1. Chapter 12: Air pollution A brief history of air pollution A brief history of air pollution Types and sources of air pollutants Types and sources of air pollutants Factors that affect air pollution Factors that affect air pollution Air pollution and the urban environment Air pollution and the urban environment Acid deposition Acid deposition

2. A brief history of air pollution

3. London’s historical problems London’s historical problems disastrous London smog event of 1952 disastrous London smog event of 1952 Donora, Pennsylvania pollution episode, 1948 Donora, Pennsylvania pollution episode, 1948 U.S. Clean Air Act, 1970, 1990 U.S. Clean Air Act, 1970, 1990

4. Types and sources of air pollutants

5. Principal air pollutants primary and secondary pollutants primary and secondary pollutants particulate matter particulate matter PM10, PM2.5 PM10, PM2.5 Carbon monoxide Carbon monoxide Sulfur dioxide Sulfur dioxide Globally, a large percentage of air pollution sources are natural. Within localized areas, however, human-caused sources are often the largest contributors Globally, a large percentage of air pollution sources are natural. Within localized areas, however, human-caused sources are often the largest contributors

6. Principal air pollutants Volatile organic compounds Volatile organic compounds nitrogen oxides nitrogen oxides Along with ozone, VOCs and NOx are major components of photochemical smog Along with ozone, VOCs and NOx are major components of photochemical smog

7. Ozone in the troposphere photochemical smog photochemical smog ozone ozone Photochemical smog is a problem on most major cities of the world Photochemical smog is a problem on most major cities of the world

8. Ozone in the stratosphere relationship to ultraviolet radiation relationship to ultraviolet radiation chlorine compounds chlorine compounds Montreal Protocol Montreal Protocol When scientists first measured extremely low ozone values in the Antarctic stratosphere, they thought the instruments were malfunctioning. When scientists first measured extremely low ozone values in the Antarctic stratosphere, they thought the instruments were malfunctioning.

9. Air pollution: trends and patterns Primary air quality standards Primary air quality standards secondary air quality standards secondary air quality standards Air Quality Index (AQI) Air Quality Index (AQI) Secondary air pollutants are particularly difficult to control, because they are not emitted directly into the atmosphere Secondary air pollutants are particularly difficult to control, because they are not emitted directly into the atmosphere

10. Factors that affect air pollution

11. The role of the wind dilution dilution turbulence turbulence mixing mixing “Dilution is the solution to pollution” - in the 1950s this motto led to the construction of tall smokestacks for large factories. Pollution was released higher in the atmosphere where winds were stronger. Air quality improved locally but suffered downwind. “Dilution is the solution to pollution” - in the 1950s this motto led to the construction of tall smokestacks for large factories. Pollution was released higher in the atmosphere where winds were stronger. Air quality improved locally but suffered downwind.

12. The role of stability and inversions temperature lapse rates temperature lapse rates inversions inversions mixing depth mixing depth The mixing layer can often be easily seen from an airplane. The mixing layer can often be easily seen from an airplane.

13. The role of topography cold air drainage cold air drainage air blockage by mountain ranges air blockage by mountain ranges

14. Severe air pollution potential sources sources high pressure high pressure inversions inversions stagnation stagnation Some locations, like Los Angeles and Mexico City, have an unfortunate combination of surrounding topography, frequent inversions, abundant emissions and plentiful sunlight - perfect conditions for photochemical smog. Some locations, like Los Angeles and Mexico City, have an unfortunate combination of surrounding topography, frequent inversions, abundant emissions and plentiful sunlight - perfect conditions for photochemical smog.

15. Air pollution and the urban environment

16. urban heat island urban heat island country breeze country breeze

17. Acid deposition

18. pH pH wet deposition wet deposition dry deposition dry deposition acid fog acid fog acid rain effects acid rain effects Strangely enough, an acidified lake looks crystal clear and beautiful. But the beauty is false; it’s only clear because nothing is alive in it. Strangely enough, an acidified lake looks crystal clear and beautiful. But the beauty is false; it’s only clear because nothing is alive in it.