Chapter 8

1. Chapter 8 Air Pollution and Energy Use

2. Sources of air pollution • The combustion of gasoline and other hydrocarbon fuels in automobiles, trucks, and jet airplanes • The burning of fossil fuels in power plants, factories, office buildings • The incineration of garbage • Petroleum refineries, iron and steel mills, metal smelters, pulp and paper mills, chemical plants, cement and asphalt.

3. Effects of air pollution • Threatening human health • Causing respiratory infections • Deteriorating cardiovascular system • Encouraging the incidence of cancer • Harming environment • Contaminating the soil and water • Endangering the existence of wildlife and plants • Warming up the globe

4. Physics of air The earth is immersed in a “sea of air”. The atmospheric pressure at the sea level is equal to the pressure at the bottom of a column of 10-meter-high water. Atmospheric pressure can be measured by a barometer.

5. Air content • ppM stands for parts per million. • One ppM is one part per million parts examined

6. Buoyant force and the vertical motion of air A solid object will float if its density is equal or less than the density of the medium it is in. A parcel of air warmer than the surrounding air will rise because its density is less. Warm air rises until it cools down to match the temperature of the surrounding air

7. Air circulation • The temperature differences between air parcels are one of the factors responsible for the air circulation • Temperature differences are also responsible for general global air circulation. • The general air circulation patterns can take pollutants to travel large distances before settling out.

8. Temperature inversion The vertical motion of the air is an important mechanism for dispersing air pollutants. But the buoy-up air can be stopped by temperature inversion layer and the pollutants are trapped The inversion layer was the blame of the 1952 Great Smoke in London when thousands died because of the highly concentrated pollutants

9. Air pollutants and their sources • Air pollutants are in the form of • Particulates (small particles of solids or liquids) • Hydrocarbons (or volatile organic compounds) • Gases • Air pollutants can come from • Stationary sources (such as power plants, industrial processes) • Moving sources (such as automobiles)

10. Major air pollutants and their sources of emission (2003)

11. Particulates from natural sources • Particles can be • Dust from dry soil • Salt from ocean spray • Volcanic ash • Forest fire • Pollen • Diameters are usually greater than 1 micron if from natural sources

12. Particulates from man-made sources • Particles can be from • Coal burning • Iron and steel mills • Cement manufacturing • Wood burning • Diameters are usually less than 1 micron if from combustion

13. How big is one micron? 100 microns human egg cell 2 microns beads 20 microns cells carbon nanotubes in nanometers A demo

14. Health effects of particulates • Small particulates can get by the body filtering system and become deposited in lungs. • The particles reaching the inner lung can directly interfere with the respiratory system. • The toxin carrying particles can cause lung cancer.

15. Hydrocarbons • Also known as volatile organic compounds (VOCs). • From natural sources • Methane released from the decay of vegetation • Terpenes released from the trees in forests • From man-made sources • Evaporation of gasoline • Organic solvent • Tobacco smoke • Play an important role in the formation of photochemical smog

16. Carbon monoxide (CO) • A colorless, odorless, poisonous gas • Produced in automobile engines by the incomplete combustion of carbon in the gasoline fuel. • The poisoning effect of CO depends on both the concentration and the duration of exposure. • High concentration and hours of exposure to CO can cause nausea, loss of consciousness, and even death.

17. Why is carbon monoxide toxic? • CO has an affinity for hemoglobin 200 times more than that of oxygen. • CO can prevent the hemoglobin from distributing O2 in the body and lead eventually to suffocation.

18. Sulfur dioxide (SO2) • A colorless gas with suffocating odor • It arises primarily from the burning of fossil fuels containing sulfur, mostly coal (containing 6% sulfur). • Most SO2 comes from fuel combustion at stationary sources. • SO2 is irritating to the upper respiratory tract, can damage lung and induce respiratory diseases.

19. Acid rain (sulfuric acid) 1/3 from human activities + 1/2O2 SO2 SO3 2/3 from natural sources H2S, SO4 +H2O H2SO4 Rain water with pH values between 4.0 to 4.5 □ acidification of lakes□ damage to vegetation and forests□ building corrosion consequences

20. Nitrogen monoxide (NO) • NO is a colorless gas. • Produced from the combustion process due to the presence of N2 in the air. • A prevalent product from combustion. • Its toxicity is minor. • Can be oxidized further by ozone to form NO2.

21. Nitrogen dioxide (NO2) • NO2 is a reddish-brown gas. • A minor product from combustion. • A product of the oxidization of NO by ozone. • Its secondary effects are of environmental concern. • Can be smelled above 0.5 ppm. • Affects lung and eyes above 5 ppm. • Cause damages to lung, liver and heart at higher concentrations.

22. What is photochemical smog? • Photochemical smog is a combination of different gaseous and particulate pollutants. http://www.nslc.wustl.edu/education/courses/edu4741/lessons00/hillman/smog.jpg

23. The reactions lead to photochemical smog In the absence of hydrocarbons, O2, O3, NO, and NO2 are in rough equilibrium. In the presence of hydrocarbons, O, NO, and NO2 can react with hydrocarbons to form active organic radicals.

24. How is photochemical smog formed? • The organic radicals are highly oxidizing and irritating to eyes. • The consumption of O, NO, and NO2 prevents the destruction of O3 (ozone) and increases its concentration in lower atmosphere. • High concentration of ozone at ground level can cause damage to plants and result in lung inflammation. • Ozone at ground level is also responsible for smog’s odor.

25. Air pollution in Shanghai Dec 2006 Dec 2003

26. Automobile emission control • The leaner mixture of gasoline can reduce the emission of CO. • A closed ventilations system can capture evaporation of hydrocarbons in a storage canister. • The exhaust gas circulation system helps reduce the formation of NOx.

27. Stationary source pollution control 1 • Removal of particles larger than 50 microns An cyclone collector can pull down the heavy particles to the collection bag as the particles collide with the collector’s wall while undergoing the down-spiral motion.

28. Stationary source pollution control 2 • Removal of particles between 5 and 50 microns. The high-voltage ionizing effect of an electrostatic precipitator is capable of removing small particles. Before vs. After

29. Stationary source pollution control 3 • Removal of particles between 0.1 and 5 microns. Fabric filters are capable of removing submicron size particulates.

30. Stationary source pollution control 4 • Removal of SO2. Scrubbers with desulfurization chemicals can remove SO2 from the exhaust gas.