Iodine Chemistry And It’s Iodine Chemistry And It’s Role In Ozone DepletionRole In Ozone Depletion

PRESENTED BY:PRESENTED BY:Farhana YasminFarhana Yasmin

IntroductionIntroductionOzone depletion in the troposphere has always been the main concern to the environment.

There are many factors, most of them coupled, that causes the depletion of the ozone, such as reactions and transport.

The reaction mechanism includes troposphericchemistry of ozone, hydrocarbon, nitrogen as well as sulfur and the halogens Cl, Br and I.

ObjectiveObjectiveModel of ozone depletion using FACIMILE that will allow us to investigate the effect of the iodine on ozone depletion.

Since iodine is a much more effective agent compared to bromine and chlorine, it is suspected that even in small amount iodine may have a profound impact on ozone depletion.

The modeling of ozone depletion will allow us to see the effect on the rate of ozone depletion with iodine concentration

OH/NOx CycleOH/NOx Cycle

OH HO2

NO2NO

O3

hv

hvH2O

CO

H2O2HO2DEPOSITION

HNO3

OH

HNO4

hv

Iodine CycleIodine Cycle

I

CH3I CH2I2 C3H7I CH2ClI

IO

hv hv hv hv

O3

+NO

+IO

I2O2

+IO

hv

HOI

HO2

hv

INO3+NO2

HI

I2

INO2+NO2

OH

hv

I-

HOIaqAerosol

OCEAN

PhotochemistryPhotochemistry

Photolysis Reactions J (1/s)O3 + hv-----> O('D)+O2 2.20E-05NO2+hv--->O3+NO 1.13E-02HNO4+hv---->NO2+HO2 5.00E-06INO2+hv-->I+NO2 2.90E-03IO+hv---> I+O3 2.20E-01INO3+hv--->IO+NO2 2.90E-03HOI+hv---->I+OH 5.90E-03I2O2+hv----->2I+O2 1.30E-02I2+hv----> 2I 1.20E-01

Bimolecular ReactionBimolecular Reaction

RT

EAk exp*

k = rate constant A = Pre-exponential constantE = activation EnergyR = Gas constantT = Temperature in K

Arrhenius Equation

Binary Reaction k (cm3molecule-1s-1)O('D)+M=O+M 3.60E-11

O('D)+H2O--->OH+OH 2.20E-10OH+CO---.>HO2+CO2 9.60E-13HO2+NO---->OH+NO2 1.29E-12OH+H2O2--->HO2+H20 1.53E-12HO2+HO2--->H2O2+O2 2.09E-14H2O2----> depH2O2 (1/s) 2.31E-06HNO3---.>depHNO3 (1/s) 2.31E-06

I+O3----IO+O2 5.69E-13I+HO2---->HI+O2 1.92E-13IO+NO---->I+NO2 2.73E-11

IO+HO2---->HOI+O2 8.40E-11IO+IO-----> I2O2 5.20E-11

IO+IO----> I+I+O2 2.80E-11HI+OH---->I+H2O 3.00E-11

HOI+OH---->IO+H2O 2.00E-13

Termolecular ReactionsTermolecular Reactions

30030000

Tkk

300

300 Tkk

The low pressure-limiting rate constant The high pressure-limiting rate constant

ABABBA kkk 211 *][/ M

Effect Second Order Rate Constant

k

Mk

f

k

MkMk

TMk

][*log1

0

0

010

6.0*][*

1

][*)],([

OH + NO2 + M -------> HNO3 + MHO2 +NO2 + M ----- HNO4 + M

I + NO2 + M -------> INO3 + M

IO + NO2 + M ----- INO3 + M

Heterogeneous ReactionsHeterogeneous Reactions

HI(g) ↔ Iֿ aqHOI(g) ↔ HOIaq

Avk f 4

1

M

RTv

8

3

3

__

__**cmvolumeair

cmvolumeaeresol

atm

airfb V

V

P

N

H

kk

Forward Reaction:

Backward Reaction

Effect of I and IO on Ozone DepletionEffect of I and IO on Ozone Depletion

Effect of I and IO on ozone depletion

0.00E+00

2.00E+10

4.00E+10

6.00E+10

8.00E+10

1.00E+11

1.20E+11

1.40E+11

0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

Time (sec)

O3

(m

ole

cu

les

/cm

^3

)

I= 7pptv , IO= 2 pptv I=9pptv, IO = 3pptv I=20pptv, IO=4pptv I=27pptv, IO=6pptv

Effect of O3 concentration on IodineEffect of O3 concentration on IodineEffect on O3 Concentration on I

0.00E+00

1.00E+08

2.00E+08

3.00E+08

4.00E+08

5.00E+08

6.00E+08

7.00E+08

0 50000 100000 150000 200000 250000

Time (sec)

I (m

ole

cu

les

/cm

^3

)

O3 1ppbv O3 5ppbv O3 10ppbv

Effect of NOx on Ozone DepletionEffect of NOx on Ozone Depletion

Effect of NOx on ozone depletion

0.00E+00

2.00E+10

4.00E+10

6.00E+10

8.00E+10

1.00E+11

1.20E+11

1.40E+11

0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

Time (sec)

O3

(mo

lecu

les/

cm^

3)

NO= 0, NO2=0 NO= 2.9pptv, NO2=2.4pptv NO=6.1pptv, NO2=4.8pptv

Effect of NOx on Ozone DepletionEffect of NOx on Ozone DepletionEffect of NOx on ozone depletion

0.00E+00

1.00E+08

2.00E+08

3.00E+08

4.00E+08

5.00E+08

6.00E+08

7.00E+08

8.00E+08

9.00E+08

1.00E+09

0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000

Time (sec)

O3

(mo

lecu

les/

cm^

3)

NO= 0, NO2=0 NO= 2.9pptv, NO2=2.4pptv NO=6.1pptv, NO2=4.8pptv

ConclusionConclusion• The magnitude of catalytic ozone destruction depends on the amount of reactive iodine present.

• As the iodine concentration increases the ozone depleted faster

• O3 depletion rate increases as NOx concentration is decreased

• I reaches steady state faster as O3 concentration decreases

RecommendationsRecommendations

• This study is highly theoretical and our conclusions, therefore, strongly need testing with observational data.

• Further identification of the marine biological processes leading to the production of organic iodine gases and their releases to the atmosphere.

• Problems using FACSIMILE:• Easy to make mistake• Does not allow to add reactions• Order of reaction matters