Chapter 15

1. Chapter 15 Air Pollution

2. HEALTH EFFECTS OF AIR POLLUTION Normal human lungs (left) and the lungs of a person who died of emphysema (right).

3. Air Pollution is a Big Killer • Spatial distribution of premature deaths from air pollution in the United States.

4. Air Pollution Throughout the Earth • Air pollution is the introduction of chemicals, particulate matter, or microorganisms into the atmosphere in high enough concentrations to cause harm • Natural (fires, volcanoes) or anthropogenic (cars, factories) • It is part of a global system • There are many inputs (sources) and outputs (what removes the sources) • In developed countries, pollution has decreased due to policies and improved technology • 6-major air pollutants

8. Primary and Secondary Pollutants • Primary pollutants are ones that are directly harmful from the source (smoke stack, exhaust pipe) • CO, CO2, SO2, NOx, VOCs, dust, microorganisms • Causes include factories, cars, wind and soil, volcanoes, forest fires, pollen, salt particles from the sea, etc. • Secondary pollutants are primary pollutants that have undergone transformation due to sunlight, water, oxygen, or other compounds • Ozone , acid rain • Harder to control • Point source pollution comes from a specific location • Nonpoint source pollution comes from many sources and is hard to trace back to its original source

10. Primary Pollutants Secondary Pollutants CO CO2 SO2 NO NO2 SO3 Most hydrocarbons HNO3 H3SO4 Most suspended particles H2O2 O3 PANs Most NO3– and SO42– salts Natural Stationary Sources Mobile Fig. 19-3, p. 442

11. Natural and Human Sources • Natural include volcanoes and fires (SOx, PM, CO, NOx), lightning (NOx), plants (VOCs), wind (dust) • Anthropogenic include on-road vehicles, non-road equipment, fires, wood combustion, industrial processes, waste disposal, fossil fuel combustion, electricity generation • Temperature inversions (when air gets warmer with height) traps pollutants • Heat island

13. Smog • Smog is an unhealthy mixture of air pollutants over urban areas • Industrial smog is a mixture of sulfur dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted mostly by burning coal. • Photochemical smog is dominated by oxidants (ozone) • One of most difficult types of pollution to control • Occurs when UV energy reacts with chemicals • Los Angeles smog kills 3,900/year and costs $28 billion/year • Happens in cities that are warm, sunny, and dry • Smog is decreased by precipitation, salty sea spray, wind, and emissions reduction • Smog is increased by urban buildings, hills, high temps, and the grasshopper effect

14. Industrial smog Photochemical smog

15. Acid Deposition • All rain is acidic, but not considered acid deposition unless pH is lower than 5.6 • Formation • NOx and SO2 is released from natural and anthropogenic sources • In presence of oxygen and water, they become secondary pollutants through chemical reactions. Forms nitric acid (HNO3) an sulfuric acid (H2SO4) • Break down further to form nitrates, sulfates, and H+, which create the acid precipitation • Travel huge distances before falling in precipitation • Clean air act has reduced this greatly

16. Continued… • Lower the pH of water bodies and reduce biodiversity • Release metals from the ground which are toxic to aquatic organisms • Nutrients leached from topsoil • Erode manmade structures • Respiratory problems • Build up of nitrogen and sulfur in soil

18. Emissions SO2 NOx Acid deposition H2O2 O3 Others PANs Susceptibility to drought, extreme cold, insects, mosses, & disease organisms Reduced photo-synthesis and growth Direct damage to leaves & bark Tree death Soil acidification Reduced nutrient & water uptake Root damage Leaching of soil nutrients Release of toxic metal ions Acids Lake Groundwater Fig. 19-9, p. 451

20. Solutions Acid Deposition Prevention Cleanup Reduce air pollution by improving energy efficiency Add lime to neutralize acidified lakes Reduce coal use Add phosphate fertilizer to neutralize acidified lakes Increase natural gas use Increase use of renewable energy resources Burn low-sulfur coal Remove SO2 particulates & NOx from smokestack gases Remove NOx from motor vehicular exhaust Tax emissions of SO2

21. Pollution Control • Use low sulfur coal and oil (more expensive), develop more efficient technologies, use less fuel… • Control of sulfur and NOx • Use fluidized bed combustion where coal is burned near calcium carbonate which absorbs ingredients and creates materials for wallboard • Cars use catalytic converters • Control of particulate matter • Let it settle with gravity, but than must dispose of ash • Filters allow gas through but not solids • Electrostatic precipitator charge particles so they stick together and then settle • Scrubbers use water and limestone that react with sulfur to produce gypsum (drywall)

23. Electrostatic Precipitator Cleaned gas Electrodes Dust discharge Dirty gas

24. Ozone Layer • Ground level ozone is harmful, stratospheric is necessary • Protect us from UV radiation (blocks 95%) • Ozone destruction • Chlorofluorocarbons (CFCs) are organic compounds that add chlorine to the atmosphere • UV radiation breaks CFCs down into chlorine and carbon atoms • Chlorine breaks down the ozone bonds O3 + Cl  ClO + O2 • In spring, UV radiation breaks the ClO apart and the free oxygen atom joins ClO + O  Cl + O2 (Cl is by itself) • Hole forms each spring over Antarctica

26. Hole over Antarctica • High-altitude polar stratospheric clouds form during the dark, frigid winter • Nitric acid in clouds splits chlorine off of CFCs • A polar vortex (swirling winds) traps chlorine • UV radiation in September (spring) sunshine dissipates the clouds and releases the chlorine • The chlorine destroys the ozone • December’s warmer air shuts down the polar vortex • Ozone-poor air diffuses, while ozone-rich air enters

27. Legislation • Air Pollution Control Act (1963) funded research and encouraged emissions standards • The Clean Air Act of 1970 • Set standards for air quality, limits on emissions • Provided funds for pollution-control research • Allowed citizens to sue parties violating the standards • The Clean Air Act of 1990 strengthened regulations for auto emissions, toxic air pollutants, acidic deposition, stratospheric ozone depletion • Introduced emissions trading for sulfur dioxide

28. The Montreal Protocol • Montreal Protocol = 196 nations agreed to cut CFC production in half by 1998 • Follow-up agreements deepened cuts, advanced timetables, and addressed other ozone-depleting chemicals • Industry shifted to safer, inexpensive, and efficient alternatives • Challenges still face us • CFCs will remain in the stratosphere for a long time • Nations can ask for exemptions to the ban

30. International agreements reduced ozone-depleting substances The hole in the ozone has stopped growing

31. Using scientific notation Anthropogenic chemicals are capable of destroying ozone in the stratosphere. One of the most threatening classes of man-made chemicals is cholorfluorocarbons, (CFCs). Chlorine enters the stratosphere through compounds known as chlorofluorocarbons (CFCs). CFC’s are a family of organic compounds whose properties make them ideal for use in refrigeration, air conditioning, and propellants in aerosol cans. Unfortunately, scientists have discovered that one chlorine atom has the ability to breakdown and destroy as many as 100,000 ozone molecules before leaving the stratosphere. Problem: Suppose that 200 CFC molecules entered the stratosphere. If one chlorine atom destroys 100,000 ozone molecules, how many ozone molecules would be destroyed by 200 CFC molecules? If the same number of CFC molecules entered the stratosphere each year for the next 30 years how many total ozone molecules would be destroyed?