1. 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

2. Who is Jason Surratt?
Assistant Professor of Atmospheric and Aerosol Chemistry, began at UNC July 2010
Born in Memphis, TN, and grew up in NC
Education:
2010, California Institute of Technology (Caltech), Ph.D., Chemistry
Thesis Title: “Analysis of the Chemical Composition of Atmospheric Organic
Aerosols by Mass Spectrometry”
2003, North Carolina State University (NCSU), B.A., Chemistry
2003, North Carolina State University (NCSU), B.S., Meteorology
Teach a graduate course entitled Aerosol Physics & Chemistry (ENVR 416, Fall)
Teach an undergraduate course entitled Environmental Chemistry (ENVR 403, Spring)
Research Focus: Directs a “smog” chamber research group in order to understand the
detailed atmospheric chemical mechanisms that cause organic aerosol formation in the
Earth’s atmosphere; we compare our experimental results with field measurements to
gain insights into adverse impacts on air quality, climate, and human health

3. What Does “Typical” Smog Look Like? a Photochemical Smog Event
Downtown LA during
a Photochemical Smog Event
Does anyone know which words “smog”
originated from?
Ingredients for SMOG:
Volatile Organic Compounds (VOCs) + Nitrogen Oxides (NOx = NO + NO2) + Sulfur Dioxide (SO2)
+ Sunlight (hν)  “SMOG” (which contains both “bad” O3 and fine aerosol [PM2.5] particles)

4. How Do We Study Smog & Thus Aerosol?
Same NOx and VOCs
Same NOx and VOCs
Wet Experiments
(RH 90%-50%)
Dry Experiments
(RH 40%-10%)
UNC 274 m3 Dual Outdoor Smog Chamber – Pittsboro, NC
Caltech 28 m3 Dual Indoor Smog Chamber
UNC 10 m3 Indoor Smog Chamber -
Located in MHRC 0016 (Surratt Lab)

5. University of Washington
Acknowledgements
UNC Surratt Group
Dr. Ying-Hsuan Lin
Dr. Theran Riedel
Dr. Matthieu Riva
Sri Hapsari Budisulistiorini
Tianqu Cui
Weruka Rattanavaraha
Xinxin Li
UNC Gold Group
Prof. Avram Gold
Dr. Zhenfa Zhang
Towson University
Prof. Kathryn Kautzman
University of Washington
Prof. Joel Thornton
Dr. Cassandra Gaston
U.S. EPA
Dr. Havala Pye
Columbia University
Prof. Faye McNeill
ARA, Inc.
Dr. Karsten Baumann
Eric Edgerton
SOAS Collaborators
Russell & Bertram Groups (UCSD)
Cappa Group (UCD)
McKinney Group (Amherst/Harvard)
Aerodyne, Inc.
Dr. John Jayne
Dr. Manjula Canagaratna
Dr. Philip Croteau
Funding
TVA
Dr. Solomon Bairai
Dr. Roger Tanner
Dr. Stephen Mueller
William Hicks

6. What are Atmospheric Aerosol?
Liquid or solid particles suspended in air
Aerosol = Particles = Particulate Matter (PM)
PMx: particles with diameters ≤ x mm
PM2.5 : Fine Aerosol
Mass Concentrations regulated by EPA
PM10 : Coarse Aerosol
Size of Atmospheric Aerosol versus Commonly Known Things:
PM10
PM2.5
Kaiser, Science (2005)

7. Why Study Atmospheric Aerosol?
Component of Photochemical Smog & Visibility Degradation
Smoggy Day
Clear Day
VOCs + h+ NOx+ SO2+ O3 + PM2.5
Charlotte, NC 
Charlotte, NC 
What is the chemical
composition (and thus, source)
of this PM2.5?

8. Why Study Atmospheric Aerosol?
Role in Global Climate Change:
[Zahardis et al., 2011, Anal. Chem.]
Intergovernmental Panel on Climate Change (IPCC), 2013

9. Why Study Atmospheric Aerosol?
Health Effects of PM2.5:
nasal cavity
[Dockery et al.,1993] – Cited 3,477 times
alveoli
Respiratory system
Each 10 g/m3 increase in PM2.5 long-term exposure has been associated with ~ a 4%, 6%,
and 8% increased risk of all-cause, cardiopulmonary, and lung cancer mortality, respectively.
[Pope III et al., 2006, JAMA]

10. National Ambient Air Quality Standards
(NAAQS)
NOTE: PM hr is now 35 mg m-3

11. U.S. Regional Differences in Health Effects Due To Aerosol Exposures
Dominici et al. [2006, JAMA]
As a Chemist, I ask: What about the chemical compositions might be causing these differences?

