Jason D. Surratt

Trees, Volatile Organic Compounds, and Fine Organic Aerosol Formation: Implications for Air

Quality, Climate and Public Health in the Southeastern U.S.

Jason D. Surratt

Department of Environmental Sciences and Engineering, Gillings School of Global Public Health

Air Quality Concerns in a Changing Climate: Professional Development Workshop for Teachers

Saturday, September 13, 2014

Research Questions We are Currently Addressing

• What are the exact environmental conditions (e.g., seed aerosol compositions, acidities, RH) that lead to SOA from reactive uptake of isoprene-derived epoxides in the S.E. USA?

• What are the potential effects of this SOA type on climate (brown carbon?)?

• What are the spatial and temporal variations of SOA formation from isoprene-derived epoxides in the S.E. USA?

• What are the exact kinetics of reactive uptake of isoprene-derived epoxides leading to SOA formation?

• What are the potential effects of isoprene-derived SOA on human health?

My Group’s Current Research Approach

UNC 120-m3 Gillings Outdoor Smog Chamber

UNC 274-m3 Dual Outdoor Smog Chamber

UNC 10-m3 Indoor Smog Chamber

• Details of synthesis for epoxides and cis/trans-3-MeTHF-3,4-diols have been published

• GC/MS and LC/ESI-MS confirm high-purity standards (>99%)

• 2-methyltetrols have been synthesized by hydrolysis of d-IEPOX; 2-methylclyceric acid has been recently synthesized by dihydroxylation of 2-methyl-acrylic acid

Organic Synthesis to Confirm Role of IEPOX and MAE in Isoprene SOA Formation – 1H NMR Data

[Lin et al., 2012, ES&T; Zhang et al., 2012, ACP; Lin et al., PNAS]

Nebulizer

10-m3 indoor flexible smog chamber

Manifold

Heated nitrogen

1. Introduce seed aerosols

2. Introduce gas-phase synthetic epoxide

3. Collect filters (off-line aerosol product analysis)

GC/MSLC/DAD-ESI-HR-

QTOFMSACSM & HR-ToF-AMS

FTIRUV-Vis

Acidic seed: MgSO4+H2SO4

Neutral seed: (NH4)2SO4

Controlled Indoor Smog Chamber Experiments

On-line aerosol size measurements

Experimental conditionsTemp: 23-25°C, RH: <10% (Dry) and ~50-60% (Wet)

[Lin et al., 2012, ES&T; Lin et al., 2013, PNAS; Lin et al., 2014, ES&T. under review]

HO

OOH

IEPOX

HO

OOH

IEPOX

HO

OOH

IEPOX HO

OOH

IEPOX

HO

OOH

IEPOX

HO

OOH

IEPOX

HO

OOH

IEPOX

Nebulizer

Manifold

Heated nitrogen


2. Introduce gas-phase synthetic epoxide

3. Collect filters (off-line aerosol product analysis)

GC/MSLC/DAD-ESI-HR-


FTIRUV-Vis

HO

OOH

IEPOX








Nebulizer

Manifold

Heated nitrogen


2. Introduce gas-phase synthetic epoxides

3. Collect filters (off-line aerosol product analysis)Gas

phaseAerosol phase

GC/MSLC/DAD-ESI-HR-


FTIRUV-Vis

HO

OOH

IEPOX

HO

OH

OH

OH

H

HO

OH

OH

O

HO OH

HO

OSO3H

OH

OH

HO

OH

OH

O

OH

OH

OH

HO

OSO3H

OH

O

OH

OH

OH



Reactive uptake






Chamberpre-seeded

Inject gas-phase IEPOX

More gas-phase epoxides are converted to particle mass under acidic conditions

(Step 1)

(Step 2)

Typical SOA Growth from IEPOX

[Lin et al., 2012, ES&T]

