavage O + radical H CH H OH 3 H butenedial methylglyoxal O H

  12. Pent-dione + OH 0.5 pent-rad +0.5 pent-oo pent-oo XO2 + 0.5 GLY+ 0.5 MGLY + 0.5 CO + 0.5HO2 +0.25 OHoxybutal +0.25 but-tricarb pent-rad  Maleic + 1.5 XO2 + HO2 + HCHO

  13. New Mechanism has 44 reactions

  14. hexadiene-dicarb butene-dicarbonyl pentene-dicarbonyl benzaldehyde cresol maleic anhydride 43 AROMATIC reactions + Carbon 4

  15. Chamber Post “Nucleation” Observations When high concentrations of toluene are added to background air chamber in sunlight, after about 10 minutes particles in the 7-12 nm range appear. O3 = 12 ppb NO = 5-6 ppb NO2= 1-2 ppb fine particles ~4-5 ug/m3 (70-120 nm) C2-C10 < 50 pppC

  16. Post nucleation (SMPS data)

  17. CH 3 O2 OH NO . 2 +O CH H * 2 3 CH 3 H H OH OH NO H . H toluene + CH 3 O O oxygen bridge There is a need to represent this initial “post nucleation” process… Klotz et al, show experimental evidence that hexadienedials produce particles when they photolyze.

  18. Gas phase reactions CH3-C-C=O CH3-C-C=O Gas and particle phases can be linked via G/P partitioning Methyl glyoxal 1Cgas + surf  1Cpart particle

  19. CH3-C-C=O O kon koff particle kon koff • [ igas] + [part] [ipart] Kp = kon/koff

  20. Optimized GAS-Particle Phase kinetics [BENZA gas]+ [C5KETALDp]  [BENZA p]+ [C5KETALDp] kon [BENZA gas]+ [BENZAp]  [BENZA p]+ [BENZAp] kon [BENZA gas]+ [seed]  [BENZA p]+ [seed] kon… … … [BENZAp]  [BENZA gas] koff TSP = n[BENZAp] +n[C4OHALDp] + n[C5OHALDp] + n[Poly3] + n[Poly1] + n[Poly2] + n[Poly4] + n[Poly5] + n[C4KETALDP] + n[C5KETALDP] + n[OPENP] + n[seed] + n[seed2] + n[RgNO3P] + n[RALDNO3p] + n[RALDACIDp] + n[GLYp] + n[MGLYP] + n[Poly6] + n[Poly7] + n[Poly8] + n[BZONO3P]; [BENZAgas]+ [TSP]  [BENZALD p]+ [TSP] kon

  21. Glyoxal in the gas and particle phase (PFBHA) H CH H H 3 methylglyoxal glyoxal Vapor pressures ~ 10 torr

  22. PFBHAO-(2,3,4,5,6-pentafluorobenzyl) -hydroxylamine for carbonyl groups Carbonyl group Carbonyl

  23. PFBHA

  24. Glyoxal in the gas and particle phase (PFBHA)

  25. Particle Phase Reactions GLY ----> GLYP @ 500*kon_glyT

  26. R[TOLP_11a] = GLYP ----> Poly1 @ 500*kpart_T; R[TOLP_11b] = Poly1 ----> GLYP @ kpart_off; GlyP  Poly1 k1 Poly1 ----> GlyP k-1 Gly4OHP + GlyAcidP ----> pre-Poly1 Pre-Poly1 + C4OHALD ----> Poly1

  27. GLYgas + part  GLYpart + part 500*kon

  28. Toluene + Propylene

  29. NO O3 NO2 Simulation of 4 ppmC Toluene + 0.4 ppm NOx experiment in sunlight

  30. Fit to Toluene data model data

  31. TSP and SMPS particle mass SMPS Filter data

  32. Model simulation of TSP Data model

  33. Model Simulation of Toluene/NOx Experiment on 11/15/04

  34. carbonyl-PAN C4-carbonyl-acid butane-tricarbonyl OH-oxobutanal polymer1

  35. A second generation Model

  36. A second generation Model