Secondary Organic Aerosol Secondary Organic Aerosol Formation from Gas and Formation from Gas and

Particle Phase Reactions of Particle Phase Reactions of Aromatic HydrocarbonsAromatic Hydrocarbons

Di HuDi HuPhD Committee MeetingPhD Committee Meeting

March 24, 2004March 24, 2004

Outline Outline

Why aromaticsWhy aromatics

SOA formation potential from SOA formation potential from aromaticsaromatics

Overall goal of my researchOverall goal of my research

Sources of AromaticsSources of Aromatics

Anthropogenic SourcesAnthropogenic SourcesTransportationTransportationSolvent useSolvent useFuel combustionFuel combustion

In the US, transportation sources In the US, transportation sources contribute contribute ~67%~67% to the total aromatic to the total aromatic emissions which range from emissions which range from 1.9 x 101.9 x 1066 to to 2.4 x 102.4 x 1066 tons/year. tons/year.

Why aromatics?Why aromatics?Total US VOC Reactivity Budget

Natural Alkanes40%

Natural Isoprene23%

Other Natural Compounds

6%

Anthropogenic Alkanes12%

Anthropogenic Aromatics

10%

Other Anthropogenic Compounds

9%

Why aromatics?Why aromatics?

TolueneToluene 23.5%23.5%

m,p-Xylenem,p-Xylene 12.6%12.6%

1,2,4-Trimetylbenzene1,2,4-Trimetylbenzene8.5%8.5%

BenzeneBenzene 7.4%7.4%

Composition, Chemistry, and Climate of the Atmosphere; New Composition, Chemistry, and Climate of the Atmosphere; New York, 1995York, 1995

Average Composition in 1ppmC Urban Air

Alkenes12%

Alkanes53%

Unspeciated

6%

Aldehydes2%

Aromatics27%

Jenkin et al. show that in their Jenkin et al. show that in their model calculations up to model calculations up to 40%40% of of photochemically produced photochemically produced ozoneozone can be attributed to emissions of can be attributed to emissions of aromatics in urban areas. aromatics in urban areas. (Atmos. Environ. 1996)(Atmos. Environ. 1996)

SOA Formation Potential of SOA Formation Potential of AromaticsAromatics

CH3

O

O

OH

CH3

O

OH

O

CHO CHO

OH

CHO

OH

O2N

CH3

O

O

OH

O

CH3

O

O

O

CH3

O

O

O

H

OO

H3C

H

O O

CH3

O

H

O

O

H

CH3

O

O

H

H

O

O

H

H

O

O

O

H

CH3

O

O

H

H

O

O

O

CH3

CH3

O

H

O

H

O

O

HO

O

H3C

OH

OHO

CH3

O

O

HO

H

O

O

OH

H

O

O

OCH3

O

OH

OOH

CH3

O

O

O

CH3

O

OH

OO

OH

OO

OH

CH3OH O

O

H

O

OH

CH3

O

OHO

H

O

H

OHO

CH3

O

H

OH

CH3 H

O

OH

O

H H

O

OH

O

H

CH3

O

O

H

OOH CH3

O

H

O

OH

OOO

OH

CH3H O

O

Aromatic aldehydes

Ring-retaining carbonyls

Ring-opening carbonyls

Ring-opening oxo-carboxylic acids

Ring-opeining hydoxy-carbonyls

SOA Formation Potential of SOA Formation Potential of AromaticsAromatics

Recent research has provided strong Recent research has provided strong evidence for polymerization evidence for polymerization reactionsreactions on aromatic aerosols. on aromatic aerosols.

This results in a much lower volatility This results in a much lower volatility SOA material and SOA material and higher aerosol higher aerosol yieldsyields than partitioning can predict. than partitioning can predict.

