1. Air Quality and Pollution The challenge to manage our atmospheric resources well

2. Outline  Atmospheric stability and pollution dispersion Vertical stability Adiabatic lapse rate Thermal Inversions  Survey of “criteria” pollutants Emissions and concentrations Atmospheric reactions Effects

3. Seeking Vertical Equilibrium  As hot air rises, the pressure decreases, the temperature drops and the density drops.  When it reaches air of the same temperature (and density), it stops rising. T2T2 T1T1 > Tair 1 = Tair 2

4. Atmospheric Stability: Part II  A vertically stable atmosphere is one in which denser air is below and less dense air, above.  BUT…, if the air below is heated, it will become less dense, and will tend to rise until it reaches air of the same density.  Because of the sun’s heating and the earth’s cooling, the air is constantly rising and falling, seeking vertical equilibrium.

5. Adiabatic Lapse Rate  Air cools as it rises. ALR = -0.65 C / 100m  The surrounding air can be cooler or warmer as you go up.  If it is warmer, the rising hot air ( e.g. pollution) is trapped.  Inversion T h ALR hshs unstable stable 320K290K270K

6. Thermal Inversions  Radiation Inversion: On clear, winter nights, the earth cools off faster than the air. Lasts the morning hours.  Subsidence Inversion: High Pressure region “subsides” onto air below, compressing and heating it. Lasts up to several days. h T Subsidence Inversion Radiative Inversion

7. Atmospheric Temperature

8. Atmospheric Dispersion  Polluted air tends to be hot, initially.  As it rises, it tends to cool and disperse.  Turbulence due to vertical and horizontal instabilities speed up dispersion, until the pollution is well mixed.  “Dilution is the solution to pollution”!  Tall stacks designed to increase dispersion.

9. Pollution Concentrations  Pollution levels are measured in either PPM (parts per million) or in  g/m 3. 1 mole of anything contains N A = 6.02 x 10 23 particles. 1 mole of gas at STP occupies 0.0224 m 3. The “particle density” is then 2.69 x 10 25 particles per m 3. A pollutant concentration of 1 ppm tells us that for every 1 MILLION of those particles, ONE of them is the pollutant. It means that in 1 m 3, 2.69 x 10 19 molecules of pollutant are present. To convert to  g/m 3, we just need to know the mass per mole

10. 6 Criteria Pollutants  The federal EPA has identified 6 critical pollutants which are monitored nationwide.  CO, SO x, O 3 (VOC’s), NO x, Pb, Particulates (PM10).  NAAQS = National Ambient Air Quality Standards.  These standards set limits on allowable concentrations over time periods from 1 hour to a year.  http://www.epa.gov/airs/criteria.html http://www.epa.gov/airs/criteria.html

11. The EPA website  http://www.epa.gov/oar/aqtrnd97/brochure/sixpri n.html http://www.epa.gov/oar/aqtrnd97/brochure/sixpri n.html  The trend is positive, however…  107 million Americans live in counties in violation of one of the standards…that’s about 40%!  Illinois, Indiana are in the top three for emissions of particulates, SO and NO.

12. Other areas of concern  Acid Rain  Visibility  Global warming  Stratospheric Ozone depletion  Radioactive wastes