Post on 15-Dec-2015
Widespread Halogen Activation by N2O5 Heterogeneous Chemistry
Joel ThorntonDepartment of Atmospheric Sciences
University of Washington, Seattlethornton@atmos.washington.edu
J.P. Kercher, T.P. Riedel, N.L. Wagner, J. Cozic, J. Holloway, W.P. Dubé,
G.M. Wolfe, P.K. Quinn, A.M. Middlebrook, B. Alexander, and S.S. Brown
UW – NOAA ESRL and PMEL Collaboration
Tropospheric Chlorine Cycling
ClCl-X
activationactivation CCxxHHyy
acid acid displacementdisplacementCl- HCl
sea spraysea spray~10,000 Tg~10,000 Tg
Anthro. +Anthro. +3 – 5 Tg3 – 5 Tg
Graedel and Keene, GBC,1995
25-35 Tg* *From methane isotopes measured in remote SH MBL
Platt, ACP 2004Allan, JGR 2007
Chlorine Cycling: New Addition
NO3
NO2 ClNO2
N2O5acid acid
displacementdisplacementpCl-
Cl
HCl
activationactivation CCxxHHyy
8 – 22 Tg Cl yr-1
Reference: Thornton, et al Nature 2010
ClNO2 Production
HX
(s)
HX(g)
XNO 2(s) + HNO3(s)
References: Finlayson-Pitts et al. 1989; Behnke et al, 1989, 1992; Thornton and Abbatt, 2005; Bertram et al 2009; Raff et al 2009
Instantaneous ClNO2 Yield
References: Benkhe, et al JGR 1997; Roberts, et al GRL 2009; Bertram and Thornton, ACP 2009
0.0
0.2
0.4
0.6
0.8
1.0
ClN
O 2 Yie
ld
Fine Mode Chloride Mass Fraction
80% RH
30% RH
10-6 10-5 10-4 10-3 10-2 10-10.0
0.2
0.4
0.6
0.8
1.0
50% RH
N2O5(aq)
ClNO2 + NO3-
2HNO3
Cl-
H2O
2 2
1
1 H O
Cl
k H O
k Cl
Population Average Instantaneous ClNO2 Yield
References: Benkhe, et al JGR 1997; Roberts, et al GRL 2009; Bertram and Thornton, ACP 2009
10 100 1000Dp (nm)
dS
/dlo
g(D
p)
(rp) ~ 0.1
=1 =0
Surface Area Distribution
Total Chlorine = pCl- + HCl(g)
Cl- HCl(g)Equilibrium Equilibrium
repartitioningrepartitioning
0 1 2 3 4 5 610
-1
100
101
102
103
104
105
pH
HC
l(g
)/p
Cl
(mo
l/m
ol)
ClNO2 as a Cl Atom Source
Erickson et al 1996 0.06 Tg Cl yr-1 (MBL only)
Osthoff et al 2008 3.2 Tg Cl yr-1 (Coastal and MBL only)
“Bottom up” global Cl atom source from ClNO2
“Top-down” global Cl atom source
Allan, et al 2004 22 - 35 Tg Cl yr-1
Platt, et al 2004 ~ 35 Tg Cl yr-1
“Bottom up” local Cl atom source from ClNO2
Pechtl and von Glasow: ClNO2 < 50 ppt in Long Island Sound (during June)
UW-Chemical Ionization Mass SpectrometerCDC
Octupole
Quadrupole
electronmultiplier
CH3I/ N2
IMR
I- + ClNO2 I-ClNO2-
I- + N2O5 I-N2O5-
McNeill, et al Atmos. Chem. Phys. 2006Kercher, et al Atmos. Meas. Tech. 2009
~ 1-5 pptv in 1 second
V. Faye McNeill (now at Columbia University)
James P. Kercher (now at Hiram College)
Theran P. Riedel (UW Graduate Student)
ClNO2 in the Long Island Sound and Beyondlog([ClNO2])
78 79 80 81 82 83 84 850
250
500
750 N
2O
5
ClNO2
N2O
5 &
ClN
O2
Mix
ing
Rat
ion
/ppt
Fractional DOY /UTC
53W
57W63W71W
1500ppt
Observed ClNO2 is 2 – 20x greater than previous model predictions for Long Island
Sound (e.g. Pechtl and von Glasow, GRL 2007)
ClNO2 production still evident in outflow 1 – 2 days downwind
N2O5
HNO3
ClNO2
Cl- Cl
NO2
N2O5
HNO3
ClNO2
Cl- Cl
NO2
ClNO2 ~0.5
Psuedo-Lagrangian Model Predictionsp
pb
vN
O2 p
pb
v
ClN
O2 o
r N
2O
5 p
ptv
Fraction of NOx Reacting via N2O5
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
A B
C D
W Sp
Su Au
~ 38% of NOx removed by N2O5 over U.S.
