Heterogeneous reaction of gaseous ozone with aqueous iodide in the presence of aqueous organic species

Article abstract of DOI:10.1021/jp101985f

The fast reaction of gaseous ozone, O₃(g), with aqueous iodide, I^-(aq), was found to be affected by environmentally relevant cosolutes in experiments using cavity ring-down spectroscopy (CRDS) and electrospray ionization mass spectrometry (ESIMS) for the detection of gaseous and interfacial products, respectively. Iodine, I₂(g), and iodine monoxide radical, IO(g), product yields were suppressed in the presence of a few millimolar phenol (pK_a = 10.0), p-methoxyphenol (10.2), or p-cresol (10.3) at pH 3 but unaffected by salicylic acid (pKa₂ = 13.6), tert-butanol, n-butanol, or malonic acid. We infer that reactive anionic phenolates inhibit I₂(g) and IO(g) emissions by competing with I ^-(aq) for O₃(g) at the air/water interface. ESIMS product analysis supports this mechanism. Atmospheric implications are discussed.

Full text of DOI:10.1021/jp101985f

6
016
J. Phys. Chem. A 2010, 114, 6016–6021
Heterogeneous Reaction of Gaseous Ozone with Aqueous Iodide in the Presence of Aqueous
Organic Species
Sayaka Hayase, Akihiro Yabushita, and Masahiro Kawasaki*
Department of Molecular Engineering, Kyoto UniVersity, Kyoto 615-8510, Japan
Shinichi Enami, Michael R. Hoffmann, and Agust ´ı n J. Colussi
W. M. Keck Laboratories, California Institute of Technology, Pasadena, California 91125
ReceiVed: March 4, 2010; ReVised Manuscript ReceiVed: April 9, 2010
-
The fast reaction of gaseous ozone, O
3
(g), with aqueous iodide, I (aq), was found to be affected by
environmentally relevant cosolutes in experiments using cavity ring-down spectroscopy (CRDS) and
electrospray ionization mass spectrometry (ESIMS) for the detection of gaseous and interfacial products,
respectively. Iodine, I
of a few millimolar phenol (pK
by salicylic acid (pKa2 ) 13.6), tert-butanol, n-butanol, or malonic acid. We infer that reactive anionic phenolates
2
(g), and iodine monoxide radical, IO(g), product yields were suppressed in the presence
a
) 10.0), p-methoxyphenol (10.2), or p-cresol (10.3) at pH g 3 but unaffected
-
inhibit I
2 3
(g) and IO(g) emissions by competing with I (aq) for O (g) at the air/water interface. ESIMS product
analysis supports this mechanism. Atmospheric implications are discussed.
Introduction
It has been recognized that halogen chemistry critically affects
the composition of the troposphere and lower stratosphere, thereby
1
affecting global climate change. Halogen atoms and halogen
monoxide radicals play essential roles in the marine boundary layer,
x x
depleting ozone, controlling the HO /NO cycle, and possibly
1,2
producing cloud condensation nuclei. The significant underes-
3
timation (by up to 50%) of tropospheric ozone losses by current
atmospheric chemistry models likely reflects missing halogen
sources and/or reactions. For example, the origin of high (up to a
few pptv) and persistent concentrations of iodine monoxide, IO(g),
4
–6
7,8
over oceans worldwide, including coastal Antarctica, and the
3
open ocean far away from biogenic coastal sources, even at
nighttime,2 remains uncertain. Recently, photoinduced oxidation
,5
of sea salt halides by photochemical agents, such as chlorophyll,
9–11
in the sea surface microlayer is reported. We have reported that
and IO are emitted into gas phase from the rapid reaction of O
I
2
3
-
with I (aq) under the dark condition using cavity ring-down
spectroscopy (CRDS) combined with a gas-liquid interaction cell.
O
Figure 1. Schematic diagram of the experimental setup that combines
CRDS and a gas/liquid reaction cell. HRM and PMT stand for high
reflective mirror and photomultiplier tube, respectively.
