Interfaces Between Gas Phase Mechanisms and Aqueous Chemistry

Transcription

1 Interfaces Between Gas Phase Mechanisms and Aqueous Chemistry Hartmut Herrmann with Andreas Tilgner, Paolo Barzaghi, Dirk Hoffmann, Yoshi Iinuma and laf Böge Leibniz-Institut für Troposphärenforschung (IfT), Leipzig UC Davis,

2 (A) Motivation (B) The IfT Chemistry Dept. Aqueous Phase Kinetics Laboratory Recent results on the reactivity of atmospheric aqueous phase radicals (e.g. H, N 3 ) (C) The CAPRAM mechanism line Recent developments: rganic chemistry extension, halogen module (D) The IfT LEAK Aerosol chamber experiments Recent results from chamber experiments on the formation of macromolecular compounds utline

3 The Atmospheric multiphase system (Jaeschke, 1986)

4 Why Radicals? Even though the concentrations of radicals in clouds and deliquescent aerosols are thought to be small they are able to convert both inorganic and especially organic particle constituents into chemically different reaction products. Tropospheric aqueous phase radical chemistry

5 Lab studies of H aqueous phase reactions

6 Facilities at the aqueous phase process laboratory of the IfT

7 Blue laser 473nm mirror Ecximer Laser KrF λ = 248 nm Trigger unit mirror Photodiode Computer Thermostated Reaction Cell lens Solution inlet Digital oscilloscope To pump Excimer mirror Laser photolysis / long path laser absorption (LP-LPLA) set-up

8 H hν (248 nm) 2 H H + SCN - SCNH - SCNH - SCN +H - SCN + SCN - (SCN) - 2 (R-a) (R-b) (R-c) (R-d) H + reactant product (R-e) k b/c (T) = exp (-15.8 kj mol -1 /RT) M -1 s -1 (Chin and Wine, 1992) k b/c (T) = exp (-11.1 kj mol -1 /RT) M -1 s -1 (Elliot and Simsons, 1984) k b/c (T) = exp (-13.8 kj mol -1 /RT) M -1 s -1 (Chin and Wine, 1994) Details: Ervens, Gligorovski and Herrmann, Phys. Chem. Chem. Phys. 2003, 5, H Competition kinetics: Experimental method

9 Compound Formule k 298K ( M -1 s -1 ) Acetone CH 3 CCH 3 (2.1 ± 0.6) 10 8 (this study) (1.7 ± 0.5) 10 8 (Monod et al., 2002) 2-Butanone CH 3 CCH 2 CH 3 (1.5 ± 0.7 ) 10 9 (this study) (George et al., 2002) Acetonylacetone CH 3 CCH 2 CH 2 CCH 3 (7.6 ± 1.1 ) 10 8 (this study) Isobutyraldehyde (CH 3 ) 2 CHCH (2.9 ± 1.0 ) 10 9 (this study) Ethyl Formate HCC 2 H 5 (3.2 ± 0.8 ) 10 8 (this study) (Adams et al., 1965) bserved rate constants for reactions of H with organic compounds in aqueous solution at 298 K

