1
1
Supplemental
Information:
Atmospheric
Fates
of
Criegee
Intermediates
in
the
Ozonolysis
of
2
Isoprene
3
Tran
B.
Nguyen,
1θ*
Geoffrey
S. Tyndall,
2
John
D.
Crounse,
1
Alexander
P. Teng,
1
Kelvin
H. Bates,
3
4
Rebecca
H. Schwantes,
1
Matthew
M.
Coggon,
3ф
Li
Zhang,
5
Philip
Feiner,
5
David
O. Milller,
5
Kate
5
M.
Skog,
6
Jean
C. Rivera-Rios,
6ξ
Matthew
Dorris,
6
Kevin
F. Olson,
7,8ψ
Abigail
Koss,
9
Robert
J.
6
Wild,
9,10
Steven
S.
Brown,
9
Allen
H.
Goldstein,
7,8
Joost
A. de
Gouw,
9
William
H.
Brune,
5
Frank
7
N. Keutsch,
6ξ
John H. Seinfeld,
3,4
and
Paul O. Wennberg
1,4
8
9
1.
Division
of
Geological
and
Planetary
Sciences,
California
Institute
of
Technology,
Pasadena,
10
California, USA
11
2.
Atmospheric
Chemistry
Observations
&
Modeling
Laboratory,
National
Center
for
Atmospheric
12
Research, Boulder, CO, USA
13
3.
Division
of
Chemistry
and
Chemical
Engineering,
California
Institute
of Technology,
Pasadena,
14
California, USA
15
4.
Division
of
Engineering
and
Applied
Science,
California
Institute
of
Technology,
Pasadena,
California,
16
USA
17
5.
Department of Meteorology, The
Pennsylvania State University, University Park,
PA,
USA
18
6.
Department of Chemistry,
University
of
Wisconsin
at
Madison, Madison, WI,
USA
19
7.
Department
of
Environmental
Science,
Policy,
and
Management,
University
of
California
at Berkeley,
20
Berkeley, CA, USA
21
8.
Department
of Civil
and
Environmental
Engineering,
University
of
California
at
Berkeley,
Berkeley,
22
CA, USA
23
9.
Earth
Systems
Research
Laboratory,
Chemical
Sciences
Division,
National
Oceanographic
and
24
Atmospheric Association, Boulder, CO,
USA
25
10.
Cooperative
Institute
for
Research
in
Environmental
Sciences,
University
of
Colorado,
Boulder,
CO,
26
USA
27
θ
Now
at Dept.
of Environmental
Toxicology, University of California,
Davis,
Davis, CA
28
ф
Now
at
Earth
Systems
Research
Laboratory,
Chemical
Sciences
Division,
National
Oceanographic
and
29
Atmospheric Association, Boulder, CO,
USA
30
ξ
Now at
Department of
Chemistry and Chemical
Biology, Harvard University,
Cambridge,
MA, USA
31
ψ
Now at Chevron Corp, San Ramon,
CA,
USA
32
33
*author to whom correspondence should be directed:
tbn@ucdavis.edu
Electronic
Supplementary
Material
(ESI)
for
Physical
Chemistry
Chemical
Physics.
This
journal
is
©
the
Owner
Societies
2016
2
1
Table S1:
Detection and quantification of compounds using negative-ion CF
3
O
–
CIMS.
2
Chemical
Name (abbrev.)
