The Heterogeneous Interaction of Atmospheric Trace Gases on Mineral Aerosols and soot Federico Karagulian (Supervisor: M.J. Rossi) Laboratoire de Pollution Atmosphérique et Sol (LPAS), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015-Lausanne (Switzerland)
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The Heterogeneous Interaction of Atmospheric Trace Gases on Mineral
Aerosols and soot
Federico Karagulian(Supervisor: M.J. Rossi)
Laboratoire de Pollution Atmosphérique et Sol (LPAS), Ecole Polytechnique Fédérale de Lausanne
(EPFL), CH-1015-Lausanne (Switzerland)
Important nitrate reactions at night (daytime photolysis in the yellow box)
Nitrate’s chemistry: nighttime
Ozone forms when precursor compounds react in the presence of sunlight and high temperatures.
Ozone chemistry: daytime
Which kind of chemistry for atmospheric pollution?
RVOCsOH
OH2D)O(OH 12
22
22
NORONORO
ROOR
33
2
32
OP)O(O
P)O(NOhνNO
23 NOOHhνHNO 32 HNONOOH
Organic radical
Polluted atmosphere Slow process, therefore HNO3 may represent a
reservoir for O3
Atmospheric chemistry: Ozone formation in the troposphere
21
3 OD)O(hυO < 320 nm
2NOD)O(ON 12
Mineral dust emission
traveling with wind
erosion and deforestation
change of land-usage: fire and wind
Intense African dust storm sent a massive dust plume westward over the Atlantic Ocean on March 2, 2003.
Images courtesy Jeffrey Schmaltz and Jacques Descloitres, MODIS Rapid Response Team, NASA GSFC Animation credit: NASA Goddard Space Flight Center, Scientific Visualization Studio
Environmental effects of aerosols (Particulate Matter PM):
Soot aerosol and black carbon (BC) have a warming effect absorbing sunlight. The contribution of BC and soot to global warming may be second only to that of CO2. 1
Mineral dust have a warming and cooling effect
1 M.A. Jacobson, Nature vol. 409, p. 695 (2001).2 S. Woodward, Geophys. Res. Lett. 32 (18) Sep 28, 2005.
Absorption and scattering of UV radiation by aerosol modify the kinetics of photochemical reactions. Temperature modification by aerosols modify the kinetics of chemical reactions
Simulation. increasing of dust load from 4.0 x 104 to 1.3 x 105 mg / m2 brings to: 0.04 0.21 W/m2 at the top of the atmosphere (heating)2
-0.74 -1.82 W/m2 at the surface (cooling)2
Mineral dust events and heterogeneous chemistry
Mineral dust = mineral aerosol (‘small mineral particle’) Size = 1 – 10 m
O3
NOx = NO+NO2
NOy = NO3 + N2O5 +HNO3+ => Reaction
products
Gas + solid reaction = heterogeneous reaction
= number of molecules taken up
total number of collision = Probability that a molecule is takenup on the solid substrate
(uptake coefficient)
HeterogeneousReactions with
trace gases
a) Reduction of the atmospheric concentration of trace gases like HNO3, NO3, N2O5, O3.
b) Strong influence on the global ozone budget
Model substances such as CaCO3, Natural Limestone,
Kaolinite, Arizona Test Dust, Saharan Dust
Mineral dust aerosol surrogates
Representative Samples
Atmospheric consequences
Real event: dust storm
DUST
O3
NO3
N2O5
HNO3
OH
HO2
NO2
SO2
NO
How does mineral dust affect atmospheric chemistry ?
Grey line = model simulationBlack line = field measurements 1
(Monte Cimone, 2000)
1 P. Bonasoni; et al., Atmos. Chem. Phys. 2004, 4, 1201-1215.2 Bauer et al., J. Geophys. Res. Atm., Vol. 109, doi:10.1029/2003JD003868, 2004.3 Bian and Zender, J. Gephys. Res. Atm, Vol 108, doi:10.1029/2002JD003143, 2003.