12
-
13–16
3
reacts with I at the air/water interface,
and IO via the IOOO and HOI intermediates at the interface
resulting in the emission
-
12
of I
2
seawater surfaces.17–19 This issue may be relevant to recent field
observations and laboratory experiments, showing that aerosols and
I- + O (g or aq) f IOOO-
(1)
3
seawater iodide is incorporated into unidentified iodine-containing
IOOO- f IO- + O2
(2a)
20–23
organic species
we show how the fast O
via hitherto unknown reaction mechanisms. Here
-
3
(g) + I (aq) reaction at the air/water interface
IOOO- f f IO(g) + products
(2b)
(3)
is affected by the presence of representative aqueous organics such as
phenols, alcohols, and dicarboxylic acid using CRDS detection of
gaseous products in conjunction with a nebulizer-assisted electrospray
IO- + H a HOI(aq) (pK ) 10.8)
+
a
13
ionization mass spectrometry (ESIMS) for the detection of air/water
interfacial products.
-
+
HOI(aq) + I + H a I (aq) + H O
(4)
(5)
2
2
Experimental Section
I (aq) f I (g)
2
2
Cavity Ring-Down Spectroscopy. The present CRDS setup
combined with a gas-liquid interaction cell is shown in Figure
One of the remaining issues is how this reaction mechanism is affected
by the presence of other species in actual atmospheric aerosols and
1
. The principle of CRDS and the experimental details are
12,24
presented in previous publications.
Ozone was produced by
flow through a high-pressure
discharge ozonizer and monitored by UV absorption by a 253.7
1
slm (standard liter per minute) O
2
*
To whom correspondence should be addressed. E-mail: kawasaki@
moleng.kyoto-u.ac.jp.
1
0.1021/jp101985f  2010 American Chemical Society
Published on Web 04/26/2010

-
Heterogeneous Reaction of O3(g) with I (aq)
J. Phys. Chem. A, Vol. 114, No. 19, 2010 6017
nm Hg lamp prior to the gas-liquid interaction cell. Gas flow
rates were controlled by mass flow controllers so that the total
flow rate was maintained at 3 slm. The concentrations of O (g)
3
1
5
-3
were (6.5 ( 0.3) × 10 molecules cm . The product
concentrations were monitored with an OPO laser (Spectra-
Physics, MOPO-SL, spectral resolution 0.2 cm ) at 435.6 nm
for the IO(g) band head of the A Π3/2 r X Π3/2 (V′ ) 3, V′′ )
) transition. The IO signal baseline was taken at 435.4 nm, a
region in which there was no IO absorption. We calibrated [I
by introducing a concentration-known I (g) to the reaction cell
-
1
2
2
0
2
]
2
with spectral fitting at 430-455 nm for the B-X band. Only in
the measurements of emission rates as a function of interaction
-
time of O
3
(g) with I , [I
2
] was monitored at 435.4 nm where
no IO absorption exists. The observed concentrations were (0.05
1
1
-3
14
to 3.5) × 10 molecules cm for IO and (0.1 to 1.6) × 10
molecules cm- for I
3
.
2
The gas-liquid interaction cell consisted of a Pyrex glass
container (21 mm i.d. and 60 cm length) fully covered with
aluminum foil. We previously showed that no secondary wall
1
2
reactions occur under the present setup condition. The cell
was maintained at 100 Torr by means of a rotary pump, a
2
mechanical booster pump, and a N (l) trap in tandem. NaI(aq)
2
Figure 2. Measured time dependences of the [IO(g)] and [I (g)] formed
solution ([NaI] ) 5 mM unless otherwise stated, volume ) 60
mL) was filled 9 ( 1 mm above the bottom of the reaction
cell. The CRDS detection region is 2 mm above the solution
surface. A slow flow of nitrogen gas (0.05 slm) was introduced
at the ends of the CRDS cavity, close to the mirrors to minimize
mirror-deterioration caused by exposure to the reactants and
products in the reaction cell. The gas in the cell was completely
replaced within a time interval of 0.70 s. Therefore, the average
during the ozonolysis of 5 mM NaI solution at pH ∼6 (broken line)
and (5 mM NaI + 1 mM phenol) mixture at pH ∼6 (solid line) and
1
5
-3
pH ∼10 (solid gray line) by 6.5 × 10 molecules cm O (g).
3
contact time of O
3
(g) with the NaI(aq) solution was ∼0.70 s.
To minimize possible secondary reactions, a freshly prepared
solution was used for the measurement of each data point, except
for emission rate measurement as a function of reaction time.
(
See below.)
Electrospray Ionization Mass Spectroscopy (ESIMS).