10 T-Dependency studies of H reactions with diols in aqueous solution

11 Compound A l/mol s E A kj/mol G kj/mol H kj/mol S J/K mol Carbonyl Compounds Acetone (2.8 ± 0.5) (18 ± 11) (26 ± 20) (16 ± 10) -(34 ± 6) 2-Butanone (1.2 ± 0.2) (23 ± 10) (21 ± 12) (20 ± 9) -(3 ± 0.4) Acetonylacetone (5.1 ± 0.1) (16 ± 8) (22 ± 13) (14 ± 7) -(29 ± 3) Isobutyraldehyde (3.0 ± 0.1) (6 ± 3) (19 ± 10) (3 ± 2) -(53 ± 3) Diacetyl (8.7 ± 1.2) (20 ± 10) (24 ± 11) (7 ± 3) -(57 ± 4) Diols 1,2-Ethanediol (9.1 ± 0.2) (10 ± 2) (20 ± 4) 7 ± 1 -(43 ± 1) 1,2-Propanediol (2.0 ± 0.3) (12 ± 8) (20 ± 17) 9 ± 7 -(37 ± 5) 1,3-Propanediol (2.7 ± 0.3) (12 ± 6) (19 ± 12) 9 ± 5 -(34 ± 3) 1,2-Butanediol (5.2 ± 0.5) (13 ± 7) (19 ± 12) 11 ± 6 -(29 ± 3) 1,4-Butanediol (1.9 ± 0.1) (10 ± 2) (19 ± 4) 7 ± 1 -(37 ± 1) Activation parameters for the reactions of H with organic compounds

12 E A = -(46 ± 32) + (0.15 ± 0.08) BDE (C-H) (n = 20; r = 0.63) : Gligorovski and Herrmann, 2004 : Weigert et al. 2006, in preparation Evans-Polanyi plot for H-atom abstraction reactions of H in aqueous solution

13 12,0 N o 1 Reactant acetone 11,5 2 tert-butanol log k H / l mol -1 s -1 11,0 10,5 10,0 9,5 9,0 8,5 8,0 7, * * * lg (k H /M -1 s -1 ) = (33 ± 3) - (0.06 ± 0.01) BDE /kj mol -1 n = 10; r = 0.99; 381 < BDE < 411 aqueous phase lg (k H /M -1 s -1 ) = (32 ± 4) - (0.06 ± 0.01) BDE /kj mol -1 n = 11; r = 0.98; 373 < BDE < 411 gas phase * 7, BDE / kj mol acetonylacetone ethyl formate 2-butanone ethanol 1-propanol 1-butanol 2-propanol 2-butanol acetaldehyde propionaldehyde butyraldehyde isobutyraldehyde Comparison of Evans-Polanyi plot for H-atom abstraction reactions of H in aqueous solution and in gas phase (Gligorovski and Herrmann, 2004)

14 Controller ST133 Spektrograph + ICCD-Camera L Moveable mirror Deuterium -Lamp Photodiode Moveable mirror Irisblende Argon-Ion-Laser (λ = 244 nm) WS 1 PC Cell V=28ml WS 2 L S Excimer Laser Pulse-Delay/ Trigger scilloscope λ = 193 nm λ = 248 nm Set-up for H/R 2 kinetic and spectroscopic studies in aqueous solution

15 Modelled aqueous phase concentrations of the H radical for the urban and remote scenario

16 Spectra Nr. Parent Compound ph λ max (nm) ε 10 (l mol -1 cm -1 ) 1 a 2-Propanol b 1-Butanol c 2-Butanol d Propionaldehyde e Butyraldehyde f Acetone g 2-Hydroxy-3-butanone ε 10 [l mol -1 cm -1 ] a b c ε 10 [l mol -1 cm -1 ] d e f g Wavelength [nm] Wavelength [nm] Spectroscopic investigations: Alcohols and ketones

17 Spectra Nr. Parent Compound ph λ max (nm) ε 10 (l mol -1 cm -1 ) A a Glutaric acid b Adipic acid c Pimelic acid d Suberic acid e Glutarate (dianion) f Adipate (dianion) g Pimelate (dianion) h Suberate (dianion) B i Tartronic acid j D,L-Malic acid k Tartronate (dianion) l Malate (dianion) Spectroscopic investigations: Carboxylic acids and their anions forms

18 Electron Transfer (ETR): ED + X > ED + + X - e.g.: Mono- and Diacids: R-C()- - + X > R-C()- + X- Then decarboxylation might occur leading to C-Chain shortening: R-C()- > R + C 2 Note: ETR involves also much transition metal chemistry Solution phase non-radical reactions, e.g. ozonolysis rganic chemistry non-radical reactions. e.g. acidcatalysed condensations ther Special Aqueous Phase Reactions Note: The decarboxylation rate constants are often grossly overstimated!!

