VOCs - a link between carbon cycle
and atmospheric aerosols
JANNE RINNE – LUND UNIVERSITY / INES
Went, 1960: Nature, 187, 641-643
Secondary organic aerosol (SOA) formation event
Figure by M.Dal Maso
SMEARII,Hyytiälä,Finland
SOA formation
Figure by H.Junninen
SOA, nucleation and growth
VOC
H2SO4
& ?
VOC: Volatile organic compound
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•
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•
Carbon skeleton
Hydrogen
Methane usually not included
Sometimes also oxygen, other elements
Biogenic global emission 1000 Tg C yr-1
Anthropogenic global emission 100 Tg C yr-1
Terpenoids
• Diverse biogenic VOC group
• Most common species isoprene
(C5H8)
• Monoterpenes (C10H16) typically
emitted by conifers
Biogenic Volatile Organic Compounds (BVOC)
Methane
oxidation
NOx
Competition
OH×
Primary
compounds,e.g.:
-terpenoids
-alcohols
-carbonyls
O3
Gasphase
chemistry
VOC
emission
fluxes
NO3×
Aerosol
particles
Ozone
production
loop
product
compounds,e.g.:
-acids
-carbonyls
-multifunctional
compounds
Gasphase
chemistry
More
products
Synthesis,
storageetc.
8
GPC
GPC
CO2
SOA growth
Growth rate depends on monoterpenes
Yli-Juuti etal.,2011
Global emission of isoprene and monoterpenes
Isoprene:520Tg Cyr-1
69%ofBVOC-C
Monoterpenes:84Tg Cyr-1
11%ofBVOC-C
Boreal coniferous forests emit monoterpenes
FluxmeasurementsatSMEARII,Hyytiälä,Finland
Rantala etal.,2014
Synthesis and emission
Isoprene, monoterpene
synthesis
• Linked to photosynthesis
• Isoprene emission typically a
few percent of photosynthesis
𝐼 = 𝐼# 𝐶% 𝐶&
Electron
transport
Protein
activity
Jardineetal.,2014
Emissions from vegetation
Monoterpenesfrom
plantswithstorage
structures
Isoprene
Monoterpenesfrom
plantswithout
storagestructures
Grote&Niinemets,2008
Isoprene emission
no storage
• Emission from de novo synthesis
without storage
• Temperature and light dependence
• Guenther model implicitly based on
electron transport (CL) and enzyme
activity (CT)
• Basal emission rates empirical
𝐸 = 𝐸# 𝐶% 𝐶&
Guentheretal.,1991
13CO
2
labeling experiment on isoprene
Tholl etal.,2006
CO2 inhibition
Youngetal.,2012
Temperature dependence
of MT emission
• Exponential temperature dependence
observed for monoterpene emissions
from conifers
• Tingey-Guenther model: Emission
from large storage pools
• Implicitly based on temperature
dependence of monoterpene
saturation vapor pressure
• Basal emission rates empirical
𝐸 = 𝐸# 𝑒 )
%*+#°Tingey etal.,1980
Light dependent MT-emission
• Light dependent monoterpene
emission observed in e.g. Holm oak,
birch species and some tropical
trees.
• These lack monoterpene storage
structures
• Thus the emission originates directly
from synthesis (de novo emission)
Staudt &Seufert 1995
13CO
2
labeling of monoterpene emission
• 80-90% of monoterpene carbon from
silver birch and holm oak labeled
• Similar to labeled fraction of isoprene
Holmoak
Labelledfraction%
MTemission
Silverbirch
Ghirardo etal.,2010
Europeanlarch
Conifers
MTemission
Norwayspruce
Scotspine
Ghirardo etal.,2010
Labelledfraction%
• Monoterpene carbon labels 2040%
• Emission continues in dark
COBACC hypothesis
• Continental Biosphere-AerosolCloud-Climate feedback
• Scattering of solar radiation:
– Increase diffuse radiation
– Increased GPP
• Acting as cloud condensation
nucleai
– Higher planetary albedo
– Lowered temperature
Kulmala etal.,2004;2014
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Not all species are emitters
• Not all plants emit isoprene or
monoterpenes
• Plants emitting are spread in the
phylogenetic tree
• Plants have acquired and lost ability
to produce isoprene several times
during their evolution
• Relatively few simple mutations
needed
Monsonetal.,2013
Chemodiversity
RelativecontributionsofdifferentmonoterpenestototalmonoterpeneemissionfromScotspineindividuals.
Bäck etal.,2012
Induced emission
• Business as usual: Constitutive
emission
• Attack by herbivores can trigger
induced emission
• These may be due to
– Mechanical damage of storages
– Newly synthesized compounds
Ghimire etal.,2013
Scotspine
Pinesawflylarvae
Monoterpene emission from a forest clearcut
Haapanala etal.,2012
Ecosystem scale emission data
Methane
Peltola,2016
VOC
Rantala,2016
Global BVOC emission models
Isoprene
Monoterpene
Sindelarova etal.,2014
Gaps in our knowledge
• We know a great deal on emission mechanisms and short term variations
• Very little understanding on interannual variation in BVOC emission
– Abiotic stresses (heat, drought)
– Herbivory
• Spatial variation uncertain
– Most of ecosystem scale emission data originates from very few locations
• Annual or multi-annual time series are rare
– Underlying reason is the complexity of measurement devices
– Calibrations uncertain