SOME CHEMICAL PROBLEMS SOME CHEMICAL PROBLEMS IN ATMOSPHERIC CHEMISTRY MODELSIN ATMOSPHERIC CHEMISTRY MODELS

Daniel J. Jacob

with in order of appearance: Rokjin Park, Colette L. Heald (now at UC Berkeley), Tzung-May Fu, Paul I. Palmer (now at U. Leeds), Dylan B. Millet, Rynda C. Hudman, Noelle E. Selin, Christopher D. Holmes

…and funding from EPRI, EPA, NSF, NASA

GEOS-Chem GLOBAL 3-D CHEMICAL TRANSPORT MODELGEOS-Chem GLOBAL 3-D CHEMICAL TRANSPORT MODEL

• Driven by assimilated meteorological data from NASA Global Modeling and Assimilation Office (GMAO) with 3-6 hour resolution

• Horizontal resolution 1ox1o to 4ox5o , ~50 vertical layers

• Applied to wide range of problems: tropospheric oxidants, aerosols, CO2, methane, hydrogen, mercury, exotic species…by over 20 groups in N. America, Europe, Australia

• Flagship tropospheric ozone-aerosol simulation includes ~120 coupled species, ~500 chemical reactions

• Serves grander purposes: (1) boundary conditions for EPA CMAQ regional model , (2) global chemical data assimilation at GMAO, (3) effects of climate change through interface with GISS GCM, (4) construction of Earth system model through NASA/GMI

OUR FIRST ORGANIC CARBON (OC) SIMULATION OUR FIRST ORGANIC CARBON (OC) SIMULATION FOR THE UNITED STATESFOR THE UNITED STATES

IMPROVE obs (1998)

U.S. source:2.7 Tg yr-1

Park et al. [2003]annual

10%terpenes

FIRST MASS CONCENTRATION MEASUREMENTSFIRST MASS CONCENTRATION MEASUREMENTSOF OC AEROSOLS IN FREE TROPOSPHEREOF OC AEROSOLS IN FREE TROPOSPHERE

ACE-Asia aircraft data over Japan (April-May 2001)

Observed (Huebert)GEOS-Chem (Chung & Seinfeld for SOA)

Observed (Russell)

OC/sulfate ratio

Heald et al. [2005]

Chung and Seinfeld scheme:,T OC

VOC SOG SOA • Observations show 1-3 g m-3 background;model too low by factor 10-100

ITCT-2K4 AIRCRAFT CAMPAIGN OVER EASTERN U.S. ITCT-2K4 AIRCRAFT CAMPAIGN OVER EASTERN U.S. IN JULY-AUGUST 2004 IN JULY-AUGUST 2004

water-soluble organic carbon (WSOC) aerosol measurementsby Rodney J. Weber (Georgia Tech)

2-6 km altitudeAlaskafireplumes

Values ~2x lower than observed in ACE-Asia; excluding fire plumesgives mean of 1.0 gC m-3 (3x lower than ACE-Asia) Heald et al., in prep.

MODEL OC AEROSOL SOURCES DURING ITCT-2K4MODEL OC AEROSOL SOURCES DURING ITCT-2K4

~10% yield ~2% yield

Large fires in Alaskaand NW Canada:60% of fire emissionsreleased above 2 km(pyro-convection)

Heald et al., in prep.

ITCT-2K4 OC AEROSOL: VERTICAL PROFILESITCT-2K4 OC AEROSOL: VERTICAL PROFILES

SOx = SO2 + SO42-:

efficient scavengingduring boundary layerventilation

ObservationsModel

hydro-phobic

Data filtered againstfire plumes (solid)and unfiltered (dotted)

Model source attribution

TotalBiomass burningAnthropogenicBiogenic SOA

Heald et al., in prep.

CORRELATION OF OBSERVED FREE TROPOSPHERIC WSOCCORRELATION OF OBSERVED FREE TROPOSPHERIC WSOCWITH OTHER CHEMICAL VARIABLES IN ITCT-2K4WITH OTHER CHEMICAL VARIABLES IN ITCT-2K4

No single variable gives R > 0.37, but toluene bivariate correlations with sulfate, acetic acid, and HNO3 give R > 0.7. No correlation with isoprene oxidation products

Heald et al., in prep.Suggest aqueous-phase mechanism involving aromatics

ALTERNATE MECHANISM FOR SOA FORMATION:ALTERNATE MECHANISM FOR SOA FORMATION:AQUEOUS-PHASE OXIDATION AND POLYMERIZATION OF DICARBONYLSAQUEOUS-PHASE OXIDATION AND POLYMERIZATION OF DICARBONYLS

