BIOGENIC VOCs

BIOGENIC VOCsBIOGENIC VOCs

TOPICS FOR TODAYTOPICS FOR TODAY

1. Why do we care about BVOCs? How are they climate-

relevant?

2. What are BVOCs? Why are they emitted?

3. How do we measure BVOC emissions?

4. How do we model BVOC emissions?

5. How well do we understand BVOC emissions?

6. How might BVOC emissions respond to a changing

climate?

LARGE SUPPLY OF BIOGENIC VOCs – LARGE SUPPLY OF BIOGENIC VOCs – unrecognized until the 1990sunrecognized until the 1990s

Isoprene (biogenic VOC)Anthropogenic VOCs

Jacob et al., [1993]

Switches polluted areas in U.S. from NOx-saturated to NOx-limited regime!recognized in Revised Clean Air Act of 1999

LATEST INVENTORIES OF BIOGENIC vs. ANTHROPOGENIC VOCsLATEST INVENTORIES OF BIOGENIC vs. ANTHROPOGENIC VOCs

Millet et al. [2007]

…notice difference in scale!

ISOPRENE: CONTROLLING AIR QUALITY AND CLIMATEISOPRENE: 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



relevant?






climate?

Guenther et al. 1995; Guenther et al. 2006

GLOBAL ESTIMATES OF BIOGENIC NON-METHANE VOC GLOBAL ESTIMATES OF BIOGENIC NON-METHANE VOC EMISSIONSEMISSIONS

Total: ~1250 Tg yrTotal: ~1250 Tg yr-1-1

Isoprene600 TgOther reactive

VOCs260 Tg

Other non-reactive VOCs

260 Tg

Monoterpenes130 Tg

WHICH BVOCs ARE IMPORTANT?

CLASS Major Emission Minor Emission

Negligible Emission

Hemiterpenes isoprene, 2,3,2-MBO 2 compounds ?

Monoterpenes a-pinene, b-pinene, carene, myrcene, sabinene, b-ocimene, limonene

30 compounds

Many

Sesquiterpenes caryophyllene, farnescence

30 compounds

Many

OxyVOC Methanol, acetone, acetaldehyde, ethanol

29 compounds

?

Other VOC Methane, ethene, propene 21 compounds

?

Unknowns ? ? ?

Christine Wiedinmyer, NCAR

BIOGENIC VOCs: MANY COMPOUNDS AND PATHWAYSBIOGENIC VOCs: MANY COMPOUNDS AND PATHWAYS

R. Fall 1999

Isoprene (C5H8)

Monoterpenes(C10H1

6)

Sesquiterpenes (C15H24)

PARTICULARLY “IMPORTANT” COMPOUNDS

MBO (2-methyl-3-buten-2-ol,

C5H10O)



relevant?






climate?

Tower-based flux

meas. systems

Years

Days

Hou

rs

TIM

E S

CA

LE

SPATIAL SCALE

Leaf Canopy Landscape Regional/global

Enclosureflux

meas. systems

Analysis using ambient

concentrations, isotopes and

oxidation productsSatellite data (e.g.

HCHO)

Aircraft and blimp-based

flux measurement

systems

Process studies

TOOLS FOR INVESTIGATING TRACE GAS FLUXES

Secon

ds

Regional Characterization

Christine Wiedinmyer, NCAR

Leaf and Branch-Level Enclosure Studies

Above Canopy Flux Studies

Aircraft Studies

-0.5

0

0.5

1

1.5

2

2.5x1016

moleculescm-2

SouthAtlanticAnomaly(disregard)

detectionlimit

Satellite Studies: GOME HCHO



relevant?






climate?

Formic acid Methyl salicylate Ocimene

Formaldehyde Octanal p-cymene

Methanol Nonanal Piperitone

Acetic acid -phellandrene Sabinene

Acetaldehyde -pinene Terpineol

Ethane -terpinene Terpinolene

Ethene -thujene Dimethyl nonatriene

Ethanol -phellandrene Bornyl acetate

Acetone -pinene Methyl jasmonate

Propene Camphene -bergamotene

Butene Camphor -cedrene

Butanone Cineole -copaene

Isoprene -3-carene -farnesene

Methylbutenol Decanal -humulene

Hexanal -limonene -caryophyllene

Hexenol -terpinene -farnesene

Toluene Linalool Longifolene

Hexenyl acetate Myrcene

MODELING BIOGENIC EMISSIONS: MEGANModel of Emissions of Gases and Aerosols from Nature

