1 Role of Glyoxal in SOA Formation from Aromatic Hydrocarbons SHUNSUKE NAKAO, Yingdi Liu, Ping Tang, Chia-Li Chen, David Cocker AAAR 2011 Orlando, FL Oct.6 (Thu) 10E.5

2 Role of glyoxal in aromatic SOA formation SOA: Secondary Organic Aerosol

3 SOA formation from glyoxal –Cloud and fog processing Aqueous oxidation (Tan et al., 2009) Evaporating droplet (Leoffler et al., 2006; De Haan et al., 2009) –“Missing sink”  uptake onto aerosol 15% of SOA formation in Mexico city (Volkamer et al., 2007) –Uptake onto wet (NH 4 ) 2 SO 4 SO 4 2- enhances Henry’s law constant (Ip et al., 2009) Catalytic effect of NH 4 + on oligomerization (Nozière et al., 2009) Chamber studies (Jang and Kamens, 2001; Kroll et al., 2005; Liggio et al., 2005; Galloway et al., 2009, 2011; Volkamer et al., 2009) –Uptake onto organic seed Fulvic acid, humic acid sodium salt, amino acids, carboxylic acids (Corrigan et al., 2008; Volkamer et al., 2009; De Haan et al., 2009)

4 SOA formation from aromatics Glyoxal inferred to play a major role in aromatic-SOA Glyoxal significant product: 8~24% from toluene (with NO x, Calvert et al., 2002) Oligomer formation (Kalberer et al., 2004) Water effect: Cocker et al., 2001  no effect (RH2~50%) Edney et al., 2000  no effect (RH 52~70%) Zhou et al., 2011  2~3 fold increase (RH 10~90%, ascribed to glyoxal) This study: synthesized glyoxal, added glyoxal into aromatic-SOA system, and evaluated its impact Kalberer et al., Science, 2004 RH 40~50%

Experimental Glyoxal synthesis - Heating glyoxal trimer dihydrate / P 2 O 5 mixture under vacuum (Galloway et al., 2009, ACP) Gas Phase Analysis Glyoxal, NO 2 – CEAS (Cavity Enhanced Absorption Spectrometer) GC-FID – hydrocarbon O 3, NO X analyzer Particle Phase Analysis SMPS – volume concentration and size distribution (Scanning Mobility Particle Sizer) V/H-TDMA –volatility/hygroscopicity (Volatility/hygroscopicity Tandem Differential Mobility Analyzer) HR-ToF-AMS – bulk chemical composition (Aerodyne High Resolution Time-of-Flight Mass Spectrometer) Dual SMPS Blacklights Dual teflon reactor APM TDMA PTRMS AMS

Glyoxal uptake onto wet (NH 4 ) 2 SO 4 Glyoxal uptake confirmed (reversible oligomerization, Galloway et al., 2009; wall-reservoir, Loza et al., 2010) RH~65% RunID: EPA1369A

7 Glyoxal and SOA formation from toluene/NO x photooxidation Solid line: model prediction by SAPRC11(Poster 5E.8) NO: 42 ppb RH 40% RunID: EPA1503A

Effect of additional glyoxal on toluene SOA formation Kinetic effect Additional 80ppb glyoxal NO x : ~40ppb RH ~70% + glyoxal + H 2 O 2

9 No glyoxal uptake onto “aromatic-SOA seed” No contribution from glyoxal during/after SOA formation Shaded area: dark

10 Thermodenuder vaporization profiles Glyoxal oligomer & aromatic SOA low volatile (<<10 -8 Pa) Aromatic SOA ~10 -6 ~10 -5 Pa ~10 -7 ~10 -8 Faulhaber et al., AMT, 2009 Residence time: ~15 sec

11 Volatility evolution

12 Toluene + NO x (RH~70%) Non-seeded vs (NH 4 ) 2 SO 4 seed

13 2-tert-butylphenol(BP) Tert-butyl AMS fragment (C 4 H 9 + )  tracer for BP SOA

14 Enhanced SOA formation by glyoxal without glyoxal oligomerization Higher SOA without decrease in C 4 H 9 fraction 2t-BP (100ppb) + H 2 O 2 (250ppb) RH 51% Added glyoxal ~ 1ppm

Conclusion The role of glyoxal in this chamber study was observed to be a radical source; insignificant contribution of reactive uptake was observed. Glyoxal uptake onto “SOA seed” needs to be evaluated Glyoxal reactive uptake onto wet (NH 4 ) 2 SO 4 confirmed No significant glyoxal uptake onto toluene SOA was observed -Addition of glyoxal/H 2 O 2 resulted in same PM formation and PM volatility -Addition of glyoxal after PM formation (dark, SOA seed) did not form SOA -Presence of (NH 4 ) 2 SO 4 seeds did not impact SOA yield significantly -Addition of glyoxal did not alter fC 4 H 9 of 2-tert-BP SOA

Acknowledgements Graduate advisor: Dr. David Cocker Current/former students: Christopher Clark, Ping Tang, Xiaochen Tang, Dr. Quentin Malloy, Dr. Li Qi, Dr. Kei Sato Undergraduate student: Sarah Bates Support staff: Kurt Bumiller, Chuck Bufalino Glyoxal synthesis: Dr. Melissa Galloway, Dr. Arthur Chan Funding sources: NSF, W.M. Keck Foundation, and University of California, Transportation Center