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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
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?
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)
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?
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
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?
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
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!
Guenther et al., 2006
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
Guenther et al., 2006
GLOBAL DISTRIBUTION OF ISOPRENE EMISSIONSGLOBAL DISTRIBUTION OF ISOPRENE EMISSIONS
Distinct seasonality due to vegetation cover and activity factors
Guenther et al., 2006
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?
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!
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?
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