The major air pollutants

The major air pollutants

• Carbon monoxide (CO)

• Nitrogen oxides (NOx)

• Ozone (O3)

• Particulate matter (PM-10, PM-2.5)

• Sulfur dioxide (SO2)

• Lead (Pb)

• Greenhouse gases (CO2 and others)

Carbon Monoxide• Impacts: Blood oxygen levels

• Headaches, alertness, death

• Sources: Vehicles (plus others)

Source: Ref. (1)

Carbon Monoxide• CO levels are improving, but still a problem

in many colder urban areas.

Source: Ref. (1)

Nitrogen Oxides• Impacts: Respiratory irritant

- Leads to ozone formation

- Leads to acidic deposition of HNO3

• Sources: High-temperature combustion

Source: Ref. (1)

Ozone• Impacts:

- Respiratory irritant

- Plant damage (forest, crops)

• Sources:

-Produced in the atmosphere

Ozone• A major urban and regional pollution problem

Source: Ref. (1)

Particulate Matter• Definitions:

- PM10 = PM < 10 um

- PM2.5 = PM < 2.5 um

• Impacts:

- Lung irritation

- Visibility

Particulate Matter• Impacts:

- Lung irritation

- Visibility

• Sources: Depends on particle size

Source: Ref. (1)

Particulate Matter• Impacts: Visibility at Shenandoah Nat’l Park

Source: Ref. (2)

Sulfur Dioxide• Impacts:

- Eye and lung irritation

- Acidic deposition of sulfuric acid.

- Damage to limestone and concrete.

• Sources:

Source: Ref. (1)

Sulfur Dioxide• Impacts: Acidic deposition of H2SO4.

Pure water pH = 5.6

Source: Ref. (3)

Lead• Impacts: Brain and kidney damage.

• Sources: Leaded gasoline was dominant,

but Pb is no longer in U.S. on-road gasolineSource: Ref. (1)

Lead• Impacts: Brain and kidney damage.

• Sources: Metals processing, battery mfr, etc

Source: Ref. (1)

Greenhouse Gases• Impacts: Global climate change

• Gases:

• Sources:

See : Ref. (4)

The Greenhouse EffectWhat determines the average temperature of the earth?

1.

Source: Ref. (5)

The Greenhouse EffectWhat determines the average temperature of the earth?

2.

The Greenhouse EffectWhat determines the average temperature of the earth?

3.

The Natural Greenhouse Effect

• Average solar radiation in:

236 W per square m

• Without the atmosphere, temperature would be:

-2 F

• Greenhouse effect of natural water and CO2:

148 W per square m

(1 lightbulb every 2 feet)

• Result: Average temperature =

57 F

The Human Contribution

Source: Ref. (6)

The Human Contribution

• Total effect until now: about 2.3 W / m2

(1 light bulb every 15 feet)

• Predicted effect by 2050: Up to 7 W / m2

(1 light bulb every 9 feet)

Expected Impacts:More precip, more energy in weather

• More extreme weather events are predicted

• On average, more precipitation, but

region-by-region, some will be wetter, some

drier.

CO2 Emissions by Nation

Developing nations

will soon be the largest

CO2 producers, but

most CO2 in the

atmosphere today came

from to industrialized

nations

Source: Ref. (8)

Particulate Activities

1. Light scattering

- Particles most effectively scatter light.

- Uncontrolled car exhaust scatters blue light.

- Atmospheric gases also scatter, blue more than red.

- Large concentrations of particle mixtures scatter all colors white haze

Haze in Los Angeles

Source: Ref. (9)

Local Issues1. Vehicle emissions

- Sources of CO, CO2, particulates, NOx, VOCs

- Strategies for reducing emissions Fuel economy (all, proportional to fuel

use) Catalytic converters and no exhaust

system leaks (CO, NOx, particulates, VOCs – no effect on CO2)

Local Issues2. Snowmobiles and wood stoves

- Snowmobiles: 2-cycle engines are light, but of the C burned,

- ~1/3 is fully burned and emitted as CO2.

- ~1/3 is emitted as CO.

- ~1/3 is not burned at all and released as gasoline.

Local Issues2. Snowmobiles and wood stoves

- Wood stoves:

- Newer wood stoves have catalysts or secondary combustion;

- those without emit more particles and VOCs

- Can compare by viewing chimney exhaust (don’t be fooled by water fog)

- Wood stoves can be a major source of indoor air pollution when smoke is pulled in from outdoors.

Local Issues3. Indoor air pollution

Key issues:

- Radon

- Molds

- Particles and smokes

PCBs

• “PolyChlorinatedBiphenyls”

• Used in transformers, as hydraulic fluids, …

• Chemically stable, thermally stable, high dielectric constants.

• Not broken down in the environment.

• Accumulate in animal fats.

• Cause birth defects.

• Manufacture in U.S. banned in 1977.

Stratospheric OzoneAntarctic ozone hole

Source: Ref (13)

Stratospheric OzoneDeclining outside of Antarctica

Source: Ref (5)

Stratospheric OzoneImpact on UV radiation

Source: Ref (5)

Stratospheric OzoneSuccess of the Montreal Protocol

Source: Ref (18)

Stratospheric OzoneSome common questions

• CFCs are heavier than air, so cannot reach the stratosphere.

• The ozone hole is natural, and is caused by volcanoes and oceans.

• Ozone depletion occurs only over Antarctica.

Roles of Ozone in the Lower Atmosphere

• Human health effects (urban and rural).

• Causes forest and crop damage (regional).

Ozone is an issue in urban areas and in large regions

Source: Ref (17)