The Atmosphere and Atmospheric Pollution

1. The Atmosphere and Atmospheric Pollution

2. Atmospheric Components • Chemical Components (elements) • Nitrogen gas (N2) makes up about 78% of the atmosphere • Oxygen gas (O2) makes up about 21% • Other gases (Ar, He, etc.) <1%

3. Atmospheric Components • Most abundant compounds: • Carbon dioxide (CO2) • Water vapor varies greatly • Evaporation () • Transpiration by plants () • Precipitation, condensation ()

4. Atmospheric Components • Other components • Ozone (O3) - UV filter in upper stratosphere; bad in troposphere • Dust - from volcanoes, sandstorms, fires, etc. (pretty sunsets!)

5. Atmospheric Layers Troposphere: • Closest to the Earth’s surface • All weather changes take place here • Most of CO2 and H2O vapor here • Height varies from about 20 km at equator to about 8 km at poles - Why? • Temperature decreases with height

6. Atmospheric Layers Stratosphere • Contains almost all the ozone (O3) in the atmosphere 3O2 +UV 2O3 • Temperature rises with altitude • Gases released from volcanic eruptions stay here for years • Tops of thunderclouds can penetrate

8. Outdoor Air Pollution

9. Outdoor Air Pollution The presence of atmospheric chemicals at concentrations high enough to harm organisms, ecosystem, or human-made materials Come from natural sources: dust, wildfires, VOCs (plants) Come from human sources: near industrialized/urban areas

10. Outdoor Air Pollution Is air pollution a recent development?

11. Outdoor Air Pollution Primary Pollutants: • emitted directly into the air Secondary Pollutants: • Products of chemical rxns of 1⁰ pollutants • Good news? • Bad news? • What is the biggest pollution threat to poor?

12. Outdoor Air Pollution Point source: specific spots where large quantities of pollutants are discharged (power plants and factories) Nonpoint source: more diffuse, consisting of many small sources (automobiles)

14. Outdoor Air Pollution Carbon Oxides: CO and CO2 • CO a result of incomplete combustion • CO from vehicle exhaust, tobacco smoke, forest fires, inefficient stoves, furnaces • Chronic exposure to CO: heart attacks, lung diseases • Acute exposure to CO: headache, nausea, drowsiness, death

15. Outdoor Air Pollution Carbon Oxides: CO and CO2 • CO2 in the atm: 93% a result of carbon cycle, rest is from human activity • Considerable evidence: human-introduced CO2 is changing the climate

17. Outdoor Air Pollution Nitrogen oxides (NOx): Nitric oxide (NO) • Formed from high-temp engines, coal plants, lightning, bacteria (N-cycle) 2NO + O2 → 2NO2 (brownish gas; photochemical smog) 2NO2 + H2O → 2HNO3 (acid deposition) • Eye, nose, throat irritant, aggravate lung ailments

19. Outdoor Air Pollution Sulfur oxides (SOx): Sulfur dioxide (SO2) • One-third comes from S cycle • Rest from coal-burning plants, oil refining, smelting • Converted to aerosols of H2SO4 – more on this later

21. Outdoor Air Pollution Particulates Solid particles and liquid droplets small enough to remain suspended • ~62% from natural sources • Human input: coal, cars, plowed fields, road construction, tobacco smoke • Fine (< 10μ) and ultrafine (<2.5μ) particles most damaging

22. Outdoor Air Pollution Particulates • Aggravate asthma, bronchitis • Shorten life Toxic particles (Pb, Cd, PCBs) • Cause mutations, reproductive problems, cancer • According to EPA: 60-70,000 deaths

23. Outdoor Air Pollution Ozone • Part of smog • Causes coughing, breathing problems, aggravates heart and lung disease • Reduce resistance to colds, etc. • Irritant; damages plants, fabrics, tires, paints • Good O3 v. bad O3

24. Outdoor Air Pollution Volatile Organic Componds (VOCs) • Organic cpds that exist as gas • Most are hydrocarbons • Methane is one example • Others: benzene, trichloroethylene, vinyl chloride are industrial solvents • Benzene →→ leukemia, blood disorders, immune damage, et al.

25. Outdoor Air Pollution Industrial Smog • Main components: SO2, H2SO4, other particulates • Most of carbon in coal, oil → CO, CO2, soot • Ammonium sulfate also produced • Not as problematic in developed countries

27. Outdoor Air Pollution Photochemical Smog • Activated by light • A mixture of 1⁰ and 2⁰ pollutants • Reactants: VOCs + NOx + sunlight • Products: O3, aldehydes, oxidants, HNO3, peroxyacyl nitrates (PANs) • Hotter days: more ozone • Natural smog: Smokey Mountains (terpenes)

29. Outdoor Air Pollution Factors Affecting: natural reduction • Settling • Precipitation • Ocean spray wash-out • Winds • Chemical reactions

30. Outdoor Air Pollution Factors Affecting: increase • Urban buildings slow winds • Hills/mountains • High temperatures (↑ rxn rates) • VOCs from oak, poplar trees, kudzu • Grasshopper effect – transport by global winds • Temperature inversion

32. Outdoor Air Pollution Control Prevention, Technology, Innovation • Fluidized bed combustion: coal burned w/ CaCO3, produces CaSO4, which is used to make sheetrock • Controlling T and O2 can reduce NOx • Catalytic converters also reduce NOx (also led to removal of Pb from gasoline) • Control of particulates: baghouse filters, electrostatic precipitators, scrubbers

34. Outdoor Air Pollution Control Prevention, Technology, Innovation • Municipal restrictions developed, including restrictions on dry-cleaners, gas stations, even bakeries (oh, no!), car use restrictions, carpool lanes • Clean Air Act amendments → reduced sulfur emissions; buying and selling of allowances that allowed release of certain amount of S

35. Acid deposition

36. Acid Deposition Industry Smokestacks • Reduce local air pollution • Increase regional pollution as SOx and NOx are carried downwind • Sulfuric and nitric acids are formed

38. Acid Deposition Acid Deposition • Remain in atmosphere 2 – 14 days • Fall as wet deposition (rain, snow) or dry deposition (crystals) • Some regional soils can buffer • Worst acid deposition - Asia

40. Acid Deposition Effects • Respiratory disease • Damages human-made structures • Leach toxic chemicals from soils/rock • Aquatic systems (ΔpH, release Al3+) • Forest, crop damage

41. Acid Deposition Reduction • Reduce coal use/use low-sulfur coal • Increase natural gas, renewable energy • Remove SOx and NOx from smokestacks • Tax emissions • Cleanup: lime to lakes, phosphate fertilizer

42. Indoor air pollution

44. Indoor Air Pollution Common Pollutants • Pesticides, lead (brought in on shoes) • Organic solvents • Dust mites, droppings • Molds and mildews • Formaldehyde & other VOCs • Radon

46. Indoor Air Pollution Alarming Facts (more harmful than outdoor) • Levels are generally higher in homes and cars (5x, 18x, respectively) • In developed countries, people spend more time inside • EPA: 18 indoor pollutants on carcinogen list

47. Indoor Air Pollution Sick Building Syndrome • Due in part to increased insulation • Indoor levels of VOCs and other materials increase • Synthetic materials (glues, etc) • Ventilation, chemical contamination, air intake, biological contamination

48. Health effects

49. Health Effects Natural Defense • Simple columnar epithelium contains cilia and produce mucus • This line of defense gets broken down • Particulates embed in alveoli • Emphysema is irreversible; alveoli damaged, lose surface area