Global (%) Bauer et al.2 (%) Bian and Zender 3
H P+H H
O3 -5.4 -0.7 -0.9
HNO3 -35.3 -3.5 -3.8
NO3 -17.7 -4.7 -5.9
N2O5 -10.6 0.0 -2.1
NO2 -1.4 +1.1 -0.3
OH -6.6 -11.1 -9.6
Experimental: Knudsen Flow Reactor
Experimental set up …in the lab
Knudsen reactor
detection chamber
control panel
pumping
REMPI cell
4
3
2
1
0NO
+ R
EM
PI
sign
al (
Vol
t x
s)
460455450445wavelength (nm)
60x10-3
50
40
30
20
10
0
Energy (m
J/cm2)
(a) (b)
REMPI detection of NO and NO2: = 252.6 nm = 511 nm
Pumping laser
Visible light emission
Molecular excitation
Ions yieldMolecular photo-ionization
eNO2hυ2hνNO 11
eNOhν3hνNO 2222
ωγk1)F
F(k ssescM
r
M0
ss ss = Steady state uptake coefficient
M0F
Example: NO3 uptake experiment on 2 g of CaCO3
MrF
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
MS
Sig
nal (
Vol
t)
1000800600400200time (s)
(a)
(b)
(c)
(d)x10
(a)
(b) (c)
(d)x10
NO3 inlet reaction on
MS Signal: (a) = m/e 30; (b) = m/e 46;(c) = NO2 REMPI signal at = 511 nm; (d) = m/e 62 (NO3)
Multi-Diagnostic Detection MS detection NO2 REMPI detection
3252 NONOON T = 500 K
Heterogeneous rate loss
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
MS
Sig
nal (
Vol
t)
800700600500400time (s)
(a)
(b)
(d)
(c)
x10
x10x10
reaction on
1.5
1.0
0.5
0.0
MS
Sig
nal (
Vol
t)
12001000800600400200time (s)
(d)x10
(c)
(b)
(a)
(a)
(b)
(c)
(d)x10(e)
NO3 inlet reaction on
5(g)2ON
NO3 uptake on 200 mg of Kaolinite
gas residence time = 1/kesc = 0.57 s (orifice = 8 mm)[NO3] = (7.0 ± 1.0) x 1011 cm-3 (30 ppb)
5(ads)223(ads) ONNONO
5(g)25(ads)2 ONON
3(g)(ads)25(ads)2 HNO2OHON
NO2 uptake on adsorbed NO3
(a) = m/e 30; (b) = m/e 46; (c) = NO2
REMPI signal; (d) = m/e 62 NO3;
(e) = m/e 63 HNO3
3(g)HNO
Determined from excess MS signal at m/e 46 after correction for NO2 REMPI signal
14x1015
12
10
8
6
4
2
0
Flo
w (
mol
ecu
le/s
)
1000800600400time (s)
(a)
(b)
NO3
inlet reaction on NO3 stopNO admission reaction on
23(ads) 2NONONO
221
23(ads)2 O2NONONO
15x1015
10
5
0
Flo
w (
mol
ecul
e/s)
12001000800600time (s)
(a)
(b)NO3 inlet reaction on
NO3 stopNO2 admission
reaction on
Proof of adsorbed NO3: NO2 REMPI detection
Titration on Arizona Test Dust surface
NO2
Saharan Dust
23 NONO 5(ads)2ON 5(g)2ON
)Ca(OH)(HCOOHCaCO 323
2(g)(s)22335(g)2 COOH)Ca(NO)Ca(OH)(HCOON
3(g)(ads)25(g)2 2HNOOHON
g)(ads,233(ads) OHNOSHNOOHS
NO3 and N2O5 reaction on CaCO3 (powder calcium carbonate)
gas phase adsorbed gas phase
3CaCO
Formation of an intermediate
Nitrate formationon the surface
Delayed formation of nitric acid
5(ads)2ON
(ads)2OH
3(g)HNO2
Adsorbed water
H2O
+Fresh CaCO3 Aged CaCO3
23 OO(SS)SSO
(SS)OOO(SS)O 223
SSO(SS)O 22
23 3O2O net r = 1.5
Ozone reactivity on mineral dust: reaction or decomposition?
OzoneDecomposition: CaCO3
OzoneReactivity: Kaolinite, Saharan Dust;Arizona Test Dust; natural limestone
Reduction in of the Ozone troposphere budget
adductSSO3
adductO(SS)O3
33
2 OP)O(O
Ozonere-formation
Mineral dust and Atmospheric implicationsExample of the N2O5 reactivity at T= 293K; lifetime increasing
A = 1.5 x 10-6 cm2 cm-3 (surface area density for Saharan Dust; = mean molecular speed; NO3, N2O5) ~ 0.2
c
Loss rate constant due to heterogeneous uptake of a gas species onto small particles (<2m)
52kONloss
5O2Nhet
32 NONO
13ONhet s2.0x10k 52
min 8.5NOk
(293)kkkτ
1
21-
1NOhetON
hetON
ss
3
5252
13NOhet s2.4x10k 3 min7τ 3NO
het 121 0.48sNOk
121 s4.6x10(293K)k 20sτ
14hydrhet s2.25x10k
)(s1/τ4
Aγck 1
hethet
[NO2] = 10 ppb
lossHNO3
1NOph 0.2sk 3 5sτ 3NO
ph
Flame Type (Decane)
Soot type
3Diameter sootparticle [nm]
Rich “gray” 40
Lean “black” 20
Soot production: incomplete fuel combustion
Black soot- low air/fuel ratios: soot highly agglomerated and consisted primarily of elemental C. Grey soot-high air/fuel ratios: soot less agglomerated and consisted of volatile organic materials.
Flame soot
Laboratory flame soot
Fuel: hexane, octane, decane, toluene, Diesel
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
MS
Sig
nal (
Vol
t)
1000800600400200time (s)
reaction on (sample exposed)plunger lowered plunger lowered
gas phase NO production
N2O5 on 10 mg of grey soot
N2O5
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
MS
Sig
nal (
Vol
t)
120010008006004002000time (s)
reaction on (sample exposed) plunger loweredplunger lowered
N2O5 on 10 mg of grey sootN2O5
gas phase NO2 production
N2O5 reaction on soot
renoxification
NOy
NOx = NO + NO2
NOy
soot
NO3 reaction on soot
HONO formation(NO3 + NO2) reaction on soot (grey)
NO + products
productsHONOsoot(grey)NO2
Soot is a potential source of tropospheric HONO
Heterogeneous reactions
1 Torr NO2
5 Torr NO2
Heterogeneous interaction of trace gases on substrates of technological importance: inkjet print paper
Samples: Polyester + AlOOH or SiO2 + Dye + additives
Fading effect
Thanks
Acknowledgment
M.J. Rossi Hubert Van den Bergh MINATROC project OFES foundation ILFORD Imaging GmbH (CH) Maria S. Cristina Flavio Comino