Chapter 17

Chapter 17
Air and Air Pollution
1. In what layers of the atmosphere are the
greatest concentrations of Ozone?
2. For each atmospheric layer you identified
in #1, how does that Ozone form?
3. What are the health benefits or harm that
result from Ozone in the atmosphere?
4. What is particulate pollution?
5. What type of particulate pollution is most
harmful to humans?
Quiz Answers
1. Troposphere and Stratosphere
2. Troposphere – ozone forms due to a
reaction between NOx (which forms as a
result of the combustion of fossil fuels) and
hydrocarbons in the presence of UV
Stratosphere – Ozone forms due to the
breakdown of O2 into 2 O’s which then recombines with O2 to make O3. This
reaction requires UV energy.
Quiz Answers Cont.
3. Tropospheric Ozone is harmful. It is an
irritant to mucus membranes
Stratospheric Ozone is beneficial. It
blocks 95% of UV rays which can be
harmful to plant and animal cells
4. Particulate pollution consists of fine airborn dust particles.
5. The very fine particles < 10microns are
most damaging to human and animal
Learning Objectives
 Students should know:
– The layers (especially the lower 2) of the
– The types and sources of outdoor air pollutants
– Two types of smog
– What acid deposition is and how it occurs
– The effects of air pollution on environmental
– Methods to reduce and prevent air pollution
Recall - Climate vs Weather
 Weather
– The day-to-day change in atmospheric
conditions on any spot on Earth
 Saturday was sunny, Monday it’s raining
 Climate
– The long-term average of temperature and
precipitation for a given region (average
weather by season)
No well defined
Very low density
High temperature
due to short-wave
solar radiation
absorption by O, N
increase due to
presence of good
Upper level
temperature due to
lower air density;
zone with weather
The Atmosphere
Major Classes of Air Pollutants
Carbon Oxides – CO, CO2
Sulfur Oxides – Sox
Nitrogen Oxides – NOx
Volatile Organics – VOC
Suspended particulate matter – SPM
Photochemical Oxidants – O3, PANS, H2O2
Radioactive Substances
Hazardous Air Pollutants – organic solvents
 Focus on Ozone
– Good Ozone
 Naturally occurring form of oxygen (O3)
 Occurs in the stratosphere
 Filters out and protects Earth from excess UV
radiation from the Sun
 Is not a greenhouse gas or contributor to
global climate change
3 O2+UV → 2O2+2O → 2O3
Ozone Depletion
 Focus on Ozone
– Bad Ozone
 Forms near ground level
 Occurs as a result of reactions with the
emissions of internal combustion engines
burning hydrocarbon fuel
 Causes respiratory irritation, often severe
NOx + VOC + 3 O2+UV → 2 O3
Ground Level Ozone Formation
OH + CO → H + CO2
H + O2 → HO2
HO2 + NO → OH + NO2
NO2 + UV → NO + O
O + O2 → O3
(The net effect of these reactions is)
CO + 2O2 → CO2 + O3
Ground Level Ozone Formation
 Photochemical Smog – formed by the
reaction between specific chemical
compounds and sunlight. Brown to orange
in color.
 Industrial Smog – results from industrial
processes, typically from the burning of
fossil fuels (coal, oil) and the emission of
particulate matter. Grey in color.
Photochemical Smog
 Source of pollutants – high temperature
combustion of fuels in the presence of air
(O2 and N2)
– N2 + O2  2NO
– 2NO + O2  2NO2
Nitrous Oxide
Nitrogen dioxide
 NO2 causes the brownish/orange haze in
areas with high traffic density or industrial
processes, especially on sunny days
 Also contributes to ground-level ozone
Industrial Smog
 Rare in developed countries with emission
 Common in developing countries which burn
leaded gasoline and coal without emission
controls (China Olympics problem)
Mexico City – 10 million people in a high-altitude
basin that has an abundance of UV and
geographically limited air flow due to mountains
around the city.
Normal – pollutants rise
up through cooler air
masses and disperse into
the upper atmosphere
Inversion – a warm air
layer is trapped between 2
cool layers. The warm air
cannot move upward and
forms a “cap” which traps
upward moving emissions
near the Earths surface
instead of dispersing
Great Smokey
Mountains National
Park – our most
polluted national park
Main pollution
SOX, Ozone
Source of Pollutants:
Neighboring states
coal-burning power
plants and auto
Acid Deposition
 The combination of compounds, that in the
atmosphere create dry or wet acids.
 Normally result from the NOx and SOx from
coal-burning power plants reacting in air to
– HNO3, H2SO4, HCO3
 Can be transported great distances (China
to U.S.)
 “Burns” plant life, causes damage to
Acid Deposition
Effects of Acid Deposition
 Damage to structures
 Alters pH of aquatic systems
– Many species have limited tolerance to low pH
– Lakes world-wide with limited aquatic life due to
acid deposition
 Alters soil pH and “burns” plants
– Soils may not buffer acid
– Plants have leaf/needle damage that limits
photosynthesis, weakens their ability to resist
insects and disease
Smokey Mountains
 Acid deposition is killing Spruce trees and
other vegetation
– Loss of native plant species is affecting
biodiversity of both terrestrial and aquatic
 Stream pH is decreasing, limiting numbers
of sensitive species like salamanders, trout,
and freshwater mollusks.
 Soils and rock have limited buffering ability
Unconventional Pollutants
• Unconventional Pollutants
o Regulated by emission standards
o Asbestos
o Mercury
o PCB’s
o Benzene
o Beryllium
o Other organics
o Aesthetic degradation
Criteria Pollutants
• Defined by U.S. Clean Air Act of
• Regulated to allow maximum
emission standards
Carbon monoxide - CO
Nitrogen Dioxides – NO2,
Sulfur Dioxide – SO2
Particulates – by size
Ozone – O3
EPA Targets Greenhouse Gases
Nitrous Oxide(s) or NOx
Sulfur hexafluoride.
April 17, 2009
Indoor Air Pollution
 Often a greater hazard than outside air
 Primary contaminants are:
– Fine particulate – lead, other metals
– Radon – naturally occurring
– Pesticides – chlordane (termite)
– Asbestos - insulation
– Formaldehyde – glues, adhesives
Solutions and change
 Outdoor Air Pollution
– Reduce use of fossil fuels
– Use low-sulfur coal and low-sulfur diesel
– Increase vehicle mileage standards (fewer emissions
per mile driven)
– Accelerate development of sustainable, non-emission
producing fuels
– Increase type and amount of pollutants removed in
scrubbing processes at point sources like power plants.
– Decrease surface disturbance of land areas (dust,
Solutions and Change
 Indoor Air Pollution
– Eliminate indoor smoking
– Change formulations to eliminate formaldehyde
in adhesives.
– Remediate/remove Asbestos
– Install more efficient air cleaners to remove
larger percentages of the particulate matter.
– Better ventilation and air exchange in buildings
Air Quality Laws and Options
 Clean Air Act (1970, 1977, 1990)
– …comprehensive federal law that regulates air
emissions from stationary and mobile sources.
This law authorizes EPA to establish National
Ambient Air Quality Standards (NAAQS) to
protect public health and public welfare and to
regulate emissions of hazardous air pollutants.
 Emission trading (cap and trade)
 Air Quality Monitoring