marine biogenic emissions, sulfate aerosol formation, and climate: constraints from oxygen isotopes...
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![Page 1: Marine biogenic emissions, sulfate aerosol formation, and climate: Constraints from oxygen isotopes Becky Alexander Harvard University University of Wisconsin,](https://reader035.vdocuments.net/reader035/viewer/2022062422/56649ea75503460f94baad27/html5/thumbnails/1.jpg)
Marine biogenic emissions, sulfate aerosol formation, and climate:
Constraints from oxygen isotopes
Becky Alexander
Harvard University
University of Wisconsin, Madison
February 21, 2005
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OverviewOverview
Introduction to aerosols, climate, and oxygen isotopes (Mass-independent fractionation)
Chemistry and climate interactions on the glacial/interglacial timescale
Influence of sea-salt aerosol alkalinity in sulfate aerosol formation climate implications
16
16 17 or 18
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Radiative Forcing: Greenhouse Radiative Forcing: Greenhouse Gases and AerosolsGases and Aerosols
IPCC report, 2001
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Effects of Aerosols on ClimateEffects of Aerosols on ClimateDirect Effect
Indirect Effect
Reflection
RefractionAbsorption
Ramanathan et al., 2001
Aerosol number density (cm-3)
Clo
ud
dro
ple
t n
um
be
r d
en
sity
(cm
-3)
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Atmospheric SulfateAtmospheric Sulfate
Cooling effect on climate
Contributes to the formation of acid rain
Anthropogenic emissions are 2 to 3 times that of natural sources – most abundant inorganic aerosol species
Transcontinental transportPark et al., 2004
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Sulfur Cycle in the AtmosphereSulfur Cycle in the Atmosphere
Surface
DMSCS2
H2SSO2 SO4
2- OH
O3, H2O2
OH, NO3
MSA
OH
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New Particle FormationNew Particle Formation
SO2 + OH (+O2 + H2O) H2SO4(g) (+HO2)
CCN> ~ 0.1 m
H2O
NH3?
H2SO4(g)
Condensation
RCOOH
Activation
Water vaporWater vapor
Updraft velocityUpdraft velocity
Aerosol number densityAerosol number density
Size distributionSize distribution
Chemical compositionChemical composition
From Boucher and Lohmann, 1995
nssSO42- (mg m-3)
CD
NC
(m
-3)
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Marine Biologic DMS and ClimateMarine Biologic DMS and ClimateCharleson Charleson et alet al. (1987), Shaw (1985). (1987), Shaw (1985)
SO2 H2SO4OH New particle
formation
CCN
Light scattering
DMSOH NO3
Phytoplankton
H 2O 2
SO42-
O3
Sea-salt aerosol
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Stable Isotope Measurements:Stable Isotope Measurements:Tracers of source strengths and/or chemical
processing of atmospheric constituents
(‰) = [(Rsample/Rstandard) – 1] 1000
R = minorX/majorX
18O: R = 18O/16O
17O: R = 17O/16O
Standard = SMOW (Standard Mean Ocean Water)
(CO2, CO, H2O, O2, O3, SO42-….)
17O/18O 0.5
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Mass-Independent Fractionation (MIF)Mass-Independent Fractionation (MIF)
17O/18O 1
-80
-60
-40
-20
0
20
40
60
-100 -80 -60 -40 -20 0 20 40 60 8018O
17O
Product Ozone
Residual Oxygen
Starting Oxygen
Thiemens and Heidenreich, 1983
17O
17O
17O = 17O – 0.5*18O 0
O + O2 O3*
Mass-dependent fractionation line: 17O/18O 0.5
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Symmetry C2v Symmetry Cs
17 or 18
16 16
16
16 17 or 18E Vibrational
StatesRotational
States
De
v = i
v=i+1
RotationalStates
VibrationalStates
De
v = i
v=i+1
O2 + O(3P) O3
*
Symmetry Based Explanation of MIFSymmetry Based Explanation of MIF
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25
10
5
50
75
100
10 20 50 100
SO4
CO
N2O
H2O2
NO3
CO2 strat.
O3
trop.
O3
strat.