Reconstitution in 150 μL H2O/CH3OH (1:1) with

0.1% acetic acid

LC/ESI-HR-Q-ToFMS Analysis

Extract filters with 20 mL CH3OH

Concentrate the extracts under nitrogen

dryer

GC/MS Analysis

Trimethylsilylation with BSTFA and pyridine

Aerosol Composition Analyses

m/z 262 m/z 231 m/z 219 m/z 335

β-IEPOX + acidic seed

Rela

tive A

bundance

m/z 215 m/z 333

β-IEPOX + acidic seed

Rela

tive A

bundance

m/z 262 =

m/z 231 =

m/z 219 =

m/z 335 =

m/z 215 =

m/z 333 =

C5-alkene triols

2-methyltetrols

IEPOX-derived dimer

IEPOX-derived organosulfate

3-methyltetrahydrofuran-3,4-diols

IEPOX-SOA tracers are significantly enhanced in the presence of acidified sulfate seed aerosols

Effects of acid-catalyzed enhancement on ambient SOA formation remain unclear

Acid-Catalyzed Enhancement of SOA Tracers

GC/MS Data: LC/ESI-MS Data:

Tracers account for ~ 60-90% of mass, dependingon conditions

[Lin et al., 2012; ES&T]

Seed Composition

RH (%) Temp (°C)SOA mass growth (g

m-3)MgSO4 Neutral Dry 6.1 23 n.d.

Wet 58.6 23 n.d.Acidified Dry 8.6 24 38.2

Wet 51.1 24 48.4

(NH4)2SO4 Neutral Dry 6.9 24 n.d.Wet 48.9 24 48.3

Acidified Dry 5.5 23 131.6Wet 58.5 23 74.5

Comparison of SOA mass growth from IEPOX uptake onto MgSO4 vs. (NH4)2SO4 seed aerosols

• Same amount of initial seed (~40-50 g m-3) and IEPOX (~300 ppb) injected in each experiment

• Aerosol acidified by adding additional 0.06 M H2SO4 into seed solutions

• Conclusion: Aerosol acidity (and to some extent RH) critical in promoting IEPOX SOA formation

Why brown carbon onlyin the dry MgSO4 + H2SO4 seed experiment?

[Limbeck et al., 2003, GRL]

[Lin et al., 2014, under review]

{MAC}290-700nm= 344 (cm2 g-1)

UV-Vis Indicates Browning of IEPOX-Derived SOA Formed from Dry Acidified MgSO4 Aerosol

Consistent with other SOA types measured by Updyke et al. (2012, Atmos. Environ.); theyObserved {MAC} between 50-500 cm2 g-1 for other biogenic SOA with NH3 present


Chemical Characterization of Non-Brown Carbon Oligomers From IEPOX Multiphase Chemistry

Tandem MS2 of m/z 495 (1 DBE Oligomer):


Chemical Characterization of Brown Carbon From IEPOX Multiphase Chemistry

Tandem MS2 of m/z 569 (10 DBE Oligomer):

Note that m/z 83 is protonated 3-methylfuran[Lin et al., 2014, under review]

Summary of Non-Brown Carbon and Brown Carbon Oligomers from Laboratory Studies

Brown Carbon Oligomers in PM2.5 from YRK, GA:


Non-Brown Carbon Oligomers

Tentatively Proposed Mechanism for Brown Carbon Oligomer Formation

We propose that IEPOX oligomers with low DBEs cyclodehydrate; this alone cannot explain the higher DBE oligomers

Additional DBEs gained by dehydrative loss of ether oxygens leading to C-C coupled 5-membered rings (ex., > 3 DBEs)


Dehydration of ethers has been documented to occur both under strong acid conditions and on coordination of ethers to metal ions (Mn+):

1. cis-β-IEPOX +H2SO4

2. trans-β-IEPOX +H2SO4

3. trans-3-MeTHF-3,4-diols +H2SO4

4. cis-3-MeTHF-3,4-diols +H2SO4

5. MAE +H2SO4

Synthetic standards (500 ug; solvent dried off) + H2SO4 (100 ul):

1 2 3 4 5

Bulk Solution Experiments with Synthetic Standards Provide Insights into Browning

• Notably, 2-methyltetrol & 2-methylglyceric acid standards in presence of concentrated H2SO4 do NOT yield brown carbon.

