Observational Constraints on Global Organic Aerosol

Telluride Science Research Center Workshop on Organic AerosolJuly 30, 2014

Colette L. HealdXuan Wang, Qi Chen

*analogous to “peak oil”?

My Talk Today

Part 1: Brown Carbon

Part 2a: Van Krevelen Diagram re-visited

Part 2b: Simulating the Global Elemental Composition of OA

H:C

O:C

IPCC AR5 Estimates that Black Carbon is the 2nd Largest Warming Agent in the Atmosphere.

(but that’s not what models say)

How can these be

reconciled?

Top-down constraints from Bond et al. come from absorption measurements.How important are organics to this?

Adding Brown Carbon to GEOS-Chem

Absorption of BrC is highly uncertain - we choose upper-range estimates

Brown Carbon

Aromatic SOA

50% of biofuel POA25% of fire POA

Absorption Coefficient

Get RI from field measurements

Mie calculation

MAE=1 m2/g MAE=0.3 m2/g

Including Brown Carbon is Critical to Capturing the Spectral Dependence of AERONET AAOD*AAOD product here using lev2 SSA with lev1.5 AOD

Including Brown Carbon is Critical to Capturing the Spectral Dependence of AAOD

*AAOD product here using lev2 SSA with lev1.5 AOD

Our Work Suggests Brown Carbon is an Important Component of Absorption Radiative Forcing

Brown Carbon contributes 35% of the DRF warming from carbonaceous aerosols.(Also: BC DRF=0.21 Wm-2, is less than methane and tropospheric ozone.)

[Wang, Heald, et al., ACPD, 2014]

The State of Dis-Union

[Heald, et al., 2011]

The State of Dis-Union: From a Mass Perspective

we Need More (Anthropogenic)

Sources and More Sinks

[Heald, et al., 2011]

*Now adding ~100 Tg/yr source of ASOA

Van Krevelen Diagram: Insight Into OA Aging

[Heald et al., 2010]

Need to re-visit: (1) more data (2) corrected AMS elemental ratios (Canagaratna et al., 2014)

Total OA (AMS data) fell on -1 slope, suggesting that aging (mixing,

chemistry, volatilization) follow consistent path.

We noted levelled off at higher O:C (alcohol addition, fragmentation?)

Updated Van Krevelen of Ambient Measurements

See clear progression in OSc.Fitted slope shallower (-0.6 slope) than Heald et al., 2014 (-1 slope),

largely because AMS correction affects O:C more than H:C.

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C-1.0 -0.5 0.0 0.5 1.0

OSc

Ground Urban Downwind Remote/Rural

(closed: HR-AMS)(open: Q-AMS, overlapped with closed)Aircraft

DC-3 (2012) MILAGRO (2006)

(smaller sizes for higher altitude)

Fit to Ambient Means (R2 = 0.67)

RMA Slope = -0.58 ± 0.04 (1)RMA Intercept = 1.96 ± 0.03

(a)

Mexico City

Whistler Mountain

Mace Head

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

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(c)Laboratory-generated OABiomass burning OADiesel exhaust, cooking POABiogenic SOA(I - isoprene; L - limonene; M - monoterpene; S - sesquiterpene; all at low-NOx)

(In - isoprene at high-NOx)

Aromatic SOA(X - xylene; T - toluene; B - benze)(Xn, Tn, Bn represent high NOx)

SVOC/IVOC SOAGlyoxal SOA

Other OAR - Marine EmissionsE - SOA products of IEPOX reactive uptake

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

-1.0 -0.5 0.0 0.5 1.0OSc

(a)

Mexico City

Whistler Mountain

Mace Head

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40

O:C

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(c)

Ground Urban Downwind Remote/Rural

Aircraft MILAGRO (2006) DC-3 (2012)

— Fitted to Ambient Means (R2 = 0.67)

Slope = -0.58 ± 0.04 (1); Intercept = 1.96 ± 0.03 Fitted to invididual datasets(shown for the data range) — Urban — Downwind — Remote/Rural — Aircraft Laboratory-generatedBiomass burning OA (b)Anthropogenic POA(d/g - diesel/gasoline exhaust; c - cooking; t - trash burning)Biogenic SOA (I - isoprene; L - limonene; M - monoterpene; S - sesquiterpene)Aromatic SOA (X - xylene; T - toluene; Z - benze; r - others)Fresh IVOC SOA(n - naphthalene; p - phenol; o - o-cresol; x - dimethylphenol; a - C8 to C19 alkane)Glyoxal uptake (G)(all at low-NOx except *n which represents high NOx) Other types of OAMarine Emissions (R)SOA products of IEPOX reactive uptake (E) Laboratory photochemical aging