18O
17O
1717OO Measurements in the AtmosphereMeasurements in the Atmosphere
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Source ofSource of 1717OO SulfateSulfateSO2 in isotopic equilibrium with H2O :
17O of SO2 = 0 ‰
1) SO32- + O3 (17O=35‰) SO4
2- 17O = 8.8 ‰
17O of SO42- a function relative amounts of OH, H2O2, and O3 oxidation
Savarino et al., 2000
3) SO2 + OH (17O=0‰) SO42- 17O = 0 ‰
2) HSO3-+ H2O2 (17O=1.7‰) SO4
2- 17O = 0.9 ‰ Aqueous
Gas
S(IV) = SO2, HSO3-, SO3
2-
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pH dependency of OpH dependency of O33 oxidation and oxidation and
its effect on its effect on 1717O of SOO of SO442-2-
1.0E-15
1.0E-14
1.0E-13
1.0E-12
1.0E-11
1.0E-10
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
pH
Oxi
dat
ion
rat
e (M
/sec
)
H2O2
O3
1.0E-151.0E-141.0E-13
1.0E-121.0E-111.0E-101.0E-091.0E-08
1.0E-071.0E-061.0E-051.0E-041.0E-03
1.0E-021.0E-011.0E+00
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
pH
Oxi
dat
ion
rat
e (M
/sec
)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
17
O (
‰)
H2O2
O3
Lee et al., 2001 Sea-spray
17Omeas = ƒOH*0‰ + ƒH2O2*0.9‰ + ƒO3*8.8‰
ƒOH + ƒH2O2 + ƒO3 = 1
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GEOS-CHEMGEOS-CHEM
• Global 3-D model of atmospheric chemistry
• 4ºx5º horizontal resolution, 26-30 layers in vertical
• Driven by assimilated meteorology (1987 –present).
• Includes aqueous and gas phase chemistry:
S(IV) + OH (gas-phase)
S(IV) + O3/H2O2 (in-cloud, pH=4.5)
• Off-line sulfur chemistry (uses monthly mean OH and O3 fields from a full chemistry, coupled aerosol simulation)
http://www-as.harvard.edu/chemistry/trop/geos/index.html
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GEOS-CHEM GEOS-CHEM 1717O Sulfate SimulationO Sulfate Simulation
SO2 + OH (gas phase) 17O=0‰
S(IV) + H2O2 (in cloud) 17O=0.9‰
S(IV) + O3 (in cloud, sea-salt) 17O=8.8‰
Assume constant, global 17O value for oxidants
17O ‰ method reference
O3 35 Photochemical model
Lyons 2001
H2O2 1.3-2.2 (1.7)
Rainwater measurements
Savarino and Thiemens 1999
OH 0 Experimental Dubey et al., 1997
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1717O sulfate: GEOS-CHEM and measurementsO sulfate: GEOS-CHEM and measurements
January 2001 July 2001
0.0‰ 2.3‰ 4.6‰
Davis, CA fogwater
4.3 ‰
Whiteface Mtn, NY
fogwater 0.3 ‰
White Mtn, CA aerosol
1-1.7‰
La Jolla rainwater
1.1 ‰
La Jolla aerosol 0.2-1.4‰
South Pole aerosol
0.8-2‰
Site A, Greenland ice core 0.5-3‰
Vostok & Dome C ice
cores 1.3-4.8‰
Desert dust traps 0.3-3.5‰
INDOEX aerosol
0.5-3‰
Alert 1.0‰
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Alkalinity in the Marine Boundary LayerAlkalinity in the Marine Boundary Layer
Na+, Cl-, CO3
2-
pH=8CO2(g)
Acids:
H2SO4(g)
HNO3(g)
RCOOH(g)
SO2(g) SO42-
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Pre-INDOEX Jan. 1997 INDOEX March 1998
INDOEX cruisesINDOEX cruises
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Analytical MethodAnalytical Method
High volume air samplerSO4
2-
Ion Chromatograph Ionic separation
O2 loop 5A mol.sieve
vent
Isotope Ratio Mass Spectrometer
Ag2SO4 O2 + SO2
Removable quartz tube
1050°C
magnet
To vacuum
To vacuumGC
SO2 trap
He flow
Sample loop 5A mol.sieve
ventSO2 port
O2 port
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pre-INDOEX 1997 INDOEX 1998
9
0
1
2
3
4
5
6
7
8
-15 -10 -5 0 5 10 15 -15 -10 -5 0 5 10 15
Latitude (°N)
0
1
2
3
4
5
6
7
8
nss
SO
42
- 1
7 O (
‰)
Na
+ (g
/m3)
bulk
finecoarse
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DMS
SO2
Free troposphere
H2SO4(g)
OH
Cloud other aerosols
(acid or neutral)
O3
CO2(g)
H 2O
2
Emission
Marine Boundary Layer
Subsidence
OH NO3
Sea-salt aerosol CO3
2-
Emission
HNO3(g)RCOOH(g)
Subsidence
Deposition
NH3(g)
GEOS-CHEM Sea-salt AlkalinityGEOS-CHEM Sea-salt Alkalinityhttp://www-as.harvard.edu/chemistry/trop/geos/index.html
SO42-
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March 1998
January 1997
Na+ [g m-3]31 119750 13
Model Sea-salt (NaModel Sea-salt (Na++) Concentrations) ConcentrationsdF/dr = 1.373u10
3.41r-3(1+0.057r1.05)101.19exp(-B2)
= (0.380 log r)/0.65
Monahan et al., 1986 (particles m-2 s-1 m-1)
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INDOEX 1998
nss
SO
42
- 1
7O
(‰
)
Latitude (°N)
Model not including sea-salt chemistry
Model including sea-salt chemistry
Observations
pre-INDOEX 1997
INDOEX 1998
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GEOS-CHEM Alkalinity BudgetGEOS-CHEM Alkalinity Budget
fSO2
fHNO3
fexcess
0.1 0.3 0.5 0.7
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[SO2] % decrease
[SO42-] % increase
SO2 + OH % decrease
10 30 50 705
GEOS-CHEM Sulfur BudgetGEOS-CHEM Sulfur Budget
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Excess Alkalinity Sources?Excess Alkalinity Sources?
