1. Nitrogen Compounds in the Atmosphere Atmospheric Chemistry Division Lecture Series 2011 8 March 2011Frank Flocke ACD FFL@ucar.edu1

2. Nitrogen “Families” N 2 N 2 O NO x (NO + NO 2 ) N 2 O 5 HNO 3 (HONO 2 ) HONO HOONO 2 PANs (RC(O)OONO 2 ) Alkyl Nitrates (RONO 2 ) XONO2 (X = halogen) NO 3 radical NO 3 - nitrate aerosol “NOy” 8 March 2011Frank Flocke ACD FFL@ucar.edu2

3. N2N2 Nitro – gen (found in HNO3 in the 18 th century) Azotos – “lifeless gas” Stickstoff – “asphyxiating substance” Extremely stable, bond energy 945 kJ/mol 8 March 2011Frank Flocke ACD FFL@ucar.edu3

4. N2ON2O Greenhouse gas 40/60 anthro/bio sources Increase of ~20% due to anthropogenic emissions 120 year atmospheric lifetime stratospheric NO x source Ledley et al, 1999 8 March 2011Frank Flocke ACD FFL@ucar.edu4

5. Stratospheric NO x Chemistry N 2 O + O( 1 D)  2 NO (~60%)  N 2 + O 2 (~40%) O 3 + hv  O 2 + O( 1 D) N 2 O + hv  N 2 + O( 1 D) Catalytic Ozone destruction “null cycle” Cycle (Stratosphere):Stratosphere + Troposphere: NO + O 3  NO 2 + O 2 NO 2 + O  NO + O 2 NO 2 + hv  NO + O O + O 3  2 O 2 O 3  O + O 2 8 March 2011Frank Flocke ACD FFL@ucar.edu5

6. Stratospheric NO x Chemistry Catalytic Ozone destruction cycles (Stratosphere): NO + O 3  NO 2 + O 2 Cl + O 3  ClO + O 2 NO 2 + O  NO + O 2 ClO + O  Cl + O 2 O + O 3  2 O 2 O + O 3  2 O 2 But… ClO + NO 2  ClONO 2 8 March 2011Frank Flocke ACD FFL@ucar.edu6

7. Ozone “hole” chemistry Lower Stratosphere “denitrified” and chlorine activated ClONO 2 + HCl(s)  Cl 2 + HNO 3 (s) ClONO 2 + H 2 O(s)  HOCl + HNO 3 (s) N 2 O 5 + HCl(s)  ClNO 2 + HNO 3 (s) N 2 O 5 + H 2 O(s)  2 HNO 3 (s) Cl + O 3  ClO + O 2 ClO + O  Cl + O 2 O + O 3  2 O 2 8 March 2011Frank Flocke ACD FFL@ucar.edu7

8. 8 March 2011Frank Flocke ACD FFL@ucar.edu8

9. Ozone “hole” chemistry Lower Stratosphere “denitrified” and chlorine activated ClONO 2 + HCl(s)  Cl 2 + HNO 3 (s) ClONO 2 + H 2 O(s)  HOCl + HNO 3 (s) N 2 O 5 + HCl(s)  ClNO 2 + HNO 3 (s) N 2 O 5 + H 2 O(s)  2 HNO 3 (s) Cl + O 3  ClO + O 2 ClO + O  Cl + O 2 Pinatubo eruption, 1991, Photo: USGS O + O 3  2 O 2 8 March 2011Frank Flocke ACD FFL@ucar.edu9

10. Tropospheric Reactive Nitrogen 8 March 2011Frank Flocke ACD FFL@ucar.edu10

11. Tropospheric Reactive Nitrogen NO x (NO + NO 2 ) N 2 O 5 HNO 3 (HONO 2 ) HONO HOONO 2 PANs (RC(O)OONO 2 ) Alkyl Nitrates (RONO 2 ) XONO2 (X = halogen) NO 3 radical NO 3 - nitrate aerosol NH 3, Amines NO y, or odd nitrogen NO z = NO y -NO x NO y reservoir species 8 March 2011Frank Flocke ACD FFL@ucar.edu11

