Biogenic Emissions of Organics:Global Budgets and Implications

IGAC Conference, Annecy, FranceSeptember 11, 2008

Colette L. Heald

Russ Monson, Mick Wilkinson, Clement Alo, Guiling Wang, Alex GuentherScot Martin, Qi Chen, Jose Jimenez, Delphine Farmer

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

Empirical parameterization from plant studies [Wilkinson et al., GCB, accepted]

To what degree does this CO2 inhibition counteract predicted increases in

isoprene (due to T and NPP)?

2100 (A1B): CO2 INHIBITION COMPENSATES FOR TEMPERATURE INCREASE

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

696 TgC/yr

Isoprene emissions in 2100Decrease when CO2 inhibition

included

31%

Dotted=2000Solid=2100

Global Model: NCAR CAM3-CLM3 (2x2.5)

CONCLUSION: ISOPRENE EMISSIONS PREDICTED TO REMAIN ~CONSTANT

Important implications for oxidative environment of the troposphere…

* With fixed vegetation

508 523

696

479

Eisop (TgCyr-1)

2000 2100 (A1B)

MEGANMEGAN with CO2 inhibition

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]

[Heald et al., GCB, accepted]

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)

PRELIMINARY EMPIRICAL PBAP SIMULATIONBased on Elbert et al. [2007] who summarize observed PBAP concentrations and

estimate 50 Tg/yr of fungal spores emitted over entire size range.

Global Annual Mean Burden

1.4

1.0

POA SOA PBAPfine

PBAPint

< 1 m 1-3 m

Tg

0.150.03

Global Model: GEOS-Chem (2x2.5)

Surface: June

? ?

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: Fire influence

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

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

What about “intermediate” size range??

NEED: (1) better understanding of emission drivers(2) More observations of PBAP

ACKNOWLEDGEMENTSMick Wilkinson, Russ Monson

Clement Alo, Guiling Wang

Alex Guenther

Qi Chen, Scot Martin

Delphine Farmer, Jose Jimenez

Andi Andreae