Chamber studies GEOS-Chem
New insights in isoprene photooxidation:from chamber studies to global model
Fabien Paulot
Environmental Science & EngineeringCaltech
Fabien Paulot (ESE Caltech) Isoprene photooxidation 1 / 10
Chamber studies GEOS-Chem
Introduction
Five carbons, two double bonds, thousands of papers and yet ...
Emissions : bottom-up and top-down inventories but the biologicalmechanism remains uncertain
Chemical mechanism :
: problems with organic nitrates, small carboxylic acidformation ...Low NOx: very poor understanding due to experimentalchallengesAerosol: what are the gas-phase precursors ofisoprene-originating aerosols
Climate change : CO2 vs Temperature influence
Fabien Paulot (ESE Caltech) Isoprene photooxidation 2 / 10
Chamber studies GEOS-Chem
Introduction
Five carbons, two double bonds, thousands of papers and yet ...
Emissions : bottom-up and top-down inventories but the biologicalmechanism remains uncertain
Chemical mechanism :
High NOx : problems with organic nitrates, smallcarboxylic acid formation ...Low NOx: very poor understanding due to experimentalchallengesAerosol: what are the gas-phase precursors ofisoprene-originating aerosols
Climate change : CO2 vs Temperature influence
Fabien Paulot (ESE Caltech) Isoprene photooxidation 2 / 10
Chamber studies GEOS-Chem
Introduction
Five carbons, two double bonds, thousands of papers and yet ...
Emissions : bottom-up and top-down inventories but the biologicalmechanism remains uncertain
Chemical mechanism :
High NOx : problems with organic nitrates, smallcarboxylic acid formation ...Low NOx: very poor understanding due to experimentalchallengesAerosol: what are the gas-phase precursors ofisoprene-originating aerosols
Climate change : CO2 vs Temperature influence
Fabien Paulot (ESE Caltech) Isoprene photooxidation 2 / 10
Chamber studies GEOS-Chem
Introduction
Five carbons, two double bonds, thousands of papers and yet ...
Emissions : bottom-up and top-down inventories but the biologicalmechanism remains uncertain
Chemical mechanism :
High NOx : problems with organic nitrates, smallcarboxylic acid formation ...Low NOx: very poor understanding due to experimentalchallengesAerosol: what are the gas-phase precursors ofisoprene-originating aerosols
Climate change : CO2 vs Temperature influence
Fabien Paulot (ESE Caltech) Isoprene photooxidation 2 / 10
Chamber studies GEOS-Chem
Introduction
Five carbons, two double bonds, thousands of papers and yet ...
Emissions : bottom-up and top-down inventories but the biologicalmechanism remains uncertain
Chemical mechanism :
High NOx : problems with organic nitrates, smallcarboxylic acid formation ...Low NOx: very poor understanding due to experimentalchallengesAerosol: what are the gas-phase precursors ofisoprene-originating aerosols
Climate change : CO2 vs Temperature influence
Unfortunately, everything is intermingled: isoprene still accounts for a verylarge fraction of the uncertainty in atmospheric chemistry(past-present-future)
Fabien Paulot (ESE Caltech) Isoprene photooxidation 2 / 10
Chamber studies GEOS-Chem
Introduction
Five carbons, two double bonds, thousands of papers and yet ...
Emissions : bottom-up and top-down inventories but the biologicalmechanism remains uncertain
Chemical mechanism :
High NOx: problems with organic nitrates, smallcarboxylic acid formation ...Low NOx: very poor understanding due to experimentalchallengesAerosol: what are the gas-phase precursors ofisoprene-originating aerosols
Climate change : CO2 vs Temperature influence
Fabien Paulot (ESE Caltech) Isoprene photooxidation 2 / 10
Chamber studies GEOS-Chem
Outline
1 Chamber studies
2 GEOS-Chem
Fabien Paulot (ESE Caltech) Isoprene photooxidation 3 / 10
Chamber studies GEOS-Chem
Framework
Crounse et al. 2006, Paulot et al. 2009Fabien Paulot (ESE Caltech) Isoprene photooxidation 4 / 10
Chamber studies GEOS-Chem
Advantages
Fast and direct measurements of a wide range of VOC (organicnitrates, small carboxylic acids, organic peroxides)Measurement of inorganic species: HONO, HO2NO2, H2O2, HNO3,N2O5 (indirect) → strong constraints to derive a mechanism
Time (min)
Sig
nal/c
ref
101
102
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5ISOPN (1,2) s: 0.84ISOPN (2,1) s: 0.85ISOPN (3,4) s: 0.83ISOPN (4,3) s: 0.84ISOPN (1,4)Z s: 1ISOPN (1,4)E s: 1ISOPN (4,1)Z s: 0.97ISOPN (4,1)E s: 0.95
0 0.5 10
2
4
6
8
10
12
Fraction of isopreneconsumed
App
aren
t α (
%)
Figure: Isoprene nitrate
.