2.01.61.20.80.40

O:C

Anthropogenic (POA+SVOC/IVOC)

(d)

SOA (gas + particle)

1086420

Biomass burning (POA+SVOC/IVOC) (day)

-1.0-0.5

Heterogeneous

(b)

Riverside

Mexico City (T0)

Fresno

Borneo

DC-3

AmazonSGP

BEACHON

IfT

Cool

Davis

SPC

UptonMILAGRO

But There is Diversity Among Campaigns

All individual slopes steeper (-0.7 to -1.1) than bulk …overall fitting compensating for various intercepts

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

Lines fitted to invididual datasets by RMA Urban Downwind Remote/Rural Aircraft

(lines are shown for the data range)

(b)

Riverside

Mexico City (T0)

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

Lines fitted to invididual datasets by RMA

Urban Downwind Remote/Rural Aircraft Fit to All Ambient Means

(lines are shown for the data range)

(b)

Riverside

Mexico City (T0)

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C-1.0 -0.5 0.0 0.5 1.0

OSc

Ground Urban Downwind Remote/Rural

(closed: HR-AMS)(open: Q-AMS, overlapped with closed)Aircraft

DC-3 (2012) MILAGRO (2006)

(smaller sizes for higher altitude)

Fit to Ambient Means (R2 = 0.67)

RMA Slope = -0.58 ± 0.04 (1)RMA Intercept = 1.96 ± 0.03

(a)

Mexico City

Whistler Mountain

Mace Head

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

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(c)Laboratory-generated OABiomass burning OADiesel exhaust, cooking POABiogenic SOA(I - isoprene; L - limonene; M - monoterpene; S - sesquiterpene; all at low-NOx)

(In - isoprene at high-NOx)

Aromatic SOA(X - xylene; T - toluene; B - benze)(Xn, Tn, Bn represent high NOx)

SVOC/IVOC SOAGlyoxal SOA

Other OAR - Marine EmissionsE - SOA products of IEPOX reactive uptake

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

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b

bbb

b

b

b

bb

bI

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InInInInSSSSSSSS

S

SMMMMMM

MLLLLLLL

dg

d

d

d

ttcc

c cccGGG

E

E

E

EE

R

(c)Laboratory-generated OABiomass burning OADiesel exhaust, cooking POABiogenic SOA(I - isoprene; L - limonene; M - monoterpene; S - sesquiterpene; all at low-NOx)

(In - isoprene at high-NOx)

Aromatic SOA(X - xylene; T - toluene; B - benze)(Xn, Tn, Bn represent high NOx)

SVOC/IVOC SOAGlyoxal SOA

Other OAR - Marine EmissionsE - SOA products of IEPOX reactive uptake

A Disconnect Between Laboratory and Ambient Elemental Composition?

Most of the laboratory data lies below the ambient line…Except isoprene-derived OA.

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

-1.0 -0.5 0.0 0.5 1.0OSc

(a)

Mexico City

Whistler Mountain

Mace Head

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

2.01.61.20.80.40

O:C

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rrrrr

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b

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b

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SMMM

MMMM

LLLLLLL

dg

d

d

d

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E

E

E

EE

R

(c)

Ground Urban Downwind Remote/Rural

Aircraft MILAGRO (2006) DC-3 (2012)

— Fitted to Ambient Means (R2 = 0.67)

Slope = -0.58 ± 0.04 (1); Intercept = 1.96 ± 0.03 Fitted to invididual datasets(shown for the data range) — Urban — Downwind — Remote/Rural — Aircraft Laboratory-generatedBiomass burning OA (b)Anthropogenic POA(d/g - diesel/gasoline exhaust; c - cooking; t - trash burning)Biogenic SOA (I - isoprene; L - limonene; M - monoterpene; S - sesquiterpene)Aromatic SOA(X - xylene; T - toluene; Z - benze; r - others)Fresh IVOC SOA(n - naphthalene; p - phenol; o - o-cresol; x - dimethylphenol; a - C8 to C19 alkane)Glyoxal uptake (G)(all at low-NOx except that *n represents high NOx) Other types of OAMarine Emissions (R)SOA products of IEPOX reactive uptake (E) Laboratory photochemical aging

2.01.61.20.80.40

O:C

Anthropogenic (POA+SVOC/IVOC)

(d)

SOA (gas + particle)

1086420

Biomass burning (POA+SVOC/IVOC) (day)

-1.0-0.5

( heterogeneous oxidation)

(b)

Riverside

Mexico City (T0)

Fresno

Borneo

DC-3

AmazonSGP

BEACHON

IfT

Cool

Davis

SPC

UptonMILAGRO

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

1086420Photochemical Age (day)

(d)

>10

A Disconnect Between Laboratory and Ambient Elemental Composition?