Chemical
Formula
MS
stage
Ion
m/z
Ionic
composition
Quantification
method
Water
dependence
1
104
13
CF
3
O·(H
2
O)
̄
FT-IR
V. Strong
Water vapor
H
2
O
1
121
CF
3
O·(H
2
O)
2
̄
FT-IR
V. Strong
1
79
HF·[O(O)CCH
3
]
̄
Gravimetric
Strong
Acetic acid
(AA)
CH
3
C(O)OH
2
145
79
CF
3
O·[AA]
̄
HF[O(O)CCH
3
]
̄
Gravimetric
Strong
Formic acid
HC(O)OH
1
65
HF·(O(O)CH)
̄
Gravimetric
Strong
Nitric acid
HNO
3
1
82
HF·(ONO
2
)
̄
Gravimetric
Weak
Peracetic acid
(PAA)
CH
3
C(O)OOH
1
161
CF
3
O·(PAA)
̄
Colorimetric
(UV-Vis)
Moderate
1
119
CF
3
O·(HOOH)
̄
Colorimetric
(UV-Vis)
Strong
Hydrogen
peroxide
HOOH
2
119
85
CF
3
O·(HOOH)
CF
3
O
̄
Colorimetric
(UV-Vis)
Strong
Methyl hydro-
peroxide (MHP)
CH
3
OOH
2
133
85
CF
3
O·(CH
3
OOH)
̄
Colorimetric
(UV-Vis)
Strong
Hydroxymethyl
hydroperoxide
(HMHP)
HOCH
2
OOH
1
149
CF
3
O·(HMHP)
̄
FT-IR
Weak
Hydroxy-
acetone
(HAC)
HOCH
2
C(O)CH
3
1
159
CF
3
O·(HAC)
̄
Gravimetric
Weak
Glycol-
aldehyde (GLYC)
HOCH
2
C(O)H
2
145
85
CF
3
O·(GLYC)
̄
CF3O
-
FT-IR
Weak
3
4
3
1
Scheme
S1
:
Model
mechanism
at T=
295
K and
P = 1 atm,
based
on
a condensed
version
of Figure
4 in
the
2
main
text.
The
OH
chemistry
of
cyclohexane
(CHX)
is monitored
as it produces
RO
2
and
consumes
HO
2
.
3
Standard
background
chemistry
(e.g.,
HOx,
NOy
reactions,
not
shown)
is
also
incorporated.
Minor
4
oxygenated
organics
(e.g.,
1-hydroperoxy-2-oxy-but-3-ene)
are
all
lumped
as
a generic
“product”
5
compound.
Rate
coefficients
for
the
background
reactions
are
based
off
IUPAC
recommendations
except
6
where noted.
7
8
9
____________________________________________________________________________________
10
11
Ozone
and OH Mechanism
for
Isoprene,
MACR,
MVK,
CHX
12
13
x34POZ=0.6;
14
x12POZ=0.4;
15
xMACR=0.68;
16
xMACROO=1-xMACR;
17
xsynMACROO=0.2;
18
xantiMACROO=0.8;
19
xMVK=0.42;
20
xMVKOO
= 1-xMVK;
21
xsynMVKOO=0.6;
22
xantiMVKOO=0.4;
23
xdioxole=0.25;
24
xdioxirane=0.72;
25
xstable
=0.03;
26
xdecarbox
= 0.7;
27
xPA_CH3CH2
= 0.35;
28
xHP
= 0.3;
29
xDC
= 0.3;
30
xRO
= 0.4;
31
32
xOH=x12POZ.*xMVKOO.*xsynMVKOO;
33
yOH
= xOH ...
34
+ xOH.*xRO
+ xOH.*xDC
+ xOH.*xRO.*xRO...
35
+ x34POZ.*xMACROO.*xantiMACROO.*xdioxirane.*xdecarbox.*xRO.*xPA_CH3CH2
...
36
+ x34POZ.*xMACROO.*xsynMACROO.*xdioxirane.*xdecarbox.*xRO.*xPA_CH3CH2
...
37
+ x12POZ.*xMVKOO.*xantiMVKOO.*xdioxirane.*xdecarbox.*xRO.*xPA_CH3CH2;
38
39
yform=
(x34POZ.*xMACROO
+ x12POZ.*xMVKOO)...
40
+
xOH.*xRO
+ xOH.*xRO.*xRO ...
41
+
x34POZ.*xMACROO.*xantiMACROO.*xdioxirane.*xdecarbox...
42
+
x34POZ.*xMACROO.*xsynMACROO.*xdioxirane.*xdecarbox
...
43
+
x12POZ.*xMVKOO.*xantiMVKOO.*xdioxirane.*xdecarbox;
44
45
yHO2
= xOH.*xDC
+ xOH.*xRO.*xRO
...
46
+
x34POZ.*xMACROO.*xantiMACROO.*xdioxirane.*xdecarbox...