Guenther et al., 2006Input files available at: http://cdp.ucar.edu

http://cdp.ucar.edu/

Model of Emissions of Gases and Aerosols from Nature: Model of Emissions of Gases and Aerosols from Nature:

MEGANMEGAN

[Guenther et al., ACP, 2006]

Model of Emissions of Gases and Aerosols from Nature: Model of Emissions of Gases and Aerosols from Nature: MEGANMEGAN

F: Emission Flux (g m-2 hr-1) i: gridbox indexj: vegetation type index: Emission Factor (g m-2 hr-1) at standard conditions for each vegetation type: fractional area coverage of vegetation type: Activity Factor (accounting for non-standard conditions): production/loss within canopy factor

HOW EMISSIONS ARE CALCULATED IN MEGAN

,i i i j jj

F

Guenther et al., 2006

VEGEATION TYPES (PLANT FUNCTIONAL TYPES)VEGEATION TYPES (PLANT FUNCTIONAL TYPES)

CLM landcover

PFT-SPECIFIC EMISSION FACTORSPFT-SPECIFIC EMISSION FACTORS

On average, emission from broadleaf trees are 6x higher than needle evergreen, 20x higher than needle deciduous, and 2 orders of magnitude higher than crop emissions!


BVOC EMISSIONS SCHEME BVOC EMISSIONS SCHEME

Flux = Emission Factor x Activity Factor ()

LIGHT TEMPERATURE LEAF AGESOIL

MOISTURE

ISOPRENE

MONTERPENES

[Guenther et al., 2006]

[Guenther et al., 1995]

ACTIVITY FACTORS: METEOROLOGICAL AND ACTIVITY FACTORS: METEOROLOGICAL AND PHENOLOGICAL VARIABLES CONTROLLING EMISSIONPHENOLOGICAL VARIABLES CONTROLLING 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

SOIL MOISTURE suppressed under drought

AMOUNT OF VEGETATION Leaf area index (LAI)

Month

LAISUMMER

LEAF AGEMax emission = mature Zero emission = new


GLOBAL DISTRIBUTION OF ISOPRENE EMISSIONSGLOBAL DISTRIBUTION OF ISOPRENE EMISSIONS

Distinct seasonality due to vegetation cover and activity factors




relevant?






climate?

HOW WELL DO WE KNOW EMISSIONS?HOW WELL DO WE KNOW EMISSIONS?

How well to we know the rates of compounds we can currently measure?

What chemical species don’t we see?

Controlling variables? Long-term ControlsChemical EnvironmentEffects of stress

DroughtOxidantsHerbivory…

LOTS YET TO LEARN!

SPRING 2006 TERPENOID EMISSIONS FROM A EUCALYPTUS FOREST NEAR TUMBARUMBA AUSTRALIA

0

0.5

1

1.5

2

2.5

313 314 315 316 317 318

Day of Year

Can

op

y E

mis

sio

n

isoprene

monoterpenesS

no

wsto

rm

We are using the We are using the controlled environment of controlled environment of a growth chamber to a growth chamber to investigate the processes investigate the processes controlling this behaviorcontrolling this behavior

Models can predict this Models can predict this

but not thisbut not this

A. Guenther

A MISSING FACTOR: ISOPRENE EMISSION INHIBITION BY A MISSING FACTOR: ISOPRENE EMISSION INHIBITION BY COCO2 2

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, in press]

LESS Isoprene in a higher CO2 environment!



relevant?






climate?

HOW WILL BVOC EMISSIONS RESPOND TO A FUTURE HOW WILL BVOC EMISSIONS RESPOND TO A FUTURE CLIMATE? CLIMATE?

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

Some/all of this negated by increasing CO2 concentrations…?

2000 2100

NPP ↑ Temperature↑

2000 2100-2000

Heald et al. [2008]

WHAT IS THE IMPACT OF THESE INCREASING EMISSIONS? WHAT IS THE IMPACT OF THESE INCREASING EMISSIONS?

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]

ADDITIONAL COMPLICATION: CHANGING VEGETATIONADDITIONAL COMPLICATION: CHANGING VEGETATION

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

[Alo and Wang, 2008; Heald et al., in press]

Greener biosphere? Shift in vegetation northwards? Changing plant species?

OTHER UNKNOWN FACTOR: DISTURBANCEOTHER UNKNOWN FACTOR: DISTURBANCE

Pine Beetle OutbreakWildfires

Running et al., 2008 Kurz et al., 2008

BIOGENIC VOCs

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