Air Pollution

• What controls the level? – Amount of pollutants entering the air.– Amount of space into which the pollutants are

dispersed.– Mechanisms that remove pollutants from the air.

• When is it a concern?– Exceed a threshold level– Threshold level depends on concentration and

duration of exposure, i.e. dose.

Dose = (concentration X exposure)

Major Primary Pollutants

1. Suspended particulate matter

2. Volatile organic compounds

3. Carbon monoxide

4. Nitrogen oxides

5. Sulfur oxides

6. Heavy metals

7. Air toxics (radon)

PANs = peroxyacetyl nitrates

The Hydroxyl Radical: Nature’s Cleanser (?)

Sources of These Emissions (Fig. 22-13)?

1) Sulfur dioxides

2) Nitrogen oxides

3) VOC’s

4) Particulate matter

5) Carbon monoxide

A) Fuel combustion

B) Transportation

C) Industrial processes

Emission Trends

Air Pollution Effects• Adversely affects human health

– Chronic– Acute– Carcinogenic

• Damages crops and forests– Necrotic – Chlorotic– Disease and Pest Susceptibility

• Damage to material & aesthetics– Corrosion– Oxidation– Smog

Smog I

Smog II

Temperature Inversions

Vehicles!

Photochemical Oxidants (Troposphere Ozone and PANs

Four Forms of Acid Deposition

pH Scale

pH = measurement of H ions in solution

Acid precipitation = pH < 5.5

Acid Deposition in the U.S.

2/3 sulfuric1/3 nitric

Coal burningpower plants

Effects of Acid Deposition on Aquatic Ecosystems

• Alteration of plant and animal reproduction

• Leaching of other toxic elements, e.g., Al

• Eutrophic to seemingly oligotrophic conditions

• Total loss of biota from aquatic ecosystems

• Alterations of food chains

Effects of Acid Deposition on Forest Ecosystems

• Leaching of nutrients• Release of aluminum into solution• Rapid changes in soil chemistry• Reduced growth and diebacks of plants

and animals• Increased flooding• Increased plant vulnerability to natural

enemies• Increased soil erosion• Increased sedimentation of waterways

Ecosystems Impacts are Not Equal.Limestone Buffers Acid Deposition.

Clean Air Act of 1970, 1977, 1990

• Identifies most widespread pollutants: e.g., particulates, SO, CO, NO, lead = criteria pollutants

• Set ambient standards = levels that protect environmental and human health

• Set national ambient air quality standards

• Set national emission standards for hazardous air pollutants

Title IV Clean Air Act 1990

• Reduce SO emission 50% below 1980 levels

• Improve methods of reducing SO emissions

• Allow emissions allowances and trading

• Emissions purchases• Reduce NO emissions

Future Responses to Air Pollution Control

• Increase fuel efficiency

• Emission-free vehicles

• Improving mass transit systems

• Reducing commuting distances

What are some potential societal reactions to these control measures?