Most of the laboratory data lies below the ambient line…Few aging experiments get to high O:C within a week of aging.

Statistical Mixtures Demonstrate the Consistencies and Inconsistencies of Lab and Field Measurements

1.61.20.80.40.0

(h) Aircraft and all means

w/. Glyoxal SOA and Aging

ALL

1.20.80.40.0

O:C

(f) Rural BSOABBOA(g/p) Aging

BSOA/ASOA(g/p) Aging

SGPIfT(s)

1.20.80.40.0

(g) Rainforest BSOA, ISOP, IEPOXBSOA/ISOP(g/p) Aging

Amazon

Borneo

w/. APOA, BBOA(g/p) Aging

Marine OA

2.4

2.0

1.6

1.2

0.8

H:C

1.20.80.40.0

(e) Manitou forest BSOABSOA(g/p) Aging

(d) downwind BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) AgingBSOA/ASOA(g/p) Aging

APOA(p) Aging

(c) Mexico City BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) Aging

(b) Fresno BSOA, ASOABBOA, APOA

2.4

2.0

1.6

1.2

0.8

H:C

(a) Riverside BSOAASOA

-1.0

-0.5

1.61.20.80.40.0

(h) Aircraft and all means

w/. Glyoxal SOA and Aging

ALL

1.20.80.40.0

O:C

(f) Rural BSOABBOA(g/p) Aging

BSOA/ASOA(g/p) Aging

SGPIfT(s)

1.20.80.40.0

(g) Rainforest BSOA, ISOP, IEPOXBSOA/ISOP(g/p) Aging

Amazon

Borneo

w/. APOA, BBOA(g/p) Aging

Marine OA

2.4

2.0

1.6

1.2

0.8

H:C

1.20.80.40.0

(e) Manitou forest BSOABSOA(g/p) Aging

(d) downwind BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) AgingBSOA/ASOA(g/p) Aging

APOA(p) Aging

(c) Mexico City BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) Aging

(b) Fresno BSOA, ASOABBOA, APOA

2.4

2.0

1.6

1.2

0.8

H:C

(a) Riverside BSOAASOA

-1.0

-0.5

1.61.20.80.40.0

(h) Aircraft and all means

w/. Glyoxal SOA and Aging

ALL

1.20.80.40.0

O:C

(f) Rural BSOABBOA(g/p) Aging

BSOA/ASOA(g/p) Aging

SGPIfT(s)

1.20.80.40.0

(g) Rainforest BSOA, ISOP, IEPOXBSOA/ISOP(g/p) Aging

Amazon

Borneo

w/. APOA, BBOA(g/p) Aging

Marine OA

2.4

2.0

1.6

1.2

0.8

H:C

1.20.80.40.0

(e) Manitou forest BSOABSOA(g/p) Aging

(d) downwind BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) AgingBSOA/ASOA(g/p) Aging

APOA(p) Aging

(c) Mexico City BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) Aging

(b) Fresno BSOA, ASOABBOA, APOA

2.4

2.0

1.6

1.2

0.8

H:C

(a) Riverside BSOAASOA

-1.0

-0.5

1.61.20.80.40.0

(h) Aircraft and all means

w/. Glyoxal SOA and Aging

ALL

1.20.80.40.0

O:C

(f) Rural BSOABBOA(g/p) Aging

BSOA/ASOA(g/p) Aging

SGPIfT(s)

1.20.80.40.0

(g) Rainforest BSOA, ISOP, IEPOXBSOA/ISOP(g/p) Aging

Amazon

Borneo

w/. APOA, BBOA(g/p) Aging

Marine OA

2.4

2.0

1.6

1.2

0.8

H:C

1.20.80.40.0

(e) Manitou forest BSOABSOA(g/p) Aging

(d) downwind BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) AgingBSOA/ASOA(g/p) Aging

APOA(p) Aging

(c) Mexico City BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) Aging

(b) Fresno BSOA, ASOABBOA, APOA

2.4

2.0

1.6

1.2

0.8

H:C

(a) Riverside BSOAASOA

-1.0

-0.5

1.61.20.80.40.0

(h) Aircraft and all means

w/. Glyoxal SOA and Aging

ALL

1.20.80.40.0

O:C

(f) Rural BSOABBOA(g/p) Aging

BSOA/ASOA(g/p) Aging

SGPIfT(s)