19 The CAPRAM mechanism line: Recent developments

20 CAPRAM 3.0i verview Box model results The air parcel model SPACCIM verview Simulation results Study case Summary utline part II

21 Gas phase mechanism consists of an updated and revised RACM mechanism, lumped mechanism Uptake processes of soluble species following the approach by Schwartz (1986) Multiphase mechanism incorporates the chemical aqueous phase radical mechanism CAPRAM 3.0 (Herrmann et al., 2005) Multiphase chemistry mechanism RACM-MIM2ext/CAPRAM3.0i

22 1. Initiation reaction RH + X R + HX ( X = H, N ) 3 2. Peroxyl radical formation 2 R R 3a. Peroxyl radical unimolecular decomposition R R 2 R H C C + H (R- = alkyl, H, H) R 3b. Peroxyl radical bimolecular decomposition (after von Sonntag and Schuchmann, 1997) R R R Basic organic chemistry in CAPRAM R C + R CHH HC CH 2 R (R- = alkyl, H, H) 4 2C + H 2 2 R R 2 R 2CH + 2

23 CH 3 CC H H H 2 Hydroxyacetone H 2 CH 3 CCH. H CH 3 CCH H H CH 3 CCH H.. H H 2 CH 3 CCH. Pyruvic Acid Gas phase input H 2 2 H CH 3 CCH 2 H CH 3 CC H H 2 H 2 H CH 3 CCH H H H CH 3 CCH. 2 H 2 2 H CH 3 CCH 3 H CH 3 CCH 2. CH 3 CCH 2 CH 3 CCH 2. Methylgloxal H. H 2 H. CH 3 CCH 3 2-Propanol 2 CH 3 CCH. 2 2 H 2 H CH 3 CCH 3. H 2 H CH3CCH3 Acetone In the remote scenario, the aqueous phase oxidation of acetone can contribute up to 40% to the production fluxes of Methyl Glyoxal (MGly) in the aqueous phase. Aqueous phase oxidation of acetone in CAPRAM 3.0

24 2.5e e-13 conc. [moles / l] 1.5e e e H CAPRAM 2.4 H CAPRAM 3.0 Aqueous phase concentrations of H obtained with CAPRAM 2.4 and 3.0 for the remote scenario

25 2.5e e-14 conc. [moles / l] 1.5e e e N3 CAPRAM 2.4 N3 CAPRAM 3.0 Aqueous phase concentrations of N 3 obtained with CAPRAM 2.4 and 3.0 for the remote scenario

26 Comparison of sinks and sources for H (aq) (remote scenario, noon 2.day)

27 meteorological scenario based on the calculations of Pruppacher and Jaenicke (1995) 8 cloud passages of about 2 hours within 4.5 days ( 4 day- and 4 nighttime clouds) intermediate aerosol state at 90 % relative humidity assumption: well diluted particles simulations for three atmospheric scenarios:[start: 0:00 19 th June, 45 N] urban, remote and marine with and without aqueous phase chemistry interactions (used acronym: wocloud) Scheme of the meteorological scenario (air parcel model trajectory)

28 Modelled gas phase concentrations of the H radical for the urban and remote scenario

29 H [aq] sinks and source fluxes (urban scenario)

30 A Case Study

31 Important multiphase aqueous phase organic oxidations in CAPRAM

32 Modelled aqueous phase sinks and sources of oxalic acid (remote case)

33 +130 ng m ng m -3 Modelled aqueous phase C 3 chemistry productions

34 Modelled aqueous phase C 3 chemistry productions

35 Significant effects on the tropospheric oxidation budget Influenced oxidation of VC s due to the changed oxidation budget Significant differences in the aqueous phase chemistry of cloud droplets and wet particles The potential importance of the deliquescent particles as a reactive chemical medium due to the in-situ production of radical oxidants and no-radical oxidants in the aqueous phase The importance of the aqueous phase for the formation substituted mono- and diacids Size-resolved organic mass productions and spectral processing of the particle distributions The importance of the consideration of aqueous phase processes in future higher scale models Summary: CAPRAM 3.0i + SPACCIM