12. Tropospheric Reactive Nitrogen Sources of reactive Nitrogen NO x (NO + NO 2 ) N 2 O 5 HNO 3 (HONO 2 ) HONO HOONO 2 PANs (RC(O)OONO 2 ) Alkyl Nitrates (RONO 2 ) XONO2 (X = halogen) NO 3 radical NO 3 - nitrate aerosol NH 3, Amines NO z = NO y -NO x NO y reservoir species NO y, or odd nitrogen 8 March 2011Frank Flocke ACD FFL@ucar.edu12

13. Combustion source for NOx No nitrogen in fuel N 2 + O = NO + N +314 kJ/mol N + O2 = NO + O N + OH = NO + H (not important) Nitrogen in Fuel HCN (g), RCN (g), NH 3, etc + OH/O  NOx Alentec Inc. 8 March 2011Frank Flocke ACD FFL@ucar.edu13

14. 14 NO x + VOC + O 3 NO x + VOCs cities (transportation) NO x emission sources 8 March 2011Frank Flocke ACD FFL@ucar.edu

15. NO x + VOC + O 3 NO x + VOCs Cities (transportation) VOCs Forests NO x power plants NO x + VOCs Industry NO x + VOCs Soils and Agriculture NO x emission sources 8 March 2011Frank Flocke ACD FFL@ucar.edu15

16. 16 NO x + VOC + O 3 NO x + VOC cities (transportation) VOC forests NO x power plants NO x + VOC industry NO x +VOC fires NO x + VOC Soils and Agriculture NO x emission sources Lightning 8 March 2011Frank Flocke ACD FFL@ucar.edu

17. 17 Sources of U.S. NO x and VOC Emissions Natural 61% Industrial 3% Solvent Use 13% Other 7% Non-Road Engines 5% On-Road Vehicles 11% VOCs Source: EPA Natural 6% Industrial 13% Other 10% Non-Road Engines 18% Electric Utility 24% On-Road Vehicles 29% NO x 8 March 2011Frank Flocke ACD FFL@ucar.edu

18. Global Budget of NO x in the Troposphere (Tg N/yr) 80s-90s Ehhalt and Drummond Logan Sanhueza (1982) (1983) (1991)Sources/Production Fossil fuel combustion13.5 (8.2-18.5)21.0 (14-28)21 Biomass burning11.5 (5.6-16.4)12.0 (4-24)2.5-8.5 Soil emission5.5 (1-10)8.0 (4-16)10-20 Lightning5.0 (2-8)8 (2-20)2-8 NH3 oxidation3.1 (1.2-4.9)? (0-10)- Ocean emission-1- Aircraft0.3 (0.2-0.4)-0.6 Stratospheric input0.6 (0.3-0.9)0.51 Total Total39 (19-59)50.5 (25-99)37-59Sinks Wet deposition24 (15-33)27 (12-42)- Dry deposition-16 (11-22)- Total Total24 (15-33)43 (23-64)- 8 March 2011Frank Flocke ACD FFL@ucar.edu18

19. 8 March 2011Frank Flocke ACD FFL@ucar.edu19

20. Modeled NO x near surface (1990s) 8 March 2011Frank Flocke ACD FFL@ucar.edu20

21. IPCC AR4 NOx in the troposphere (2000) 8 March 2011Frank Flocke ACD FFL@ucar.edu21

22. SCIAMACHY global mean NO2 (2004) 8 March 2011Frank Flocke ACD FFL@ucar.edu22

23. Developments in Asia 1000 cars / day are added to the Beijing road system China GDP and NO 2 trends ~ 10 % / year (Steve Massie) 8 March 2011Frank Flocke ACD FFL@ucar.edu23

24. NO x emissions 8 March 2011Frank Flocke ACD FFL@ucar.edu24 … a moving target

25. NO x emissions http://www.iiasa.ac.at/web- apps/tnt/RcpDb/dsd?Action=htmlpage&page=c ompare 8 March 2011Frank Flocke ACD FFL@ucar.edu25

26. NOx chemistry in the troposphere NO x is synonymous with “photochemical smog” or ozone photochemistry 8 March 2011Frank Flocke ACD FFL@ucar.edu26

