1 Ozone good & bad. 2 Ozone (parts per million) 0 20 40 60 80 100 Altitude (km) Troposphere Mesosphere Thermosphere Ozone In the Atmosphere Altitude (miles)

1

Ozonegood & bad

2Ozone (parts per million)

0

20

40

60

80

100

Alt

itud

e (k

m)

Troposphere

Mesosphere

Thermosphere

Ozone In the AtmosphereA

ltitude (miles)

10

0

20

30

40

50

60

90% of ozone is in the stratosphere

0 2 4 6 8

10% of ozone is in the troposphere

3

UVc - 100% AbsorptionUVb - 90% Absorption

UVa - 50% Absorption & Scattering

Ozone is the Earth’s natural sunscreen

Ozone (parts per million)

0

20

40

60

80

100

Alt

itud

e (k

m)

Troposphere

Mesosphere

Thermosphere

Altitude (m

iles)

10

0

20

30

40

50

60

0 2 4 6 8

4

16%

32%

23%

12%

7%5%

1%4%

0

3400

3000

2000

1000

(CH3CCl3)

(e.g., HCFC-22 = CHClF2)

(CCl2FCClF2)

Naturalsources

Other gasesMethyl chloroform

HCFCs

CFC-113

Carbon tetrachloride (CCl4)

CFC-11 (CCl3F)

CFC-12 (CCl2F2)

Methyl chloride (CH3Cl)

0

20

15

10

5

15%

27-42%

5-20%20%

14%

4%

Methyl bromide (CH3Br)

Halon-1211 (CBrCIF 2)

Halon-1301 (CBrF3)

Other halons

Very-short lived gases (e.g., bromoform = CHBr3)

Chemicals that Destroy Stratospheric Ozone

• Cl is much more abundant than Br• Br is about 50 times more effective at O3 destruction

From Ozone FAQ - see http://www.unep.org/ozone/faq.shtml

5

October Average Ozone HoleOctober Average Ozone Hole

LowOzone

HighOzone

NOx

NMVOCs

NOx

NMVOCs

CONTINENT 2 OCEAN

O3

Boundary layer

(0-2.5 km)

Free Troposphere

CONTINENT 1

Tropospheric ozone links air pollution & climate change (1) primary constituent of smog in surface air [NRC, 1991]

(2) 3rd most important greenhouse gas [IPCC, 2001]

OH HO2

VOC, CH4, CO

NONO2

hO3

O3

Hemispheric Pollution

Direct Intercontinental Transport

greenhouse gas

air pollution (smog)

air pollution (smog)