Evidences for Polymer Evidences for Polymer Formation in SOA from the Formation in SOA from the

Photo-oxidation of Photo-oxidation of Aromatics/NOx SystemAromatics/NOx System

FTIR Spectra of Toluene and FTIR Spectra of Toluene and Glyoxal AerosolsGlyoxal Aerosols

Slide from Dr. Myoseon Jang Slide from Dr. Myoseon Jang

-0.004

0.000

0.004

0.008

0.012

0.016

0.020

0.024

0.028

0.032

0.036

0.040

8001200160020002400280032003600

wavelength (cm-1)

ab

so

rban

ce (

gly

oxal)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

ab

so

rban

ce (

tolu

en

e)

Glyoxal/Acid-Catalyst

OH & COOH

15

59

, N

O217

25

, C

=O

16

45

, O

NO

2

13

40

, N

O2

12

82

, O

NO

2 s

t

C-O

-C s

tretc

h

Toluene/NOx

(NH

4)2

SO

4, 1

10

0

Toluene/NOx/Acid-Catalyst

Kalberer et al. recently have identified Kalberer et al. recently have identified polymers as the main constituents of polymers as the main constituents of SOA formed from the photo-oxidation SOA formed from the photo-oxidation of 1,3,5-trimethylbezene, which of 1,3,5-trimethylbezene, which account for about account for about 50%50% of the aerosol of the aerosol mass after 30 hours of aging. mass after 30 hours of aging. ((Science, 2004Science, 2004))

LDI-TOFMS Spectrum of SOA from LDI-TOFMS Spectrum of SOA from Photo-oxidation of 1,3,5-Photo-oxidation of 1,3,5-

TrimethylbezeneTrimethylbezene

Time Evolution of Polymer in Time Evolution of Polymer in SOA Measured by LDI-MSSOA Measured by LDI-MS

Overall Goal of This ProjectOverall Goal of This Project

Integrate particle phase Integrate particle phase heterogeneous processes with gas heterogeneous processes with gas phase reaction as a unified, multi-phase reaction as a unified, multi-phase, chemical reaction phase, chemical reaction mechanism, which will ultimately mechanism, which will ultimately permit the prediction of amounts of permit the prediction of amounts of SOA that result from aromatics SOA that result from aromatics reacting in the atmosphere.reacting in the atmosphere.

Overall ApproachOverall Approach

Kinetic mechanism developmentKinetic mechanism development

Outdoor chamber experimentsOutdoor chamber experiments

Simulation of chamber experimentsSimulation of chamber experiments

Gas Phase ReactionsGas Phase Reactions

Toluene react with OHToluene react with OH

OCH3

OHO

.

Recent research from Mario Molina’s Recent research from Mario Molina’s group has shown that the pathway to group has shown that the pathway to form epoxide radicals are neglectable.form epoxide radicals are neglectable.

Existing MechanismsExisting Mechanisms

Carbon BondCarbon Bond

Carter’s MechanismCarter’s Mechanism

Master Chemical MechanismMaster Chemical Mechanism

Toluene react with OHToluene react with OH

'C7H8' + OH ---->'C7H8' + OH ----> 0.720.72*'CH3-C6H5(OH)-OO.' +*'CH3-C6H5(OH)-OO.' +

0.10.1*'C6H5CO-H' +*'C6H5CO-H' + 0.180.18*'CRESOL’*'CRESOL’

++0.280.28*HO2*HO2 ++ 0.10.1*XO2 *XO2

@ @ 1.18E-121.18E-12* EXP(* EXP(338.0338.0/TK)/TK)

'CH3-C6H5(OH)-OO.' + NO ---->'CH3-C6H5(OH)-OO.' + NO ----> 0.550.55*'H-CO-CH=CH-CO-H‘*'H-CO-CH=CH-CO-H‘

++ 0.110.11*'CH3-CO-CH=CH-CO-H'*'CH3-CO-CH=CH-CO-H' ++ 0.340.34*'H-CO-C(CH3)=CH-CO-*'H-CO-C(CH3)=CH-CO-

H'H' ++ 0.550.55*'CH3-CO-CO-H' +*'CH3-CO-CO-H' +

0.450.45*'H-CO-CO-H'+ NO2 +HO*'H-CO-CO-H'+ NO2 +HO

@@ 8.1E-128.1E-12

Reaction of 1Reaction of 1stst Generation Generation ProductProduct

'CH3-CO-CH=CH-CO-H' + OH ----> 'CH3-CO-CH=CH-CO-H' + OH ----> 0.20.2*('CH3-CO-CH=CH-CO-O2.‘*('CH3-CO-CH=CH-CO-O2.‘ +H2O) + +H2O) + 0.40.4*'OXOCYL_RAD' + *'OXOCYL_RAD' + 0.20.2*'CH3-CO-CH(OH)-CH(OO.)-CO-H'*'CH3-CO-CH(OH)-CH(OO.)-CO-H' + + 0.20.2*'CH3-CO-CH(OO.)-CH(OH)-CO-H'*'CH3-CO-CH(OO.)-CH(OH)-CO-H' @ @ 5.58E-115.58E-11

