Air Pollution and Stratospheric
Ozone Depletion
Chapter 15
Air Pollution
• “introduction of chemicals, particulate matter
(PM), or microorganisms into the atmosphere
at concentrations high enough to harm plants,
animals, and materials such as buildings or
alter ecosystems”
• “pollution of troposphere” or “ground-level
pollution”
• Sources
a. natural
- volcanoes
- forest fires
- plants
b. anthropogenic
- on-road vehicles (largest source of CO and NOx)
- industry
- power plants
Major Air Pollutants
• Six pollutants (criteria) – U.S. Clean Air Act
a. SO2
b. NOx
c. CO
d. PM
e. tropospheric ozone
f. lead
• Sulfur Dioxide (SO2)
a. corrosive gas
b. combustion of fossil fuels (coal and oil)
c. respiratory irritant
d. released from volcanoes and forest fires
• Nitrogen Oxides
a. NOx (NO or NO2)
b. NO
1. colorless, odorless gas
c. NO2
1. pungent, reddish-brown gas
d. nitrogen (N2)
1. makes up 78% of atmosphere
• Carbon Oxides
a. CO
1. colorless, odorless gas
2. vehicle exhaust
b. CO2
1. colorless, odorless gas
2. photosynthesis/cellular respiration
3. burning of fossil fuels
• Particulate Matter (PM)
a. solid or liquid particles suspended in the air
b. sizes
1. ranges 0.001 micrometer to 100 micrometer
2. larger than 10
- can be filtered out by nose and throat
3. PM10 – not filtered and deposited in
respiratory tract
4. PM2.5 – BIG health concern
c. scatter and absorb sunlight
• Photochemical Oxidants
a. sunlight acting on NOx and SO2
b. main focus – O3 (ozone)
1. most abundant in troposphere
2. respiratory inflammation
3. reacts with NOx and sulfur to form smog
- photochemical
* LA type, brown
- sulfurous
* London type, gray
- atmospheric brown cloud
* seen in Asia
• Lead (Pb)
a. occurs naturally in rocks and soil
b. has been added to gasoline
c. persistent
• Mercury (Hg)
a. coal and oil – released into atmosphere
b. toxic to CNS
• VOCs (volatile organic compounds)
a. become vapors at typical atmospheric
temperatures
b. hydrocarbons
c. gasoline, lighter-fluid, oil-based paints
d. strong aromas
e. lead to ozone formation
Primary and Secondary Pollutants
• Primary
a. direct source
b. CO, CO2, SO2, NOx, most PM and VOCs
• Secondary
a. product of primary pollutant undergoing a
reaction
ex) ozone (O3)
Photochemical Smog
• Smog
a. originally – smoke, fog, and sometimes SO2
due to burning of coal
b. today – brown smog still a problem
c. typically urban areas, but some rural (trees and
shrubs, forest fires)
d. atmospheric conditions (higher temperatures)
1. emission of VOCs
2. NOx emissions from electric utilities
c. no VOCs or photochemical oxidants
1. ozone (O3) forms during the day and breaks
down at night
2. little to no photochemical smog
d. VOCs present
1. VOCs combines with NOx
2. NOx no longer available to recombine with
O3 in atmosphere, therefore the O3
accumulates over time
e. Thermal inversion
1. warm layer of air at mid-altitude covers
a layer of cold, dense air below
2. warm inversion layer
- traps emissions causing severe pollution
- vehicle exhaust and industrial emissions
http://news.bbc.co.uk/2/hi/uk_news/magazine/7532603.stm
Acid Deposition
• Formation
a. NOx and SOx released into atmosphere
(primary)  nitric acid and sulfuric acid
(secondary)  nitrate, sulfate, and hydrogen
ions (generate acidity in acid deposition
b. fall as wet or dry deposition
c. reduced in US due to Clean Air Act
• Effects
a. lowers pH of water
b. detrimental to aquatic organisms
c. decrease in species diversity
d. erode statues, monuments, and buildings
e. harm tree species (Red Spruce in NE US)
Stratospheric Ozone
Tropospheric Ozone
Stratospheric Ozone
Oxidant that harms respiratory
systems
Protective shield against
radiation from Sun (UV-B)
Air pollutant damaging lung
tissue and plants
Critically important to life
“ground-level ozone”
“global sunscreen”
UV-A reaches this layer
Absorbs UV-B and UV-C
• Formation and Breakdown of Ozone
- occurs in closed loop cycle
a. O2 + UV-C  2O
b. O2 + O  O3
c. O3 + UV-B or UV-C  O2 + O
• Ozone continuously formed/broken down in
presence of sunlight
• Anthropogenic Contributions to Ozone
Destruction
a. Chlorine
1. major source – CFCs
2. O3 + CL  ClO + O2
ClO + O  Cl + O2
O3 + O  2 O 2
3. catalyst, does not get used up
4. ozone no longer able to absorb UV-B
• Depletion of Ozone layer
a. greatest at the poles since 1970
b. “ozone hole” in Antarctica
1. seasonal depletion
2. cold weather
- build up of ice crystals mix with NO
- accumulation of Cl
3. sunny weather
- UV breaks down more Cl catalyzing
ozone destruction
• Effort to reduce ozone depletion
a. Montreal Protocol on Substances that
Deplete the Ozone Layer
- reduce CFC production 50% by 2000
Indoor Air Pollution
• Causes more deaths each year than outdoor
air pollution
• Developing v. developed
• Asbestos
a. insulating properties
b. respiratory diseases (lung cancer)
c. not dangerous until disturbed
• Carbon Monoxide
a. malfunctioning exhaust system
- typically natural gas
b. binds with hemoglobin more efficiently
than O2
c. lead to oxygen deprivation in brain
• Radon
a. Radon-222, decay of uranium
b. exists in bedrock
c. seep through crack in foundation
d. second leading cause of lung cancer
• VOCs in home products
a. strong aroma
b. glues, paints, formaldehyde
c. burning sensation of eyes, throat
• Sick Building Syndrome
a. high levels of VOCs and other pollutants
b. headaches, sore throat, fatigue
c. sources
- mold, pollen
- cleaning agents