ESIMS experiments simulate reactive O
interactions in microdroplets, generated by spraying NaI/phenol
mixture solutions into dilute O (g)/N (g) mixtures, whose
3
(g)/aqueous surface
3
2
interfacial composition is continuously monitored via online
ESIMS after submillisecond contact times. Solutions are pumped
-1
(
50 µL min ) into the spraying chamber (maintained at
atmospheric pressure) of a commercial electrospray ionization
mass spectrometer (Agilent, 1100 MSD Series) through a
grounded stainless steel needle coaxial with a sheath issuing
4
Figure 3. [IO(g)] and [I
2
(g)] formed during the ozonolysis (with 6.5
(g)) of 5 mM NaI (4) or 5 mM NaI + 1
mM phenol (b, O) as functions of initial bulk pH. Estimated systematic
errors are ∼6% for IO and ∼15% for I
nebulizer with N
s ) shears the liquid jet (10.6 cm s ), and separates ions already
present in solution, into charged microdroplets,
2
(g). The fast nebulizer gas (2.65 × 10 cm
1
5
-3
×
10 molecules cm
O
3
-1
-1
2
5,26
carrying
2
.
2
7,28
excess anions or cations.
microdroplets thus created exceed ∼10 cm s , leading to τ
(g) plume.
The terminal velocities of the
3
-1 26
Notably, the bulk pH changed from an initial value of 5.8 to
.5, 3 min after introducing O , whereas it increases up to 10.3
<
1 ms transit times across the ∼0.5 cm wide O
3
8
3
This technique probes, within <1 ms, the composition of
in the absence of phenol under the same condition. Figure 3
shows the initial bulk pH dependence of the suppression effect
with 1 mM phenol. IO was monitored at t ) 20 s after
nanodroplets produced from the interfacial layers of the liquid
microdroplets that had just reacted with O
3
(g), prior to charge
separation, warming up, and solvent evaporation. Experimental
1
3,14
introducing O
0 s to measure the asymptotic concentrations. (See Figure 2.)
The formation of both IO and I was found to be significantly
3 2
into the cell, whereas I was monitored at t )
details have been described in detail elsewhere.
8
2
Results
suppressed by the presence of phenol, except for the case of
initial pH 2. In the absence of phenol, [IO] is independent of
CRDS Measurements. In the measurements of emission rates
as a function of measurement time (t), the suppression of IO(g)
12
bulk pH, whereas [I
Figure 4 shows the ratios of [IO] and [I
2
] is enhanced at pH < 4.
and I
observed during ozonolysis of a NaI solution, as shown in Figure
. Both IO and I concentrations promptly increased upon
introducing O to the cell and then decayed asymptotically.
2
(g) emissions by the presence of 1 mM phenol was
2
] with and without
phenol as a function of initial pH to qualify the suppression
effect by phenol addition. The suppression effect by phenol was
found to be independent of initial pH in the range of 4-10 in
2
2
3

6
018 J. Phys. Chem. A, Vol. 114, No. 19, 2010
Hayase et al.
Figure 4. [X]/[X]
phenol) for [IO(g)] (b) and [I
mM NaI solution by 6.5 × 10 molecules cm
functions of initial bulk pH.
0
ratios ([X] with 1 mM phenol and [X]
0
without
2
(g)] (O) formed during ozonolysis of a
1
5
-3
5
3
O (g) measured as
-
Figure 6. ESIMS signal intensity of C
OH solutions as a function of [C
6
H
5
O (m/z ) 93) from aqueous
5
OH] at pH 8.0. The signal
C
6
H
5
6
H
-
29
intensity directly corresponds to [C
6
H
5
O ] at the air/water interface.
3
is otherwise inert to O , we infer that OH radicals, should they
be formed in our system, do not play a significant role in the
suppression effect by phenol.
-
ESIMS Measurements. Figure 6 shows how C
at the air/water interface of aqueous C
changes as a function of bulk concentration of [C
6
H
5
O anion
6
H
5
OH microdroplets
OH] at
6
H
5
pH 8.0. The plot shows a typical Langmuir adsorption at the
surface. Note that the signal intensity directly corresponds to
-
29
the concentration of C
apparent that C H O
6 5
6
H
5
O at the air/water interface. It is
is not saturated at the surface of
microdroplets in the present [C OH] range.