GEOS-Chem output from B. Alexander
25.5 26.0 26.50
200
400
600
800
1000
N2O
5
ClNO2
Mix
ing
Ra
tio (
pp
tv)
February 2008 (local time)
(*Parking Lot behind ESRL’s David H. Skaags Building)
ClNO2 and N2O5 in Boulder, CO*
37Cl (cps)
35 C
l (cp
s)
Detailed Behavior of N2O5 and ClNO2
1 1.2 1.40
100
200
300
400
500
600
700
Hour of Day (local)
Mix
ing
Ra
tio
(p
ptv
)
6 7 8 9 10 110
200
400
600
800
1000
1200
1400
Hour of Day (local)
N2O
5
ClNO2
NO /10
BA
ACCRONIM February 11 - 25 2009
N2O5 and ClNO2
CO, O3
NO, NO2
Particle surface area
Water-soluble particle composition
Meteorology (RH, T, Winds)
Kohler Mesa, Boulder, CO
Reference: Thornton, et al Nature 2010
ACCRONIM Overview
12 14 16 18 20 22 240
50
100
0
500
1000
1500
0
100
200
300
400
500
February 2009
pC
l- (p
ptv
)
N2O
5 (p
ptv
)
ClN
O2 (
pp
tv)
Reactant and Product Relationships
12 14 16 18 20 22 240
50
100
0
500
1000
1500
0
100
200
300
400
500
February 2009
pC
l- (p
ptv
)
N2O
5 (p
ptv
)
ClN
O2 (
pp
tv)
47.5 47.55 47.6
250
500
750
300
600
900
1200N2O
5
ClNO2
0 200 400 600 800 1000 1200 14000
100
200
300
400
500
Feb. 13 - 14th
Feb. 15 - 16th
Feb. 21 - 22nd
ClN
O2 (
pp
tv)
N2O
5 (pptv)
ClNO2 and N2O5 broadly correlated
But relationship changes night-to-night and within a night
Total Chloride
0 3 6 9 12 15 18 21 240
50
100
150
200
0 4 8 12
0
100
200
300
400
500
600
ClNO2
4X pCl-
Mix
ing
Rat
io (
pptv
)
Hour of Day (local)
A
ClNO2
pCl-
B
Mix
ing
Rat
io (
pptv
)
Hours Since Sunset
Feb. 15 - 16 Observations and Modeling
0 3 6 9 12 15 18 21 240
50
100
150
200
0 4 8 12
0
100
200
300
400
500
600
ClNO2
4X pCl-
Mix
ing
Rat
io (
pptv
)
Hour of Day (local)
A
ClNO2
pCl-
B
Mix
ing
Rat
io (
pptv
)
Hours Since Sunset
Feb. 15 - 16 Observations and Modeling
ClNO2 routinely 4 – 10x greater than particulate Cl-, suggesting important role for HCl(g)
Consistent with observationally constrained thermodynamic aerosol model
Chemical Box Modeling – 2 Examples
12 14 16 18 20 22 240
50
100
0
500
1000
1500
0
100
200
300
400
500
February 2009
pC
l- (p
ptv
)
N2O
5 (p
ptv
)
ClN
O2 (
pp
tv)
Chemical Modeling Example -2
0
10
20
30
40
O3
pp
bv
0
10
20
30
40
NO2
0 2 4 6 8 10 120
500
1000
1500
2000
2500
N2O
5
pp
tv
Hours Since Sunset
0 2 4 6 8 10 120
50
100
150
200
250
300
350
ClNO2
pCl-
Hours Since Sunset
ClNO2 over campaign ranged from ~ 7 – 36%
February 22nd-23rd
N2O5
HNO3
ClNO2
Cl- Cl
NO2
N2O5
HNO3
ClNO2
Cl- Cl
NO2
ClNO2 ~0.18
135oW 120oW 105oW 90oW 75oW 24oN
30oN
36oN
42oN
48oN
54oN
135oW 120oW 105oW 90oW 75oW 24oN
30oN
36oN
42oN
48oN
54oN
IMPROVE Network NADP Network
Is Boulder Special?
