Gas-Particle Partitioning of Carbonyls inSimulation Chamber Studies of

Secondary Organic Aerosol Formation

John Wenger, Robert Healy, Kristina Kuprovskyte, Shouming Zhou

Department of Chemistry and Environmental Research InstituteUniversity College Cork

Ireland

Gas/Particle Partitioning

• Many organic compounds partition between gas and particle phase

• Kp=[particle phase]/[gas phase][aerosol]

VOC

Gas phase products

oxidized

KpOrganic aerosol

Denuder-Filter Sampling

Particle phase

Gas phase

Air Flow

Denuder tube coated with XAD-4 resin

Filter

Sorbent

Typically used for non-polar organic compounds

• Aim: to apply denuder-filter sampling to studies of SOA formation

• Secondary organic fraction represents up to 70% of the organic fraction of fine aerosols

• Composition of SOA ?

• Formation mechanisms ?

• Main species contributing to SOA ?

Secondary Organic Aerosol (SOA)

Biogenic Precursors of SOA

Seinfeld & Pankow, Annu. Rev. Phys. Chem. 2003. 54:121–40

Anthropogenic Precursors of SOA

Seinfeld & Pankow, Annu. Rev. Phys. Chem. 2003. 54:121–40

SOA Formation

Emission ofVolatile Organic

Compounds

SOA PrecursorsAlkanes (>C7)

AromaticsAlkenes (>C6)

~100 compounds

High volatility productsCarbonyls

Low volatility productsMultifunctional oxygenates

Reaction withOH, O3, NO3 Gas-particle

Partitioning

Derivatization of oxygenated organics

Yu et al. ES&T 1998, 32, 2357-2370

FF

F

F F

O N

N O

F

F

F

F

F

MW = 448

Fragment mass = 181

Glyoxal derivatizedfragments here

More than one isomer possible- (multiple peaks)

O

Oglyoxal derivatizes

Example: OH + Limonene SOA

Jaoui et al., ES&T, 2006, 40, 3819-3828

Denuder-Filter Sampling at UCC

• 5-channel glass denuder

• Coated with XAD-4 resin

• Denuder and filter doped with pentafluorobenzyl hydroxyl amine (PFBHA) to convert polar carbonyls to oximes

Denuder Tube(gas collection)

Filter pack (particle collection)

Air flow

Trapping Efficiency Tests• Range of carbonyls introduced to chamber (10 - 200 ppbv)

To pump To pump

Denuder tube coated withXAD-4 and PFBHA

Sampling ports

Impinger system

PFBHA in H2O

6000 L FEP Teflon chamber

Trapping efficiency =100*(1-Cout/Cin)

XAD-4 vs XAD-4/PFBHABenzaldehyde

0

20

40

60

80

100

120

10 20 30 40 50

Time (min)

Trap

ping

Effi

cien

cy (%

) XAD-4

XAD-4 +PFBHA

O

XAD-4 vs XAD-4/PFBHAMethylglyoxal

0

20

40

60

80

100

120

10 20 30 40 50

Time (min)

Trap

ping

Effi

cien

cy (%

) XAD-4

XAD-4 +PFBHA

O

O

Temime et al., ES&T, 2007, 41, 6514-6520

Atmospheric Simulation Chamber at UCC

• FEP foil (6000 litres)• Dry purified air• Atmospheric P and T• Humidity control

• on-line GC• NOx and O3 analysers• denuder – filter, GC-MS• Particle Sizer and counter

p-xylene photo-oxidation experiment

• Aerosol mass yield=3.84%

0

100

200

300

400

500

600

700

800

-30 70 170 270 370 470

Time (min)

ppbv

0

50

100

150

200

250

300

350

400

450

ugm

-3

Lights OffLights On

NO NO2

Aerosol mass

O3

p-xylene/5

p-xylene photo-oxidation

OH

O

O

O

O

O

O

O

O

O

OH additionH-abstraction

ringcleavage

OH addition

O

O

GC-MS Analysis of p-xylene extracts (filter)

1

2

3

4

5

6

7

8

Reconstructed ion chromatogram (m/z 181) of a filter extract from XYL_NOx_11: glyoxal 2: methylglyoxal 3: oxopropanedial 4: 2,3-dioxobutanal 5: 3-hexene-2,5-dione6: 2-hydroxy-3-oxobutanal 7: 2,3-dioxobutanal 8: oxopropanedial.

