Stratospheric Chemistry

Question 1

Chapman Mechanism

Answer 1

theory for why there are high concentrations of ozone at high altitudes- says that ozone is made from the photolysis of O2.
O2 + hv –> O + O(3P)
O(3P) + O2 –> O3

O3 + hv –> O2 + O(1D)
O + O2 –> O3

Question 2

Why does Chapman mechanism for O3 production not really occur in troposphere?

Answer 2

Need high energy photons to photolyze O2, they are more abundant in stratosphere

Question 3

What was wrong with Chapman’s Mechanism

Answer 3

Reproduced the shape but underestimates [O3]. Shows that we are missing a sink for O3-

Question 4

Important source of HOx in Stratosphere

Answer 4

H2O + O(1D) –> OH

Question 5

Why is their no OH at night?

Answer 5

No O(1D), since there is no light

Question 6

In the stratosphere- what two species act as reservoirs for NOx?

Answer 6

HNO3 and N2O5

HNO3 +hv –> NO2 + OH
HNO3 + OH –> NO3 + H2O
NO3 + hv –> NO2 + o
N2O5 + HV –> NO3 + NO2

Question 7

What are the two loss pathways for N2O in the stratosphere

Answer 7

N2O + O(1D) –> 2NO (5%)

95% is converted to N2

Question 8

How is NOy removed from stratosphere?

Answer 8

Deposition through HNO3, transport

Question 9

How does stratospheric N2O contribute to ozone depletion

Answer 9

N2O + O(1D) –> 2NO (5%)

NO goes on to deplete ozone.