CHOCHO

Isoprene

350 TgC/yr * (Y ~ 4.5%)

= 16 TgC/yr

Aromatics

20 TgC/yr * (Y~ 20%)

= 4 TgC/yr

Monoterpenes

100 TgC/yr * (Y ~ 0.09%) = 0.9 TgC/yr

Oxidation by OH

Photolysis

Deposition

~ 1.3 h

CH(OH)2CH(OH)2

OxidationPolymerization

AQUEOUS PHASE

Liggio et al. [2005],Lim et al. [2005],Hastings et al. [2005]Kroll et al. [2005]

H* = 4x105 M atm-1glyoxal

MODEL REPRESENTATION OF AQUEOUS-PHASE SOA FORMATION MODEL REPRESENTATION OF AQUEOUS-PHASE SOA FORMATION USING REACTION PROBABILITY USING REACTION PROBABILITY APPLIED TO GLYOXALAPPLIED TO GLYOXAL

Liggio et al. [2005]

0.56 ppb

0.28 ppb

Z (

km)

Z (

km)

GEOS-Chem glyoxal and GEOS-Chem glyoxal and methylglyoxal in surface air (July)methylglyoxal in surface air (July)

Production: isoprene, monoterpene, aromatics

Loss: photolysis, oxidation

No aerosol uptake, dry/wet deposition yet

GLYX [ppb] at 0E

MGLY [ppb] at 0E

Tzung-May Fu, Harvard

OXYGENATED VOCs OXYGENATED VOCs OVER TROPICAL OVER TROPICAL PACIFIC (PEM-PACIFIC (PEM-

TROPICS B DATA)TROPICS B DATA)SH

NH

Singh et al. [2001]

Methanol and acetone arethe principal contributors

GLOBAL MODEL BUDGET OF METHANOL (Tg yrGLOBAL MODEL BUDGET OF METHANOL (Tg yr-1-1))with (in parentheses) ranges of previous budgets from Singh et al. [2000],

Heikes et al. [2002], Galbally and Kirstine [2003], Tie et al. [2003]

Plant growth: 128 (50-312)

Oceanuptake:11 (0-50)

Plant decay: 23 (13-20)

Biomass burning: 9 (6-13)Biofuels: 3

Urban: 4 (3-8)

CH3OHlifetime 10 days

(5-12)

VOC CH3O2

CH3O2 (85%)RO2 (15%)

Atmosphericproduction:37(18-31)

OH

130

OH(aq) - clouds

<1 (5-10)

Dry dep. (land) : 56Wet dep.: 12NPP based,

x3 for youngleaves

Jacob et al. [2005]

SIMULATED METHANOL CONCENTRATIONS IN SURFACE AIRSIMULATED METHANOL CONCENTRATIONS IN SURFACE AIR

Representative observationsIn ppbv [Heikes et al., 2002]:

• Urban: 20 (<1-47)• Forests: 10 (1-37)• Grasslands: 6 (4-9)• Cont. background: 2 (1-4)• NH oceans: 0.9 (0.3-1.4)

Tropics: obs model

Rondonia 1-6 10

Costa Rica 2.2 2.1

Jacob et al. [2005]

METHANOL VERTICAL PROFILES OVER S. PACIFICMETHANOL VERTICAL PROFILES OVER S. PACIFIC

Could the atmospheric source from CH3O2 + CH3O2 be underestimated?

Could there be a biogenic VOC “soup” driving organic and HOx chemistryin the remote troposphere?

In model over S. Pacific,CH4

OHCH3O2

HO2 CH3OOHNO

HCHOCH3O2

0.6 CH3OH +…

~ 70%

~ 20%

5-10%

Photochemical model calculations for same data set [Olson et al., 2001] are 50% too high for CH3OOH, factor of 2 too low for HCHO

0 0.6 1.2 1.8 2.4 3 0 0.6 1.2 1.8 2.4 3 0 0.6 1.2 1.8 2.4 3Methanol, ppbv

model atmospheric source

obs. FromH.B. Singh

Jacob et al. [2005]

GLOBAL GEOS-CHEM BUDGET OF ACETONE (Tg yrGLOBAL GEOS-CHEM BUDGET OF ACETONE (Tg yr-1-1))from Jacob et al. [2002] with photolysis update from Blitz et al. [2004]with photolysis update from Blitz et al. [2004]

Vegetation: 33 (22-42)

Oceanuptake:14 19

Plant decay: 2 (-3 - 7)

Biomass burning: 5 (3-7)

Urban: 1 (1-2)

(CH3)2CO

lifetime 15 days 18 days

OH

46

27

Dry dep. (land) : 9

propanei-butane

OH

terpenesMBO

OH, O3

h

microbes DOC+hv

Oceansource:27 (21-33)

