Lecture 8

Question 1

What is the stratosphere?

Answer 1

Between mesosphere and troposphere, is the the layer of atmosphere that protects life on earth

Question 2

Whats the stratopause?

Answer 2

Boundary between stratosphere and mesosphere

Question 3

What’s the tropopause?

Answer 3

Boundary between stratosphere and troposphere

Question 4

What is the troposphere?

Answer 4

First region of atmosphere, keeps average temperature at 15 degrees

Question 5

Why is water not included in the standard atmosphere?

Answer 5

Because it is highly variable

Question 6

What is the distribution of water in the atmosphere?

Answer 6

A lot of water vapour in troposphere, less water vapour in stratosphere and tropopause

Question 7

What is the distribution of ozone in the atmosphere?

Answer 7

Less than 1 but then increased in stratisphere and then decreases peak.

Question 8

The sun emits black body radiation at what temperature?

Answer 8

T = 5770 K

Question 9

What percent of radiation from the sun is visible?

Answer 9

43%

Question 10

What is Weins displacement law?

Answer 10

A temp of object increases, the wavelength at which it emits most of it’s radiation becomes shorter.

Question 11

What are the five types of major electromagnetic radiation?

Answer 11

X-rays, Ultraviolet, Visible, Infrared, microwave

Question 12

What is the UV-C wavelength range?

Answer 12

200-280 nm

Question 13

What is the UV-B wavelength range?

Answer 13

280-320 nm

Question 14

What is the UV-A wavelength range?

Answer 14

320-400 nm

Question 15

Where is absorption radiation highest of O2?

Answer 15

In the ionization continuum

Question 16

Where is absorption radiation second highest of O2?

Answer 16

Schumann-Runge continuum

Question 17

Where is absorption radiation third highest of O2?

Answer 17

Schumann-Runge bands

Question 18

Where is absorption radiation the fourth highest of O2?

Answer 18

Herzberg continuum

Question 19

Where is absorption of radiation highest in O3?

Answer 19

Hartley Band

Question 20

Where is the absorption of radiation by oxygen and nitrogen highest? (include altitude and wavelength)

Answer 20

From 100-160 km, from 0-120 nm

Question 21

Where is the absorption of molecular oxygen?

Answer 21

30 km to 110 km, 120-220 nm

Question 22

Where does Ozone absorption begin?

Answer 22

0-40km, 220-300 nm

Question 23

Why is there little UV B or C at the surface of the atmosphere?

Answer 23

Because Ozone absorption of Uv-c in hartley band, uv-b gets partially asborbed towards the end of the hartley band

Question 24

What is the impact of UV radiation?

Answer 24

DNA mutations, skin cancer (melanoma), death
cataracts
crop failure

Question 25

When light intensity increases what happens to the relative biological sensitivity per photon?

Answer 25

It increases, with lower wavelengths (280 nm) holding the highest sensitivies.

Question 26

Does melanoma skin cancer increase with UV light intensity?

Answer 26

Yes

Question 27

How does the chapman mechanism work?

Answer 27

first step- High energy Uv-C photons with wavelengths smaller than 240 nm break O2 into two oxygen atoms. second step- a free oxygen atoms reacts with a O2 molecule in the presence of a third molecule (N2 or O2), this results in an O3 molecule, heat, and molecule third step- ozone absorbs UV-B and UV-C photons (wavelengths smaller than 330 nm), and splits it into oxygen and O2 fourth step- free oxygen atoms can react with ozone (O3), leading to it's destruction and producing two oxygen molecules.

Question 28

The concentration of ozone in the stratosphere never exceeds what?

Answer 28

10 ppm

Question 29

The chapman mechanism absorbs what?

Answer 29

all remaining UV-C and much of UV-B

Question 30

The chapman mechanism creates what?

Answer 30

a steady state concentration of O3

Question 31

What is the minimum photon energy required to dissociate 1 molecule of O2?

Answer 31

498 kJ/mol

Question 32

What is a dobson unit?

Answer 32

is a measure of ozone abundance in the atmosphere, is equivalent to 2.69x10^16 molecules/cm^2. Is 0.01 mm of pure ozone at 273.15 K and 1 atm pressure

Question 33

What are the 3 main catalytic cycles that cause stratospheric ozone destruction?

Answer 33

1. HO (hydroxyl) 2. NO (nitric oxide) 3. Reactive Halogens (Cl, Br)

Question 34

How does the hydroxyl reaction work?

Answer 34

hydroxyl reacts with O3 to produce HO2 and O2, HO2 and O (free oxygen) react to regenerate OH and produce O2 (molecular oxygen), the overall reaction is OH + O3 + HO2 +O -> Ho2 +O2 + OH + O2

Question 35

How does the nitric oxide reaction work?

Answer 35

NO + O₃ + NO₂ + O → NO₂ + O₂ + NO + O₂ NO react with ozone to create NO2 and O2 and No2 reacts with oxygen to create No and O2, removing ozone but recreating the radical

Question 36

How does the CL radical reaction work?

Answer 36

Cl+ O3 →ClO+ O2 ClO+ O → Cl + O2 Cl+ O3+ ClO+ O → ClO+ O2+ Cl+ O2

Question 37

What are chlorofluorocarbons?

Answer 37

compounds containing only C, F, and Cl * nontoxic * nonflammable * volatile * non-bioaccumulative * inert => widely used since the 1940s in fridges and spray cans

Question 38

What researches found what about chlorofluorocarbons?

Answer 38

Identified CFCs are a source of reactive chlorine in the stratosphere and predicted catalytic ozone depletion

Question 39

What was the first observation of polar stratospheric ozone loss?

Answer 39

in the mis 1990s, ozone depletion occurred from the poles to australia and New Zealand in the south and Canada and russia in the north

Question 40

Much of the stratospheric chlorine is tied up in what?

Answer 40

reservoir species such as chlorine nitrate and hydrochloric acid

Question 41

What are reservoir species?

Answer 41

are species that are relatively long lived, they tie up large amounts of active (short-lived) species but can slowly re-release them.

Question 42

How is chlorine nitrate formed?

Answer 42

The combination of CLO and N2O, with sunlight

Question 43

How is HCL formed?

Answer 43

the Cl + CH4 react in an endothermic slow reaction to create the HCL and CH4

Question 44

How is chlorine formed?

Answer 44

The hydroxyl radical reacts with HCL, producing water, and regenerating the chlorine atom. OH + HCl → H2O + Cl

Question 45

For chlorine, which species are active species that participate in chemical reactions such as ozone depletion?

Answer 45

active species are Cl and ClO since they are highly reactive free radicals and participate in chemical reactions

Question 46

What is the impact of Polar stratospheric cloud on active chlorine (HCL & CLNO3)?

Answer 46

chlorine nitrate and HCL can react on the surface on PSCs to form CL2

Question 47

What was the Montreal protocol?

Answer 47

In 1987, Ban/phase-out of chlorofluorocarbons (CFCs) – used mainly as refrigerants and in air conditioners also gradual ban of HCFCs some countries initially exempted (India, China) Halons (contain Br; used in fire extinguishers) are also banned/phased-out Regular "Ozone assessments"

Question 48

What were the results of the montreal protocol and follow up treaties?

Answer 48

CFC's decreased in the northern hemisphere, CCL4 decreased

Question 49

The hole in earth's ozone layer is the _______ since 1998

Answer 49

smallest it's been