1. Yuzhi Chen 13th CMAS Assessment of SAPRC07 with Updated Isoprene Chemistry against Outdoor Chamber Experiments Yuzhi Chen a, Roger Jerry a, Kenneth Sexton a, Jason Surratt a, William Vizuete a a University of North Carolina at Chapel Hill 1 13th Annual CMAS Conference, Chapel Hill, NC 27 Oct 2014

2. Introduction

3. Yuzhi Chen 13th CMAS Motivation - Updated SAPRC07 in CMAQ Xie et al. (2013) updated SAPRC07 with more explicit isoprene chemistry with additional OH and NO 3 oxidation pathways that produce SOA precursors. Isoprene epoxydiols (IEPOX) OH/HO2 from Hydrox-peroxy aldehydes (HPALD) Isoprene nitrates more explicit Yuzhi Chen [Xie et al., 2013, ACP] 3 Updated isoprene oxidation scheme for isoprene + OH

4. Yuzhi Chen 13th CMAS 4 CMAQ runs suggest improved model performance Uncertainties Remain: isoprene nitrates yield from ISOPO2 + NO pathway & NO X recycling efficiency Chemistry Good Enough?Compensating Error? [Xie et al., 2013, ACP] Objective Can Xie model ozone? How radical budgets and nitrogen cycling altered?

5. Yuzhi Chen 13th CMAS Methodologies 5 Modeling: MORPHO (UNC) PERMM (Python-based Environment for Reaction Mechanisms/Mathematics) UNC dual gas-phase chamber, Pittsboro, NC, 1994 Experimental: 24 isoprene runs Compounds measured: O 3, NO X, Isoprene,CO, HCHO…

6. Result

7. Yuzhi Chen 13th CMAS Model Performance Ozone Peak NO-NO2 crossover time time 7

8. Yuzhi Chen 13th CMAS 8 NO/NO2 Crossover Time MechNMB(%)R2R2 SAPRC07-5.40.022 Xie-16.00.032 MechNMB(%)R2R2 SAPRC07-24.10.77 Xie-32.30.68 Lower NO X High NO X

9. Yuzhi Chen 13th CMAS 9 NO/NO2 Crossover Time Lower NO X High NO X Xie predicts earlier NO-NO2 crossover for all isoprene runs

10. Yuzhi Chen 13th CMAS Xie is better But not significant Both over-predict Xie is worse Ozone Peak MechNMB (%)R2R2 P value SAPRC074.920.859.51E-06 Xie11.080.761.42E-16 MechNMB(%)R2R2 P value SAPRC07-9.790.130.38 Xie0.580.140.36 10 Lower NO X High NO X

11. Yuzhi Chen 13th CMAS Ozone Peak 11 Xie predicts higher ozone for all isoprene runs Lower NO X High NO X

12. Yuzhi Chen 13th CMAS 12 Model Performance Summary For All Runs: Xie predicts earlier crossover Xie predicts higher ozone For Lower NO X experiments Xie pushes the performance towards the wrong direction However, statistics doesn’t tell us the story!

13. Case Study

14. Yuzhi Chen 13th CMAS 14 O 3, NO X, isoprene concentration times series ISOP: 0.26 ppm, NO X : 0.45 ppm, (ISOP/NO X : 0.58) ISOP: 1.26 ppm, NO X : 0.35 ppm (ISOP/NO X : 3.73) 0.75 ppm 0.97 ppm 0.61 ppm 0.53 ppm 0.52 ppm 0.57 ppm Lower NO X 0.53 ppm 0.64 ppm 0.85 ppm High NO X

15. Yuzhi Chen 13th CMAS 15 Reaction Rate of VOCs + OH High NO X ISOP: 1.26 ppm, NOX: 0.35 ppm (ISOP/NO X : 3.73)

16. Yuzhi Chen 13th CMAS 16 Integrated Reaction Rate of VOCs + OH Lower NO X High NO X

17. Yuzhi Chen 13th CMAS 17 OH conc. HO 2 from Aldehydes Lower NO X High NO X

18. Yuzhi Chen 13th CMAS High NOx 18 Why Xie makes more Ozone? Sources of NO 2 Lower NOx High NO X — 65% NO 2 made through NO + O3 for SAPRC07; 47% made through recycling from NO Z for Xie Lower NO X — 77% more NO2 recycled from NO Z for Xie