47
+
x34POZ.*xMACROO.*xsynMACROO.*xdioxirane.*xdecarbox;
48
49
ymacr=x34POZ.*xMACR;
50
ymvk=x12POZ.*xMVK;
51
52
Isop
+ O3;
53
k=1.3e-17;
54
Y(MACR)
= ymacr;
55
Y(MVK)
= ymvk;
56
Y(HCHO)
= yform;
4
1
Y(CH2OO_SCI)
= ymacr
+ ymvk;
2
Y(MACROO_SCI)
= x34POZ.*xMACROO.*xstable;
3
Y(MVKOO_SCI)
= x12POZ.*xMVKOO.*xstable;
4
Y(OH)
= yOH
5
Y(HO2)
= yHO2;
6
Y(products)
= xOH*xHP
+ xOH.*xDC
+ xOH.*xRO
+
7
x34POZ.*xMACROO.*xantiMACROO.*xdioxole
+
8
x12POZ.*xMVKOO.*xantiMVKOO.*xdioxole;
9
10
MACR
+ O3;
11
k=1.8e-18;
12
Y(products)
= 1;
13
14
MVK
+ O3;
15
k=4.8e-18;
16
Y(products)
= 1;
17
18
Isop
+ OH;
19
k=1e-10;
20
Y(products)
= 1;
21
22
MACR
+ OH;
23
k=3.4e-11;
24
Y(products)
= 1;
25
26
MACR
+ OH;
27
k=1.9e-11;
28
Y(products)
= 1;
29
30
CHX
+ OH;
31
k=7.3e-12;
32
Y(CHX_RO2)
= 1;
33
34
CHX_RO2
+ CHX_RO2;
35
k=5.7e-12;
36
Y(cyclohexanone)
= 0.5;
37
Y(cyclohexanol)
= 0.5;
38
39
CHX_RO2
+ HO2;
40
k= 1.612e-11;
41
Y(cyclohexane
hydroperoxide)
= 1;
42
43
CHX_RO2
+ SCI;
44
k= 5e-12;
45
Y(products)
= 1;
46
47
CH2OO_SCI
+ H2O;
48
k=0.9e-15;
49
Y(HMHP)
= 0.73;
50
Y(H2O2)
= 0.06;
51
Y(HCHO)
= 0.06;
52
Y(HCOOH)
= 0.21;
53
54
CH2OO_SCI
+ (H2O)2;
55
k=0.8e-12;
56
Y(HMHP)
= 0.40;
57
Y(H2O2)
= 0.06;
5
1
Y(HCHO)
= 0.06;
2
Y(HCOOH)
= 0.54;
3
4
CH2OO_SCI
+ Isop;
5
k=1.78e-13;
6
Y(products)
= 1;
7
8
CH2OO_SCI
+ O3;
9
k=1e-12;
10
Y(HCHO)
= 0.7;
11
12
MACROO_SCI
+ H2O;
13
k=1.8e-15;
14
Y(products)
= 1;
15
16
MACROO_SCI;
17
k=250;
18
Y(products)
= 1;
19
20
MVKOO_SCI
+ H2O;
21
k=1.8e-15;
22
Y(products)
= 1;
23
24
MVKOO_SCI;
25
k=250;
26
Y(products)
= 1;
27
28
____________________________________________________________________________________
29
Background
Mechanism
30
31
HO2
+ HO2;
%water
dependent,
k based
on Stone and
Rowley
PCCP
2005
32
k= 1.8e-14.*exp(1500/T)*(1+1e-25.*fH2O.*M.*exp(4670/T));
33
Y(H2O2)
= 1;
34
Y(O2)
= 1;
35
36
OH + H2O2;
37
k= 1.69e-12;
38
Y(H2O)
= 1;
39
Y(HO2)
= 1;
40
41
OH + HO2;
42
k= 1e-10;
43
Y(H2O)
= 1;
44
Y(O2)
= 1;
45
46
OH + OH;
47
k0=7.0e-31.*(T./300).^(-1);
48
kinf=2.6e-11.*(T./300).^(-0);
49
Fc=0.6;
50
k=(k0.*M)./(1+(k0.*M./kinf)).*Fc.^((1+(log10(k0.*M./kinf)).^2).^(-1));
51
Y(H2O2)
= 1;
52
53
OH + HONO;
54
k0=7.0e-31.*(T./300).^(-1);
55
kinf=2.6e-11.*(T./300).^(-0);
56
Fc=0.6;
57
k=(k0.*M)./(1+(k0.*M./kinf)).*Fc.^((1+(log10(k0.*M./kinf)).^2).^(-1));
6
1
Y(H2O)
= 1;
2
Y(H2O2)
= 1;
3
4
OH + HNO3;
5
k0=2.4e-14*exp(460/T);
6
k2=2.7e-17*exp(2199/T);
7
k3=6.5e-34*exp(1335/T);
8
k=k0+k3.*M./(1+k3.*M./k2);
9
Y(H2O)
= 1;
10
Y(NO3)
= 1;
11
12
OH + NO;
13
k0=7.0e-31.*(T./300).^(-2.6);
14
kinf=3.6e-11.*(T./300).^(-0.1);
15
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
16
Y(HONO)
= 1;
17
18
OH + NO2;
19
k0=1.51e-30.*(T./300).^(-3.0);
% Updated
