1. Unusual oxidation mechanism for unsaturated
organics on sea salt
Federico Karagulian
Newport Beach (USA), January 2008
Department of Chemistry, University of California, Irvine, CA, 92697-2025

2. Why Sea Salts aerosols?
Sea salts (NaCl) are an excellent medium for
reactions of pollutants and organics susbtances
Organic membranes
+
+
O =
+ O3
3
aerosols
medium
(NaCl)
Polluted atmosphere (ozone formation)

3. Organic membranes and sea salts
 As organism die, they decompose and the hydrophobic cellular constituents rise
toward the ocean’s surface.
 Marine aerosol particles are formed by mechanical ejection from the ocean’s
surface and, as they form, they acquire a coating of hydrocarbon surfactants.

4. Phosphocholines constitute the most abundant class of phospholipids
NaCl coated with
1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC)
R2
NaCl crystal
=
NaCl coated with OPPC
Coating with OPPC
R1
=O
O=
more agglomeration
O
O
H
less agglomeration
O
N+
O
P =O
O-
Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl-

5. Phosphocholines
Phosphocholines are common organics
floating on the oceans and coming from
living organisms (also important
constituents of human lungs)
R2
=
double bond
R1
=
O
the experiment:
NaCl coated with
1-oleoyl-2-palmitoyl-sn-glycero-3phosphocholine (OPPC)
Cl-
=
O
O
Organic membrane
(OPPC)
O
H
O
N+
Na+ Cl-
O
Na+ Cl-
salt
P= O
ONa+ Cl-
Na+ Cl-

6. After reacting with OH, O3 and O2,
the marine aerosol particle become
coated with alcohol, aldehyde,
ketone, and carboxylic functional group
Model of marine aerosols
pictures them as inverted
micelles
CH3
HOCH2
CH3
CHO
CH3
O2, OH, O3
NaCl/H2O
NaCl/H2O
CH3
CH3
hydrophobic
HOOC
CH3
hydrophilic
 A major source of this organic layer is the decomposition of marine organisms, which
have biomembranes that are mixture of lipids, hydrophobic proteins and
carbohydrates (B. Alberts et al., 1989; G.B. Ellison et al., 1999)
 Phospholipids and fatty acids (mainly C12-18) are common products of biomembrane
disintegration (R.B. Gagosian et al.,1981; J.C. Marty et al., 1979)

7. DRIFTS
Diffuse Reflection Infrared Fourier Transform Spectroscopy
DRIFTS
O3 + He + H2O

8. Reaction of 2 ppm O3 with NaCl coated with OPPC at 0% RH
0
-5
3008
absorbance
-10x10
3050
3000
2950
1385
(-CH2-)
(-CH2-)
-3
3100
2850
2919
(C=C)
1.0
1110
(-CH3-)
5
absorbance
1.5x10
2948
-2
(O-C-H)
2900
-1
2850
2800
2750
wavenumber (cm )
t
1347
(C-H)
0.5
1751
(R-COOH)
1708
(R-CHO)
1210
0.0
1800
1600
1400
1200
-1
wavenumber (cm )
1000

9. Reaction of 2ppm O3 with NaCl/OPPC in
the presence of water (100 min)
1.5x10
absorbance
1110
0% RH
2% RH
10% RH
25% RH
-2
1.0
(SOZ)
1385
(O-C-H)
1708
0.5
1751
1347
(CH)
1210
(C-O)
(R-COH)
(R-COOH)
0.0
1261
-0.5
(PO2)
1800
1600
-
1400
1200
-1
wavenumber (cm )
1090
(PO2)
-
970
+
(-N(CH3)3
1000

10. Classic Criegee mechanism
H2O2 + R2-CHO
R1-COOH
PL carboxylic acid
Hydroxyhydroperoxide
(HHP)
H2O2 + R1-CHO
R2-COOH

11. Kinetics
[O3] = 7.0 x 10
-2
2.0x10
13
[O3] = 5.0 x 10
13
cm
-3
cm
-3
abs(SOZ)
1.5
[O3] = 2.2 x 10
1.0
[O3] = 7.8 x 10
0.5
[O3] = 1.7 x 10
13
12
12
cm
cm
cm
-3
-3
-3
0.0
0
20
40
60
80
time (min)
100
120
 Unexpectedly, the final amount of SOZ increases with the O3 concentration
 At high O3 concentration, SOZ converged to a common value
(Karagulian et al., 2008)

12. Modified reaction mechanism
 We found lifetime t for the
primary ozonide (POZ) of
~ 100 ms, ([O3] ~ 100 ppb,
~ 50% RH)
 Typical lifetime for the
decomposition of POZ in
solution is ~ 1 ms,
(Mile et al., 1979)
 POZ has as sufficiently long
lifetime that can undergo
further reaction with O3 and
water vapor (F.Karagulian et
al., 2008)

13. Summary
 Secondary ozonide (SOZ) is not the only species formed on the surface, also
primary ozonide (POZ) is sufficiently stable to undergo secondary reactions…
…this is a very nice “interface” finding.
 POZ may react with O3 or H2O in addition to decomposition
(F.Karagulian et al., 2008)
In polluted and dry areas such as Mexico City with O3 peaks of ~ 400 ppb and RH ~ 20 %,
the lifetime of the POZ is about 90 ms for reaction with O3 and 5 ms for reaction with H2O.
 Stable SOZ may be formed in the atmosphere at low RH or if the
double bond is protected from water

14. Acknowledgements
National Science Foundation
AirUCI
Barbara Finlayson-Pitts’s group
John Greaves
UCI MS facility
W.R. Wiley Environmental Molecular Science Laboratory
Pacific Northwest National Laboratory (PNNL)