4/12. There is so much pollution in the air now that if it weren t for our lungs there d be no place to put it all. Robert Orben

Transcription

1 4/12 There is so much pollution in the air now that if it weren t for our lungs there d be no place to put it all. Robert Orben

2 Chapter 15 Air Pollution and Stratospheric Ozone Depletion

3 Air Pollution Air pollution- the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems.

4 Major Air Pollutants Sulfur Dioxide Nitrogen Oxides Carbon Oxides Particulate Matter Volatiles Organic Compounds Ozone Lead Mercury

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7 Primary Pollutants Primary pollutants- polluting compounds that come directly out of the smoke-stack, exhaust pip, or natural emission source. Examples: CO, SO2, NOx, and most suspended particulate matter.

8 Secondary Pollutants Secondary pollutants- pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds. Examples: ozone, sulfate and nitrate

9 Primary Pollutants CO CO 2 SO 2 NO NO 2 Most hydrocarbons Most suspended particles Secondary Pollutants SO 3 HNO 3 H 2 SO 4 H 2 O 2 O 3 PANs Most NO 3 and SO 2 4 salts Sources Natural Stationary Mobile

10 Primary Pollutants CO CO 2 SO 2 NO NO 2 Most hydrocarbons Most suspended particles Secondary Pollutants SO 3 HNO 3 H 2 SO 4 H 2 O 2 O 3 PANs Most NO 3 and SO 2 4 salts Sources Natural Stationary Mobile

11 Natural Sources of Air Pollution Volcanoes Lightning Forest fires Plants

12 Anthropogenic Sources of Air Pollution On-road vehicles Power plants Industrial processes Waste disposal

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14 Photochemical Smog

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16 Thermal Inversions Thermal Inversion- when a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below. The warm inversion layer traps emissions that then accumulate beneath it.

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18 Acid Deposition Acid deposition- occurs when nitrogen oxides and sulfur oxides are released into the atmosphere and combine with atmospheric oxygen and water. These form the secondary pollutants nitric acid and sulfuric acid. These secondary pollutants further break down into nitrate and sulfate which cause the acid in acid deposition.

19 Acid Deposition

20 Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Nitric oxide (NO) Acid fog Sulfur dioxide (SO 2 ) and NO Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Wet acid deposition (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) Ocean Farm Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic General formation of acid rain

21 ph of rainfall across the US in relation to coalburning power plants and industrial plants

22 ph of rainfall across the US in relation to coalburning power plants and industrial plants

23 Effects of Acid Deposition Lowering the ph of lake water Decreasing species diversity of aquatic organisms Mobilizing metals that are found in soils and releasing these into surface waters Damaging statues, monuments, and buildings

24 Acid deposition Emission SO 2 H 2 O 2 PANs NO X O 3 Others Effects of Acid Rain on plants and soil Direct damage to leaves and bark Reduced photosynthesis and growth Increased Susceptibility to drought, extreme cold, insects, mosses, and disease organisms Soil acidification Tree death Leaching of Soil nutrients Acid Release of toxic metal icons Root damage Reduced nutrient and water uptake Groundwater

25 Ways to Prevent Air Pollution Removing sulfur dioxide from coal by fluidized bed combustion Catalytic converters on cars Scrubbers on smoke stacks Baghouse filters Electrostatic precipitators

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29 CLEAN AIR LEGISLATION Clean Air Act (1963) - First national air pollution control. (using incentives and federal grants to states) Clean Air Act (1970) rewrote original Act. Identified critical pollutants Established ambient air quality standards. Primary Standards - Human health Secondary Standards - Materials, environment, aesthetic and comfort. 38

30 4/14 When I was a kid, we never heard of smog, ozone depletion, acid rain, green house gasses. Dennis Weaver

31 Stratospheric Ozone The stratospheric ozone layer exists roughly kilometers above the Earth. Ozone has the ability to absorb ultraviolet radiation and protect life on Earth.

32 Formation and Breakdown of Ozone First, UV-C radiation breaks the bonds holding together the oxygen molecule O2, leaving two free oxygen atoms: O2 + UV-C -> 2O Sometimes the free oxygen atoms result in ozone: O2 + O -> O3 Ozone is broken down into O2 and free oxygen atoms when it absorbs both UV-C and UV-B ultraviolet light: O3 + UV-B or UV-C -> O2 + O

33 Anthropogenic Contributions to Ozone Destruction Certain chemicals can break down ozone, particularly chlorine. The major source of chlorine in the stratosphere is a compound known as chlorofluorocarbons (CFCs) CFCs are used in refrigeration and air conditioning, as propellants in aerosol cans and as blowing agents to inject air into foam products like Styrofoam.

34 Anthropogenic Contributions to Ozone Destruction When CFCs are released into the troposphere they make their way to the stratosphere. The ultraviolet radiation present has enough energy to break the bond connecting chlorine to the CFC molecule. Which can then break apart the ozone molecules.

35 Anthropogenic Contributions to Ozone Destruction First, chlorine breaks ozone s bonds and pulls off one atom of oxygen, forming a chlorine monoxide molecule and O2: O3 + Cl -> ClO + O2 Next, a free oxygen atoms pulls the oxygen atom from ClO, liberating the chlorine and creating one oxygen molecule: ClO + O -> Cl + O2 One chlorine atom can catalyze the breakdown of as many as 100,000 ozone molecules before it leaves the stratosphere.

36 Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl 3, breaking off a chlorine atom and leaving CFCl 2. Sun Cl Cl C Cl F UV radiation Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. Cl Cl O O The chlorine atom attacks an ozone (O 3 ) molecule, pulling an oxygen atom off it and leaving O an oxygen O O molecule (O 2 ). Cl A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O 2. Cl O O The chlorine Cl atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). O O O

37 Depletion of the Ozone Layer Global Ozone concentrations had decreased by more than 10%. Depletion was greatest at the poles Decreased stratospheric ozone has increased the amount of UV-B radiation that reaches the surface of Earth.

38 Indoor Air Pollutants Wood, animal manure or coal used for cooking and heating in developing countries. Asbestos Carbon Monoxide Radon VOCs in home products

39 Chloroform 1, 1, 1- Trichloroethane Para-dichlorobenzene Tetrachloroethylene Formaldehyde Nitrogen Oxides Styrene Benzo-α-pyrene Particulates Asbestos Tobacco Smoke Radon-222 Carbon Monoxide Methylene Chloride Fig , p. 453