organic carbon in the troposphere

Organic Carbon in the Troposphere

NOAA SeminarJune 11, 2008

Colette L. Heald* (heald@atmos.colostate.edu)

*With acknowledgements to many people at the end!

CARBON IN THE ATMOSPHERE

CO2 (820 PgC)

CH4 (4 PgC)

Organic Carbon (~10s TgC) +

Short-lived (reactive)

BUT important climate role : • direct aerosol radiative forcing• indirect via CCN• oxidant chemistry (O3, CH4, …)

CO(150 TgC)

RECONCILING THE ORGANIC AEROSOL BUDGETSOA measured/modeled = 4-100!

[Volkamer et al., 2006]

Global measurements (surface 0.5-32 μgm-3)[Zhang et al., 2007]

Good agreement between global model and IMPROVE observations for OC aerosol

concentrations in the US[Park et al., 2003]

OBS

MO

DE

L

GAS-PHASE CARBON MASS CLOSURE?2847 organic compounds identified in the atmosphere [Graedel et al., 1986]~104 compounds estimated to be present [Goldstein and Galbally, 2006]30-100 compounds quantified in typical measurement campaigns

[Roberts et al., 1998]

Chebogue Pt, 1993 (NARE)

ΣC2-C7 agree with total measured within measurement uncertainty

Total T=

Speciated S

T/S ~ 1+

UCLA, 1999-2000

WINTER

SUMMER

T/S ~ 1+

T/S =1.4-2.2

Suggest that 20-45% NMOC unmeasured in photochemically aged airmasses

[Chung et al., 2003]

TOPICS FOR TODAY

I. Total Observed Organic Carbon: Concept and Field Observations

II. Isoprene Emissions: Global Budgets and Predictions

III. Primary Biological Aerosol Particles and AMAZE-08

I. Total Observed Organic Carbon: Concept and Field Observations

PHASES OF ORGANIC CARBON GENERALLY CONSIDERED SEPARATELY OR ‘ONE-WAY’

Oxidation &Condensation

POA

SOA

Deposition Deposition

Oxidation toCO/CO2

CONSIDER TOTAL ORGANIC CARBON (TOC)

Oxidation &Condensation

Deposition

Oxidation toCO/CO2

Oxidation &Re-volatization

TOC

Note:Similar to defining

nitrogen family (NOy)

SEMI-VOLATILES

CH4 Oxidation

FIELD SITES AND CAMPAIGNS

Eleven datasets upwind/over/downwind of North America with simultaneous observations of gas phase and particle phase OC.

(Over 130 organic compounds measured)

TOC = Σgas-phase OC + aerosol-phase OCTOOC = Total Observed Organic Carbon [μgCm-3 @ STP]

MEAN DAYTIME TOOC OVER NORTH AMERICA

0

10

20

30

40

50

60

Mex

ico C

ity (T

0) /

8

Pittsb

urgh (P

AQS-S

)

Pittsb

urgh (P

AQS-W

)

R/V R

on Bro

wn (RHB)

Thompso

n Far

m (T

F)

Chebogue

Pt (CHB)

Trinid

ad H

ead (T

HD)

Mex

ico (M

EX)

NE US (W

P3)

NE Pac

ific

(IPX)

Azore

s (B

AE)

Fire P

lum

es (W

P3)

Org

anic

Car

bo

n [m

gC

m-3

] OC aerosol ethanepropane butaneacetone methanolethanol acetic acidformic acid acetaldehydeformaldehyde monoterpenesisoprene MVK+MACRaromatics PANssum(halogens) other

SURFACE AIRCRAFT

Increasing “age”

Mean TOOC ranges from 4.0 μgCm-3 (Trinidad Head, cleanest) to 456 μgCm-3 (Mexico City, polluted) and generally decreases with age.

Aerosol makes up 3-17% of TOOC.

ORGANIC AEROSOL VS SULFATE OVER NORTH AMERICA

Mean POM ranges from < 1 to 24 μgm-3

OC aerosol equal/dominates sulfate at all sites, consistent with NH picture of Zhang et al. [2007]. No discernable trend with “age”.

0

5

10

15

20

25

30

35

Mex

ico C

ity (T

0)

Pittsb

urgh

(PAQ

S-S)

Pittsb

urgh

(PAQ

S-W)

R/V R

on Bro

wn (R

HB)

Thom

pson F

arm

(TF)

Chebogu

e Pt (

CHB)

Trinid

ad H

ead

(THD)

Mex

ico (M

EX)

NE US (W

P3)

NE Pac

ific

(IPX)

Azore

s (B

AE)

Fire P

lum

es (W

P3)

Aer

oso

l M

ass

Co

nce

ntr

atio

n [

mg

m-3

]

POM

SO4

SURFACE AIRCRAFT

VARIABILITY OF TOOC OVER NORTH AMERICA

Organic carbon concentrations span 2 orders of magnitude.Minimum of 2 μgCm-3 observed at any site.

