AN ATMOSPHERIC CHEMISTS VIEW OF THE WORLD

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AN ATMOSPHERIC CHEMISTS VIEW OF THE WORLD
Lightning
Fires
Land biosphere
Human activity
physics chemistry biology
Ocean
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SHORT-LIVED CLIMATICALLY RELEVANT COMPOUNDSthe
role of air-sea exchange

• Recognized priorities sulfur and halogen
  chemistry
• What controls DMS emission to the atmosphere?
• What reactions control sulfate production in the
  MBL?
• What controls the nucleation of sulfate aerosol?
• What are the abundances and sources of halogen
  radicals in the MBL?
• Two new directions
• Atmospheric budgets of O- and N-containing
  organics (carbonyls, alcohols, cyanides,)
• Oceanic tracers of marine convection in
  meterorological models

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ATMOSPHERIC ACETONE (0.2-3 ppbv) major source
of HOx radicals in upper troposphere,agent for
conversion of NOx to PAN
Aircraft observations over the NW Pacific Singh
et al., 1995
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Atmospheric observations of acetone
ABLE -3B
Surface sites
PEM -WB
SONEX
PEM-TB
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GLOBAL BUDGET OF ATMOSPHERIC ACETONE Singh et
al., 2000

• SOURCES (Tg yr-1) 56 (37-80)
  
• Atm oxidation of propane, other iso-HCs 17
  (12-24)
• Terrestrial vegetation 15 (10-20)
• Atm oxidation of terpenes, methylbutenol 11
  (7-15)
• Plant decay 6 (4-8)
• Biomass burning 5 (3-10)
• Industry 2 (1-3)
• Terrestrial vegetation 33 /- 9
• SINKS (Tg yr-1) 56 (37-80)
• Photolysis 36 (24-51)
• Oxidation by OH 13 (9-19)
• Dry deposition 7 (4-10)
• ATMOSPHERIC LIFETIME 16 days

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OCEANIC SIGNATURE IN ATMOSPHERIC ACETONE
OBSERVATIONS?
South Pacific Singh et al., 2001
southern Sweden Solberg et al., 1996
High values over South Pacific ocean source?
Low winter values over Europe ocean sink?
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ROLE OF OCEANIN ATMOSPHERIC BUDGET OF ACETONE
SOURCE?
SINK?
H298 30 M atm-1 physical uptake limited by
both gas- and aqueous-phase transfer
Zhou and Mopper (1997)
organic microlayer
Biological uptake (Kieber et al., 1990)
measurements of oceanic acetone are very few!
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INVERSE MODEL ANALYSIS OF ACETONE BUDGET
Global 3-D model (forward model) defines
sensitivity of atmospheric concentrations to
global sources/sinks (state vector)

Observed atmospheric concentrations (with
errors)
A priori best estimate of sources/sinks (with
errors)
Optimized estimate of sources/sinks
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GLOBAL 3-D MODEL SIMULATION OF ATMOSPHERIC
ACETONE
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OPTIMIZED BUDGET OF ATMOSPHERIC ACETONE

• SOURCES (Tg yr-1) 95 /- 15
• Ocean (photochemical) 27 /- 6
  
• Atm oxidation of propane, other iso-HCs 21 /- 5
• Atm oxidation of terpenes, methylbutenol 7 /- 4
• Biomass burning 5 /- 2
• Plant decay 2 /- 5
• Industry 1 /- 1
• SINKS (Tg yr-1) 95
• Photolysis 46
• Oxidation by OH 27
• Ocean uptake 14
• Dry deposition to land 9
• ATMOSPHERIC LIFETIME 15 days

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HENRYS LAW ALONE WOULD IMPLY A LARGE OCEAN
EFFECT ON THE ATMOSPHERIC BUDGETSOF A RANGE OF
MODERATELY SOLUBLE GASES
Species Atm lifetime H
Atm lifetime mOceanML/mAtm
(chemical loss) (M atm-1) (ocean
uptake) ( Henrys law,

dimensionless)
Acetone 20
days 70 17 days
10 Methanol 17 days
500 11 days
80 HCN 2.5 years 30
20 days 5
T-dependent!
Assuming ocean T 283K, ML depth 50m, surface
wind U 5 m s-1
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ATMOSPHERIC COLUMN OBSERVATIONS OF HCNSHOW
VARIABILITY CONSISTENT WITH OCEAN SINK
Symbols Observations Zhao et al., 2000
Lines global 3D model with biomass burning
source, ocean uptake Li et al., 2000
Implied ocean uptake of 1-3 Tg N yr-1 would
make significant contribution to N deposition to
open ocean
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TIP OF THE ICEBERG?LARGE MARINE SOURCE
OFACETALDEHYDEPEM-TB South Pacific observations
Singh et al., 2001
Model without marine source
HCHO
PAN
(CH3)2CO
CH3CHO
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METHYL IODIDE POTENTIAL TRACER OF MARINE
CONVECTION IN GLOBAL METEOROLOGICAL MODELSLoss
by photolysis (4 days), relatively uniform ocean
source, large aircraft data base D.R. Blake, UCI
Emission
hn
Simple model for ocean source
CH3I(aq)
DOC
Cl-
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MODEL AND OBSERVED CH3I(aq) FIELDS (r20.40)
Need to improve definition of source!