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OXIDATION AND REPLACEMENT OF OLEIC ACID AT THE AIR/WATER INTERFACE TO UNDERSTAND FAT-COATED AEROSOLS Laura F. Voss, Kandice L. Harper, Gang Ma, Christopher M. Hadad, & Heather C. Allen Department of Chemistry The Ohio State University Columbus, Ohio Funding Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry NSF-ATM NSF-Ohio State EMSI NSF-CHE CAREER Beckman Young Investigator Award
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3.3 billion metric tons of salt spray enters the atmosphere yearly Inverse micelle first proposed by Gill et al. (1983), furthered by Ellison, Tuck, & Vaida (1999) Field samples of marine and continental aerosols collected and analyzed by Tervahattu et al. (2002, 2005) Dobson et al., PNAS., 97, 11864, 2000 Fat-Coated Aerosols Tervahattu et al., J. Geophys. Res., 107, D7, 4053, 2002; D16, 4319, 2002.
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TOF-SIMS Analysis of Coated Aerosols C 16 C 18 palmitic acid cis-oleic acid Tervahattu et al., J. Geophys. Res., 107, D7, 4053, 2002.
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Oleic Acid Monolayers Studied using sum frequency generation spectroscopy Oxidation of oleic acid by ozone Replacement of oxidation products by less soluble species
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Sum Frequency Generation Spectroscopy 2 ps, 800 100 fs, IR 800nm + IR = sum 300 cm - 1 bandwidth spectrum from every laser pulse ground state IR excited state virtual state Energy
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Coupling BBSFG with Langmuir trough allows simultaneous collection of spectroscopic and thermodynamic data. Langmuir Isotherms
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Concurrent Langmuir Isotherm & SFG: Oleic Acid
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Oleic Acid Compression Snapshots
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Oleic Acid Monolayer
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R1R1 R2R2
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+ + · · · · · · · · · · + · · oleic acid primary ozonide nonanal oxononanoic acid (a) (b) (a) (b) azelaic acid octanoic acid nonanoic acid
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Oleic Acid-Ozone Reaction Snapshots T=0 min T=1 min T=10 min T=2 min T=30 min CH 2 SS CH 3 SS CH 3 FR CH 2 FR R1R1 R2R2 Voss et al., J. Geophys. Res. submitted
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Oleic Acid Oxidation on 0.6 M NaCl T=0 min T=1 min T=10 min T=2 min T=30 min CH 2 SS CH 3 SS CH 3 FR CH 2 FR R1R1 R2R2
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nonanoic acidoctanoic acidazelaic acid nonanal9-oxononanoic acid productsolubility in water, g/L nonanal0.096 nonanoic acid0.28 octanoic acid0.79 azelaic acid2.4 9-oxononanoic acid 19 Oleic Acid-Ozone Reaction Products
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nonanal oleic acid monolayer after 2 minute of ozone Nonanal vs. Oxidation of Oleic Acid
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oleic acid monolayer after 1 minute of ozone oleic acid monolayer in disordered liquid state Compression Data vs. Oxidation of Oleic Acid
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Oleic Acid-Ozone Reaction
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Oleic Acid Monolayer Replaces d 31 -Palmitic Acid Monolayer
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Monolayer Replacement Voss et al., J. Chem. Phys. B. submitted
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Monolayer Replacement Voss et al., J. Chem. Phys. B. submitted After Oxidation
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d 31 -Palmitic Acid Monolayer Reforms
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Conclusions No spectroscopic evidence of oxidation products at the air/water interface Least soluble surfactants at interface Dissolved surfactants replace reaction products Results same on 0.6 molar sodium chloride solution
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Acknowledgements Funding Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry NSF-ATM NSF-Ohio State EMSI NSF-CHE CAREER Beckman Young Investigator Award Jeremy Beck Mohamad F. Bazerbashi Allen Group Hadad Group
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