-
6
H
5
-
Figure 7 shows how C
of 0.1 mM aqueous C
6
H
5
O anion at the air/water interface
6
H
5
OH microdroplets changes as a
-
function of bulk pH from 2 to 11. The C
6
H
5
O signal increases
from pH 2-4, plateaus between pH 4 and 7, and dramatically
>10 times) increases from pH 7 to 11. The latter effect is due
to the acid dissociation of C OH with pK ) 10.0. Remark-
ably, phenolate appears at the interface to some extent, even at
pH 4. This result is consistent with the recent vibrational sum
(
2
Figure 5. [IO(g)] (b) and [I (g)] (O) formed during the ozonolysis
1
5
-3
6
H
5
a
(
with 6.5 × 10 molecules cm
functions of added [phenol] at pH ∼6. Estimated systematic errors are
% for IO and 15% for I
3
O (g)) of 30 mM NaI solutions as
6
2
.
frequency generation (VSFG) experiment by Eisenthal and
coworkers.30 Therefore, it is expected that C
H
5
O
-
could
TABLE 1: Summary of the Suppression Effects of Various
Cosolutes on the Formation of I (g) and IO(g)
6
2
contribute to the interfacial reaction at even lower pH.
Figure 8 shows negative ion ESI mass spectra of an aqueous
5
5
O3/M-1 s-1 33,34,56 suppression
reactant
pK
a
k
equimolar (NaI + phenol) solution at bulk pH 8.3 (A), pH 10.3
I-
1.2 ×10
9
9
(B) and of a phenol solution at pH 9.0 (C) during <1 ms contact
phenolate
phenol
p-cresol
1.4 ×10
1.3 ×10
3.0 ×10
3.0 ×10
3.0 ×10
5.5
yes
yes
yes
yes
no
no
no
no
-
3
4
4
4
with O
(g) or N
(g). The reaction of C
H
3
O (aq) with O
·
(g or
Note
10.0
10.3
3
2
6
5
3
-
31,32
aq) predominantly produces C
6
H
5
O· + O
radicals.
-
p-methoxyphenol 10.2
that without O
than those of C
rable at pH 10 (Figure 8B). The two ozonation products of I ,
(g), at pH 8.3, I signals are ∼10 times larger
- 29
6 5
3
a
salicylic acid
malonic acid
n-butanol
3.0 (13.6)
2.9 (5.7)
17.1
17.2
H O (Figure 8A), but they become compa-
a
-
0.58
-
-
-
3
IO
of C
3
, and I
3
, were observed in both the absence and presence
tert-butanol
3.0 × 10
H
5
OH.13–15 There is no evidence of the formation of anionic
6
a
-
Parenthetic values correspond to pKa2
.
organoiodine products such as iodophenolate, C
6
H
4
IO (m/z )
0–22
-
2
19) (Figures 8A,B).2
not decrease as a function of [O
A), whereas it is largely consumed by similar [O
Significantly, the C
(g)] in the presence of I (Figure
(g)] in the
and I are reactive
6 5
H O signal does
-
the ozonolysis of 5-30 mM NaI. Figure 5 shows a behavior of
the suppression effects as functions of [C OH]. Similar
suppression effects were observed for p-cresol and p-methoxy-
phenol at pH 6. In contrast, the addition of 5 mM n-butanol, 10
mM malonic acid, or 5 mM salicylic acid at pH 7 affects neither
3
8
3
6
H
5
-
-
-
absence of I (Figure 8C). Both C
toward O
6 5
H O
3
(g) at bulk pH ∼10 (Figure 8B). These findings are
consistent with the CRDS results and the reaction mechanism
discussed below.
IO nor I
tert-butanol has no effect on IO(g) and I
confirmed that tert-butanol does not affect the extent of
suppression of IO(g) and I (g) by the presence of phenol.
Because tert-butanol is an efficient OH radical scavenger that
2
production (see Table 1). The addition of a large excess
2
(g) formation. We also
Discussion
2
We have previously reported that reactions 1-4 reach
completion within a second under similar CRDS experimental

-
Heterogeneous Reaction of O3(g) with I (aq)
J. Phys. Chem. A, Vol. 114, No. 19, 2010 6019
6 5
H
O- (m/z ) 93) from
Figure 7. (A) ESIMS signal intensity of C
aqueous 0.1 mM phenol microdroplets as a function of bulk pH and
B) the same plot in semilog scale. The solid curve is visual guide.
(
-
6 5
Note that the signal intensity directly corresponds to [C H O ] at the
air/water interface.
