parameterization of soa formation for α- pinene , based on a detailed mechanism
Post on 24-Feb-2016
47 Views
Preview:
DESCRIPTION
TRANSCRIPT
Parameterization of SOA formation for α-pinene, based on a detailed mechanism
Karl Ceulemans– Steven Compernolle – Jean-François Müller Belgian Institute for Space Aeronomy, Brussels, Belgium
Eurochamp 2 Workshop, Manchester, 2011
Outline
BOREAM: Detailed model for α-pinene SOA
Simulations of smog chamber experiments
10-product model parameterization including ageing
BOREAM : explicit model for α-pinene SOA
Gas phase reaction model with additional generic chemistry and aerosol formation module
10000 reactions, 2500 compoundsUsing KPP solverCapouet et al. (2008), Ceulemans et al. (2010)
Explicit chemistry• Based on
advanced theoretical calculations and SARs
• Oxidation by OH, O3 and NO3
• Oxidation products react with OH or photolyse (now also in aerosol phase)
• Vapour pressure method: Capouet & Müller (2006)
Generic chemistrySecond generation oxidation products lumped
into semi-generic and generic products
• Semi-generic: carbon number and functional groups
• Generic: carbon number, vapour pressure classes (11) and 1explicit functional group
LA10HPP
10 carbons1 alcohol &2 hydroperoxide
Implicit parent structure, with pvap,im
LX9cONO2
Smog chamber Photo-oxidationlow-NOx experiments (Ng et al. 2007) α-pinene and O3 given in Valorso et al. (2011) Initial: 330 ppt NO, 330 ppt NO2 , 4 ppb O3 ,
blacklights
α-pinene decay well-reproducedozone : reasonable agreement, sensitive to
assumptions!
Smog chamber Photo-oxidation: SOA evolution
for Ng et al. 2007 exp. 1 (low NOx):
SOA mass yields are overestimated: experimental SOA yield is 40%, BOREAM simulation: 60%
Smog chamber Photo-oxidation: SOA composition
Molar composition for Ng et al. (2007) exp. 1 (low NOx):
SOA is dominated by hydroxy dihydroperoxidesParticle phase chemistry of hydroperoxides?
Model performance: Photo-oxidation
two low-NOx experiments, (Ng et al. 2007) ; somewhat overestimated
most SOA yields within factor 2
*
10-product parameter model5 scenarios:
◦ OH (low and high-NOx )◦ O3 (low and high-NOx ) ◦ NO3 (high-NOx)
Products fit to full model simulations with ageing
Diurnal cycle for VOC, OH, HO2 and O3 ; deposition
SOA equilibrium after 12 days
APOHHO22' APOHHO21' HO APINOHO2
NO APOHNO2' APOHNO1' NO APINOHO2APINOHO2 OH APIN
432
221
Two-product model parameterizations Odum (1996)
Y : SOA mass yield M0 : absorbing organic mass αi : mass stoichiometric coefficient of product i Ki : Pankow (1994) absorption equilibrium constant
i i
ii
MKKMY
00 1
gasi
aerii CM
CK
,0
,
.
Temperature dependence of parameters
Absorption equilibrium constant:
Stoichiometric coefficient )())11(exp()()()( ,,
rr
i
rripip m
mTTR
HTTTKTK
))298(exp()( 10 TT iii 0°C
30°C
10-product model parameters
)())11(exp()()()( ,,rr
i
rripip m
mTTR
HTTTKTK
))298(exp()( 10 TT iii
0i 1
i )298(,ipK iHscenario product m3 µg-1 kJ mol-1
α-pinene + OH, low NOx
1 0.307 -0.022 6.98 85.62 0.211 -
0.01350.117 22.2
α-pinene + OH, high NOx
3 0.028 -0.040 0.762 132.24 0.109 -0.025 0.0048
685.3
α-pinene + O3, low NOx
5 0.282 -0.0132
4.155 86.8
6 0.142 -0.025 0.0158 77.1α-pinene + O3,
high NOx 7 0.016 -0.057 0.837 161.88 0.213 -
0.00540.0032
6111.4
α-pinene + NO3 high NOx
9 0.018 -0.049 0.493 172.410 0.251 -0.015 0.00092 147.6
i i
ii
MKKMY
00 1
APOHHO22' APOHHO21' HO APINOHO2
NO APOHNO2' APOHNO1' NO APINOHO2APINOHO2 OH APIN
432
221
APO3HO22' APO3HO21' HO APINO3O2
NO APO3NO2' APO3NO1' NO APINO3O2APINO3O2 O APIN
872
265
3
Reactions
APNO32.' APNO31' NO APIN 1093
OA
pineneii MW
MWTT ).()('
10-product model curves at 298K
More SOA in low-NOx than in high-NOx (factor 8 difference)
α-pinene + OH leads to more SOA than α-pinene + O3
Why more SOA in low than high-NOx ?
++ O2
OH OHO O
+ NO
OHO NO210%
+ NO 90%OH
O
decomposition
OO
pinonaldehyde
+ HO2
OHO OH
++ O2
OH
O
OHO OH
O
+ HO2
O
OHO OH
OH
O2
OH++
OO
O O
NONO2+ +O
O
O ON O
O CH2
O + CO2
High-NOx
Low-NOx
Hydroperoxides (condensable)
Peroxy acyl nitrates
nitrates
More decompositionsMore volatile products
Verification at intermediate NOx
Full modelparameter model(modified)
Sensitivity to photolysis and oxidants
Not accounting for photolysis of SOA during ageing Accumulation of condensables very high
yields Not very sensitive to chosen OH or HO2
Comparison with other parameterizations
Low-NOx : Yields in this
study are higher than for others, ◦ Aging impact◦ Very low-NO x
But, also high yields in
Ng et al. (2007)
High-NOx : similar to Presto
et al. (2005)
T = 298 K
SummaryBOREAM simulations of smog chamber photo-
oxidation: most SOA yields within factor 2Some overestimations for low-NOx
10-product model fit to explicit box model BOREAM including aging
Low-NOx SOA higher than previous parameterizations based on smog chambers (impact aging)
Photolysis of compounds in aerosol phase important
EVAPORATION: New vapour pressure estimation method
Thank you for your attention!
α-pinene + O3 and pinonaldehyde chemistry
top related