Sustainable Air Quality

ME 449

Jan 14, 16; 2002

The Earth System• Atmosphere

– Conveyer of mass, moves mass source to receptor

– Small storage capacity• Hydrosphere

– River system – conveyer collects substances in watershed

– Oceans – long-term geochemical reservoir

• Lithosphere– Solid shell of inorganic matter at

surface of the Earth made of up of soil particles and rock down to 50km

– Within soil, biochemical reactions by microorganisms are responsible for most of the chemical changes of matter

• Biosphere– Thin shell of organic matter on the

Earth’s surface (occupies the least volume)

– Chemical pump for much of the flow of matter through nature

– Responsible for grand scale recycling of energy and matter on the Earth

Source Types and Emissions• Primary pollutants

– Substances that are emitted directly into the atmosphere– E.g. VOCs, NOX, CO, particulate matter (PM)

• Secondary pollutants– Pollutants formed in the environment through chemical or

photochemical transformations of primary pollutants– E.g. tropospheric ozone, PM

• Anthropogenic sources– Cars: NOX, VOCs, Pb, CO– Power plants: NOX, CO2, CO, SO2

– Agriculture: PM, NH4

• Natural sources– Wind blown dust: PM– Plants: VOCs– Volcanoes: SO2, PM– Fires: smoke (PM), CO2, Hg

Effects of Air Pollution

• Air pollution affects the following:– Human health (acute and chronic effects)– Animals– Plants– Materials– Visibility– climate

• The activities of humans result in direct emissions of pollutants to the atmosphere

• Once airborne, these pollutants are transported, transformed, and concentrated

• The resulting pollutants may have negative effects on humans, plants, animals, and nature

• As a result of negative effects, laws and regulations are promulgated to either alter the activities or control their emissions with “end of the pipe” controls. Both of these strategies aim to reduce emissions.

Example: London Fog• Population: London, a cold December week in 1957• Activity: home heating using soft, high-sulfur coal

• Emissions: SO2

• Transport: low wind speed – SO2 is accumulated

• Chemical transformation: SO2 SO42- acid aerosols

(H2SO4)

• Effect: 4000 deaths above normal (2.6% increase)• Regulation: Reduce the use of soft coal• Change Activity: fuel switching – change to hard coal, oil,

gas, electricity

Air Quality Management Feedback System