2
9
conditions to produce I
presence of phenol, I and IO are suppressed immediately after
(g) and IO(g).12 However, in the
2
2
ozonolysis, as shown in Figure 2. Because reactions 3 and 4
consume protons, the bulk pH actually increased from 5.8 to
1
5
1
0.3 during 3 min of ozonolysis of 5 mM NaI with 6.5 × 10
-3
molecules cm
3 3
O (g). The heterogeneous reaction of O (g) with
I (aq) causes the rapid change of pH from acidic/neutral to basic
-
conditions, where the phenol is rapidly converted into phenolate,
-
Figure 8. Negative ion ESI mass spectra of (1 mM NaI + 1 mM
which reacts with O
3
faster than I . Therefore, the emissions
6 5
C H OH) microdroplets (A) at pH 8.3 and (B) at pH 10.3 and (C) of
of the gas-phase products, I
the presence of phenol.
2
(g) and IO(g), are suppressed in
1
6 5 3
1 mM C H OH at pH 9.0 with (green, red)/without (blue) O (g).
The significant (several times) difference in the extent to
which IO and I are suppressed (Figure 4) must be related to
the reactivity of their intermediate precursors or themselves
-
+
C H OH f C H O + H
(pK ) 10.0)
(6)
(7)
6
5
6
5
a
2
-
toward C
radical, which may accumulate at the surface for a longer time
Figure 2). Actually, the production of IO radical is almost
completely suppressed (to less than ∼10%) compared with I
molecule. This observation suggests that the reaction of IO with
6
H
5
O
6 5
and/or secondary species such as C H O·
-
-
C H O + O (g or aq) f C H O· + O ·
6
5
3
6
5
3
(
2
C H OH + O (g or aq) f products
(8)
6
5
3
-
6 5
C H O must be very effective, in accord with the estimated
9
o
-
The aqueous reaction rate constants, k
7
and k
Note that k
6 5
H O engages in the
8
, are 1.4 × 10
reduction potential E (IO/IO ) ≈ 1.8 V (from other halogen
3
-1 -1
33,34
o
-
35
and 1.3 × 10
comparable to k
(g) reaction at the air/water interface as well as I (aq), which
M
s , respectively.
7
is
analogues) versus E (C
6
H
5
O/C
6
H
5
O ) ) 0.86 V
9
-1 -1
-
1
) 1.2 × 10 M s . C
-
O
3
-
-
IO· + C H O f IO + C H O·
(9)
-
6
5
6
5
becomes competitive with the reaction of I (aq) with O
3
(g),
radicals. Similar reaction mecha-
nisms would apply in the case of p-methoxyphenol and p-cresol
whose pK
≈ 10 (cf. salicylic acid, pKa2 ≈ 14).
-
31
forming C
6
H
5
O· and O ·
3
Note that IO- is converted into I
Therefore, this reaction 9 would account for the significant
(g) via reactions 3-5.
2
a

6
020 J. Phys. Chem. A, Vol. 114, No. 19, 2010
Hayase et al.
difference between dominant inhibition of IO(g) and incomplete
the ESIMS experimental condition within 1 ms (Figure 8). Here
inhibition of I (g) (Figure 4).
2
we showed that I
are significantly hindered in the presence of typical phenols
whose pK
2
(g)/IO(g) emissions from the reactions 1-4
The surfaces of aqueous electrolyte solutions as a rule are
negatively charged relative to the bulk; that is, anions approach
a
≈ 10, but not by excess amounts of tert-butanol,
2
9,36,37
n-butanol, and a representative dicarboxylic acid, indicating that
the interface closer than cations.
that the surface affinity of C
ESIMS results confirmed
-
-
the reaction of HOI (and IOOO ) with these species are
6
H
5
O is non-negligible, even at
-
relatively slow. Our results imply that only extremely fast
bulk pH 4-7, and becomes comparable to that of I at bulk
9
-1 -1
reaction, for example, k > 10 M s , such as the reaction 7
can compete with the reaction 1 under atmospheric relevant
condition. Organic matters in atmospheric aerosols/seawater
pH ∼10 (Figures 7 and 8). The apparent increase in surface
-
C
6
H
5
O from bulk pH 2 to 4 may be an evidence that water
surface acidity is much lower than that in the bulk and the
contain complex-structured phenols.54 Therefore, the pK of
-
+
36–38
interfacial OH is neutralized by H
3
O only at bulk pH < 4.
a
-
these phenols and the actual pH of the aerosols/seawater
Significant detection of C
6
H
5
O
at the air/water interface is
-
30
determine the fate of I and control the emission of reactive
consistent with a recent VSFG experiment. The rapid (<1 ms)
-
-
halogen species.
ozonolysis of the I + C
6
H
5
OH mixture shows that the C
(g) (Figure 8A), which
O with O (g) cannot compete
3
(g) at the air/water interface of bulk pH
6 5
H O
signal looks almost inert toward O
implies that the reaction of C
with that of I with O
3
-
Acknowledgment. This project was financially supported by
the Grant-in-Aid from JSPS (no. 20245005) and National
Science Foundation (ATM-0714329). S.E. thanks the Japan
Society for the Promotion of Sciences Postdoctoral Fellowships
for Research Abroad.