OH chemistryOH chemistry
Na+, Cl-
OH(g) + Cl-(interface) (HO…Cl-)interface
(HO…Cl-)interface + (HO…Cl-)interface Cl2 + 2OH-
2OH•
2OH-
Cl2
Laskin et al., 2003
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Excess Alkalinity Sources?Excess Alkalinity Sources?
Biogenic CaCOBiogenic CaCO33
Coccolithophore phytoplankton cell Image credit: Dr Jeremy R. Young, the Natural History
Museum of London
Coccolithophore bloom in the Bering Sea
Image credit: NASA
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Latitude (°N)
nss
SO
42
- 1
7O
(‰
)
Model with excess alkalinity
Observations
Model with doubled alkalinity supply
Excess alkalinity
(OH chemistry)
Biogenic alkalinity
(CaCO3)
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SeaWiFS Ocean ColorSeaWiFS Ocean Color(NASA)(NASA)
January 1998 March 1998
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Dust AlkalinityDust Alkalinity
Fe, Si, …
CaCO3
CO2(g)
Acids:
H2SO4(g)
HNO3(g)
RCOOH(g)
SO2(g) SO42-
> 1: Fe mobilizationAlkalinity
Acid
Meskhidze et al., 2005
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SOSO22 Oxidation, Iron Mobilization, Oxidation, Iron Mobilization,
and Oceanic Productivityand Oceanic Productivity
From Meskhidze et al., 2005
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ConclusionsConclusions
•Sulfate formation in sea-salt aerosols is limited by:
Low to mid-latitudes: sea-salt flux to the atmosphere (wind)
Mid to high-latitudes: gas-to-particle transfer rate of SO2
•Decreases in SO2 concentrations and the rate of gas-phase sulfate production (10 - 30%) in the MBL
•Inclusion of sea-salt chemistry in global models is important for interpretation of Antarctic ice core 17O sulfate
measurements
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Vostok Ice Core Vostok Ice Core
1717O (SOO (SO442-2-) variability) variability
Ts data: Kuffey and Vimeux, 2001, Vimeux et al., 2002
Alexander et al., 2002
0
1
2
3
4
5
6
0 20 40 60 80 100 120 140
Age (kyr)
17O
-6
-5
-4
-3
-2
-1
0
1
2
3
Ts
17O
(‰
)
Ts
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Climate Variations in the Oxidation Climate Variations in the Oxidation Pathways of Sulfate FormationPathways of Sulfate Formation
OH (gas-phase) oxidation greater in glacial period compared to interglacial
Age (kyr)
% O
H
0
10
20
30
40
50
60
70
80
90
0 20 40 60 80 100 120 140
Age (kyr)
-6
-5
-4
-3
-2
-1
0
1
2
3
T
s
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Secondary Species
CO2, H2SO4, O3, …
Oxidizing Power of the AtmosphereOxidizing Power of the Atmosphere
VolcanoesMarine Biogenics
Biomass burning
Continental Biogenics
Primary Species H2S, SO2, CH4, CO, DMS, CO2, NO, N2O,
particulates
?
Climate change
OHhH2O
Primary Emissions
DMS, SO2, CH4, …
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AcknowledgementsAcknowledgements
Mark H. Thiemens
Charles Lee
Joël Savarino
Daniel Jacob
Rokjin Park
Qinbin Li
Bob Yantosca
Duncan Fairlie