Unit 7– Atmospheric Pollution

Module 42: Introduction to Air pollution

Air pollution sources are widespread and their effects vary
- Classifying pollutants
  - Six defined by clean air act: sulfur dioxide, nitrogen oxides, carbon monoxide, particulate matter, trophospheric ozone, and lead (and carbon dioxide)
  - Coal and oil
  - Major air pollutants
    - Sulfur dioxide: combustion of fuels w sulfur, respiratory irritant
    - Nitrogen oxides: all combustion, respiratory irritant
    - Carbon monoxide: incomplete combustion, kills ppl
    - Particulate matter: physical combustion of matter, respiratory disease/ haze and smog
    - Lead: gas, paint, lining, impairs nervous system
    - Ozone: sunlight combined by VOCs and nitrogen oxide, degrades plants, reduces lung function
    - VOC: evaporation of fuel, precursor to ozone
    - Mercury: mining, coal etc, bioaccumulates, impair central nervous system
    - Carbon dioxide: combustion, global warming/ greenhouse gases
Primary and secondary pollutants have decreased over time
- Primary pollutants come out of smokestacks
- Secondary pollutants undergo transformations, like ozone, acid rain, etc
Air pollution sources can be identified and hav decreased over time
- Monitor concentrations etc

Module 43: Photochemical smog, thermal inversions, atmospheric CO2, and particulates

Photochemical smog is a complex combination of compounds and it can be reduced by decreasing emissions of its precursors
- Ozone concentration increases throughout the day w sunlight
- Chemistry of ozone and photochemical smog formation
  - Sunlight and ultraviolet causes heat which causes conversion, then reverts back
  - Importance of temperature: only happens in heat and sun
  - Smog and human health: smog is bad for humans
Thermal inversions trap air pollutants close to earth’s surface
- Trapped air traps pollutants under the cool air that doesn’t rise, causing pollution events
- Example: Tianjin
Volcanoes, forest fires, respiration, and decomposition are natural processes responsible for particulate emissions and carbon dioxide
- Natural sources of particulates
  - Dust
  - Volcanoes, forest fires
  - Particulates of smaller sizes are a bigger threat
  - Cause haze
- Natural sources of carbon dioxide:
  - Anaerobic decomposition

Module 44: Indoor air pollutants

Indoor air pollutants come from natural, human made, and combustion sources
- Carbon monoxide: incomplete combustion that kills ppl
- Particulates:
  - Smoke: respiratory infections
  - Dust and mold: waste from humans and bacteria
- Asbestos: from human insulation, causes mesothelioma
- Radon: gas that forms from uranium decay, leads to cancer
- VOCs: used in building really anything, harmful when inhaled
- Lead: piping, causes brain issues
- Other pollutants: nitrogen oxide, sulfur
Indoor air pollution in the developing world comes mostly from indoor combustion while the developed world tightly sealed buildings and VOCs are a bigger problem
- Developing countries
  - Manure, coal, wood, increases particulates
- Developed countries
  - Improved insulation can help save energy but traps pollutants

Module 45: Reduction of Air pollutants

Air pollution can be controlled by prevention, conservation, fuel switching, and regulatory practices
- Avoiding in the first place decreases emissions
- Regulatory practices
  - Measures like vapor recovery nozzles
  - Cap and trade, where ppl are given an allowance for a certain amount and pay penalties, that can be bought and sold by anyone
Control devices convert pollutants to less harmful compounds or remove them from the exhaust stream
- Converting pollutants to less harmful compounds
  - Catalytic converter nitrogen oxide —> carbon dioxide
- Removing pollutants from waste streams
  - Scrubbers use water to remove particles
  - Electrostatic precipitators use electrical charges to remove particles from the exhaust stream

Module 46: Acid Rain and Noise Pollution