0.0
0.2
0.4
0.6
0.8
1.0
ClN
O 2 Yie
ld
Fine Mode Chloride Mass Fraction
80% RH
30% RH
10-6 10-5 10-4 10-3 10-2 10-10.0
0.2
0.4
0.6
0.8
1.0
50% RH
fine mode mCl/mtotal
Aerosol Inorganics Model
nCl-/nNO3-
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
A B
C D
W Sp
Su Au
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
A B
C D
W Sp
Su Au
W Sp
Su Au
nCl-/(fN2O5nNO3-)
135oW 120oW 105oW 90oW 75oW 24oN
30oN
36oN
42oN
48oN
54oN
135oW 120oW 105oW 90oW 75oW 24oN
30oN
36oN
42oN
48oN
54oN
IMPROVE Network NADP Network
Is Boulder Special?
Aerosol Inorganics Model
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
A B
C D
W Sp
Su Au
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
120 W 110
W 100
W 90
W 80
W 70
W
30 N
35 N
40 N
45 N
0.1 0.2 0.3 0.4 0.5 0.6 0.7
A B
C D
W Sp
Su Au
W Sp
Su Au
Aerosol Chloride Based Yield Chloride moles per N2O5 moles reacted
Estimating ClNO2 Production over U.S.
N2O5
HNO3
ClNO2
Cl- Cl
NO2
N2O5
HNO3
ClNO2
Cl- Cl
NO2
fN2O5
ClNO2
PClNO2 =ClNO2 fN2O5ENOx
Constrain withObservations
GEOS-Chem EDGAR Database
HNO3
ENOx = LNOx
NOx
ENOx
LNOx
Estimating ClNO2 Production over U.S.
Log(ENOx)
ClNO2
fN2O5
Log(PClNO2)
U.S. PClNO2 = 1.4 - 3.5 Tg Cl yr-1
ClNO2 and the Global Cl Atom Source
Erickson et al 0.06 Tg Cl yr-1
Osthoff et al 3.2 Tg Cl yr-1
“Bottom up” global Cl atom source from ClNO2
“Top-down” total global Cl atom source
Allan, et al 2004 22 - 35 Tg Cl yr-1
Platt, et al 2004 ~ 35 Tg Cl yr-1
Our estimates 8 – 22 Tg Cl yr-1
MAP OF NO2
Chlorine Cycling: New Addition
Anthropogenic NOx represents a large perturbation of Cl-atom budget
Cl-atom source tied to our understanding of N2O5 reactive uptake
Nighttime chemistry not just a sink of Ox – but a potential source
NO3
NO2 ClNO2
N2O5acid acid
displacementdisplacementCl-
Cl
HCl
activationactivation CCxxHHyy
8 – 22 Tg Cl yr-1
Implications: e.g. Wintertime Oxidants
0
1
2
3
4 x 104
Cl
Mo
lec
cm
-3
0 5 10 15 200
5
10 x 104
ClO
Mo
lec
cm
-3
Hours Since Midnight
0
2
4x 10
6
OH
0
1
2
3x 10
7
HO2
Mo
lec
cm-3
0 5 10 15 200
5
10
15x 10
6
RO2
Hours Since Midnight
ClNO2 = 600 pptvClNO2 = 350 pptvClNO2 = 0 pptv
For 600 pptv ClNO2 in FebruaryCl + RH dominates HOx production (by >10x) from sunrise to 10AM
Cl + RH leads to >30% more daytime HOx production
Some Outstanding Issues
1. Studies of wintertime nocturnal reactive nitrogen and morning HOx chemistry
2. HCl measurements are likely necessary to demonstrate “closure” between integrated LN2O5 and PClNO2
3. ClNO2 yields inferred from [N2O5] and [ClNO2] are often lower than predictions based on [pCl-] Chloride distribution? Phase? Losses of N2O5 and/or ClNO2?
4. Can we better validate/constrain fN2O5?
Where does the chloride in come from?