36 Goto : More about CAPRAM

37 Recent results from laboratory experiments on SA formation following ozonolysis of terpenes

38 Volume: 17.7 m 3 S/V ratio: 2.1 m -1 Temperature range: K Material: FEP-Teflon Block Diagram of the new IfT Aerosol Chamber LEAK (Leipziger Aerosol Kammer)

39 The LEAK Building

40 Material: Volume: S/V Ratio: Temperature Range: Humidity Range: UV Lamps: Gas Measurements: Particle Measurements: FEP-Teflon 17.7 m m K (16-35 C) 10-85% sram Eversun 5.6kW total 3 monitor, nline GC/FID, PTR/MS Denuder-Filter (CE/MS, HPLC/MS, GC/MS), TF-AMS, DMPS The new IfT Aerosol Chamber LEAK (Leipziger Aerosol Kammer)

41 β-pinene Limonene Initial HC Conc. [ppbv] [ppbv] RH% Temp [ºC] Reaction Time [h] Sampling Time [h] No. of Exp No. of Samples (for each condition) (2 m 3 ) 5 x Neutral 5 x Acidic 5 x Strongly Acidic 3 x QF ( TC) 2 x PTFE (Speciation) (2 m 3 ) 5 x Neutral 5 x Acidic 5 x Strongly Acidic 3 x QF ( TC) 2 x PTFE (Speciation) Experimental Condition

42 Thermography Quantification of TC on seed particle CE/ESI-ITMS Quantification of monomeric compounds 1D or 2D HPLC/ESI-TFMS&/ESI-ITMS Characterisation of dimers/oligomers Analytical Methods

43 Formation of Dimers and ligomers

44 TC [µgc m -3 ] Neutral 650&850 C Acidic 650&850 C Strongly Acidic 650 C Strongly Acidic 850 C 20 0 Methylencyclohexane β-pinene Limonene No significant difference found between neutral and acidic seed particles. Much higher TC was observed for methylenecyclohexane and β-pinene in presence of strongly acidic particles whereas limonene did not exhibit this behaviour. The effect possibly hidden by extremely high SA yield of limonene Not all organics evaporated at 650 C for strongly acidic cases. 850 C was required. Indirect evidence of influence of strong acidity on particle phase products? TC

45 Limonene

46 Total Ion Chromatogram No significant difference except lower intensities for the strongly acidic case (confirms the CE/ESI-ITMS result) Mass Spectra min m/z 281 under acidic conditions min m/z under acidic conditions min m/z 465, under acidic conditions Limonene Dimer/ligomer Analysis

47 201 Base Peak Chromatogram (m/z ) m/z 281 detected only under acidic conditions , Base Peak Chromatogram (m/z ) Clear influence of acidity Larger peaks under acidic conditions Although TIC was smaller for the strongly acidic case, no such trend was observed for BPC Limonene Dimer/ligomer Analysis

48 m/z TF Suggested Elemental Composition 281 C 10 H 17 5 S- 453 C 18 H S- 465 C 20 H S- 481 C 20 H S- 483 C 23 H 31 9 S- Bond Neutral Acidic R S H R S R R S R R S R R S R Strongly Acidic x x x x x m/z TF Suggested Elemental Composition 369 C 19 H C 18 H C 19 H Bond Neutral Acidic R R/ H R C CH R R R/ H R C CH R R R/ H R C CH R Strongly Acidic 387 C 22 H R R 401 C 19 H C 20 H R R/ H R C CH R R R/ H R C CH R 355 C 18 H R R/ H R C CH R >500???? Influence of seed particle acidity on m/z 281 and compounds > m/z 400 TFMS suggested elemental compositions and MS/MS fragments suggests sulphate ester structures for these compounds Most dimers between m/z are detected regardless of seed particle acidities (i.e. no influence of acidity possibly peroxycarboxylic acid dimers) Summary of Limonene Dimer/ligomer Products

