Atmospheric Organic Aerosol: More Than Primary Emissions Brent J. Williams Brent J. Williams Raymond...

Atmospheric Organic Aerosol: More Than Primary Emissions

Brent J. Williams

Raymond R. Tucker ICARES Career-Development Assistant ProfessorWashington University in St. Louis

Department of Energy, Environmental, & Chemical Engineering

PI: Atmospheric Chemistry & Technology (ACT) Laboratory

Mumbai: December 7, 2012

2 main questions to discuss today:

1) Why do we care?

2) Where does it come from?

Organic Aerosol

Why Do We Care: Size-dependent Health Effects

[NARSTO, 2003]

Course aerosols deposit by impaction in nose and throat.

Ultrafine aerosol deposit by diffusion deeper in lungs in smaller pathways.

Fine aerosol has a minimum in deposition efficiency at approximately 0.5 micron diameter.

Many organic species in Fine PM are classified as toxins, mutagens, and carcinogens.

IPCC-Climate Change, 2007

Radiative forcing components

Why Do We Care: Climate Effects

Changes since 1750 (preindustrial)

Not accounting for many aerosol indirect effects.


• Sulfate• Primary Organic Carbon from Fossil Fuels • Black Carbon from Fossil Fuels• Biomass burning• Nitrate• Mineral Dust


• Sulfate• Primary Organic Carbon from Fossil Fuels • Black Carbon from Fossil Fuels• Biomass burning• Nitrate• Mineral Dust

Not Accounting for Secondary Organic Aerosol (SOA). Is there

enough SOA to make a difference?

2 main questions to discuss today:

1) Why do we care?

2) Where does it come from?

-primary vs. secondary

Organic Aerosol

Organic Aerosol is Most Abundant Fine PM Component Globally

Zhang et al., 2007organics sulfate nitrate ammonium

Organics44%

Sulfate32%

Ammonium13%

Nitrate10%

Chloride1%

• Northern Hemisphere Average (37 studies)• More Summer data than Winter • Non-Refractory Only (doesn’t include metals and elemental carbon)• Sulfate and Nitrate are formed through secondary processes• Organics previously thought of as mostly primary emissions, but that view has changed.

Major Atmospheric Species (fine PM)

Zhang et al., Geophys Res Lett, 2007

Sources of Atmospheric Aerosols

Meng et al. 1997, Science, 277, 116.

aerosol

ORIGINS OF ATMOSPHERIC AEROSOL

Soil/dust/Sea salt

Combustion

Atmospheric Organic Matter:Oxidation state and carbon numbers

oleicacid

ethane

acetaldehydephenanthrene

sucrose levoglucosan

sesquiterpene monoterpene isoprene

C5 tetrol

CH2O

glyoxalglyoxaldimer

oxalicacid

pinonic

pinic

C8triacid

butaneoctane

toluene

CH4

CO2

CO

MVK

methylglyoxal

fulvicacid

dodecane CH3OH

elementalcarbon

Ox. State ≈ 2 (O/C) – (H/C)

Kroll, Nature Chemistry, 2011.

C40

Chemical complexity of atmospheric organics

carbonyls, alcohols, acids only

Ox. State ≈ 2 (O/C) – (H/C) C40

Ambient Mass Concentrations Decrease


Oxidation state of organic aerosol

Organic aerosol is an intermediate in the oxidationof most organics to CO2

CO2

CO

C40


Organic Aerosol

gas

particle

Jimenez, Canagaratna, Donahue, et al., Science, 2009

2D – Volatility Basis Set space

Illustration of SOA evolution through 2D-VBS space

Secondary Organic Aerosol (SOA) Formation: Example

- 10 days of measurements from thermal desorption aerosol gas chromatograph (TAG)- PAR = visible light

Naphthalene: C10H8 (mostly in Gas-phase)Phthalic acid: C8H6O4 (In both Gas- and Particle-phase)

Williams et al., PNAS, 2010

Fractional Time Of Day

Na

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ng

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Jimenez et al, Science, 2009

Major Chemical Composition of Atmospheric Fine Particulate Matter

Primary vs Secondary Organic Aerosol (OA)


Effects of organic gases and organic particles can NOT be thought of as separate issues.

Secondary OA > Primary OA

Observed SOA > modeled SOALack in our fundamental knowledge of SOA formation and transformation.At least partially due to lack of measurements for semivolatile compounds.

Volkamer et al., Geophys Res Lett, 2006.

Major discrepancy between measured and modeled SOA

Organics make up 20-90% of fine particle mass and contain tens of thousands of compounds that can be used to determine sources and transformations (much is Secondary).

What we need to know about atmospheric organic matter:

-Physical Properties of Particles

-Chemical Properties-composition and concentrations (gases and particles)-composition transformations as air masses age

-Want to determine all sources and fate of atmospheric gases and particles.

-What effects do these particles and gases have on the environment?