27. 8 March 2011Frank Flocke ACD FFL@ucar.edu27 NOx chemistry in the troposphere

28. 8 March 2011Frank Flocke ACD FFL@ucar.edu28 NOx chemistry in the troposphere

29. 8 March 2011Frank Flocke ACD FFL@ucar.edu29 NOx chemistry in the troposphere

30. 30 Photochemical Smog – 1950 ’ s Arie-Jan Haagen-Smit: “ Ozone from smog and sunlight ” 8 March 2011Frank Flocke ACD FFL@ucar.edu

31. 31 Edgar Stephens, et al, 1956: Discovery of PAN ( “ compound X ” ) Photochemical Smog – 1950 ’ s 8 March 2011Frank Flocke ACD FFL@ucar.edu

32. 32 Edgar Stephens, et al, 1956: Discovery of PAN ( the first NOx reservoir species ) Photochemical Smog – 1950 ’ s 8 March 2011Frank Flocke ACD FFL@ucar.edu

33. 33 Photochemical processes involving NO x Leighton, 1961: “O 3 and NO x live in photostationary state” 8 March 2011Frank Flocke ACD FFL@ucar.edu

34. NO x photostationary state O 3 + NO  NO 2 + O 2 NO 2 + hv  NO + O O + O 2 + M  O 3 + M ______________________ Null t ≈ 100 seconds [NO]/[NO 2 ] = k[O 3 ] / J NO2 P(O 3 ) = 0 O x = O 3 + NO 2 8 March 2011Frank Flocke ACD FFL@ucar.edu34

35. 35 Photochemical processes and tropospheric ozone formation Leighton, 1961: O 3 and NO x (NO+NO 2 ) live in a “ photostationary state ” H. Levy, 1972: OH radical oxidizes CO, CH 4, VOC P. Crutzen et al., W. Chameides et al., J. Logan et al. late 70 ’ s: HO x and NO x cycles responsible for ozone production in the troposphere 8 March 2011Frank Flocke ACD FFL@ucar.edu

36. Role of NO x in ozone production OH + CO  CO 2 + H H + O 2 +M  HO 2 + M HO 2 + NO  NO 2 + OH NO 2 + hv  NO + O O + O 2 + M  O 3 + M ______________________ CO + 2 O 2 +hv  CO 2 + O 3 OH + CH 4 +O 2  CH 3 O 2 + H 2 O CH 3 O 2 + NO  NO 2 + CH 3 O CH 3 O + O 2  HO 2 + CH 2 O 8 March 2011Frank Flocke ACD FFL@ucar.edu36

37. k k’ k” Role of NO x in ozone production 8 March 2011Frank Flocke ACD FFL@ucar.edu37 HO 2 + NO  NO 2 + OH CH 3 O 2 + NO  NO 2 + CH 3 O CH 3 O + O 2  HO 2 + CH 2 O NO 2 + hv  NO + O O + O 2 + M  O 3 + M O 3 + NO  NO 2 + O 2 P(O 3 ) = [NO] * (k’[HO 2 ] + k”[CH 3 O 2 ]) [NO]/[NO 2 ] = (k[O 3 ] + k’[HO 2 ] + k”[CH 3 O 2 ]) / J NO2

38. 8 March 2011Frank Flocke ACD FFL@ucar.edu38

39. 8 March 2011Frank Flocke ACD FFL@ucar.edu39

40. 8 March 2011Frank Flocke ACD FFL@ucar.edu40

41. Near-Zero NO x troposphere OH + CO  CO 2 + H H + O 2 +M  HO 2 + M HO 2 + O 3  2 O 2 + OH HO + O 3  O 2 + HO 2 ___________________ CO + O 3  CO 2 + O 2 O 3 + hv  O( 1 D) + O 2 O( 1 D) + M  O + M O( 1 D) + H 2 O  2 OH kl’kl’ kl”kl” J O1D f 8 March 2011Frank Flocke ACD FFL@ucar.edu41