12. Typical Fine Particulate Matter (PM2.5) Composition
Inorganics
complex mixture of thousands of individual organic compounds
Aerosol composition from Duke Forest, NC.
(9/13/2004-9/21/2004)
[Zhang et al., GRL, 2007]

13. Organic Material Contributes Significantly to
PM2.5 Mass Across the Globe!
[Zhang et al., 2007, GRL]
Organic Sources = Primary + SECONDARY
Most of Organic Mass!

14. Types of Organic Aerosol (OA)
Primary organic aerosols (POA)
Directly emitted from the sources
Examples: Diesel soot, wild fire, cooking particles
Secondary organic aerosols (SOA)
Formed as a result of atmospheric reactions
SOA precursors: volatile organic compounds (VOCs)
Biogenic emissions
Examples:
Anthropogenic emissions
isoprene
a-pinene
toluene
naphthalene

15. “Traditional” View of Secondary Organic Aerosol
(SOA) Formation
(VOCs)
VOCs Known to Yield SOA:
Isoprene
Monterpenes (C10H16)
Sesquiterpenes (C15H24)
-pinene
-caryophyllene
This Process is Parameterized by Laboratory Chamber Experiments
SOA Yield = Mo/VOC
Mo= organic mass produced (g/m)
VOC = mass of reacted VOC (g/m3)

16. What is the Current Motivation For Studying Secondary Organic Aerosol?
Field Studies Indicate HIGHER SOA Formation in the Atmosphere than Models Predict
SOAmeas /SOAmod >> 1
Volkamer et al., GRL (2006)
Possible Explanations For Discrepancy:
Other Unidentified SOA Precursors
Chemical Formation Mechanisms Not Fully Established or Identified
Role of Aerosol Acidity & Heterogeneous Chemistry
Chemical Conditions in Laboratory Chambers Not Same as in Troposphere
IMPACT of Aerosols on Climate & Health Cannot be Fully Assessed!

17. Global Isoprene Emissions
Isoprene is the most abundant
non-methane hydrocarbon in the atmosphere
Observe global distribution of isoprene in January and July
What factor(s) might be responsible for varying distribution of isoprene over space and time?
Why do you think the Southeastern US has elevated isoprene levels in July?
Guenther et al., ACP (2006)

18. Global Isoprene Emissions
Guenther et al., ACP (2006)
The yearly production of isoprene emissions by vegetation is around 600 million tons!
Previously thought not to yield SOA due to high volatility of its known oxidation products
[Pandis et al., 1991, Atmospheric Environment]
Question of how isoprene oxidation yields SOA re-opened by detection of molecular tracers in
Amazonian PM2.5 [Claeys et al., 2004, Science]

19. (biogenic + anthropogenic)
My Current Work: Do the Interactions Between Human Activities and Natural VOC Emissions Enhance Secondary Organic Aerosol Formation in S.E. USA?
Total emissions
(biogenic + anthropogenic)
Biogenic emissions only
Modeled biogenic SOA
When all anthropogenic emissions were removed, secondary organic aerosol (SOA) formation from natural emissions is reduced by more than 50% or ∼1 µg m-3 in the eastern U.S.
[Carlton et al., 2010, ES&T]
Notably, this interaction could be more pronounced than currently understood
since models currently under predict PM2.5 mass concentrations in eastern USA

20. Isoprene-Derived Epoxides Are Critical in SOA Formation from Isoprene Oxidation
[Paulot et al., 2009, Science; Surratt et al., 2010, PNAS; Lin et al., 2012, ES&T; Zhang et al., 2012, ACP; Lin et al., 2013, ACP; Lin et al., 2013, PNAS;
Nguyen et al., 2014, ACP; Jacobs et al., 2014, ACP]

21. 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