Transcript Ch 21 Air Pollution 2008-9

Ch. 21 Air Pollution
Air pollutants consist of chemicals in the
atmosphere that have harmful effects on
living organisms and/or inanimate objects.
Why Do We Care?
(humans)
• We inhale 20,000 liters of air each day
• Causes 150,000 premature deaths in the world each
year (53,000 in U.S.); aggravates other diseases
• U.S. human health costs from outdoor air pollution
range from $40 to $50 billion per year (CDC)
• Health impacts
- acute – pollutants bring on life-threatening
reactions w/in a period of hours or days; causes
headache, nausea, irritation
- Chronic – pollutants cause gradual deterioration of
health over years and low exposure
- Carcinogenic – pollutions that causes cancer e.g.
benzene
Why Do We Care? (not
human)
• Damage to Plants
- Agriculture – crops loss ~$5
billion/year
- Forests – significant damage to
Jeffrey and Ponderosa Pine along Sierra
Nevada; tree growth declined 75% in
San Bernardino Mountains
- suspected to increase plant diseases
and pests
• Damages buildings, bridges, statues,
books
• Aesthetics: It looks ugly. We all try to
avoid living in polluted areas (admit
it…)
Major Outdoor Air
Pollutants
•
•
1.
2.
3.
4.
5.
6.
Primary – direct products of combustion and evaporation
Secondary – when primary pollutants undergo further
reactions in atmosphere
Suspended particulate matter (primary)
Volatile Organic Compounds (secondary)
Carbon Monoxide (primary)
Nitrogen Oxides (can be both)
Sulfur Oxides(primary from combustion of coal)
Ozone and other photochemical oxidants (secondary)
Acid Deposition
• Acidic precipitation and dry fallout
• Acids and Bases
pH-log of hydrogen ions in a solution. Therefore
each number higher on the pH scale is 10X more
basic
Basic- OH- (hydroxyl ions) over 7 on the pH scale
Acidic-H+ ions under 7 on the pH scale
Neutral- pure water is 7 on the pH scale
Normal rain is slightly acidic-pH 6.4
Acid rain is defined as less than a pH of 5.5
Sources
Natural:
a. Sulfur: Volcanoes, sea spray, microbial
b. Nitrogen oxides: lightening, forest fires, microbial
Anthropogenic (human caused)
a. Sulfur oxides: coal burning plants, industry, fossil
fuels.
b. Nitrogen oxides: power plants, industrial fuel
combustion, transportation
c. Effect areas hundreds of miles from the source of
emissions, generally not the whole globe
d. Both sulfur oxides and nitrogen oxides are primary
components of acid rain.
Indoor Air Pollutants
1. Types: benzene, formaldehyde,
radon, cigarette smoke
2. Sources: off gassing from furniture,
rugs and building materials, dry
cleaning, cleaning fluids,
disinfectants, pesticides, heaters
3. Buildings with too many indoor air
pollutants are called “sick buildings”
because more than 20% of the
people are sick due to occupying the
building.
Solutions: Reducing
Emissions
Best way = Conservation, just use less!
Input Control (pollution prevention)
a.
Cleaner burning gasoline and coal with
low-sulfur
b. increased fuel efficiency and appliance
efficiency
c. alternative modes of transportation
-Mass transit, Walking, Bicycling,
Electric vehicles
d. Switch to renewable forms of energy
Reducing Emissions (input
control)
d. catalytic converter- complete oxidation of
hydrocarbons (VOCs) and carbon monoxide
to CO2 and H2O
Output Pollution
Control
•
•
Coal washing-using large
amount of H2O to leach
out the sulfur
Fluidized bed combustionproduces a waste ash that
must be disposed of
Output Control
Technologies
Scrubbers are “liquid filters”
• The exhaust from burning fossil fuels runs
through a spray of H2O containing lime
(CaCO3)
• SO2 + CaCO3  CaSO3 + O2
• Required since 1977