Fabien Paulot (ESE Caltech) Isoprene photooxidation 5 / 10
Chamber studies GEOS-Chem
Major conclusions
δ hydroxy channel
HO O
nd O o
n n i
O
o n k d
n h d O h o n d
NO 2
h o
n i
h O o h
D
d
?
o
i
h h o
OH
OH
O
O
O
HO
HO
O
HO O
O
HO
HO
O O
OH
HO
HO
O
O
HO
O
O
O HO
OH
O
O
OH
O
O
OH
O
O
OH O
O
O
O HO
O
O
O
O
O
O O N
HO
O
OH
O
OH
OH
O
O O
O
O
O
O OH
HO
OH
O
O OH
O
O O
H H
h o
h O
o n
n
O
h Oh o
OH
O
O
OH
O
O
OH
O
OH O
O
O O O OH
O
O HO O O
OH
OH
O
O
OH
O
O
O
O
n O
HC5 Z(4,1)
HACET
HC5 E(4,1)
HACET
MOBA Z(4,1) MPDL
GLYX
O O O
H
H D
ISOPN E(4,1) ISOPN Z(4,1)
DHMOB (4,1)
O
OH
O OH
1
23
4
OBLh o
n i
d k
i n
O
n k do
d h n o O
1
2 3
4
n
MOBA Z(1,4)
DHMOB
HMPL
MHBL
DHPN
HOPL
HOBL
HC5 Z(1,4)
GLYC
GLYC
PAN (m/z=250)
MPDL
MGLYX
MBDL
ISOPN (1,4)E ISOPN (1,4)Z
OBL
n i
h o n d
d
o n o d
n
O
k
n k do
O
1
2 3
4
*
OH
O
*
*
*
E 1-4 Z 1-4 Z 4-1E 4-1
1 2
3
4
O
O OH
O OH O
O
OH
O
O OH
O
O
O
OH
O O
OH
O
MACRMVK
1,4
1,2
2,1 3,4
4,3
4,1
41%
15%
23%
14 %
2.0 % 5.0 %
h
O
ISOPN (1,2) ISOPN (2,1) ISOPN (3,4) ISOPN (4,3)
o
OH OH
OH
OH
O
OH HO
OH
OH
OH
OH
HO
OH
OH
O
OH HO
o
O O
ho
o
15% 85 %
3-MF
?Surface Surface?
65% 35% 70%
30%
65% 35%
95% 5%
65% 35%
30%
70%
65% 35%
a
b
43% 28%
25.5%3.5%
43%28%
25.5%3.5%
15% 85 %
6.7%6.7%6.7% 6.7%
24% 24% 24% 24%
Isoprene nitrates
Overall yield: 12± 3%Large discrepancy between the β (∼ 6.7%) and δ hydroxychannels(∼ 24%)Short-lived (δ-hydroxy isoprene nitrates) with substantial recycling ofNOx: need to be included in the mechanismOther nitrates may have a significant role
MVK and MACR nitrates are formed with yields exceeding 10%MVK nitrate and propanone nitrate (∼ 1%) are very long-lived
Large formation of small carboxylic acid
Glycolaldehyde and hydroxyacetone (Butkovskaya 2006)Isoprene nitrates
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Major conclusions
δ hydroxy channelConstraints on ∼ 30% of the carbonFormation of large acids
Isoprene nitrates
Overall yield: 12± 3%Large discrepancy between the β (∼ 6.7%) and δ hydroxychannels(∼ 24%)Short-lived (δ-hydroxy isoprene nitrates) with substantial recycling ofNOx: need to be included in the mechanismOther nitrates may have a significant role
MVK and MACR nitrates are formed with yields exceeding 10%MVK nitrate and propanone nitrate (∼ 1%) are very long-lived
Large formation of small carboxylic acid
Glycolaldehyde and hydroxyacetone (Butkovskaya 2006)Isoprene nitrates
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Major conclusions
δ hydroxy channelConstraints on ∼ 30% of the carbonFormation of large acids
Isoprene nitratesOverall yield: 12± 3%Large discrepancy between the β (∼ 6.7%) and δ hydroxychannels(∼ 24%)Short-lived (δ-hydroxy isoprene nitrates) with substantial recycling ofNOx: need to be included in the mechanism
Other nitrates may have a significant roleMVK and MACR nitrates are formed with yields exceeding 10%MVK nitrate and propanone nitrate (∼ 1%) are very long-lived
Large formation of small carboxylic acid
Glycolaldehyde and hydroxyacetone (Butkovskaya 2006)Isoprene nitrates
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Major conclusions
δ hydroxy channelConstraints on ∼ 30% of the carbonFormation of large acids
