Iodine Chemistry And It’s Role In Ozone Depletion

1. Iodine Chemistry And It’s Role In Ozone Depletion PRESENTED BY: Farhana Yasmin

2. Introduction Ozone 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 tropospheric chemistry of ozone, hydrocarbon, nitrogen as well as sulfur and the halogens Cl, Br and I.

3. Objective Model 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

4. OH/NOx Cycle CO hv H2O OH HO2 H2O2 DEPOSITION HO2 HNO4 O3 OH HNO3 hv NO2 NO hv

5. Iodine Cycle +NO2 INO3 +IO IO +IO HO2 HOIaq O3 I2O2 HOI +NO Aerosol HI OH hv I- I I2 hv hv hv hv hv hv INO2 +NO2 CH3I CH2I2 C3H7I CH2ClI OCEAN

6. Photochemistry

7. Bimolecular Reaction Arrhenius Equation k = rate constant A = Pre-exponential constant E = activation Energy R = Gas constant T = Temperature in K

8. Termolecular Reactions OH + NO2 + M -------> HNO3 + M HO2 +NO2 + M ----- HNO4 + M I + NO2 + M -------> INO3 + M IO + NO2 + M ----- INO3 + M M The low pressure-limiting rate constant The high pressure-limiting rate constant Effect Second Order Rate Constant

9. Heterogeneous Reactions Forward Reaction: Backward Reaction

10. Effect of I and IO on Ozone Depletion

11. Effect of O3 concentration on Iodine

12. Effect of NOx on Ozone Depletion

13. Effect of NOx on Ozone Depletion

14. Conclusion • The magnitude of catalytic ozone destruction • depends on the amount of reactive iodine present. • As the iodine concentration increases the ozone depleted faster • I reaches steady state faster as O3 concentration • decreases • O3 depletion rate increases as NOx concentration is decreased

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

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