to Mollner,
Science,
2010
20
kinf=2.58e-11.*(T./300).^(-0.0);
21
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
22
Y(HNO3)
= 1;
23
24
OH + NO2;
25
k0=6.2e-32.*(T./300).^(-3.9);
26
kinf=8.1e-11.*(T./300).^(-0.5);
27
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
28
Y(HOONO)
= 1;
29
30
HOONO;
31
eq=3.9e-27.*exp(10125./T);
32
k0=6.2e-32.*(T./300).^(-3.9);
33
kinf=8.1e-11.*(T./300).^(-0.5);
34
kf=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
35
k=kf/eq;
36
Y(HO)
= 1;
37
Y(NO2)
= 1;
38
39
HO2
+ NO;
40
k=8.17E-12;
41
Y(OH)
= 1;
42
Y(NO2)
= 1;
43
44
O(3P)
+ HO2;
45
k= 5.9e-11;
46
Y(OH)
= 1;
47
Y(O2)
= 1;
48
49
O(3P)
+ O2;
50
k= 6.0e-34*(T/300)^(-2.4)*M;
51
Y(O3)
= 1;
52
53
O3 + HO2;
54
k= 1.9e-15;
55
Y(OH)
= 1;
56
Y(O2)
= 2;
57
7
1
O3 + OH;
2
k= 7e-14;
3
Y(HO2)
= 1;
4
Y(O2)
= 1;
5
6
O(1D)
+ H2O;
7
k= 2e-10;
8
Y(OH)
= 2;
9
10
O(1D);
11
k= 3.2e-11*exp(67/T)*M;
12
Y(O3P)
= 1;
13
14
O(3P)
+ NO;
15
k0=9.0e-32.*(T./300).^(-1.5);
16
kinf=3.0e-11.*(T./300).^(-0.0);
17
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
18
Y(NO2)
= 1;
19
20
O(3P)
+ NO2;
21
k= 1.04e-11;
22
Y(NO)
= 1;
23
Y(O2)
= 1;
24
25
O(3P)
+ NO2;
26
k0=2.5e-31.*(T./300).^(-1.8);
27
kinf=2.2e-11.*(T./300).^(-0.7);
28
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
29
Y(NO3)
= 1;
30
31
O3 + NO;
32
k=1.86e-14;
33
Y(NO2)
= 1;
34
Y(O2)
= 1;
35
36
O3 + NO + NO;
37
k= 2e-38.*cO2;
38
Y(NO)
= 1;
39
Y(NO3)
= 1;
40
41
O3 + NO2;
42
k= 3.46e-11;
43
Y(NO3)
= 1;
44
Y(O2)
= 1;
45
46
NO3
+ NO2;
47
k0=2.7e-27.*(T./300).^(-4.4);
48
kinf=1.4e-12.*(T./300).^(-0.7);
49
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
50
Y(N2O5)
= 1;
51
52
N2O5
+ H2O;
53
k= 2.5e-22;
54
Y(HNO3)
= 2;
55
56
N2O5
+ H2O + H2O;
57
k= 1.8E-39*fH2O*M;
8
1
Y(HNO3)
= 2;
2
Y(H2O)
= 1;
3
4
N2O5;
5
eq=2.7e-27.*exp(11000./T);
6
k0=9.0e-29.*(T./300).^(-4.4);
7
kinf=1.4e-12.*(T./300).^(-0.7);
8
kf=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
9
k=kf/eq;
10
Y(NO3)
= 1;
11
Y(NO2)
= 1;
12
13
NO3
+ NO;
14
k= 2.27e-11;
15
Y(NO2)
= 2;
16
17
NO3
+ NO3;
18
k= 2.1e-16;
19
Y(NO2)
= 2;
20
Y(O2)
= 1;
21
22
NO3
+ HO2;
23
k= 3.5e-12;
24
Y(NO2)
= 1;
25
Y(O2)
= 1;
26
Y(OH)
= 1;
27
28
HO2
+ NO2;
29
k0=2.0e-31.*(T./300).^(-3.4);
30
kinf=2.9e-12.*(T./300).^(-1.1);
31
k=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
32
Y(HO2NO2)
= 1;
33
34
HO2NO2;
35
eq=2.1e-27.*exp(10900/T);
36
k0=2.0e-31.*(T./300).^(-3.4);
37
kinf=2.9e-12.*(T./300).^(-1.1);
38
kf=k0.*M./(1+(k0.*M./kinf)).*0.6.^((1+(log10(k0.*M./kinf)).^2).^(-1));
39
k=kf./eq;
40
Y(HO2)
= 1;
41
Y(NO2)
= 1;
42
43
OH + HO2NO2;
44
k=4.71e-12;
45
Y(HO2)
= 1;
46
Y(NO2)
= 1;
47
48
9
1
Scheme S2
:
Possible
rearrangement of dioxiranes with allylic functionality.
