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-m 3 Gillings Outdoor Smog Chamber UNC 274-m 3 Dual Outdoor Smog Chamber UNC 10-m 3 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  -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 – 1 H NMR Data [Lin et al., 2012, ES&T; Zhang et al., 2012, ACP; Lin et al., PNAS]

Nebulizer 10-m 3 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/MS LC/DAD-ESI-HR-QTOFMS ACSM & HR-ToF-AMS FTIR UV-Vis Acidic seed: MgSO 4 +H 2 SO 4 Neutral seed: (NH 4 ) 2 SO 4 Controlled Indoor Smog Chamber Experiments On-line aerosol size measurements Experimental conditions Temp: 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]

Nebulizer Manifold Heated nitrogen 1. Introduce seed aerosols 2. Introduce gas-phase synthetic epoxide 3. Collect filters (off-line aerosol product analysis) GC/MS LC/DAD-ESI-HR-QTOFMS ACSM & HR-ToF-AMS FTIR UV-Vis Acidic seed: MgSO 4 +H 2 SO 4 Neutral seed: (NH 4 ) 2 SO 4 On-line aerosol size measurements Controlled Indoor Smog Chamber Experiments Experimental conditions Temp: 23-25°C, RH: <10% (Dry) and ~50-60% (Wet) 10-m 3 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 phase Aerosol phase GC/MS LC/DAD-ESI-HR-QTOFMS ACSM & HR-ToF-AMS FTIR UV-Vis Acidic seed: MgSO 4 +H 2 SO 4 Neutral seed: (NH 4 ) 2 SO 4 Reactive uptake On-line aerosol size measurements Controlled Indoor Smog Chamber Experiments 10-m 3 indoor flexible smog chamber Experimental conditions Temp: 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]

Chamber pre-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 H 2 O/CH 3 OH (1:1) with 0.1% acetic acid LC/ESI-HR-Q-ToFMS Analysis Extract filters with 20 mL CH 3 OH 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 = m/z 215 = m/z 333 = C 5 -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, depending on conditions [Lin et al., 2012; ES&T]

Seed CompositionRH (%) Temp (°C) SOA mass growth (  g m -3 ) MgSO 4 NeutralDry6.123n.d. Wet58.623n.d. AcidifiedDry Wet (NH4) 2 SO 4 NeutralDry6.924 n.d. Wet AcidifiedDry Wet Comparison of SOA mass growth from IEPOX uptake onto MgSO 4 vs. (NH 4 ) 2 SO 4 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 H 2 SO 4 into seed solutions Conclusion: Aerosol acidity (and to some extent RH) critical in promoting IEPOX SOA formation Why brown carbon only in the dry MgSO 4 + H 2 SO 4 seed experiment? [Limbeck et al., 2003, GRL] [Lin et al., 2014, under review]

{MAC} nm = 344 (cm 2 g -1 ) UV-Vis Indicates Browning of IEPOX-Derived SOA Formed from Dry Acidified MgSO 4 Aerosol Consistent with other SOA types measured by Updyke et al. (2012, Atmos. Environ.); they Observed {MAC} between cm 2 g -1 for other biogenic SOA with NH 3 present [Lin et al., 2014, under review]

Chemical Characterization of Non-Brown Carbon Oligomers From IEPOX Multiphase Chemistry Tandem MS 2 of m/z 495 (1 DBE Oligomer): [Lin et al., 2014, under review]

Chemical Characterization of Brown Carbon From IEPOX Multiphase Chemistry Tandem MS 2 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 PM 2.5 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 (M n+ ):

1. cis- β -IEPOX +H 2 SO 4 2. trans- β -IEPOX +H 2 SO 4 3. trans-3-MeTHF-3,4-diols +H 2 SO 4 4. cis-3-MeTHF-3,4-diols +H 2 SO 4 5. MAE +H 2 SO 4 Synthetic standards (500 ug; solvent dried off) + H 2 SO 4 (100 ul): Bulk Solution Experiments with Synthetic Standards Provide Insights into Browning Notably, 2-methyltetrol & 2-methylglyceric acid standards in presence of concentrated H 2 SO 4 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 Urban Sites: Downwind Urban Site: Rural Sites:

Conditional Sampling of PM 2.5 at Yorkville, GA –Rural site within the SEARCH network –High isoprene emissions –Influenced by anthropogenic activities SO 2 from local coal-fired power plants: ≥ 0.50 ppbv (high) and ≤ 0.25 ppbv (low) NH 3 from local poultry operations: ≥ 2 ppbv (high) and ≤ 1 ppbv (low) [Zhang et al., 2012, ACP] HighLow Two high-volume samplers operated side by side

3-methyltetrahydrofuran-3,4-diols dimers 2-methyltetrols C 5 -alkene triols Chamber samples Yorkville, GA Field Observations Match Chamber Samples [Lin et al., 2012, ES&T; Lin et al., 2013; ACP]

SO 2 conditions (06/25/10-07/14/10) NH 3 conditions (07/29/10-08/06/10) ConditionsHigh SO 2 Low SO 2 ∑tracers/OM 13.3%11.9% ConditionsHigh NH 3 Low NH 3 ∑tracers/OM 19.1%18.6% Paired t-test (n=16); p= 0.012* Paired t-test (n=9); p= More IEPOX SOA tracers measured under high-SO 2 conditions; weakly acid No statistical significance for NH 3 conditional samples [Lin et al., 2013, ACP] Atmospheric Abundance of IEPOX-Derived SOA at 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 Matrix Factorization (PMF) to Organic Mass Spectra to Obtain 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 PTR-MS Data Indicate isoprene > monoterpenes Average Diurnal Profiles

PM 1 Chemical Composition and Size Distribution During SOAS at Look Rock 2013

ACSM OA Source Apportionment During SOAS At 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]

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 (R 2 ~ 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  g m -3 MgSO 4 + H 2 SO 4 [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 of BEAS-2B Cells to 20  g 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 MarkerOxidative 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 (SO 2 ) emissions will likely decrease the amount of fine organic aerosol from isoprene in the S.E. USA region