'OXOCYL_RAD' + NO -O2-> 'Maleic anhydrid' + 'CH3.' + NO2 'OXOCYL_RAD' + NO -O2-> 'Maleic anhydrid' + 'CH3.' + NO2 @ @ 3.03.0*k_MEO2_NO*k_MEO2_NO

'CH3-CO-CH(OH)-CH(OO.)-CO-H' + NO ---->'CH3-CO-CH(OH)-CH(OO.)-CO-H' + NO ---->0.130.13*C5OHNO3 *C5OHNO3 + + 0.870.87*('CH3-CO-CH(OH)*('CH3-CO-CH(OH)--CH(O.)-CO-H' + CH(O.)-CO-H' +

NO2)NO2) @ @ 0.710.71*k_MEO2_NO*k_MEO2_NO

'CH3-CO-CH(OH)-CH(O.)-CO-H' + O2 ----> 'CH3-CO-CH(OH)-CH(O.)-CO-H' + O2 ----> 0.30.3*(C4OHALD + CO + H2O) *(C4OHALD + CO + H2O) + + 0.50.5*('CH3-CO-CO-H'+ 'H-CO-CO-H'+ HO2)*('CH3-CO-CO-H'+ 'H-CO-CO-H'+ HO2) + + 0.20.2*(C5OHALD+ HO2)*(C5OHALD+ HO2) @ k_DEC@ k_DEC

22ndnd Generation Gas Phase Generation Gas Phase ProductsProducts

33rdrd Generation Gas Phase Generation Gas Phase ProductsProducts

Simulation Results of Gas Simulation Results of Gas Phase ChemistryPhase Chemistry

Particle Formation Particle Formation ProcessesProcesses

G/P PartitioningG/P Partitioning

Particle Phase ReactionsParticle Phase Reactions

G/P PartitioningG/P Partitioning

CH3

O

OH

O

KKpp = =kkonon//kkoffoff = 7.501RTf = 7.501RTfomom/(10/(1099MwMwpp00LL))

kkoffoff=k=kbbT/T/hh exp(-E exp(-Eaa/RT)/RT)

kkbbT/T/h h = 6.21= 6.2110101212 sec sec-1 -1 at 298Kat 298K

Relate ERelate Eaa to log to log ppooLL

kkonon==KKPPkkoffoff

CH3

O

OH

O

To Represent These To Represent These Processes in the MechanismProcesses in the Mechanism

C4OHALDC4OHALDgasgas + SEED ----> C4OHALD + SEED ----> C4OHALDpartpart + SEED+ SEED @ kon@ kon

C4OHALDC4OHALDgasgas + TSP ----> C4OHALD + TSP ----> C4OHALDpartpart + TSP + TSP @ kon@ kon

C4OHALDC4OHALDpartpart ----> C4OHALD ----> C4OHALDgasgas @ koff @ koff

Particle Phase ReactionsParticle Phase Reactions

Particle Phase ReactionsParticle Phase Reactions

Particle Phase ReactionsParticle Phase Reactions

HH

O

O

CH3

O

OH

O

HH

O

O CH3

O

OH

O

GlyP + H2O ----> Gly2OHP @ kpart1 GlyP + H2O ----> Gly2OHP @ kpart1

Gly2OHP + H2O ----> Gly4OHPGly2OHP + H2O ----> Gly4OHP @ kpart2 @ kpart2

Gly4OHP + GlyAcidP ----> pre-Poly1 @ kpart3Gly4OHP + GlyAcidP ----> pre-Poly1 @ kpart3

Pre-Poly1 + C4OHALD ----> Poly1Pre-Poly1 + C4OHALD ----> Poly1 @ @ kpart4kpart4

Do these reactions well represent what Do these reactions well represent what really happens in the particle phase?really happens in the particle phase?

Particle phase reaction rate coefficientsParticle phase reaction rate coefficients

Outdoor Chamber Outdoor Chamber ExperimentsExperiments

The Outdoor Chamber Reactor The Outdoor Chamber Reactor SystemSystem

Hanging TeflonHanging Teflon

Dual 270mDual 270m33 chamber chamber fine particle t fine particle t 1/21/2 >17 h >17 h

Product AnalysisProduct Analysis

Toluene/propylene/NOx/sunlight Toluene/propylene/NOx/sunlight chamber experiments were carried chamber experiments were carried out with neutral seed and acidic out with neutral seed and acidic seed. seed.