• However, isomeric 3-MeTHF-3,4-diols yields brown carbon, indicating that their further reaction might have role or share similar pathway

• Could the isomeric 3-MeTHF-3,4-diols observed in ambient aerosols serve as tracers for browning and is this relevant to ambient aerosol?

Ambient Sampling Sites in S.E. USA

Look Rock (LRK), TN 2013

Atlanta (JST), GA 2011-2012 & 2014Birmingham (BHM), AL 2013

Urban Sites:

Downwind Urban Site:

Rural Sites:Yorkville (YRK), GA 2010Centerville (CTR), AL 2013

Conditional Sampling of PM2.5 at Yorkville, GA

– Rural site within the SEARCH network– High isoprene emissions– Influenced by anthropogenic activities

• SO2 from local coal-fired power plants:

≥ 0.50 ppbv (high) and ≤ 0.25 ppbv (low)

• NH3 from local poultry operations:

≥ 2 ppbv (high) and ≤ 1 ppbv (low)

[Zhang et al., 2012, ACP]

High

Low

Two high-volume samplers operated side by side

3-methyltetrahydrofuran-3,4-diols

dimers

2-methyltetrols

C5-alkene triols

Chamber samples Yorkville, GA

Field Observations Match Chamber Samples

[Lin et al., 2012, ES&T; Lin et al., 2013; ACP]

SO2 conditions (06/25/10-07/14/10)

NH3 conditions (07/29/10-08/06/10)

Conditions

High SO2 Low SO2

∑tracers/OM 13.3% 11.9%

Conditions

High NH3 Low NH3

∑tracers/OM 19.1% 18.6%Paired t-test (n=16); p= 0.012*

Paired t-test (n=9); p= 0.830

More IEPOX SOA tracers measured under high-SO2 conditions; weakly acid

No statistical significance for NH3 conditional samples

2-methyl-tetrols

3-MeTHF-3,4-diols

C5H12O7S

0 50 100150200250300350

High SO2

Mass concentrations (ng m-3)

2-methyl-tetrols

3-MeTHF-3,4-diols

C5H12O7S

0 100200300400500600700

High NH3

Mass concentrations (ng m-3)

[Lin et al., 2013, ACP]

Atmospheric Abundance of IEPOX-Derived SOAat Yorkville, GA During Summer

Real-Time Measurements in S.E. USA Also Show Importance of Aerosol from Isoprene Epoxides

[Budisulistiorini et al., 2013, Environ. Sci. Technol.]

Apply Positive MatrixFactorization (PMF) toOrganic Mass Spectra toObtain Sources

What are the diurnal variations of these sources?

Chemical Characterization of Look Rock Organic Aerosol During SOAS 2013

BVOC Emissions and Certain Oxidation Products

12

10

8

6

4

2

0

PT

R-M

S I

sop

ren

e (

pp

b)

6/11/2013 6/16/2013 6/21/2013 6/26/2013 7/1/2013 7/6/2013 7/11/2013 7/16/2013

Date and Time (Local)

12

10

8

6

4

2

0

PT

R-M

S M

VK

+M

AC

R (

pp

b)

1000

800

600

400

200

0

CIM

S M

AE

m/z

10

1 (

ion

s-1

)

6/5/2013 6/10/2013 6/15/2013 6/20/2013 6/25/2013 6/30/2013 7/5/2013 7/10/2013 7/15/2013

Date and Time (Local)

100

80

60

40

20

0

CIM

S I

EP

OX

m/z

17

7 (

ion

s-1

)

16

14

12

10

8

6

4

2

0

AC

SM

Org

an

ic (µg

m-3)

PTR-MS Data Indicate isoprene > monoterpenes

Average Diurnal Profiles

PM1 Chemical Composition and Size Distribution During SOAS at Look Rock 2013

69.6%

6.9% 19.6%

3.8% 0.1%

INT3 avg.=7.5±2.2 µg m-3

16

14

12

10

8

6

4

2

0

Mas

s C

once

ntra

tion

(µg

m-3

)

6/5/2013 6/10/2013 6/15/2013 6/20/2013 6/25/2013 6/30/2013 7/5/2013 7/10/2013 7/15/2013Date and Time (Local)

