1. Office of Research and Development National Exposure Research Laboratory Atmospheric Modeling Division, Research Triangle Park, NC September 17, 2015 Annmarie Carlton, Rob Pinder, Prakash Bhave, George Pouliot CMAS – Chapel HIll, NC To What Extent Can Biogenic SOA be Controlled?

2. 1 Important Findings CMAQ Simulations indicate anthropogenic pollution enhances predicted biogenic SOA concentrations in the U.S. substantially ~ 50% –Effects are largest in eastern U.S. –POC and NOx are largest individual pollutant classes contributing to overall biogenic SOA

3. 2 Non-fossil (biogenic) carbon is a dominant component of atmospheric organic aerosol Substantial portion of PM 2.5 carbon is ‘modern’ even in urban areas (Lewis et al., 2004; Szidat et al., 2006; Bench et al., 2007; Gelencsér, et al., 2007) Tracer-based ambient SOA ‘measurements’ dominated by contributions from biogenic hydrocarbons (Edney et al., 2003; Kleindienst et al., 2007) Ambient WSOC, AMS OOA spectra and other indicators of SOA correlate strongly with tracers of anthropogenic pollution (Weber et al., 2007; de Gouw et al., 2005; Goldstein et al., 2009) If anthropogenic pollution is enhancing biogenic SOA how can this contribution be quantified? MOTIVATION

4. 3 controllable emissions (e.g., anthropogenic VOCs) non-controllable (e.g., biogenic VOCs) POA anthropogenic VOCs oxidants biogenic VOCs oxidants SVOC POA SOA A SOA B SOA A SOA B Anthropogenic/Biogenic Interactions in SOA Formation H + effects not shown

5. 4 Estimating Anthropogenic Contribution to “Biogenic” SOA Difficult to directly measure in the atmosphere –O 3, OH ambient measurements – no insight as to whether the precursor was anthropogenic or biogenic –PM mass - can make estimates only about organic precursors with detailed chemical analysis Can investigate large scale trends and relationships with an atmospheric model (CMAQ) by manipulating emissions

6. 5 accumulation mode organic PM AOLGB AISO3 H+H+ AORGC ∙OH dissolution cloud water glyoxal methylglyoxal VOCs EMISSIONS isoprene sesquiterpenes monoterpene EMISSIONS Non-volatile EMISSIONS POA SV_TRP1 SV_TRP2 SV_ISO1, SV_ISO2 SV_SQT O 3 P, NO 3 O 3,O 3 P, or NO 3 ∙ OH Pathways do not contribute to SOA ∙ OH,O 3, or NO 3 ∙OH,O 3 ASQT ATRP1, ATRP2 AISO1, AISO2

7. 6 Modeling experiment Simulation of August 15 - September 4, 2003 Continental US Time period has high biogenic contribution to SOA Emissions: controllable versus not controllable Not ControllableControllable Wildfire Prescribed burning VOCs from plants / trees Soil NO x Lightning NO x Everything else: Power plants Vehicles Agricultural burning Area sources

8. 7 Percent of emitted species from controllable and uncontrollable sources controllable sources – gray uncontrollable sources - white Carlton et al., ES&T (2010)

9. 8 Base CMAQ simulation all emissions Fraction of biogenic SOA from controllable pollution non-controllable emissions = biogenic emissions + wildfires + prescribed burns Biogenic SOA at the Surface (<~34 m): 18 day average Results averaged from Aug. 18 th – Sep. 4 th, 2003 Carlton et al., ES&T (2010) fraction

10. 9 Additional simulations to estimate effects and contributions of individual species POC, NO x, VOC, SO 2, NH 3 Difference in predicted biogenic SOA mass concentrations Maxima for time periodAverage for time period On Average ~ 1 ug/m3 of Biogenic SOA in SE is from controllable sources

11. 10 To control biogenic SOA – what should regulators focus on? What emitted species are most important? What locations are most impacted? Group the anthropogenic emissions into –VOC: Volatile Organic Carbon –POC: Primary Organic Carbon Particles –NO x Remove one of these species at a time Calculate change in biogenic SOA

12. 11 Regional Influence of Controllable Emissions on “Biogenic” SOA Surface (<~34 m) Concentration; 18 day average Controllable SO 2 Controllable NO x Controllable POC

13. 12 Change in population-weighted AQ metrics

14. 13 2003 Monthly-Averaged CMAQ Results at RTP Cloud SOA

15. 14 glyoxal 2003 Monthly-Averaged CMAQ Results at RTP methylglyoxal Cloud SOA Precursors

16. 15 ∙ OH Cloud SOA Precursors SOA formation is photochemistry

17. 16 Conclusions Used CMAQ to estimate fraction of biogenic SOA that is controllable. In the Eastern US, ~50% of the biogenic SOA can be controlled by reducing anthropogenic emissions To reduce concentrations of biogenic SOA, focus on –primary organic carbonaceous particles (POC) and NO x –SO 2 impacts biogenic SOA in the southeastern US Cloud-produced SOA exhibits seasonal cycle similar to ∙ OH and biogenic VOCs

18. 17 Acknowledgements Sergey Napelenok Marc Houyoux Alice Gilliland Rohit Mathur Golam Sarwar Ed Edney, Tad Kleindist, John Offenburg, Michael Lewandowski Charles Chang & Ryan Cleary