OC aerosol never makes up more than 50% of TOOC.Clean marine sites similar (IPX, BAE)

Similar variability for platforms in the NE (RHB, TF, WP3)

WHAT CONTROLS THE VARIABILITY OF TOOC AND ORGANIC AEROSOL?

Gas-phase > particle-phase in ALL air masses, highest in NE US

CO is a good predictor for TOOC (46-86% of variability), but could be of biogenic or anthropogenic origin in US

Sulfate / Aerosol OC relationship driven by: sources, oxidants, loss?

BIOGENIC CONTROL ON TOOC? (SOA?)

Isoprene

HCHO

MVK/MACR

Isoprene + oxidation products predict some of TOOC

variability (but not OC aerosol)Methanol is best correlated tracer, with longest lifetime

(~7days), but not solely biogenic

Anthro sources

Conundrum: No strong indication of biogenic source of OC aerosol from observations,

but 14C indicates most OC aerosol is modern (=SOA?). Biogenic tracers too short-

lived? Need an anthropogenic “trigger” for aerosol formation?

QUESTIONS RAISED?

1. More routine total NMVOC measurements alongside speciated measurements, and semi-volatiles

2. More ambient sampling in diverse environments (tropics, Asia, polar)3. Time-resolved 14C observations (with aerosol and gas-phase measurements)

1. How much of TOC is accounted for in TOOC? (key missing compounds?)2. How representative are these observations of the atmosphere?

WHAT DO WE NEED?

[Heald et al., ACP, 2008]

TOPICS FOR TODAY

I. Total Observed Organic Carbon: Concept and Field Observations

II. Isoprene Emissions: Global Budgets and Predictions

III. Primary Biological Aerosol Particles and AMAZE-08

ISOPRENE: CONTROLLING AIR QUALITY AND CLIMATE

C5 H8: Reactive hydrocarbon emitted from plants (primarily broadleaf trees)

Annual global emissions ~ equivalent to methane emissions

+ OH

O3

Depletes OH = ↑ CH4 lifetime

IPCC, 2007Beijing

CLIMATE

AIR QUALITY

METEOROLOGICAL AND PHENOLOGICAL VARIABLES CONTROLLING ISOPRENE EMISSION

LIGHTDiffuse and direct radiationInstantaneous and accumulated (24 hrs and 10 days)

TEMPERATURE (Leaf-level)instantaneous and accumulated (24 hrs, 10 days)

TPAR

L

T

[Guenther et al., 2006]SOIL MOISTURE suppressed under drought

AMOUNT OF VEGETATION Leaf area index (LAI)

Month

LAISUMMER

LEAF AGEMax emission = mature Zero emission = new

ISOPRENE IN THE FUTURE

Isoprene emissions projected to increase substantially due to warmer climate and increasing vegetation density.

LARGE impact on oxidant chemistry and climate

2000 2100

NPP ↑ Temperature↑

Surface O3 ↑ 10-30 ppb [Sanderson et al., 2003]

Methane lifetime increases[Shindell et al., 2007] SOA burden ↑ > 20%

[Heald et al., 2008]

A MISSING FACTOR: ISOPRENE EMISSION INHIBITION BY CO2

Long-Term growth environment: gene adaptationDependent on ambient CO2

Short-term exposure: changes in metabolite pools and enzyme activityDependent on intercellular CO2

(varies with photosynthesis and stomatal resistance)

Mick Wilkinson and Russ Monson (UC Boulder) investigated these separately for 4 plant species and developed an empirical parameterization [Wilkinson et

al., submitted]

To what degree does this CO2 inhibition counteract predicted increases in

isoprene (due to T and NPP)?

MODELING FRAMEWORK

Community Land Model (CLM3)Datasets: Lawrence and Chase [2007]

LAI (MODIS)Plant Functional Types

Soil moistureVegetation Temperature

BVOC Algorithms[Guenther et al., 1995; 2006]

Monterpenes: GEIAIsoprene: MEGAN

Community Atmospheric Model (CAM3)

ChemistryTransportRadiation

BVOC Emissions

VegetationMeteorology

RadiationPrecipitation

AnthropogenicEmissions,

GHG concentrations,SST

2100 (A1B): CO2 INHIBITION COMPENSATES FOR TEMPERATURE INCREASE

Future projected emissions drop from 696 TgC/yr to 479TgC/yr

See that ↑in T activity factor ~ compensated by ↓ in CO2 activity factor

Dotted=2000Solid=2100

CONCLUSION: ISOPRENE EMISSIONS PREDICTED TO REMAIN ~CONSTANT

Important implications for oxidative environment of the troposphere…

* With fixed vegetation

UNLESS…CO2 FERTILIZATION IS STRONG

CLM DGVM projects a 3x increase in LAI associated with NPP and a northward expansion of vegetation.

