R. Losno,

LISA, Universités Paris 7 - 12, UMR 7583 CNRS

The objet cloud

• Space extension (vertical motion)
• Micro-Physic (size distribution and water exchange)
• Gas-Dissolved exchange (Henry Law, diffusion, ....)
• Gas chemistry
• Aqueous chemistry

What situation: Non polluted cloud, with or without dissolution of trace metals

• H₂O₂
• Ozone
• Methanol
• Sulphur dioxide

Influence of trace metal

• Iron (Fe^III/Fe^II)
• Manganese (Mn^III/Mn^II)
• Copper (Cu^II/Cu^I)

Why use trace metals into models?

Is it time consuming?

Examples:

• gaseous O₃ and dissolved O₃
• solid Fe(OH)₃ and dissolved Fe(OH)₂⁺

Heterogeneous reactions (water-gas, water-solid)

Homogeneous reactions within the waterNON POLLUTED AREA REACTION SET

Reactants and products, mol.L^­1:

O₃: 3.000E-10 H₂O₂: 2.800E-05 HO₂: 0.000E+00

O₂^-: 0.000E+00 OH: 1.000E-14 H⁺: 1.000E-05

hv: 1.000E+00 O₂: 3.000E-04 Fe^II: 2.000E-08

Fe^III: 4.000E-08 Mn^II: 3.000E-09 Mn^III: 0.000E+00

Cu^I: 0.000E+00 Cu^II: 1.000E-09

Constant (mol.L^­1):

H+: 1.000E-05 O3: 3.000E-10

Reactions:

(01) H2O2 + hv --> OH + OH k=5.700E-07

(02) HO2 + OH --> O2 k=7.000E+09

(03) O2- + OH --> O2 k=1.100E+10

(04) H2O2 + OH --> HO2 k=2.700E+07

(05) O3 + OH --> HO2 + O2- k=2.000E+09

(06) HO2 + HO2 --> H2O2 + O2 k=8.600E+05

(07) HO2 + O2- --> H2O2 + O2 k=1.000E+08

(08) H2O2 + HO2 --> OH + O2 k=5.000E-01

(09) H2O2 + O2- --> OH + O2 k=1.300E-01

(10) O3 + O2- --> OH + O2 + O2 k=1.500E+09

(11) OH + MnII --> MnIII k=3.400E+07

(12) HO2 + MnII --> MnIII + H2O2 k=6.000E+06

(13) O2- + MnII --> MnIII + H2O2 k=1.100E+08

(14) HO2 + MnIII --> MnII + O2 + H+ k=2.000E+04

(15) O2- + MnIII --> MnII + O2 k=1.500E+08

(16) H2O2 + MnIII --> MnII + HO2 + H+ k=3.200E+04

(17) HO2 + FeIII --> FeII + H+ + O2 k=2.000E+04

(18) O2- + FeIII --> FeII + O2 k=1.500E+08

(19) hv + FeIII --> FeII + OH k=5.900E-04 (at pH 5)

(20) HO2 + FeII --> FeIII + H2O2 k=1.200E+06

(21) O2- + FeII --> FeIII + H2O2 k=1.000E+07

(22) OH + FeII --> FeIII k=3.000E+08

(23) O3 + FeII --> FeIII + OH + O2 k=1.700E+05

(24) FeII + MnIII --> FeIII + MnII k=2.100E+04

(25) H2O2 + FeII --> FeIII + OH k=6.010E+01

(26) O2 + FeII --> FeIII + O2- k=7.900E-04

(27) FeIII + CuI --> FeII + CuII k=1.000E+07

(28) OH + CuI --> CuII k=3.000E+08

(29) HO2 + CuI --> CuII + H2O2 k=1.500E+09

(30) O2- + CuI --> CuII + H2O2 k=1.000E+10

(31) H2O2 + CuI --> CuII + OH k=4.000E+05

(32) MnIII + CuI --> CuII + MnII k=2.100E+04

(33) HO2 + CuII --> CuI + O2 + H+ k=1.000E+08

(34) O2- + CuII --> CuI + O2 k=5.000E+09

Acid/Base Couples:

HO2 / O2- pKa= 4.68

Simple system without trace metal dissolution

Simple system with trace amounts of Fe, Cu and Mn

Short system:

(01) H2O2 + hv --> OH + OH k=5.700E-07

(04) H2O2 + OH --> HO2 k=2.700E+07

(18) O2- + FeIII --> FeII + O2 k=1.500E+08

(19) hv + FeIII --> FeII + OH k=5.900E-04 at pH 5

(25) H2O2 + FeII --> FeIII + OH k=6.010E+01

(31) H2O2 + CuI --> CuII + OH k=4.000E+05

(34) O2- + CuII --> CuI + O2 k=5.000E+09

[O₂^-] =

[OH] =

Methanol: 1.000E-07 mol.L^­1

(39) OH + CH3OH --> CH2O k=9.700E+08

(40) OH + CH2O --> HCOOH + HO2 k=7.700E+08

(41) OH + HCOOH --> HO2 k=1.100E+08

(42) OH + HCOO- --> HO2 k=3.100E+09

OH concentration variations

HO₂ concentration variations

Iron and HO2 with methanol

Methanol oxidation

Adding trace metals completely change the reaction scheme

Adding trace metals make the system very less sensitive to other reactive species

Adding trace metals let hope to use photostationary equilibrium instead of kinetics

The trace metal amounts injected in the model are an average value measured in rainwater. We must go further to include particulate-dissolved dynamic modelisation.