-What can be done about it? (Policy and Management)

Organics44%

Sulfate32%

Ammonium13%

Nitrate10%

Chloride1%

• Northern Hemisphere Average (37 studies)• More Summer data than Winter • Non-Refractory Only (doesn’t include metals and elemental carbon)

General Speciation: AMS Speciation (PM1)


Organics44%

Sulfate32%

Ammonium13%

Nitrate10%

Chloride1%

Low Volatility Oxygenated Organic Aerosol (LV-OOA)

x%

y%

z%Semivolatile OOA (SV-OOA)

Hydrocarbon-like OA (HOA)

• x, y, z% varies (x > y > z in urban locations, z > y > x in remote locations)• Can also provide estimate of Biomass OA, but some interference exists• Still lacks specifics on sources of OA • Specifics are crucial for Regulation and Modeling Efforts

More Specific: AMS Speciation (w/ PMF of OA)

TAG

Thermal Desorption Aerosol Gas Chromatograph (TAG)

An in-situ instrument used to study the Sources and Transformation of Organic Particulate Matter

Hourly measurements of organic aerosol molecular composition

Williams et al., Aerosol Sci Technol, 2006

More Specific Yet: TAG

1. Collection technique:– Inertial Impaction (300C)

2. Sample transfer:– Thermal Desorption (50-3000C)

3. Chemical separation:– Gas Chromatography

4. Compound identification and quantification:– Electron Impact Mass Spectrometry

Gas Chromatograph

MassSpectrometer

Heated valve

Aerosol Collector &

Thermal Desorption Cell

Cyclone Precut(PM2.5)

Humidifier(adhesion)

Filter (field blank)

x

1

2

34

Note: many particles will be internally mixed.

Factor Analysisto group compounds

15.00 20.00 25.00 30.00 35.00 40.00 45.000

500000

1000000

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2000000

2500000

3000000

3500000

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Time-->

Abundance

TIC: 33702-12.DTIC: 33702-13.D (*)

Various forms of Petroleum Combustion

Coffee

Residential Wood Combustion

Plant WaxesRela

tive

Abun

danc

e

Retention Time

Secondary Organic Aerosol

• Organic portion (20-90% of total mass) is helpful in determining and understanding:- Particle sources- Particle formation processes- Particle transformations

Williams et al., Aerosol Sci Technol, 2006

Organics44%

Sulfate32%

Ammonium13%

Nitrate10%

Chloride1%

• Example Sources• Positive Matrix Factorization of Molecular Marker Compounds• Multivariate fit of TAG PMF factors to total OA from AMS

Primary Vehicle EmissionsFood Cooking

Plant Waxes

Biomass Burning:Softwood

Biomass Burning:Hardwood

Pesticides

Pharmaceuticals

Anthropogenic Secondary Organic Aerosol (SOA)

Biogenic SOA: Isoprene SOA

Biogenic SOA: Terpene SOA

More Specific Yet: TAG Speciation(scaling to AMS OA mass)

Plasticizers

Further Aged Anthro-SOA

Los Angeles Riverside

N

80 km

San Diego

135 km

PM2.5 Gridded Emissions (short tons/ozone season day/grid cell)

Williams et al., Atmos Chem Phys Discuss, 2010

Example TAG Field Study:Study of Organic Aerosol at Riverside (SOAR)

• Use hundreds of TAG compound timelines in Positive Matrix Factorization (PMF)• Determine major OA components (sources)• Scale TAG factors to AMS OA mass

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TAG’s 1-hour time resolution provides diurnal trends

Main methods to determine particle sources:

Chemical Mass Balance:

Factor Analysis (e.g., Positive Matrix Factorization):

cik= concentration of chemical species i in the fine particles at receptor site kaij = relative concentration of species i in the fine particle emissions from source jsjk = increment to total fine PM concentration at receptor site k originating from source jm= # of source types

Schauer and Cass, ES&T, 2000

Ulbrich et al., Atm Chem Phys, 2009

X = concentration of chemical speciesG = Factor Profile F = Factor Time SeriesE = Residualsp = Factor#s = estimated errors (uncertainty)Q = quality of fit parameter

G and F are determined by minimizing sum of least squares between residuals and errors:

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Hydrocarbon Oxygenated Biogenic N-Containing Other


TAG PMF Components (SOAR)Biogenic Particles

Biomass Burning

Food Cooking

Local Vehicles

Regional Primary Anthropogenics

Aged SOA + Biogenic SOA

Aged SOA

Regional Fresh SOA

Local Fresh SOA

5

10

15N

S

W E

SOA

Supporting Information

Local Meteorology Backward Trajectory Modeling Correlations

RHTemp

O3

COOC/EC

gas-phase organics

AMS species

ATOFMS (single particles)

Etc.

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6.8 mg m-3

8.6

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0:002:00

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14:00

16:00

18:00

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SOA1SOA2SOA3

SOA4+SemivolatileRegional Primary AnthropogenicLocal Vehicle

Food CookingBiomass BurningPrimary BiogenicMeasured OA


TAG PMF Components (summer)

SOA1 = Local Fresh SOA

SOA2 = Regional Fresh SOA

SOA3 = Aged SOA

SOA4 = Aged SOA + Biogenic SOA

SOA~70% of fine OAImmediately downwind of large urban area

Previous Studies: SOA~20-50% of fine OA

Docherty et al., ES&T, 2008

Spracklen et al., ACPD, 2011

What Models are still missing

Atmospheric Organic Aerosol: More Than Primary Emissions Brent J. Williams Brent J. Williams Raymond...

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