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

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

What Does “Typical” Smog Look Like?

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)

Downtown LA duringa Photochemical Smog Event

Does anyone know which words “smog”originated from?

How Do We Study Smog & Thus Aerosol?

Dry Experiments(RH 40%-10%)

Wet Experiments(RH 90%-50%)

Same NOx and VOCs

Same NOx and VOCs

Caltech 28 m3 Dual Indoor Smog Chamber

UNC 274 m3 Dual Outdoor Smog Chamber – Pittsboro, NC

UNC 10 m3 Indoor Smog Chamber - Located in MHRC 0016 (Surratt Lab)

Acknowledgements

UNC Surratt GroupDr. Ying-Hsuan LinDr. Theran RiedelDr. Matthieu Riva

Sri Hapsari BudisulistioriniTianqu Cui

Weruka RattanavarahaXinxin Li

UNC Gold GroupProf. Avram GoldDr. Zhenfa Zhang

Towson UniversityProf. Kathryn Kautzman

University of WashingtonProf. Joel Thornton

Dr. Cassandra Gaston

U.S. EPADr. Havala Pye

Columbia UniversityProf. Faye McNeill

Funding

ARA, Inc.Dr. Karsten Baumann

Eric Edgerton

Aerodyne, Inc.Dr. John Jayne

Dr. Manjula CanagaratnaDr. Philip Croteau

TVADr. Solomon BairaiDr. Roger Tanner

Dr. Stephen MuellerWilliam Hicks

SOAS CollaboratorsRussell & Bertram Groups (UCSD)

Cappa Group (UCD)McKinney Group (Amherst/Harvard)

83540401

What are Atmospheric Aerosol?

• Liquid or solid particles suspended in air

• PMx: particles with diameters ≤ x mm

• Size of Atmospheric Aerosol versus Commonly Known Things:

PM2.5 : Fine Aerosol

PM10 : Coarse Aerosol

PM2.5

PM10

Kaiser, Science (2005)

Mass Concentrations regulated by EPA

• Aerosol = Particles = Particulate Matter (PM)

Why Study Atmospheric Aerosol?

What is the chemical composition (and thus, source)

of this PM2.5?

VOCs + h+ NOx+ SO2+ O3 + PM2.5

• Component of Photochemical Smog & Visibility Degradation

Charlotte,

NC 

Clear Day

Smoggy Day

Charlotte,

NC http://www.southernenvironment.org/cases/southern_air_smog

Intergovernmental Panel on Climate Change (IPCC), 2013

• Role in Global Climate Change:

Why Study Atmospheric Aerosol?

[Zahardis et al., 2011, Anal. Chem.]

Why Study Atmospheric Aerosol?

• Health Effects of PM2.5:

Respiratory system

nasal cavity

alveoli

[Dockery et al.,1993] – Cited 3,477 times

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]

National Ambient Air Quality Standards (NAAQS)

NOTE: PM2.5 24 hr is now 35 mg m-3

U.S. Regional Differences in Health Effects Due To Aerosol Exposures

As a Chemist, I ask: What about the chemical compositions might be causing these differences?

Dominici et al. [2006, JAMA]

Typical Fine Particulate Matter (PM2.5) Composition

Aerosol composition from Duke Forest, NC. (9/13/2004-9/21/2004)

[Zhang et al., GRL, 2007]

Sulfate

Nitrate

Ammonium

Organics

Inorganics

complex mixture of thousands of individual organic compounds

Organic Material Contributes Significantly to PM2.5 Mass Across the Globe!

Organic Sources = Primary + SECONDARY[Zhang et al., 2007, GRL]

Most of Organic Mass!

• 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• Examples:

Types of Organic Aerosol (OA)

isoprene a-pinene

naphthalenetoluene

SOA Yield = Mo/VOC Mo= organic mass produced (g/m)

VOC = mass of reacted VOC (g/m3)

This Process is Parameterized by Laboratory Chamber Experiments

(VOCs)

VOCs Known to Yield SOA:Isoprene

Monterpenes (C10H16)

Sesquiterpenes (C15H24)

-pinene

-caryophyllene

“Traditional” View of Secondary Organic Aerosol (SOA) Formation

• Field Studies Indicate HIGHER SOA Formation in the Atmosphere than Models Predict

• Possible Explanations For Discrepancy:

– Chemical Conditions in Laboratory Chambers Not Same as in Troposphere

– Chemical Formation Mechanisms Not Fully Established or Identified

– Other Unidentified SOA Precursors

– Role of Aerosol Acidity & Heterogeneous Chemistry

IMPACT of Aerosols on Climate & Health Cannot be Fully Assessed!

What is the Current Motivation For Studying Secondary Organic Aerosol?

Volkamer et al., GRL (2006)

SOAmeas /SOAmod >> 1

Guenther et al., ACP (2006)

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)

Global Isoprene Emissions

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]

My Current Work: Do the Interactions Between Human Activities and Natural VOC Emissions Enhance Secondary Organic Aerosol Formation in S.E. USA?

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.

Biogenic emissions onlyTotal emissions

(biogenic + anthropogenic)

[Carlton et al., 2010, ES&T]

Mo

del

ed b

iog

en

ic S

OA

Notably, this interaction could be more pronounced than currently understood since models currently under predict PM2.5 mass concentrations in eastern USA

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]

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