42. Ozone production and loss P(O 3 ) = [NO] * (k’[HO 2 ] + k”[CH 3 O 2 ]) L(O 3 ) = [O 3 ] * (k l ’[OH] + k l ”[HO 2 ] + f J O1D ) P(O 3 ) = L(O 3 ) [O 3 ] * (k l ’[OH] + k l ”[HO 2 ] + f J O1D ) NO’ = k’[HO 2 ] + k”[CH 3 O 2 ] 8 March 2011Frank Flocke ACD FFL@ucar.edu42

43. Mauna Loa Hawaii 8 March 2011Frank Flocke ACD FFL@ucar.edu43

44. Mauna Loa Hawaii 8 March 2011Frank Flocke ACD FFL@ucar.edu44

45. Mauna Loa Hawaii 8 March 2011Frank Flocke ACD FFL@ucar.edu45

46. Ozone budget: Box model simulations Profiles of NO and net O 3 production rates during PEM-WEST B, 1994 Separation into two distinct air mass types (high NO x and low NO x ) [Crawford et al., JGR 102, 1997] NO profilesNet P(O 3 ) profiles 8 March 2011Frank Flocke ACD FFL@ucar.edu46

47. Near-Zero NO x troposphere OH + CO  CO 2 + H H + O 2 +M  HO 2 + M HO 2 + O 3  2 O 2 + OH HO + O 3  O 2 + HO 2 ___________________ CO + O 3  CO 2 + O 2 HO 2 + HO 2  H 2 O 2 HO 2 + HO  H 2 O + O 2 H 2 O 2 +hv  2 OH H 2 O 2 + H 2 O (liq)  H 2 O 2(liq) 8 March 2011Frank Flocke ACD FFL@ucar.edu47

48. Back to the role of NO x in the chemistry of the troposphere 8 March 2011Frank Flocke ACD FFL@ucar.edu48

49. HO 2 + NO  NO 2 + OH CH 3 O 2 + NO  NO 2 + CH 3 O CH 3 O + O 2  HO 2 + CH 2 O NO 2 + hv  NO + O O + O 2 + M  O 3 + M O 3 + NO  NO 2 + O 2 P(O 3 ) = [NO] * (k’[HO 2 ] + k”[CH 3 O 2 ]) [NO]/[NO 2 ] = (k[O 3 ] + k’[HO 2 ] + k”[CH 3 O 2 ]) / J NO2 k k’ k” Does NO x cycle around forever? 8 March 2011Frank Flocke ACD FFL@ucar.edu49

50. NO x loss reactions (remote trop) NO 2 + OH + M  HNO 3 + M k n NO x lifetime: τ(NO x ) = τ(NO 2 ) (1+[NO]/[NO 2 ]) Catalytic efficiency: CE ≈ P(O 3 ) / L(NO x ) CO cycle only: CE ≈ k’[NO][HO 2 ] / k n [OH][NO 2 ] 8 March 2011Frank Flocke ACD FFL@ucar.edu50

51. NO x influence on HO x partitioning 8 March 2011Frank Flocke ACD FFL@ucar.edu51

52. Problems 1.Calculate the “critical NO” (P(O3) = L(O3)) for the following conditions: – Surface, t=298K, [HO 2 ] = 40 ppt, [CH3O2] = 25 ppt, [O3] = 40 ppb, [OH] = 1x10 6 ; f = 0.15; J(O 1 D) = 2.5x10 -5 – k’=k”= 8.5x10 -12 cm 3 molecule -1 s -1 – k l ’ = 7.3x10 -14 cm 3 molecule -1 s -1 ; k l ” = 2x10 -15 cm 3 molecule -1 s -1 2.Which of these reactions are the most important? 3.Calculate the lifetime of NO x at the surface and at 10km altitude, considering only losses to HNO 3 1.[OH] = 1x 10 6, J(NO 2 )=1x10 -2 ; consider alt-independent 2.[O 3 ] = 40 ppb / 100 ppb; T=298K / 220K at surf/10km, resp. 3.k = 1.4 x 10 -12 exp(-1310/T) cm 3 molecule -1 s -1 4.k n = 3.3 x 10 -30 (T/300) -3.0 [N 2 ] cm 3 molecule -1 s -1 4.What are the [NO]/NO 2 ] ratios at 0 and 10 km? 8 March 2011Frank Flocke ACD FFL@ucar.edu52

