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 OH HO 2 NO 2 NO O3O3 hv H 2 O CO H2O2H2O2 HO 2 DEPOSITION HNO 3 OH HNO 4 hv

Iodine Cycle I CH 3 ICH 2 I 2 C3H7IC3H7ICH 2 ClI IO hv O3O3 +NO +IO I2O2I2O2 hv HOI HO 2 hv INO 3 +NO 2 HI I2I2 INO 2 +NO 2 OH hv I-I- HOIaq Aerosol OCEAN

Photochemistry

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

Termolecular Reactions The low pressure-limiting rate constantThe high pressure-limiting rate constant M Effect Second Order Rate Constant 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

Heterogeneous Reactions Forward Reaction: Backward Reaction

Effect of I and IO on Ozone Depletion

Effect of O3 concentration on Iodine

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 O3 depletion rate increases as NOx concentration is decreased I reaches steady state faster as O3 concentration decreases

Recommendations 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