1.20.80.40.0

(g) Rainforest BSOA, ISOP, IEPOXBSOA/ISOP(g/p) Aging

Amazon

Borneo

w/. APOA, BBOA(g/p) Aging

Marine OA

2.4

2.0

1.6

1.2

0.8

H:C

1.20.80.40.0

(e) Manitou forest BSOABSOA(g/p) Aging

(d) downwind BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) AgingBSOA/ASOA(g/p) Aging

APOA(p) Aging

(c) Mexico City BSOA, ASOABBOA, APOA

BBOA/APOA(g/p) Aging

(b) Fresno BSOA, ASOABBOA, APOA

2.4

2.0

1.6

1.2

0.8

H:C

(a) Riverside BSOAASOA

-1.0

-0.5

Anthropogenic Biogenic ALL

A Disconnect Between Lab and Ambient Elemental Composition?

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

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SMMMMMM

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dg

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(c)Laboratory-generated OABiomass burning OADiesel exhaust, cooking POABiogenic SOA(I - isoprene; L - limonene; M - monoterpene; S - sesquiterpene; all at low-NOx)

(In - isoprene at high-NOx)

Aromatic SOA(X - xylene; T - toluene; B - benze)(Xn, Tn, Bn represent high NOx)

SVOC/IVOC SOAGlyoxal SOA

Other OAR - Marine EmissionsE - SOA products of IEPOX reactive uptake

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

1086420Photochemical Age (day)

(d)

>10Aging Experiments

Mis-match suggests that either/both (1)Have not identified important OA source types

(2)Laboratory studies are not representative of ambient composition (mixtures?)[Chen et al., 2014a, in prep]

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

H:C

1.61.20.80.40.0

O:C

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b

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b

b

b

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InInInInSSSSSSSS

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SMMMMMM

MLLLLLLL

dg

d

d

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E

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(c)Laboratory-generated OABiomass burning OADiesel exhaust, cooking POABiogenic SOA(I - isoprene; L - limonene; M - monoterpene;

S - sesquiterpene; all at low-NOx)

(In - isoprene at high-NOx)

Aromatic SOA(X - xylene; T - toluene; B - benze)(Xn, Tn, Bn represent high NOx)

SVOC/IVOC SOAGlyoxal SOA

Other OAR - Marine EmissionsE - SOA products of IEPOX reactive uptake

Goal: Develop an Observationally-Based Model Simulation of OA Elemental Composition (and Aging)

Step 1: Re-fit 2 product SOA yields (I’ll spare you this)Step 2: Assign elemental ratios to POA/SOA types simulated in model based on lab data

Simulated surface composition occupies a narrow range (O:C = 0.3 to 0.5), compared to wider range seen in ambient.

Updated (Very Simple) Aging SchemeStep 3: Account for semi-volatile POA emissionsStep 4: Age gas-phase organics

End point:O:C=1.1H:C=1.4(defined by field obs)

Laboratory-Based Parameterization of Aging Rates

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.00.80.60.40.20 1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

2.2

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

1.0

0.8

0.6

0.4

0.2

0

Nor

mal

ized

Mas

s C

once

ntra

tion

toluenexylene

pineneisoprene

(a) fossil fuel (b) biomass burning, biofuel (e) biogenic SOG

(f) aromatic SOG

grassoakpinesage

H:CO:C

(c) (d)

POASVOC-SOA

× 5 kcarbon

× 0.2 kcarbon

× 10 kage

× 0.1kage

Step 5: Estimate all rates from lab photochemical aging experiments

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.00.80.60.40.20 1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

2.2

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

1.0

0.8

0.6

0.4

0.2

0

Nor

mal

ized

Mas

s C

once

ntra

tion

toluenexylene

pineneisoprene

(a) fossil fuel (b) biomass burning, biofuel (e) biogenic SOG

(f) aromatic SOG

grassoakpinesage

H:CO:C

(c) (d)

POASVOC-SOA

× 5 kcarbon

× 0.2 kcarbon

× 10 kage

× 0.1kage1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.00.80.60.40.20 1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

2.2

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

1.0

0.8

0.6

0.4

0.2

0

Nor

mal

ized

Mas

s C

once

ntra

tion

toluenexylene

pineneisoprene

(a) fossil fuel (b) biomass burning, biofuel (e) biogenic SOG

(f) aromatic SOG

grassoakpinesage

H:CO:C

(c) (d)

POASVOC-SOA

× 5 kcarbon

× 0.2 kcarbon

× 10 kage

× 0.1kage

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.00.80.60.40.20 1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

2.2

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.8

1.4

1.0

0.6

0.2

Elem

enta

l Rat

ios

1.21.00.80.60.40.20

OH Exposure (1012

molecule cm-3 s)

