Download - 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
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
HO
OOH
IEPOX
Acidic seed: MgSO4+H2SO4
Neutral seed: (NH4)2SO4
On-line aerosol size measurements
Controlled Indoor Smog Chamber Experiments
Experimental conditionsTemp: 23-25°C, RH: <10% (Dry) and ~50-60% (Wet)
10-m3 indoor flexible smog chamber
[Lin et al., 2012, ES&T; Lin et al., 2013, PNAS; Lin et al., 2014, ES&T. under review]
Nebulizer
Manifold
Heated nitrogen
1. Introduce seed aerosols
2. Introduce gas-phase synthetic epoxides
3. Collect filters (off-line aerosol product analysis)Gas
phaseAerosol phase
GC/MSLC/DAD-ESI-HR-
QTOFMSACSM & HR-ToF-AMS
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
Acidic seed: MgSO4+H2SO4
Neutral seed: (NH4)2SO4
Reactive uptake
On-line aerosol size measurements
Controlled Indoor Smog Chamber Experiments
10-m3 indoor flexible smog chamber
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]
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
[Lin et al., 2014, under review]
Chemical Characterization of Non-Brown Carbon Oligomers From IEPOX Multiphase Chemistry
Tandem MS2 of m/z 495 (1 DBE Oligomer):
[Lin et al., 2014, under review]
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:
[Lin et al., 2014, under review]
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)
[Lin et al., 2014, under review]
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)
6/6/2013 6/11/2013 6/16/2013 6/21/2013 6/26/2013 7/1/2013 7/6/2013 7/11/2013 7/16/2013Date and Time (Local)
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
)
6/6/2013 6/11/2013 6/16/2013 6/21/2013 6/26/2013 7/1/2013 7/6/2013 7/11/2013 7/16/2013Date and Time (Local)
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