6
H
5
3
-
6
∼
6 5
8. Note that undissociated C H OH is 10 times less reactive
-
33,34
-
3 6 5
toward O (aq) than C H O .
At bulk pH ∼ 10, C
6 5
H O and
-
I competitively react with O
3
(g). Rapid reactions 1-4 consume
protons to make the liquid basic, resulting in the efficient
-
conversion of C
6
H
5
OH into C
6
H
5
O on the CRDS time scale.
References and Notes
Note that the reaction time scale of ESIMS experiment is <1
ms, but that of CRDS is 0.7 s. Therefore, the significant
(
1) von Glasow, R.; Crutzen, P. J. Tropospheric Halogen Chemistry.
In Treatise on Geochemistry; Holland, H. D., Turekian, K. K., Eds.; 2007.
(2) Saiz-Lopez, A.; Plane, J. M. C. Geophys. Res. Lett. 2004, 31,
L03111.
hindrance of I
seconds after exposure to O
2
(g)/IO(g) formation observed within a few
(g) in Figure 2 could be explained
3
(
3) Read, K. A.; Mahajan, A. S.; Carpenter, L. J.; Evans, M. J.; Faria,
if reaction 7 dominates over reaction 1 after the rapid pH
increase induced by reaction 1. The difference of the suppression
B. V. E.; Heard, D. E.; Hopkins, J. R.; Lee, J. D.; Moller, S. J.; Lewis,
A. C.; Mendes, L.; McQuaid, J. B.; Oetjen, H.; Saiz-Lopez, A.; Pilling,
M. J.; Plane, J. M. C. Nature 2008, 453, 1232.
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a
(
4) Saiz-Lopez, A.; Chance, K.; Liu, X.; Kurosu, T. P.; Sander, S. P.
Geophys. Res. Lett. 2007, 34, L12812.
5) Saiz-Lopez, A.; Shillito, J. A.; Coe, H.; Plane, J. M. C. Atmos.
versus salicylic acid (pKa2 ) 13.6) is consistent with the
proposed reaction mechanism. Table 1 presents a summary of
(
2
IO(g)/I (g) suppression effects. As noted above, the differential
Chem. Phys. 2006, 6, 1513.
suppression of IO(g) and I
reaction 9.
2
(g) (Figure 4) can be accounted for
(6) Seitz, K.; Buxmann, J.; Pohler, D.; Sommer, T.; Tschritter, J.; Neary,
T.; O’Dowd, C.; Platt, U. Atmos. Chem. Phys. 2010, 10, 2117.
(7) Saiz-Lopez, A.; Mahajan, A. S.; Salmon, R. A.; Bauguitte, S. J. B.;
It should be noted that no effects were observed in the case
of addition of n-butanol or malonic acid, which are ubiquitously
Jones, A. E.; Roscoe, H. K.; Plane, J. M. C. Science 2007, 317, 348.
(8) Friess, U.; Deutschmann, T.; Gilfedder, B. S.; Weller, R.; Platt, U.
Atmos. Chem. Phys. 2010, 10, 2439.
1
8
found in atmospheric aerosols. Present results imply that they
are inert toward O (g) and also with HOI and other intermediate
(
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species, such as the IOOO intermediate. It is also revealed
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1
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(
4
4
(
Atmospheric Implications. The rapid interaction between
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with various compounds including organic species.
(g) contacts these media, the initial reaction will be reaction
, even in the presence of such compounds, because the reaction
When
O
3
1
-
rate constant is extremely large, I is significantly surface
active,2
and sea-salt aerosols.
9,49
-
and I is found ubiquitously on the surface of oceans
5
0,51
Importantly, I- is 10 to 10 times
2
4
concentrated in fine sea-salt aerosols as compared with seawa-
1
ter.
An intermediate HOI(aq), which is formed after the reactions
14
12–15
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(
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0–23
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-

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Heterogeneous Reaction of O3(g) with I (aq)
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