Denuder-Filter vs Filter Alone

0

10000

20000

30000

40000

50000

60000

70000

80000

glyoxal methylglyoxal hexenedione p-tolualdehyde

GC

-MS

resp

onse

Denuder FilterFilter alone

GC-MS Analysis of p-xylene extracts (filter)

XYL_NOx_1 XYL_NOx_2

Relative humidity (%) <5 24

glyoxal 3.88 ± 0.26 4.37 ± 0.70

methylglyoxal 3.72 ± 0.12 3.47 ± 0.74

oxopropanedial 0.66 ± 0.06 0.79 ± 0.14

2,3-dioxobutanal 5.22 ± 0.11 6.19 ± 0.57

2-hydroxy-3-oxobutanal 0.38 ± 0.04 0.31 ± 0.03

p-tolualdehyde not observed 0.84

3-hexene-2,5-dione 2.06 ± 0.28 2.44 ± 0.34

Total identified 15.92 ± 0.87 18.41 ± 2.52

% Contribution to SOA mass

Gas/Particle Partitioning Values

• Kp calculated both theoretically:

610760

×°×××××

=Lomom

omltheoretica PMW

TRfKpγ

• MWom= Average molecular weight of organic species in particles (=120)

• fom= fraction of particle that is organic (= 1)• γom = Activity coefficient (assumed =1)• Po

L = sub-cooled vapour pressure

Pankow,Atmos Environ,1994

Gas/Particle Partitioning Values

• Kp calculated both theoretically:

• and experimentally:

][exp aerosolCC

Kpgas

particle

×=

610760

×°×××××

=Lomom

omltheoretica PMW

TRfKpγPankow,

Atmos Environ,1994

Gas/Particle Partitioning Values

• Glyoxal and methylglyoxal Kp several orders of magnitude higher than expected

p-tolualdehyde Hexenedione Glyoxal Methylglyoxal

Kptheoretical 3.2x10-07 1.3x10-06 9.8x10-10 2.0x10-09

Kpexperimental 4.3x10-06 3.8x10-05 4.2x10-05 3.3x10-05

Kpexp/theory 13 29 43238 16963

(vapour pressures from SPARC on line calculator- University of Georgia)

Experiments at PSI Chamber

Healy et al., ACP, 2008, 8, 3215-3230

Denuder-Filter Configurations

• Setup 2 allows for the trapping efficiency of the tube to be tested for each experiment

Tube 1

Tube 2

FilterTube 1

Filter

Tube 2

AIR

FLOW

Setup 1(Typical)

Setup 2(Gas-phase breakthrough)

AIR

FLOW

Gas phase

Particle phase

Gas phase breakthrough

glyoxal Methylglyoxal

Denuder vs Filter Extracts

Photooxidation of Isoprene

O

methacrolein

O

methyl vinyl ketoneO

Oglyoxal

O

O

methylglyoxal

OHO

glycolaldehyde

O

HO

hydroxyacetone

OHO

C4 hydroxycarbonyl

O

C5 carbonyl

Photooxidation products

Gas/Particle Partitioning Values

• methacrolein, methylvinylketone not detected in particle phase

• Glyoxal and methylglyoxal Kp several orders of magnitude higher than expected

glycolaldehyde Hydroxyacetone Glyoxal Methylglyoxal

Kptheoretical 3.6x10-07 7.2x10-07 9.8x10-10 2.0x10-09

Kpexperimental 2.2x10-05 1.5x10-05 4.4x10-05 6.7x10-06

Kpexp/theory 59 20 45538 3476

Photooxidation of 1,3,5-TMB

Gas/Particle Partitioning Values

2-methyl-4-oxo-2-pentenal Methylglyoxal

Kptheoretical 9.3x10-07 2.0x10-09

Kpexperimental 1.8x10-04

*1.3x10-04

1.2x10-05

*2.0x10-05

Kpexp/theory 190 6256

*Obtained using PTR-MS with denuder and heated inlet to vapourize SOA;Hellen et al, ES&T, (2008), 42, 7347-7353.

SOA Formation mechanisms

Emission ofVolatile Organic

Compounds

SOA PrecursorsAlkanes (>C7)

AromaticsAlkenes (>C6)

~100 compounds

High volatility productsCarbonyls

Low volatility productsMultifunctional oxygenates

Reaction withOH, O3, NO3 Gas-particle

Partitioning

Kp exp ≈ Kp calc

Kp exp >> Kp calc

HeterogeneousReactions*

Acid-catalyzed Oligomerization-uptake of glyoxal to particles

Liggio et al.,ES&T, 2005, 39, 1532-1541

O

H

OH

OH

H

OH

OH

H

OH

OH

OH

HOOH

OH

H

HOOH

OH

H

OOH

H2O

H+

H2O

- H+

H

HOOH

+

HO

OH

OH

O

H

OH

OH

OH

- H+

HO

OH

OH

O

OH

OH

OH

H+

Conclusions• Small dicarbonyls (glyoxal and methyl glyoxal)

partition to the particle phase much more than expected from vapour pressure calculations. Consistent with oligomerization hypothesis (in chambers at least!).