53. Beyond the remote troposphere Addition of a reactive hydrocarbon (isoprene): Enhances [HO x ] Shifts O 3 production peak to larger NO x values Still eventually turns over at high NO x 8 March 2011Frank Flocke ACD FFL@ucar.edu53

54. NO 2 + O 3  NO 3 + O 2 NO 3 + NO 2 + M N 2 O 5 + M NO 2 + NO 2 + H2O liq  HONO g + HNO 3liq NO y : nitrogen “reservoir” species NO 2 + OH + M  HNO 3 + M NO 2 + RO 2 + M ROONO 2 + M NO 2 + RC(O)O 2 + M RC(O)OONO 2 + M NO + RO 2 + M  RONO 2 + M (0-30%) RONO 2 + hv  RO + NO 2 NO + OH + M  HONO + M 8 March 2011Frank Flocke ACD FFL@ucar.edu54

55. NO x catalytic efficiency CE ≈ P(O 3 ) / L(NO x ) [NO]{k’[HO 2 ] + Σ (k’ i [RO 2 ] i )} CE ≈ k n [OH][NO 2 ]+k m [NO 2 ][RC(O)O 2 ] +..+.. ….or determine it experimentally CE ≈ P(O 3 ) / P(NO y -NO x ) 8 March 2011Frank Flocke ACD FFL@ucar.edu55

56. A day in NO x city 8 March 2011Frank Flocke ACD FFL@ucar.edu56 100 75 50 O3O3

57. Experimental determination of CE 8 March 2011Frank Flocke ACD FFL@ucar.edu57

58. NO 2 + O 3  NO 3 + O 2 NO 3 + NO 2 + M N 2 O 5 + M NO 2 + NO 2 + H2O liq  HONO g + HNO 3liq NO y : nitrogen “reservoir” species NO 2 + OH + M  HNO 3 + M NO 2 + RO 2 + M ROONO 2 + M NO 2 + RC(O)O 2 + M RC(O)OONO 2 + M NO + RO 2 + M  RONO 2 + M (0-30%) RONO 2 + hv  RO + NO 2 NO + OH + M  HONO + M 8 March 2011Frank Flocke ACD FFL@ucar.edu58

59. HONO and ClNO 2 NO + OH + M  HONO + M NO 2 + NO 2 + H2O liq  HONO g + HNO3 liq N2O5 + NaCl liq  NaNO 3(liq) + ClNO 2 HONO + hv  OH + NO ClNO 2 + hv  Cl + NO 2 Early morning sources of radicals 8 March 2011Frank Flocke ACD FFL@ucar.edu59

60. Organic Nitrates Peroxy nitrates NO 2 + RO 2 + M ROONO 2 + M Alkyl nitrates NO + RO 2 + M  RONO 2 + M (0-30%) NO + RO 2  NO 2 + RO (70-100%) Peroxy Acyl Nitrates (PANs) NO 2 + RC(O)O 2 + M  RC(O)OONO 2 + M 8 March 2011Frank Flocke ACD FFL@ucar.edu60

61. Alkyl nitrates NO + RO 2 + M  RONO 2 + M (α) NO + RO 2  NO 2 + RO (1-α) P(O 3 ) = (1-α) k [NO][RO 2 ] α ≈ 0.05-0.08 RONO 2 + hv  RO + NO 2 RONO 2  dry deposition − − − 8 March 2011Frank Flocke ACD FFL@ucar.edu61

62. Peroxyacyl nitrates (PANs) NO 2 + RC(O)O 2 + M RC(O)OONO 2 + M Equilibrium is strongly temperature dependent NO + RC(O)O 2  NO 2 + CO 2 + RO 2 In very cold environments / lower stratosphere: RC(O)OONO 2 + hv  RC(O)O + NO 2 RC(O)OONO 2 + OH  products (NO 2 ) 8 March 2011Frank Flocke ACD FFL@ucar.edu62