21 (16-26)

7 (3-11)

28

37

12

OCEANIC SOURCE OF ACETONE IN MODELOCEANIC SOURCE OF ACETONE IN MODELNEEDED TO MATCH OBSERVATIONS OVER S. PACIFICNEEDED TO MATCH OBSERVATIONS OVER S. PACIFIC

a priori sources/sinks; 2 = 1.3 Optimized sources/sinks(including “microbial” ocean sink,photochemical ocean source); 2 = 0.39

from Jacob et al. [2002]

obs from Solberg et al.[1996]

obs. FromH.B. Singh

……BUT MORE RECENT AIRCRAFT DATA IMPLY BUT MORE RECENT AIRCRAFT DATA IMPLY A NET OCEANIC SINK FOR ACETONEA NET OCEANIC SINK FOR ACETONE

ObservedModel

TRACE-P observations over tropical North Pacific in spring [Singh et al., 2003]

ETHANE [pptv]

AC

ET

ON

E [p

ptv

]

500 1000 1500 2000 2500 3000 3500

500

100

01

500

200

02

500

Correlation between ACETONE and other tracers during TRACEP (Stratospheric influence filtered out)

CO [pptv]

AC

ET

ON

E [p

ptv

]100 200 300 400 500

500

100

01

500

200

02

500

HCN [pptv]

AC

ET

ON

E [p

ptv

]

200 400 600 800 1000

500

100

01

500

200

02

500

METHANOL [pptv]

AC

ET

ON

E [p

ptv

]

0 2000 4000 6000

500

100

01

500

200

02

500

CORRELATION OF ACETONE WITH TRACERS OF SOURCES IN ASIAN OUTFLOW (TRACE-P DATA)

Ace

ton

e [

pp

tv]

CO [pptv]

Methanol [pptv]HCN [pptv]

Ethane [pptv]

Ace

ton

e [

pp

tv]

Ace

ton

e [

pp

tv]

Ace

ton

e [

pp

tv]

Acetone = 0

+1 [Ethane]

+2 [HCN]

+ 3 [Methanol]

Intercept = 200 pptv

Acetone = 0

+1 [CO]

+2 [HCN]

+ 3 [Methanol]

Intercept = 238 pptv

Multiple regression:Propane source Continentalsource

Biomass burning source

Biogenicsource

How to explain thepervasive 200 pptv acetone background?Tzung-May Fu (Harvard)

HCHO COLUMN DATA FROM OMI SATELLITE INSTRUMENTHCHO COLUMN DATA FROM OMI SATELLITE INSTRUMENT

Thomas Kurosu (Harvard/SAO) and Dylan Millet (Harvard)

July 2005

SPACE-BASED MEASUREMENTS OF HCHO COLUMNSSPACE-BASED MEASUREMENTS OF HCHO COLUMNSAS CONSTRAINTS ON VOLATILE ORGANIC COMPOUND AS CONSTRAINTS ON VOLATILE ORGANIC COMPOUND

(VOC) EMISSIONS(VOC) EMISSIONS

VOC HCHOOxidation (OH, O3, NO3)

several steps

hnm), OH

lifetime of hours

340 nm

VOCs important as • precursors of tropospheric ozone• precursors of organic aerosols• sinks of OH

Vegetation Anthropogenic Biomass burning ~1000 ~200 ~100 Tg C yr-1

RELATING HCHO COLUMNS TO VOC EMISSIONRELATING HCHO COLUMNS TO VOC EMISSION

VOCi HCHOh (<345 nm), OHoxn.

k ~ 0.5 h-1

Emission Ei

smearing, displacement

In absence of horizontal wind, mass balance for HCHO column HCHO:

i ii

HCHO

y E

k

yield yi

… but wind smears this local relationship between HCHO and Ei depending on the lifetime of the parent VOC with respect to HCHO production:

Local linear relationshipbetween HCHO and E

VOC source Distance downwind

HCHOIsoprene

-pinenepropane

100 km

TIME-DEPENDENT HCHO YIELDS FROM VOC OXIDATIONTIME-DEPENDENT HCHO YIELDS FROM VOC OXIDATION

Palmer et al, [2006]

High HCHO signal from isoprene with little smearing, weak and smeared signal from terpenes; GEOS-Chem yields from isoprene may be too low by 10-40% depending on NOx

Box model simulations with state-of-science MCM v3.1 mechanism

methylbutenol

HCHO YIELDS FROM ISOPRENE OXIDATIONHCHO YIELDS FROM ISOPRENE OXIDATION

Palmer et al. [2003], Millet et al. [2006]