49 Influence of Acidity on Compounds > m/z 500

50 3mer 3mer 4mer 4mer 3mer 3mer 4mer 4mer 5mer 3mer 3mer 4mer 4mer 5mer Much higher amounts of compounds over m/z 500 are found under acidic conditions Acidity does influence the Mw of oligomeric compounds acid catalysed reactions still important Much larger molecules were observed in endo-exo-cyclic limonene than β-pinene or α-pinene (previous work) It seems more complex the structure is (i.e. reaction mechanisms), higher the molecular weights of early generation oligomers The distribution of compounds > m/z 500 can be explained by the combination of Cn, Cn-1, Cn-2, Cn-3 etc. oxidation products (hence 14 or 16 differences) and a number of sulphate ester units or peroxyacid units. There is not a DINSAUR. Compounds beyond m/z 500

51 A possible formation pathway for limonene sulphate ester m/z 281 S 2 H 2 HS 3 - S 3 2- xidation (l) CH (g) CH Limononaldehyde 3 H 2 S 4 HS 4 - S HS 4 CH S H H H + hydroxylimononaldehyde sulphate ester H 2 2 or RC()H (l) CH (g) CH Epoxylimononaldehyde or 3-(2-methyloxiran-2-yl)-6-oxoheptanal Potential Atmospheric Relevance? Bridging Inorganic and rganic Chemistry

52 Cn-1 compounds accounts 60-70wt% of the total detected monomers for β-pinene and a model compound (methylenecyclohexane) whereas Cn and Cn-1 monomers were found in similar amounts in limonene SA Dimers found regardless of seed particle acidities appear to be peroxycarboxylic acid dimers Sulphate esters (inc. m/z < 300) were detected only from terpenes (or a model compound) with an exocyclic double bond under our experimental conditions (the location of double bond important) The exact formation mechanisms of sulphate esters are not still clear though it seems to involve acid catalysed nucleophilic addition of sulphate Sulphate esters from terpene oxidation are not only chamber compounds. There is evidence of sulphate esters in atmosphere. Summary oligomer studies

53 The troposphere is a multiphase system. Complex chemistry occurs in aqueous particles. Radical chemistry is studied with emphasis on organics oxidation further to pure gas phase reactions Lab results are being used to further develop CAPRAM (and other schemes). Emphasis is on organics, currently up to C 4 Further development of schemes such as CAPRAM might be performed applying reactivity correlations for the estimation of rate constants rather than applying directly measured data only rganic reactions in the tropospheric particle phase are able to produce high-molecular weight products including organic sulphate esters verall Summary

54 Particle phase chemistry should be better described There are coupling to important issues in atmospheric chemistry: Acid production Change of atmospheric oxidation capacity Production of particle mass and, especially, organic mass Particle radiative properties Particle hygroscopicity and CCN efficiency, ACI In both cloud drops as well as in deliquescent particles aqueous phase reactions occur VC chemistry is linked to particle chemistry both for AVC and BVC Wider Issues and utlook

55 H H + + H 2 H+ H + H H H H Aerosol Chamber: Yoshi Iinuma, laf Böge, Yunkun Miao, Conny Müller Aqueous Phase Kinetics: Paolo Barzaghi, Dirk Hoffmann, Kshama Parajuli, Saso Gligorovski (now Marseille) CAPRAM: Andreas Tilgner Funding: EC (MST (EVK2-CT ) BMBF (BEWA, MDMEP, FEBUK) DFG (HE-3086/4-1) Acknowledgements