2
3
10
1
2
Figure S1
: (A)
Partial
calibration of
the
humidity dependence of
HMHP
ion sensitivity in CIMS. The
3
HO
2
+
HCHO
reaction
(from the
photolysis
of 4ppmv of formaldehyde, yellow shaded region) was
used
4
to produce approximately 5.7 ppbv of
HMHP in the atmospheric chamber at 298K and
1 atm. The HMHP
5
mixing ratio was allowed to stabilize for
1 hour
before water-dependent calibration started.
The
stabilized
6
HMHP mixing
ratio from the chamber was sampled in the dark
by CIMS, with nitrogen dilution streams
7
that contained
various mixing ratios of water:
Gray regions denote 147 sccm
of chamber air (dry) mixed
8
with 1600 sccm of a dry
([H
2
O ] <
100 ppmv) nitrogen flow (similar to standard
operation), blue regions
9
denote 147 sccm of chamber
air mixed with 1600 sccm of a
humid ([H
2
O ] up to 4000 ppmv) nitrogen
10
flow, and white regions
denote a
break
in sampling or sampling of 147 sccm
of clean air mixed with 1600
11
sccm of a dry
nitrogen flow.
Data from the gray regions were used to confirm that the
mixing ratio of
12
HMHP in the chamber
did not change significantly throughout the calibration period. Data
from the
white
13
regions were
used to confirm that the background (free of
HMHP) did not shift throughout the
calibration
14
period.
(B) The complete
relationship
of CIMS ion sensitivity vs. water
vapor in the CIMS flow region
15
for H
2
O
2
, HCOOH,
and
HMHP for the
instrument
used in this
study.
11
1
2
3
Figure
S2
:
Wall
loss
rates
of
HMHP,
HCOOH,
and
H
2
O
2
at
two
representative
relative
humidity
conditions.
4
12
1
2
Figure
S3
:
An
ozonolysis
experiment,
where
formic
acid
was
injected
halfway
through
the
experiment.
3
The
signal
for
HPMF
was
the
only
one
(besides
formic
acid)
that
increased
due
to
the
reaction
of
CH
2
OO
4
+ HCOOH.
5
13
1
2
3
Figure
S4
:
CF
3
O
-
CIMS
mass
spectra
shown
for
three
RH
experiments.
In
general
acidic
compounds
are
4
quantified
by
their
fluoride
transfer
(M
+ F
-
)
ion
and
most
other
compounds
by
the
cluster
ion
(M
+ CF
3
O
-
5
).
Each
compound
has
a water-dependent
calibration
that
has
not
been
applied
to
the
figure,
so
the
ion
6
signals
should
be
interpreted
qualitatively.
The
peak
labels
correspond
to:
(a)
HCOOH
–
m/z
65
(transfer)
7
and
m/z
131
(cluster),
(b)
H
2
O
2
–
m/z
119
(cluster),
(c)
Glycolaldehyde
or isobaric
compound
–
m/z
145
8
(cluster),
(d)
HMHP
–
m/z
149
(cluster),
(e)
Hydroxyacetone
or
methylvinylhydroperoxide
–
m/z
159
9
(cluster),
(f)
Unidentified
–
m/z
171,
(g)
HPMF
–
m/z
177
(cluster),
(h)
Unidentified
–
m/z
191,
(i)
10
Unidentified
–
m/z
217,
(j) Acetic
acid
–
m/z
79
(transfer)
and
m/z
145
(cluster),
(k)
Methyl
hydroperoxide
11
–
m/z
133
(cluster).