INTEX-A observations imply a per carbon yield of 0.32 ± 0.1

HCHO vs. isoprene columnsin INTEX-A

observed

H

CH

O,

1016

cm

-2

ISOP, 1016 cm-2

m = 3.3

m = 3.5

GEOS-Chem

Sensitivity to peroxide recycling(standard model assumes recycling)

UltimateHCHO yield

RADICAL CHEMISTRY IN UPPER TROPOSPHERE:RADICAL CHEMISTRY IN UPPER TROPOSPHERE:INTEX-A aircraft data over southeast U.S. (Jul-Aug 04)INTEX-A aircraft data over southeast U.S. (Jul-Aug 04)

NOxO3 HO2

OH

Black: observations by Cohen (NO2), Avery (ozone), Brune (HO2 and OH)Red: standard model simulation Green: model simulation with 4x lightning

Fixing NOx (and ozone!) results in 3x overestimate of OH in upper troposphere;IF we could fix OH, the NOx and ozone underestimates would fix themselves…

Hudman et al. (in prep.)

BrOBrOxx CHEMISTRY IN TROPOSPHERE CHEMISTRY IN TROPOSPHERE

due to Arctic BL spring bloom

Satellites observe 0.5-2pptv BrO in excess of what stratospheric models can explain.

Yang et al. [2005] global model including bromocarbon oxidation/photolysis and sea salt debromination

Tropospheric BrO ?

Significant consequences for tropospheric ozone and NOx budgets

MERCURY IN THE ATMOSPHEREMERCURY IN THE ATMOSPHERE

Hg(0)(gas)

Hg(II)(gas)Oxidation

OH, O3, Br(?)

TOTAL GASEOUS MERCURY (TGM)

DRY AND WET DEPOSITION

REACTIVE GASEOUS MERCURY (RGM)

RELATIVELY INSOLUBLE

ATMOSPHERIC LIFETIME: ABOUT 1 YEAR

TYPICAL LEVELS: 1.7 ng m-3

LIFETIME: DAYS TO WEEKS

TYPICAL LEVELS: 1-100 pg m-3

ReductionPhotochemical aqueous (?)

Hg(II)(aqueous)

Hg(P)(solid)

ECOSYSTEM INPUTS

VERY SOLUBLE

EMITTED BY COAL-EMITTED BY COAL-FIRED POWER PLANTSFIRED POWER PLANTS

LARGE UNCERTAINTY IN ATMOSPHERIC Hg CHEMISTRYLARGE UNCERTAINTY IN ATMOSPHERIC Hg CHEMISTRY

Hg(II) 16d

Hg(II) 20maq

TGM 0.79y

(parenthetical reactions not in model)

Large discrepancies in reported rates!

8.7(±2.8) x 10-14 Sommar et al., AE 20019.0(±1.3) x 10-14 Pal & Ariya, ES&T 2004much slower Calvert & Lindberg, AE

2005

0Hg +OHk [cm3 s-1]

3(±2) x 10-20 Hall, WASP 19951.7 x 10-18 Iverfeldt & Lindqvist, AE 198

03Hg +O

k [cm3 s-1]

0Hg120d

Deposition

In standard GEOS-Chem, 80% ofHg(0) oxidation is by OH; 60% of produced Hg(II) is reduced back to Hg(0) photochemically in clouds

RAPID CONVERSION OF Hg(0) to Hg(II) IN ARCTIC SPRINGRAPID CONVERSION OF Hg(0) to Hg(II) IN ARCTIC SPRINGObservation ofObservation of Mercury Depletion Events (MDEs)Mercury Depletion Events (MDEs)

Hg0 HgBr HgBrX

1

Br Br, OH

T

2

3

Spitzbergen: Sprovieri et al., ES&T 2005

MDEs correlate with ODEs and reactive halogens (up to 30pptv BrO).

Goodsite et al., ES&T 2005

EVIDENCE FOR OXIDATION OF Hg(0) BY Br EVIDENCE FOR OXIDATION OF Hg(0) BY Br IN MARINE BOUNDARY LAYERIN MARINE BOUNDARY LAYER

Jaffe et al [2005]; Selin et al. [2006]

ObservationsGEOS-Chem (OH,O3)

Residual diurnal cycle of Hg(0) observed at Okinawa in April

Consistent with Br release fromBr2 or HOBr at sunrise

COULD Br BE THE MISSING GLOBAL Hg(0) OXIDANT?COULD Br BE THE MISSING GLOBAL Hg(0) OXIDANT?

Br mixing ratio (Yang et al., 2005) Hg0 Lifetime

Holmes et al., GRL 2006

Global lifetime of Hg(0) against oxidation by Br: 0.6 y (range 0.2-1.6 y); Compare to observational constraint of ~1 y for Hg lifetime against deposition