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.

http://svs.gsfc.nasa.gov/stories/dust_20030306/index.html

Images courtesy Jeffrey Schmaltz and Jacques Descloitres, MODIS Rapid Response Team, NASA GSFC Animation credit: NASA Goddard Space Flight Center, Scientific Visualization Studio

Izaña and Sta. Cruz de Tenerife

Mineral Dust eventsNormal situation

MINATROC field campaign (July, 2002)

Izaña and Sta. Cruz de Tenerife

Mineral Dust eventsNormal situation

MINATROC field campaign (July, 2002)

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