Isoprene nitratesOverall yield: 12± 3%Large discrepancy between the β (∼ 6.7%) and δ hydroxychannels(∼ 24%)Short-lived (δ-hydroxy isoprene nitrates) with substantial recycling ofNOx: need to be included in the mechanismOther nitrates may have a significant role
MVK and MACR nitrates are formed with yields exceeding 10%MVK nitrate and propanone nitrate (∼ 1%) are very long-lived
Large formation of small carboxylic acid
Glycolaldehyde and hydroxyacetone (Butkovskaya 2006)Isoprene nitrates
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Major conclusions
Time (min)
ppb
101
102
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1ISOPN (4,1)ISOPN (2,1)Other sources
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Major conclusions
δ hydroxy channelConstraints on ∼ 30% of the carbonFormation of large acids
Isoprene nitratesOverall yield: 12± 3%Large discrepancy between the β (∼ 6.7%) and δ hydroxychannels(∼ 24%)Short-lived (δ-hydroxy isoprene nitrates) with substantial recycling ofNOx: need to be included in the mechanismOther nitrates may have a significant role
MVK and MACR nitrates are formed with yields exceeding 10%MVK nitrate and propanone nitrate (∼ 1%) are very long-lived
Large formation of small carboxylic acid
Glycolaldehyde and hydroxyacetone (Butkovskaya 2006)Isoprene nitrates
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Major conclusions
Time (min)
ppb
100
101
102
0
1
2
3
4
5
6
7
8
9
10
GLYCHACETMVKNHMHPISOPN (1,4)3−MFHC5 Z41Other sources
0 200 400 6000
5
10
15
Fabien Paulot (ESE Caltech) Isoprene photooxidation 6 / 10
Chamber studies GEOS-Chem
Outline
1 Chamber studies
2 GEOS-Chem
Fabien Paulot (ESE Caltech) Isoprene photooxidation 7 / 10
Chamber studies GEOS-Chem
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55
180° W 135° W 90° W 45° W 0° 45° E 90° E 135° E
90° S
60° S
30° S
0°
30° N
60° N
Summer NH Isoprene nitrate
Fabien Paulot (ESE Caltech) Isoprene photooxidation 8 / 10
Chamber studies GEOS-Chem
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
180° W 135° W 90° W 45° W 0° 45° E 90° E 135° E
90° S
60° S
30° S
0°
30° N
60° N
Formic acid Northern Hemisphere summer
Fabien Paulot (ESE Caltech) Isoprene photooxidation 9 / 10
Chamber studies GEOS-Chem
Work in progress and acknowledgements
Low NOx chemistry: isoprene (Paulot et al. in review) andatmospheric relevant products: MVK, MACR, MBO, ... (Crounse etal. in preparation)
Fate of the peroxidesOH recycling
Current chemical schemes are very wrong over tropical regions(not specific to GEOS-Chem).
Compare model with CIMS measurements collected during INTEX-B,TC4 and ARCTAS.
Fabien Paulot (ESE Caltech) Isoprene photooxidation 10 / 10
Chamber studies GEOS-Chem
Work in progress and acknowledgements
Low NOx chemistry: isoprene (Paulot et al. in review) andatmospheric relevant products: MVK, MACR, MBO, ... (Crounse etal. in preparation)
Fate of the peroxidesOH recycling
Current chemical schemes are very wrong over tropical regions(not specific to GEOS-Chem).
Compare model with CIMS measurements collected during INTEX-B,TC4 and ARCTAS.
John D. Crounse, Henrik G. Kjaergaard (University of Otago, NewZealand), Jesse H. Kroll (now at MIT), John H. Seinfeld, Paul O.
Wennberg
NSF, NASA, EPA, Davidow Fellowship, Davidow Fund
Fabien Paulot (ESE Caltech) Isoprene photooxidation 10 / 10