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Ozone depletion: BrO x -HO x -NO x chemistry. Dian Putrasahan. Objective. Introduction BrO x chemistry HO x -NO x chemistry Modelling input Results Summary. Introduction. Near total ozone depletion events are due to both physical and chemical mechanism
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Ozone depletion: BrOx-HOx-NOx chemistry Dian Putrasahan
Objective • Introduction • BrOx chemistry • HOx-NOx chemistry • Modelling input • Results • Summary
Introduction • Near total ozone depletion events are due to both physical and chemical mechanism • Chemical mechanism include fast catalytic loss driven by bromine oxide radicals (BrOx = Br + BrO) • Presence of aerosols allows heterogeneous reactions that further enhances ozone depletion.
BrOx and O3 Catalytic mechanism for O3 depletion: 2 x (Br + O3→ BrO + O2) BrO + BrO → Br2 + O2 Br2 + hν → 2Br ____________________________________________________________________________________________________________________ Net: 2 O3 → 3 O2 Aerosol effect: Br- + HOBr + H+ → Br2 + H2O Br2 + hν → 2Br
Modeling of BrOx-NOx-HOx Chemistry • Facsimile Program • Input of 37 reactions (8 aqueous reactions, 5 vapor-liquid equilibrium reactions, 24 gas phase reactions) • Set condition: O3 (5ppbv), Br- (23pptv), BrO (10pptv), NO (2.9pptv), NO2 (2.4pptv) pH (0.5)
Summary • Increase in BrO and/or Br will increase the rate of ozone depletion • Br reaches steady state faster as O3 concentration decreases • Br- reaches depletes faster as O3 concentration increases • Increase in NOx concentrations can prevent total ozone depletion • NOx acquires steady state faster as O3 concentration decreases