Analytical MethodsAnalytical Methods

DerivatizationDerivatization methods to identify methods to identify the the precursors of polymersprecursors of polymers..

LC-ESIMS/MSLC-ESIMS/MS to identify to identify structure of structure of polymers. polymers.

PFBHA PFBHA O-(2,3,4,5,6-O-(2,3,4,5,6-pentafluorobenzyl) -hydroxylamine for pentafluorobenzyl) -hydroxylamine for

carbonyl groupscarbonyl groups

FF

F

F F

CH2 O NH2

H2O

PFBHA

R1

C

O

R2

CH2

F F

F

FF

ONC

R1

R2

acetone or ketone

PFBBrPFBBr, Pentafluorobenzyl bromide , Pentafluorobenzyl bromide derivatization for carboxylic and aromatic-OHderivatization for carboxylic and aromatic-OH

CH2 C

O

OH

H3C CH3

C

O

H O

FF

F

F F

CH2Br

C CH2

O

HO C O CH2

F F

F

FF

OH3C CH3

HBr

PFBBr

C CH2

O

O C O CH2

F F

F

FF

OCH3 CH3

CH2

FF

F

F F

2 HBr

The three slides are from Prof. Rich KamensThe three slides are from Prof. Rich Kamens

BSTFA BSTFA for hydroxyl, and/or carboxylic for hydroxyl, and/or carboxylic groupsgroups

BSTFA

R OH

carboxylic acid or alcohol

C N

Si(CH3)3

CF3

O(CH3)3Si

R

O(CH3)3Si

BFBF33-CH-CH33OH + BSTFA OH + BSTFA Derivatization MethodDerivatization Method

C

O

HO CH2 C

OH

C

CH3

O

OH + CH3 OHBF3

excess

C

O

CH3O CH2 C

OH

C

CH3

O

OCH3

C

O

CH3O CH2 C

O

C

CH3

O

OCH3

Si(CH3)3

C NSi(CH3)3F3C

O

Si(CH3)3

C

O

CH3O CH2 C

OH

C

CH3

O

OCH3 +

excess

+

C NHSi(CH3)3F3C

O

C NH2F3C

O

TMCS

GC-ITMS analysisGC-ITMS analysis

- electron impact ionization (EI)- electron impact ionization (EI)

- methane chemical ionization (CI-methane)- methane chemical ionization (CI-methane)

- tandem mass spectrometry (MS/MS)- tandem mass spectrometry (MS/MS)Slide from Dr. Mohammed JaouiSlide from Dr. Mohammed Jaoui

Citramalic acid

Particle Phase Reaction Rate Particle Phase Reaction Rate CoefficientsCoefficients

Too ambitious to measure the rate Too ambitious to measure the rate coefficient of each single particle phase coefficient of each single particle phase reaction.reaction.

Cross reaction of the multi-functional Cross reaction of the multi-functional aldehydesaldehydes

Many products are not commercially Many products are not commercially available.available.

Simple methyglyoxal experiments (daytime/NOx, Simple methyglyoxal experiments (daytime/NOx, nighttime)nighttime)

Do chamber experiment with different toluene and Do chamber experiment with different toluene and NOx concentrations at different RH and NOx concentrations at different RH and temperature.temperature.

Measure particle mass, acidity and HNO3 in particle Measure particle mass, acidity and HNO3 in particle phase.phase.

Explore relationships that influence rates of Explore relationships that influence rates of particle formationparticle formation– particle HNO3particle HNO3– RH and temperatureRH and temperature

Overall ApproachOverall Approach

Kinetic mechanism developmentKinetic mechanism development

Outdoor chamber experimentsOutdoor chamber experiments

Simulation of chamber experimentsSimulation of chamber experiments

Future PlanFuture Plan

Methylglyoxal experiments in this summerMethylglyoxal experiments in this summer

Some of the toluene/NOSome of the toluene/NOx x chamber chamber

experimentsexperiments

Proposal at the end of this summerProposal at the end of this summer

Thank you for your Thank you for your timetime