Iodine Chemistry And Its Role In Ozone Depletion

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

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.

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

OH/NOx Cycle CO hv H 2 O O 3 OH HO 2 H 2 O 2 HNO 4 hv hv OH NO 2 NO HNO 3 DEPOSITION

Iodine Cycle +NO 2 +IO INO 3 IO +IO HO 2 O 3 I 2 O 2 +NO HOIaq HOI hv Aerosol OH HI I hv hv CH 3 I hv hv CH 2 I 2 hv hv C 3 H 7 I OCEAN +NO 2 CH 2 Cl. I I 2 INO 2 I-

Photochemistry

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

Termolecular Reactions OH + NO 2 + M -------> HNO 3 + M HO 2 +NO 2 + M ----- HNO 4 + M I + NO 2 + M -------> INO 3 + M IO + NO 2 + M ----- INO 3 + M M The low pressure-limiting rate constant Effect Second Order Rate Constant The high pressure-limiting rate constant

Heterogeneous Reactions Forward Reaction: Backward Reaction

Effect of I and IO on Ozone Depletion

Effect of O 3 concentration on Iodine

Effect of NOx on Ozone Depletion

Effect of NOx on Ozone Depletion

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 O 3 concentration decreases • O 3 depletion rate increases as NOx concentration is decreased

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.