19. Yuzhi Chen 13th CMAS 19 NO 2 Recycling Rate Yuzhi Chen Xie predicts 64% more PANs than SAPRC07 Which accounts for 85% of the total increase in recycled NO 2 Lower NO X

20. Summary

21. Yuzhi Chen 13th CMAS 21 Xie predicts earlier NO-NO2 crossover time and higher ozone peak than original SAPRC07; The cause is increased VOC + OH reactions and thus elevated HO X (OH & HO2) production from aldehydes; Under low NO X condition, Xie goes in the wrong direction (bias 4.92% to 11.08%); Over-prediction of second ozone peak driven by increased NO 2 recycling from organic nitrates, mostly PANs (85%). Modeling gas-phase SOA precursors (Methacrolein) Incorporating the CMAQ SOA module into MORPHO and test the Xie mechanism against aerosol chamber experiments Conclusion Future Work

22. Yuzhi Chen 13th CMAS 22 Acknowledgment Yuzhi Chen Special Thanks Dr. William Vizuete, Dr. Jason Surratt, Dr. Ken Sexton, Dr. Evan Couzo, MAQ/CHAQ group, Dr. Harvey Jeffries, Dr. Harshal Parikh We thank Dr. Ying Xie and Deborah Luecken at EPA for providing the CMAQ source code of the Xie mechanism and CSQY file. We are also grateful to Blaine Heffron for technical assistance in modeling, and our former colleague Dr. Haofei Zhang, who provided insight and expertise that greatly assisted this research.

23. Yuzhi Chen 13th CMAS References 23 Xie et al., 2013, Atmos. Chem. Phys., 13(16):8439–8455. Available at: http://www.atmos-chem-phys.net/13/8439/2013/ Hutzell et al., 2011, Atmos. Environment, 46: 417-429. Crounse et al., 2011, PCCP, 13:13607-13613. da Silva et al., 2010, Environ. Sci. & Tech. 44 (1) :250-6. Henderson et al., 2009, Poster at the 8th CMAS Conference, Chapel Hill, NC.

24. Thank you! Questions?

25. Backup Slides

26. Yuzhi Chen 13th CMAS 26 Sensitivity Runs Yuzhi Chen CaseDescription*K isom,ISOPO2 ISOPN yields RunBASEK0.06 Run Alower K isom,ISOPO2 0.5K0.06 Run B lower ISOPN yield K0 Halving ISOPO2 isomerization rate has no impact on O 3 ISOPN yields zero-out reduces O 3 peak by 5.5% Lower NO X case: JN2697RED * K = (4.07e+8*EXP(-7694/TK) cm3/s

27. Yuzhi Chen 13th CMAS 27 Radical Cycle OH NO Lower NO X High NO X

28. Yuzhi Chen 13th CMAS 28 Radical Cycle Overview High NOx ————> Lower NO X

29. Yuzhi Chen 13th CMAS 29 Radical Cycles New Radical New Radical Termination Loss of Radicals Propagation Products Termination Loss of Radicals Propagation Products New NO New NO Oxidation, Photolysis & Reaction Nitrogen products Loss of NO and NO2 Oxidation, Photolysis & Reaction Nitrogen products Loss of NO and NO2 O 3 Production ＋ H2O Net O 3 Production Net O 3 Production O 3 Reaction Loss inorganic processes organic processes hv qQ E e OH cycle = Q/q NO cycle = E/e NO —> NO2 (NO Z )

30. Yuzhi Chen 13th CMAS 30 Radical Cycles - High NO X Case New Radical New Radical Termination Loss of Radicals Propagation Products Termination Loss of Radicals Propagation Products New NO New NO Oxidation, Photolysis & Reaction Nitrogen products Loss of NO and NO2 Oxidation, Photolysis & Reaction Nitrogen products Loss of NO and NO2 O 3 Production ＋ H2O Net O 3 Production Net O 3 Production O 3 Reaction Loss inorganic processes organic processes hv qQ E e OH cycle = Q/q NO cycle = E/e NO —> NO2 (NO Z )

31. Yuzhi Chen 13th CMAS Generic Atmospheric Ozone Chemistry 31 VOC + OH RO2 HO2 RCHO RO + NO OH + NO2 O3 hv O3P O2 RONO 2 HNO3 O2 (ISOP + OH) NO + O3NO2 hv