• Monofunctional carbonyl compounds much less likely to undergo reactive uptake

• Models that incorporate Kp for oxidation products should use compound-specific values (Johnson et al., 2005, 2006; Jenkin et al., 2004).

Future Directions

• On-tube derivatization of acids/phenols

• Further chamber experiments on oxygenated aromatics, PAHs and BVOCs

• What happens in the real atmosphere?

36

Sampling site

500 m

N

City centre

Tivoli Docks

50 m

Sampling point

Denuder-filter sampling

To pump

Quartz fibre filters (2)(PFBHA-treated)

Annular denuder(XAD-4 coated & PFBHA-treated)

(KI-coated denuder)

Cyclone(PM2.5 fraction)

Inlet

GC-MS data (denuder & filter extracts) after sampling for 24 hr 23-24th September 2008

* Impurities or column peaks

Carbonyls at Tivoli Docks

Sampling for 24 hours at 16.7 L/min. Weather conditions dry, mainly cloudy, lightwind from SW

Gas phase conc. Particle phase conc.

Detection limit for standard

ng/m3 (ppbv) ng/m3 ngMVK 1087 (0.38) * 3.5Methacrolein 380 (0.13) * 1.0Glycolaldehyde 1006 (0.48) * 4.0Hexanal 409 (0.10) 2.0Heptanal 144 (0.03) 2.0Benzaldehyde 263 (0.06) 2.0p-Tolualdehyde 55 (0.01) 0.6Nonanal 404 (0.07) 5.0Decanal 343 (0.05) 5.0Glyoxal 77 (0.03) ? 0.6Methylglyoxal 69 (0.02) ? 0.3Dimethylglyoxal 102 (0.03) ? 0.6

3,5-dimethylbenzaldehyde 73 (0.01) 0.6

First studies on SOA formation from naphthalene

Odum yield curves

SOA mass concentration (M0)

0 100 200 300 400 500

SOA

yie

ld (Y

)

0.00

0.05

0.10

0.15

0.20

0.25

RH=0%, HC/NOx=1.0-2.2

RH=0%, HC/NOx=3.0-4.4

RH=25%, HC/NOx=1.0-1.8

RH=50%, HC/NOx=1.0-1.8

HONO as OH source

∑∑==

⎟⎠⎞

⎜⎝⎛

×+×

==n

1i i0

ii0

n

1ii

KM1KαMYY

Aerosol yield parameters

One compound model

Two compounds model

a K a1 K1 a2 K2

RH=0, HC/NOx=1.0-1.8

0.1636 0.0113 0.1477 0.013 1 3.19E-5

RH=0, HC/NOx=3.0-4.4

0.2198 0.0125 0.2198 0.0125 3.52E-7 1.32E-8

RH=25, HC/NOx=1.0-1.8

0.2324 0.0081 0.2324 0.0081 3.65E-5 1.22E-6

RH=50, HC/NOx=1.0-1.8

0.2548 0.0095 0.2548 0.0095 1.96E-7 6.44E-9

Acknowledgements

• Robert Healy, Shouming Zhou

• Kristina Kuprovskyte, Ashley Allshire

• Brice Temime (now in Marseille)

• Josef Dommen, Axel Metzger et al. (PSI)

XAD-4 vs XAD-4/PFBHA2,6-dimethylbenzoquinone

0

20

40

60

80

100

120

10 20 30 40 50

Time (min)

Trap

ping

Effi

cien

cy (%

) XAD-4

XAD-4 +PFBHA

O

O

Glyoxal trimer dissolved in solvent mix vs dissolved in methanol

Kp calculations

• MWom= Average molecular weight of organic species in particles (=120)

• fom= fraction of particle that is organic (= 1)• γom = Activity coefficient (assumed =1)• Po

L = sub-cooled vapour pressure • Adsorption to particle surface not considered

for Kp values

610760

×°×××××

=Lomom

omltheoretica PMW

TRfKpγ

Polymerization reactions in aromatics-SOApolymer-”backbone”

Gas-phase Carbonyl yields for p-xylene

methylglyoxal 35%methylbutenedial 3%

Glyoxal 30%Hexenedione 5%

P-tolualdehyde 10%

Minimize Artefacts

• Direct filter sampling is prone to artefacts• Adsorption of gases to filter - Positive artefact• Desorption of semi-volatiles – Negative artefact• Denuder-filter sampling minimizes artefacts• Mainly used for non-polar organic compounds

that partition between both gas and particle phases, e.g. PAHs