Org SO42-

NO3-

NH4+

Cl-

69.7%

6.6% 19.6%

4.0% 0.1%

INT1 avg.=10.5±3.0 µg m-3

68.5%

6.7% 21.2%

3.5% 0.1%

INT2 avg.=13.4±3.8 µg m-3

63.7%

7.6% 24.8%

3.8% 0.1%

INT4 avg.=6.0±1.6 µg m-3

40

30

20

10

0

AC

SM

NR

PM

1 (µ

g m

-3)

2520151050

SEMS PM1 (µm3 cm

-3)

Intercept = 1.00±0.08Slope = 1.44±0.01

64.1%

7.7% 24.3%

3.8% 0.1%

Avg. Total: 7.6±4.7 (µg m-3

)

5

10

15

20

25

0

45

90

135

180

225

270

315

Wind speed (m s-1

)0 - 1 1 - 2 2 - 3 3+

ACSM OA Source Apportionment During SOASAt Look Rock 2013

Fraction of IEPOX-OA of similar magnitude as what we have observed in downtown Atlanta, GA[Budisulistiorini et al., 2013, ES&T]

600

500

400

300

200

100

0

LC-M

S M

ass

Con

c. (

ng m

-3)


8

6

4

2

0

IEP

OX

-OA

(µg m

-3)

IEPOX OrganosulfateIEPOX Dimer OrganosulfateMAE Organosulfatea-pinene SOA tracers

4000

3000

2000

1000

0

GC

-MS

Mas

s C

onc.

(ng

m-3

)


8

6

4

2

0

IEP

OX

-OA

. (µg m

-3)

methylthreitol methylerythritol(Z)-3-methylbut-3-ene-1,2,4-triol2-methylbut-3-ene-1,2,3-triol (E)-3-methylbut-3-ene-1,2,4-trioltrans-3-methylTHF-3,4-diol cis-3-methylTHF-3,4-diol2-methylglyceric acid

Isoprene-Derived SOA Tracers From Off-line Chemical Analyses vs. ACSM IEPOX-OA Factor

IEPOX Tracers Account for Upwards of 25% of the total Fine Organic Mass!!

IEPOX-derived SOA Tracers correlate strongly (R2 ~ 0.8) only with IEPOX-OA PMF Factor!

Understanding the Biological Effects of Isoprene-Derived SOA Exposed to Human Bronchial Epithelial Cells

Electrostatic Aerosol In Vitro Exposure System (EAVES):

Injection:5 ppmv isoprene 400 ppbv NO 100 mg m-3 MgSO4 + H2SO4

[de Bruijne et al., 2009, Inhal. Tox.][Lichtveld et al., 2012, ES&T]

EAVES Exposure

Model Predictions and Chemical Measurements Indicate IEPOX-derived SOA will dominate the Exposure to BEAS-2B Cells

• EAVES operated 1hr• Cells transferred to clean media• Cell material collected 9hr post-

exposure

Chamber Sample

Yorkville, GA

Gene Expression Measured by qRT-PCR Indicates Exposure ofBEAS-2B Cells to 20 mg m-3 Isoprene-derived SOA Enhances Markers for Inflammation and Oxidative Stress

These results suggest that it is potentially important for field studies like SOAS to improve our fundamental understanding of isoprene SOA formation

Inflammation Marker Oxidative Stress Marker

Implications & Conclusions

• IEPOX-derived epoxides appears to be major source (~1/3) of fine organic aerosol mass in both rural and urban areas of S.E. U.S. during summer

• Brown carbon from IEPOX occurs in the laboratory due to light-absorbing oligomer formation; results from field suggest some could be there but further work is needed to determine how important (abundant) in order to fully assess impact on radiative budgets.

• IEPOX-derived SOA appears to yield potential inflammation and oxidative stress in human bronchial epithelial cells; more work is underway systematically examining gene arrays and investigating individual SOA components

• Importantly, further reductions in sulfate (SO2) emissions will likely decrease the amount of fine organic aerosol from isoprene in the S.E. USA region

Jason D. Surratt

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