63. 63 CH 3 – C O O – O – NO 2 Peroxyacetyl nitrate (Peroxyacetic nitric anhydride) PAN structure CH 3 – CH 3 Ethane PAN 8 March 2011Frank Flocke ACD FFL@ucar.edu

64. 64 CH 3 – C O O – O – NO 2 CH 3 – C + O 2 O CH 3 – C + NO 2 O O – O PAN formation Strongly temperature dependent equilibrium hv, OH peroxyacetyl radical 8 March 2011Frank Flocke ACD FFL@ucar.edu

65. 65 CH 3 – C O O – O – NO 2 CH 3 – C + O 2 O CH 3 – C + NO 2 O O – O PAN formation Strongly temperature dependent equilibrium CH 3 C(O)H + OH or + hv (CH 3 ) 2 C=O + hv hv, OH 8 March 2011Frank Flocke ACD FFL@ucar.edu

66. 66 CH 3 – C O O – O – NO 2 CH 3 – C + O 2 O CH 3 – C + NO 2 O O – O PAN formation Strongly temperature dependent equilibrium CH 3 C(O)H + OH or + hv (CH 3 ) 2 C=O + hv Many VOC + OH hv, OH 8 March 2011Frank Flocke ACD FFL@ucar.edu

67. 67 Atmospheric Lifetime of PAN Thermal Photolysis OH 40 minutes2 months 2 years 4 hrs. 1 day 1 week 1 month 1 year3 months 4 years °F°F°C°C 8 March 2011Frank Flocke ACD FFL@ucar.edu

68. a PAN ’ s life HNO 3, PANsPANs VOC NOx (cold) (warm) NO NO 2 O3O3 CO, CH4, long lived VOC O3O3 NOx 8 March 2011Frank Flocke ACD FFL@ucar.edu68

69. NOy partitioning polluted vs. remote Singh et al., NASA 8 March 2011Frank Flocke ACD FFL@ucar.edu69

70. Arctic NOy 8 March 2011Frank Flocke ACD FFL@ucar.edu70

71. 71 ATL, Cumb.,Johnsv.,PP, SOS99 Atlanta: High anthropogenic and biogenic NMHC Power plants: Mainly biogenic NMHC from surrounding forest Johnsonville power plant: NO x emission controlled Cumberland power plant: very high NO x emission (no control) 8 March 2011Frank Flocke ACD FFL@ucar.edu

72. Mexico City Outflow New York City Outflow NYC – low level outflow, lower VOC: Rapid conversion of NOx into HNO 3. Very little NOx remains one day downwind to produce additional ozone. MC –high VOC, and outflow at higher altitudes: Reactive nitrogen is carried out in its organic forms (PANs), which release NOx on a regional scale. This results in additional ozone production further downwind. The high NOx and very high hydrocarbon emissions typical for a megacity like MC combine non-linearly to extend its impacts to a much larger region. New York City vs. Mexico City 8 March 2011Frank Flocke ACD FFL@ucar.edu72

73. CO emissions (PANs ?) 8 March 2011Frank Flocke ACD FFL@ucar.edu73

74. 74 Ratios of different PANs species as indicators of the relative importance of certain hydrocarbon species (and emitters) for the photochemical production of ozone biogenic or anthropogenic ? 8 March 2011Frank Flocke ACD FFL@ucar.edu

75. 75 CH 3 – CH 2 – C O O – O – NO 2 Peroxypropionyl nitrate (Peroxypropionic nitric anhydride) PPN structure CH 3 – CH 2 – CH 3 Propane PPN 8 March 2011Frank Flocke ACD FFL@ucar.edu

76. 76 Alkanes>C 3 + OH + NO x  O 3 PAN PPN PiBN MPAN Propane + OH + NO x  O 3 PAN PPN PiBN MPAN Ethane + OH + NO x  O 3 PAN PPN PiBN MPAN Formation of PANs from NMHC – Summary1 What does PAN/PPN look like for anthropogenically polluted air? 8 March 2011Frank Flocke ACD FFL@ucar.edu

77. 77 PAN/PPN Houston all data TexAQS 2000 campaign, urban and industrial pollution PAN vs. PPN Slope ~ 6 8 March 2011Frank Flocke ACD FFL@ucar.edu