[Alo and Wang, 2008]

Isoprene emissions more than double! (1242 TgCyr-1)

BUT, recent work suggests that NPP increases may be

overestimated by 74% when neglecting the role of

nutrient limitation [Thornton et al., 2007]

IMPLICATIONS FOR THE PAST?

VOSTOK ICE CORE RECORD

While the balance between T and CO2 is critical to future predictions of isoprene, the large T fluctuations over the last 400 thousand year remain the

primary control on isoprene emission in the recent geological past.

Vostok data source: Petit et al. [1999]

TOPICS FOR TODAY

I. Total Observed Organic Carbon: Concept and Field Observations

II. Isoprene Emissions: Global Budgets and Predictions

III. Primary Biological Aerosol Particles and AMAZE-08

PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP)

POLLEN

BACTERIA VIRUSES

FUNGUS

ALGAEPLANTDEBRIS

How much does this source contribute to sub-micron OC?

Jaenicke [2005] suggests may be as large a source as dust/sea salt (1000s Tg/yr)Elbert et al. [2007] suggest emission of fungal spores ~ 50 Tg/yr

LARGE particles (> 10 µm)

1.0E-2

1.0E-1

1.0E+0

1.0E+1

1.0E-1 1.0E+0 1.0E+1 1.0E+2

Diameter d , µm

dV

/dlo

gd, µ

m3 /c

m3

0%20%

40%60%

80%100%120%

140%160%

180%200%

Total

Cellular

Fraction

From Andi Andreae (unpublished data)

ANY INDICATION OF PBAP IN AMAZE-08?

***PRELIMINARY AMS obs: Scot Martin, Qi Chen (Harvard). Jose Jimenez, Delphine Farmer (CU Boulder)

SIMULATED OC

Early Feb: observe

significantly more organic aerosol than simulated (rain ends this

period). PBAP?

Field site: close to Manaus, Brazil (in Amazonia), Feb-Mar

Observations = 1-4 µg/m3

OR A ANOTHER EXPLANATION…?

Feb 1-9 Feb 21-29MODIS fire counts: http://maps.geog.umd.edu/firms/maps.asp

Consistent air flow throughout campaign:

No obvious indication of an important sub-micron PBAP in the “pristine” Amazon at this early stage…

Fires in the region during early Feb. These are not reflected in model emission inventories.

Acetonitrile concentrations are also elevated early in the campaign … but so is isoprene…

ACKNOWLEDGEMENTSMeasurement Teams for ICARTT, PAQS, MILAGRO, IMPEX, ITCT-2K2:James D. Allan, Allison C. Aiken, Eric Apel, Elliot L. Atlas, Angela K. Baker, Timothy S. Bates, Andreas J. Beyersdorf, Donald R. Blake, Teresa Campos, Hugh Coe, John D. Crounse, Peter F. DeCarlo, Joost A. de Gouw, Edward J. Dunlea, Frank M. Flocke, Alan Fried, Paul Goldan, Robert J. Griffin, Scott C. Herndon, John S. Holloway, Rupert Holzinger, Jose L. Jimenez, Wolfgang Junkermann, William C. Kuster, Alastair C. Lewis, Simone Meinardi, Dylan B. Millet, Timothy Onasch, Andrea Polidori, Patricia K. Quinn, Daniel D. Riemer James M. Roberts, Dara Salcedo, Barkley Sive, Aaron L. Swanson, Robert Talbot, Carsten Warneke, Rodney J. Weber, Petter Weibring, Paul O. Wennberg, Douglas R. Worsnop, Ann E. Wittig, Renyi Zhang, Jun Zheng, Wengang Zheng

NSF, NOAA, NASA Funding for TOOC Measurements

NOAA Climate and Global Change Postdoctoral Fellowship

CO2 – Isoprene work: Mick Wilkinson, Russ Monson, Clement Alo, Guiling Wang, Alex Guenther

AMAZE-08 work:Qi Chen, Scot Martin, Delphine Farmer, Jose Jimenez, Andi Andreae