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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 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.

3 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.

4 Oleic Acid Monolayers Studied using sum frequency generation spectroscopy Oxidation of oleic acid by ozone Replacement of oxidation products by less soluble species

5 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

6 Coupling BBSFG with Langmuir trough allows simultaneous collection of spectroscopic and thermodynamic data. Langmuir Isotherms

7 Concurrent Langmuir Isotherm & SFG: Oleic Acid

8

9 Oleic Acid Compression Snapshots

10 Oleic Acid Monolayer

11 R1R1 R2R2

12 + + · · · · · · · · · · + · · oleic acid primary ozonide nonanal oxononanoic acid (a) (b) (a) (b) azelaic acid octanoic acid nonanoic acid

13 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

14 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

15 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

16 nonanal oleic acid monolayer after 2 minute of ozone Nonanal vs. Oxidation of Oleic Acid

17 oleic acid monolayer after 1 minute of ozone oleic acid monolayer in disordered liquid state Compression Data vs. Oxidation of Oleic Acid

18 Oleic Acid-Ozone Reaction

19 Oleic Acid Monolayer Replaces d 31 -Palmitic Acid Monolayer

20 Monolayer Replacement Voss et al., J. Chem. Phys. B. submitted

21 Monolayer Replacement Voss et al., J. Chem. Phys. B. submitted After Oxidation

22 d 31 -Palmitic Acid Monolayer Reforms

23 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

24 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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