Lecture 8 Part 2

Question 1

How is ozone produced?

Answer 1

by photolysis of O2 in the stratosphere

Question 2

Is there enough UV radiation in the troposphere to generate O3 by photolysis?

Answer 2

No

Question 3

Is the transport of stratospheric O3 to the troposphere limited?

Answer 3

yes

Question 4

What are the sinks for O3 in the troposphere?

Answer 4

photodissociation, surface deposition, and chemical reactions

Question 5

Is there reduced O3 in the troposphere because of the sinks? What does this imply?

Answer 5

No, this implies that there’s another source of ozone at the surface

Question 6

What is a source of ozone in the troposphere that involves NO2?

Answer 6

NO2 + UV-A -> NO + O
O + O2 -> O3

NO2 absorbs UV-A radiation, breaking down into nitric oxide (NO) and atomic oxygen (O). The atomic oxygen (O) reacts with molecular oxygen (O2) to form ozone (O3).

Question 7

What is a source of ozone in the troposphere that involves VOC?

Answer 7

VOC + OH -> VOC (radical)

Volatile organic compounds (VOCs) react with hydroxyl radicals (OH), forming reactive organic radicals (VOC radicals).

VOC (radical) + O2 -> VOC-O2(radical) + NO -> VOC-O + NO2

The VOC radicals react with molecular oxygen to form peroxy radicals, these peroxy radicals react with NO to form organic oxygenated compounds (VOC-O) and nitrogen dioxide (NO2)

Question 8

What is a source of ozone that involves O3 and NO?

Answer 8

O3+NO -> O2 + NO2
NO2 then contributes to NO2+UVA rxn

Question 9

What is source of the hydroxyl radical?

Answer 9

race O3 + UV-B → O2 + O* (excited oxygen atom)
O* + H2O→2OH (radical)

Question 10

What does the ozone layer range from?

Answer 10

Start of the troposphere to 40 km altitude

Question 11

What does the hydroxyl radical do for CO, NO, SO2, H2S, NH3, CH4? VOCs?

Answer 11

is the primary atmospheric oxidant for them, is sourced from ozone