Peaks
from
CF
3
O
-
reagent
have
been
subtracted
and
suspected
impurities
are
not
12
labelled.
Glycolaldehyde
and
acetic
acid
cluster
(
m/z
145)
are
isobaric;
however,
the
m/z
145
signal
is
13
mainly
due
to
glycolaldehyde
at
low
RH
and
acetic
acid
at
higher
RH
(confirmed
by
a corresponding
14
transfer ion).
14
1
2
Figure
S5
:
The
population
of (A)
water
monomer
molecules
and
(B)
water
dimer
molecules
as
a function
3
of
RH,
based
on
cluster
association
equilibrium
thermodynamic
functions
reported
in
Ref.
1
The
fraction
of
4
each reaction, using rate coefficients reported
in the main text and
in Scheme
S1, is shown in panel
C.
5
15
1
2
Figure
S6
:
Comparison
between
H
2
O
2
observed
by
CIMS
(filled
markers)
and
calculated
H
2
O
2
3
using
observed
HO
2
data
from
GTHOS
(Fig.
S8,
lines)
for
(A)
dry
conditions,
k
HO2+HO2,
295K
=
2.92
4
x 10
-12
cm
3
molec
-1
s
-1
and
(B)
RH
37%
conditions,
k
HO2+HO2,
295K
=
3.53
x 10
-12
cm
3
molec
-1
s
-1
.
5
Uncertainty
bounds
are
used
as
reported
in
the
main
text.
Rate
coefficients
are
derived
the
6
temperature and RH dependence reported by Stone and Rowley
(2005).
2
7
16
Rate
coefficients
used
RH = 51%
RH = 1.3%
CASE 1
The rates
used in our
model
k
H2O
= 0.1 x 10
-15
k
(H2O)2
= 0.8 x 10
-12
CASE 2
Our monomer
rate + Chao
et al dimer
rate
k
H2O
= 0.9 x 10
-15
k
(H2O)2
= 6.5 x 10
-12
CASE 3
Low monomer
rate + Chao
et al dimer
rate
k
H2O
= 0.1 x 10
-15
k
(H2O)2
= 6.5 x 10
-12
17
CASE 4
High Welz et
al maximum
monomer rate
+ Chao
et al
dimer rate
k
H2O
= 4 x 10
-15
k
(H2O)2
= 6.5 x 10
-12
CASE 5
Unreasonably
high monomer
rate + Chao
et al dimer
rate
k
H2O
= 8 x 10
-15
k
(H2O)2
= 6.5 x 10
-12
1
2
Figure S7
: Model sensitivity study using
two RH conditions (RH = 51%, where the water dimer and
3
water monomer rate are both important, and
RH = 1.2%,
where only the water monomer rate is
4
important). Results
from
5 sensitivity cases,
using
different monomer
and dimer rate coefficients, are
5
shown. Case #1,
shown in the red border,
successfully reproduces all data reported in this work (Figure 5
6
in the manuscript). Cases 2-5 explored the dimer rate coefficient of Chao et
al (2015).
For
the
Chao et al.
7
(2015) dimer rate coefficient
to reproduce the RH = 51% results, the
monomer rate coefficient would
8
need to be adjusted to be
higher than the
upper
bound reported by Welz et al.
(2012) – shown in the blue
9
border, Case #5. The
high monomer rate in Case #5 now over
predicts CH
2
OO water
products
in the dry
10
case.
11
12
18
1
2
Figure S8
: Simulated
and measured HO
2
mixing ratios at two RH conditions during the
FIXCIT
3
campaign. The model mechanism does
not yet
include second-generation sources
of
HO
2
.
4
19
1
2
Figure
S9
:
Atmospheric
mixing
ratios
of
(A)
water
vapor,
(B)
sulfur
dioxide,
(C)
exocyclic
VOCs
isoprene
3
and beta-pinene, and (D)
ozone during the measurement period of the SOAS
campaign.
4