Sea SprayCoal BurningBiomass/crop burningBiofuelWaste incineration (e.g. PVC)Playa dustRoad salt (?)Cooling towersSwimming pools (?)…
References: Graedel and Keene, 1995; Reff, et al, 2009
Kholer Mesa Often Above Nocturnal Surface Layer
Predicting Annual Average U.S. PClNO2
Log(ENOx)
ClNO2
fN2O5
Log(PClNO2)
U.S. PClNO2 = 1.4 - 3.5 Tg Cl yr-1
Measured Chloride Deposition
Log(mCl) kg ha-1 yr-1
From the National Atmospheric Deposition Program (NADP)
Aerosol Chloride is Ubiquitous
1E-4
1E-3
0.01
0.1
Ch
lori
de
Mas
s F
ract
ion ClNO2 >90%
ClNO2 >50%
Q. Zhang, et al GRL 2007
NOx, Air Quality, and Climate Forcings
Catalyze ozone production
Regulate oxidant abundance
Shindell, et al Science 2009
NOx
NOx emissions couple air quality and climate concerns
Chlorine Activation by N2O5: Model Predictions
1996 Erickson, et al JGR•Global ClNO2 Production From Sea Spray 0.06 Tg Cl/yr
2007 Pechtl and von Glasow, GRL Chlorine Activation in Long Island Sound
Maximum ClNO2 mixing ratio ~ 50 pptv (only on “first night”)
1-2 days downwind negligible
Always less than 5% of Cl atom source
Atomic Chlorine: powerful oxidant
CH4 + OH Products
CH4 + Cl Products
CH4oxidant
0.05 ppt ~10 years
0.05 ppt 0.5 years
Tropospheric Cl atoms
We know they exist, but their sources, distribution, and abundance are poorly constrained
Baring Head, New Zealand
Jobson, et al JGR 1994
Platt, et al ACP 2004
Where there’s chloride for ClNO2 production
U.S. IMPROVE Network fine-mode particle chloride
ClNO2 Yield
From U.S. NADP precipitation Cl- and NO3
-
Chlorine Availability:[Cl-] / f[NO3
-]
Current Constraints from ClNO2 Observations
1. TexAQS – GoMACCS[ClNO2] ~ 50 - > 1000 ppt Osthoff, et al, Nature Geo. 2008
1
2. ICEALOT-LILAQS[ClNO2] ~ 50 - > 1000 pptKercher, et al, AMT 2009
2 3. ACCRONIM-Boulder, CO[ClNO2] ~ 50 – 450Thornton, et al submitted 2009
3
Current Constraints from ClNO2 Observations
1. TexAQS – GoMACCS[ClNO2] ~ 50 - > 1000 ppt Osthoff, et al, Nature Geo. 2008
1
2. ICEALOT-LILAQS[ClNO2] ~ 50 - > 1000 pptKercher, et al, AMT 2009
2 3. ACCRONIM-Boulder, CO[ClNO2] ~ 50 – 450 pptvThornton, et al submitted 2009
3
Where there’s NOx
Courtesy of NASA GSFC
Cl
NO2
Chlorine Activation by N2O5
N2O5
2HNO3
HNO3 + ClNO2
Cl-
H2O
Finlayson-Pitts, Nature 1989Benkhe, et al JGR 1997
0 1 2 3 4 5
x 104
0
10
20
30
40
50
60
NO2 (pptv)
Ma
x C
lNO
pro
du
ce
d (
pp
tv)
Tropospheric Chlorine Cycling
ClCl-X
activationactivation CCxxHHyy
acid acid displacementdisplacementCl- HCl
sea spraysea spray~10,000 Tg~10,000 Tg
Anthro. +Anthro. +3 – 5 Tg3 – 5 Tg
Graedel and Keene, GBC,1995
22-35 Tg* *From methane isotopes measured in remote SH MBL
Platt, ACP 2004Allan, JGR 2007
Chemical Modeling Example - 10 3 6 9 12 15 18 21 24
0
50
100
150
200
0 4 8 12 160
100
200
300
400
500
600
ClNO2
4X pCl-
Mix
ing
Rat
io (
pptv
)Hour of Day (local)
a
ClNO2
pCl-b
Mix
ing
Rat
io (
pptv
)
Hours Since Sunset
Feb. 15 - 16 Observations and Modeling
N2O5
HNO3
ClNO2
Cl- Cl
NO2
N2O5
HNO3
ClNO2
Cl- Cl
NO2
ClNO2 ~0.14
Feb 15 – 16th -highest ClNO2
-low winds-constant yield captures ClNO2 growth