1 / 22

Chapman Mechanism (~1930, Sidney Chapman)

Chapman Mechanism (~1930, Sidney Chapman). O 2 + h   O + O (<242.4 nm). O + O 2 + M  O 3 + M. O 3 + h   O + O 2 (<280 nm). O + O 3  2O 2. O + O + M  O 2 + M. http://www.epa.gov/indicators/roe/html/roeAirInfo.htm United States Environmental Protection Agency

zoie
Download Presentation

Chapman Mechanism (~1930, Sidney Chapman)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapman Mechanism(~1930, Sidney Chapman) O2 + h  O + O (<242.4 nm) O + O2 + M  O3 + M O3 + h  O + O2 (<280 nm) O + O3  2O2 O + O + M  O2 + M

  2. http://www.epa.gov/indicators/roe/html/roeAirInfo.htm United States Environmental Protection Agency EPA Report on the Environment (ROE) http://www.atm.ch.cam.ac.uk/tour/part2.html “The Ozone Tour” Centre for Atmospheric Science, University of Cambridge

  3. “The Ozone Tour” -- http://www.atm.ch.cam.ac.uk/tour/part3.html Centre for Atmospheric Science, University of Cambridge Nobel Prize 1995 (1/3 each) Mario J. Molina USA M.I.T. Cambridge, Mass. Paul J. Crutzen The Netherlands Max-Planck Institut Mainz, Germany F. Sherwood Rowland USA University of California Irvine, California

  4. Catalytic Decomposition of Ozone X + O3 XO + O2 XO + O  X + O2 ________________________________ O3 + O  2O2 X = HOx (H, OH, HOO) NOx (NO, NO2) ClOx (Cl, ClO) N2O from troposphere: N2O + O*  2NO in middle & upper stratosphere NO + O3 NO2 + O2 NO2 + O  NO + O2 ________________________________ O3 + O  2O2 Above 45 km,OH dominates, from: O* + H2O  OH + OH and O* + CH4 OH + CH3 HO + O3 HOO + O2 HOO + O  HO + O2 ________________________________ O3 + O  2O2

  5. In lower stratosphere (~15-25 km), [O] is relatively low: UV-C absorbed by ozone. [O2] is high (so most O quickly reacts with it). Therefore, the dominant ozone loss mechanism is: X + O3 XO + O2 X + O3 XO + O2 XO + XO  X + X+ O2 ________________________________ 2O3  3O2 Reaction goes by: XO + XO  [XOOX]  X + X+ O2 Rate of O3 production depends on [O2], [O3], h (UV-C) Destruction is more complex, but depends on [X], UV-B. If something changes, generally [O3] increases or decreases until it reaches a steady state. Self-healing: [O3], UV-C, more O3 forms below. Next: Atomic Cl and Br as X.

  6. Atomic Cl and Br as X: Cl can destroy tens of thousands of O3 molecules each, but is mainly in inactive forms (HCl, ClONO2) in stratosphere. ClO + NO2  ClONO2 Cl + CH4 HCl + CH3 CH3 does not operate as an X catalyst, since it combines with O2 to give CO2.

  7. On crystals: ClONO2g + HCls Cl2g + HNO3aq Cl2 + hn 2Cl or: ClONO2g + HsOaq HOClaq + HNO3aq HClg H+aq + Cl-aq Cl -aq + HOClaq Cl2g + OH-aq Crystals bind NO2 that would normally deactivate Cl, removing it to the troposphere (denitrification). Conditions in the Arctic are similar to those in the Antarctic, but not as severe, because the temperature is not as low there as in the Antarctic.

More Related