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

• Primary – direct products of combustion and evaporation

• Secondary – when primary pollutants undergo further reactions in atmosphere

1. Suspended particulate matter (primary)

2. Volatile Organic Compounds (secondary)

3. Carbon Monoxide (primary)

4. Nitrogen Oxides (can be both)

5. Sulfur Oxides(primary from combustion of coal)

6. Ozone and other photochemical oxidants (secondary)

Acid Deposition• Acidic precipitation and dry fallout• Acids and BasespH-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 scaleAcidic-H+ ions under 7 on the pH scaleNeutral- pure water is 7 on the pH scaleNormal rain is slightly acidic-pH 6.4Acid rain is defined as less than a pH of 5.5

SourcesNatural: a. Sulfur: Volcanoes, sea spray, microbialb. Nitrogen oxides: lightening, forest fires, microbialAnthropogenic (human caused) a. Sulfur oxides: coal burning plants, industry, fossil

fuels.b. Nitrogen oxides: power plants, industrial fuel

combustion, transportationc. Effect areas hundreds of miles from the source of

emissions, generally not the whole globed. 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-sulfurb. increased fuel efficiency and appliance

efficiencyc. 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 combustion-produces 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