Stratospheric Ozone Depletion

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Nitric oxide • NO is produced abundantly in the troposphere, but all of it is converted into NO2 HNO3 (removed through precipitation) • NO in the stratosphere produced from nitrous oxide (N2 O), which is much less reactive than NO. N2 O + hv N2 + O (90%) N2 O + O 2 NO (~10%) • Removal processes: NO2 + . OH HNO3 ClO . + NO2 ClONO2 Inhibit the HOx and ClOx cycles
The two-sided effect of NOx • NOx provides a catalytic chain mechanism for O 3 destruction. • NOx inhibit the HOx and ClOx cycles for O 3 destruction by removing radical species in the two cycles. • The relative magnitude of the two effects is altitude dependent. – >25 km, the net effect is to destruct O 3 . – (NOx accounts for >50% of total ozone destruction in the middle and upper troposphere.) – In the lower stratosphere, the net effect is to protect O 3 from destruction.
Page 1 and 2: Environmental Chemistry Part 2 Atmo
Page 3 and 4: The ozone layer
Page 5 and 6: Ultraviolet protection by ozone The
Page 7 and 8: Typical ozone column values • Tot
Page 9 and 10: Ozone formation and destruction in
Page 11 and 12: Prediction by Chapman theory vs. Ob
Page 13 and 14: The important catalysts for stratos
Page 15 and 16: Chlorine atom Sources: Photolysis o
Page 17: Chlorine atom (Continued) Terminati
Page 21 and 22: Numbering system for CFCs and HCFCs
Page 23: The discovery of the ozone hole •
Page 26 and 27: Features of the ozone hole • Ozon
Page 28 and 29: Polar vortex • The polar vortex i
Page 30 and 31: Why do PSCs occur at heights of 15-
Page 32 and 33: PSCs promote the conversion of inor
Page 34 and 35: Active Cl species can rapidly yield
Page 36 and 37: How does the polar ClOx cycle stop?
Page 38 and 39: Denitrification by PSCs enhances po
Page 40 and 41: Summary of the roles played by PSCs
Page 42 and 43: Schematic of photochemical and dyna
Page 44 and 45: Does ozone hole occur in the north
Page 46 and 47: Summary on ozone hole (Continued)
Page 48 and 49: What influences ODP? • Lifetime i
Page 50 and 51: ODPs of Selected Compounds Compound

Stratospheric Ozone Depletion

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