What Causes Air Pollution? Chapter 12-1 What Causes Air Pollution?

Warm-up

Layers of the atmosphere Four layers: Troposphere Stratosphere Mesosphere Thermosphere

troposphere Densest of the atmospheric layers Almost all weather occurs here

stratosphere Ozone layer (O3) Ozone absorbs UV radiation 3O2 + UV  2O3

Mesosphere Very cold! Meteorites

thermosphere Very high temperatures Absorbs harmful solar radiation (X rays and gamma rays)

Temperature in the atmosphere

What Causes Air Pollution? Solids, liquids, or gases. Most air pollution is the result of human activities

What Causes Air Pollution? Some natural: dust, pollen, spores, and sulfur dioxide from volcanic eruptions Condensation nuclei

Categories of air pollutants Primary pollutants Secondary pollutants

Major outdoor air pollutants Carbon oxides: Carbon monoxide (CO) Carbon dioxide (CO2)

Major outdoor air pollutants NOx (nitrogen oxide and nitrogen dioxide) Nitrogen oxide (NO) Nitrogen dioxide (NO2) NOx play a role in the formation of photochemical smog

Major outdoor air pollutants SOx (sulfur dioxide and sulfuric acid) Sulfur dioxide (SO2) Sulfuric acid (H2SO4)

Major outdoor air pollutants Particulates Suspended particulate matter (SPM) – consists of a variety of solid particles and liquid droplets. Remain suspended in air. Sources Natural – Human –

Major outdoor air pollutants

Major outdoor air pollutants Ozone (O3) Volatile organic compounds (VOCs)

Major outdoor air pollutants

Secondary pollutant formation

Primary pollutants

History of air pollution The world’s air quality problem is much worse today because modern industrial societies burn large amounts of fossil fuels. Most air pollution in urban areas comes from vehicles and industry. London Smog

Case Study: Donora, PA

Motor vehicle emissions Almost 1/3 of our air pollution comes from gasoline burned by vehicles. Over 90% of that mileage was driven by passenger vehicles. The rest was driven by trucks and buses.

Controlling vehicle emissions The Clean Air Act (1970, strengthened in 1990) Environmental Protection Agency (EPA) the authority to regulate vehicle emissions in the USA Gradual elimination of lead in gasoline Catalytic converters required in all automobiles

Controlling Vehicle Emissions

California Zero-Emission Vehicle Program In 1990, the California Air Resources Board established the zero-emission vehicle (ZEV) program. Zero-emission vehicles are vehicles that have no tailpipe emissions, no emissions from gasoline, and no emission-control systems that deteriorate over time. By 2016, 16 percent of all vehicles sold in California are required to be zero- emission vehicles, including SUVs and trucks.

California Zero-Emission Vehicle Program ZEVs: Electric vehicles Hydrogen fuel cells vehicles Hybrid-electric cars (Partial ZEV)