78. 78 PAN/PPN TRACE TRACE-P 2001 campaign - Asian urban and industr. pollution PAN vs. PPN Slope ~ 6 8 March 2011Frank Flocke ACD FFL@ucar.edu

79. 79 C – C O O – O – NO 2 Peroxymethacryloyl nitrate (Methacryl-PAN) MPAN structure H2CH2C CH 3 C – CH H2CH2C CH 3 Isoprene CH 2 MPAN 8 March 2011Frank Flocke ACD FFL@ucar.edu

80. 80 Isoprene + OH + NOx  O 3 PAN PPN PiBN MPAN Alkanes>C 3 + OH + NOx  O 3 PAN PPN PiBN MPAN Alkanes>C 2 + OH + NOx  O 3 PAN PPN PiBN MPAN Ethane + OH + NOx  O 3 PAN PPN PiBN MPAN Formation of PANs from NMHC – Summary alk/iso1 8 March 2011Frank Flocke ACD FFL@ucar.edu

81. 81 SOS 99, all flights PAN – PPN correlation 8 March 2011Frank Flocke ACD FFL@ucar.edu

82. 82 PAN / PPN / MPAN multiple regression PAN/PPN ~ 6, PAN/MPAN ~ 3 8 March 2011Frank Flocke ACD FFL@ucar.edu

83. 83 What about Ozone / PAN ? 8 March 2011Frank Flocke ACD FFL@ucar.edu

84. 84 Cumberland/Johnsonville PAN/O3 8 March 2011Frank Flocke ACD FFL@ucar.edu

85. 85 O3 production from Isoprene in power plant plumes: The yield of PAN from isoprene oxidation is about 20% (we know this from laboratory experiments) The slope of ozone vs. PAN is about 15 molecules of ozone formed per molecule of PAN formed in the plumes (measured) Most of the ozone is formed following oxidation of isoprene (we know this by the absence of PPN and presence of MPAN in these plumes)  The number of ozone molecules formed per isoprene molecule oxidized can be calculated to about 15 · 0.2 = 3 Important result to test plume models, photochemical point models (test of understanding of chemistry by comparison with isoprene flux estimates – isoprene is VERY short-lived!) 8 March 2011Frank Flocke ACD FFL@ucar.edu

86. Problem - Homework The photolysis of acetone, (CH3)2CO and reaction of Acetaldehyde, CH3CHO with OH, are sources of PAN in the atmosphere. Consider only acetone photolysis CH 3 C(O)CH 3 + hv + O 2  CH 3 C(O)OO + CH 3 CH 3 C(O)OO + NO  CH 3 + CO 2 + NO 2 CH 3 C(O)OO + NO 2  PAN PAN  CH 3 C(O)OO + NO 2 Show that: Steady-state [PAN] is independent of [NO x ] [PAN] increases with increasing O 3 and Acetone *use reaction constants from ACD Textbook 8 March 2011Frank Flocke ACD FFL@ucar.edu86

87. So does NO x just cycle between reservoir species and NO,NO 2 and hang around forever? 8 March 2011Frank Flocke ACD FFL@ucar.edu87

88. NO 2 + O 3  NO 3 + O 2 NO 3 + NO 2 + M N 2 O 5 + M N 2 O 5 + H 2 O (liq)  HNO 3(liq) Tropospheric sinks of NO x NO 2 + OH + M  HNO 3 + M HNO 3 + hv  OH + NO 2 HNO 3 + OH  H 2 O + NO 3 NO 3 + NO  2 NO 2 NO 3 + hv  NO + O 2 (8%) HNO 3 +H 2 O (liq)  HNO 3 (liq) 8 March 2011Frank Flocke ACD FFL@ucar.edu88 -3O x -HO x,-O x -2O x

89. Tropospheric sinks of NO x 8 March 2011Frank Flocke ACD FFL@ucar.edu89 Formation of nitrate aerosol* Uptake of HNO 3 onto dust Deposition of (multifunctional) RONO 2, RC(O)OONO 2 onto plants and soils Deposition of (multifunctional) RONO 2 onto aerosols * Reversible for NH 4 NO 3