1.0

0.8

0.6

0.4

0.2

0N

orm

aliz

ed M

ass

Con

cent

ratio

n

toluenexylene

pineneisoprene

(a) fossil fuel (b) biomass burning, biofuel (e) biogenic SOG

(f) aromatic SOG

grassoakpinesage

H:CO:C

(c) (d)

POASVOC-SOA

× 5 kcarbon

× 0.2 kcarbon

× 10 kage

× 0.1kage

kcarbon FF = 1.5 × 10−11 cm3 molecule−1 s−1

BB = 6 × 10−12 cm3 molecule−1 s−1 SOG = 3 × 10−13 cm3 molecule−1 s−1

kage FF = 2.5 × 10−12 cm3 molecule−1 s−1 BB = 1 × 10−11 cm3 molecule−1 s−1 SOG = 1 × 10−10 cm3 molecule−1 s−1

New Scheme Increases Overall OA Burden by 40%

µg/m3

New Scheme Dramatically Alters Simulation of Elemental Composition

Now simulate a wider range of oxygen content, and also more pronounced seasonality in continental regions.

O:C Base O:C Updated Aging OSc Updated Aging

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ba

se

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

O:C

foss

il fu

el o

f 0.

03

inst

ead

of

0.1

1.21.00.80.60.40.20.0

Observed O:C

2.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.2

2.22.01.81.61.41.2

Observed H:C

0.1

1

10

0.1

1

10

0.1

1

10

0.1 1 10

Observed OA [µg m-3

]

UrbanDownwindRemote/Rural

Urban (JJA)

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ba

se

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

O:C

foss

il fu

el o

f 0.

03

inst

ead

of

0.1

1.21.00.80.60.40.20.0

Observed O:C

2.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.2

2.22.01.81.61.41.2

Observed H:C

0.1

1

10

0.1

1

10

0.1

1

10

0.1 1 10

Observed OA [µg m-3

]

UrbanDownwindRemote/Rural

Urban (JJA)

Comparison With Surface AMS Observations

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ba

se

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

O:C

foss

il fu

el o

f 0.

03

inst

ead

of

0.1

1.21.00.80.60.40.20.0

Observed O:C

2.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.2

2.22.01.81.61.41.2

Observed H:C

0.1

1

10

0.1

1

10

0.1

1

10

0.1 1 10

Observed OA [µg m-3

]

UrbanDownwindRemote/Rural

Urban (JJA)

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ba

se

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Ag

ing

O:C

foss

il fu

el o

f 0.

03

inst

ead

of

0.1

1.21.00.80.60.40.20.0

Observed O:C

2.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.22.2

2.0

1.8

1.6

1.4

1.2

2.22.01.81.61.41.2

Observed H:C

0.1

1

10

0.1

1

10

0.1

1

10

0.1 1 10

Observed OA [µg m-3

]

UrbanDownwindRemote/Rural

Urban (JJA)

Aging drastically improves ability to capture high O:C in remote regions - but at the cost of mis-representing urban (low O:C, high H:C)?

Missing source (i.e. lab vs. ambient disconnect?) or inherent scale limitation?New scheme also demonstrates better match to observed mass.

Vertical Comparison From Airborne Campaigns

10

8

6

4

2

0

Alti

tude

(km

)

1.21.00.80.60.4

O:C

Observation Base Aging Aging w/. SOA heterogeneous aging Aging w/. 5xSOG -> SOA Aging w/. 25 KJ/mol enthalpy Aging w/. 2xEpoa

Similarly, aging is critical to reproducing observed O:C. Cannot simulate O:C>1, or variability in observed H:C. But for airborne measurements, including heterogeneous

oxidation helps to reproduce the vertical gradient.

[Chen et al., 2014b, in prep]

10

8

6

4

2

0

Alti

tude

(km

)

1.21.00.80.60.4

O:C

Observation Base Aging Aging w/. SOA heterogeneous aging Aging w/. 5xSOG -> SOA Aging w/. 25 KJ/mol enthalpy Aging w/. 2xEpoa

1086420

OA

(b) DC-3

1.701.601.501.401.30

H:C

4.03.02.01.00.0

OA

10

8

6

4

2

0

Alti

tude

(km

)

1.21.00.80.60.4

O:C

(a) IMPEX

Conclusions

Brown Carbon likely contributes important source of UV absorption; ignoring this may artificially inflate BC

DRF estimates.

There is a disconnect between laboratory and ambient OA elemental composition.

Simple, measurement-based aging scheme dramatically improves simulation of elemental

composition in remote conditions. Including heterogeneous oxidation important for remote/aloft.