Chapter 17 Air and Air Pollution

Transcription

1 Chapter 17 Air and Air Pollution

2 The Atmosphere Each layer characterized by abrupt changes in temperature, the result of differences in the absorption of incoming solar energy. Troposphere: Weather Breeder Stratosphere: Earth s Global Sunscreen

3 Outdoor Air Pollutants Air pollution: presence of one or more chemicals in the atmosphere in sufficient quantities and duration that 1) cause harm to us and 2) alter the weather Come from both natural and human activities Natural pollutants are spread out and rarely reach harmful levels In urban areas pollutants enter through stationary sources (power plants, factories) and mobile sources (vehicles)

4 Types of Outdoor Pollutants Primary Pollutants: emitted directly into the troposphere in a potentially harmful form. Soot or particulate matter (PM 10 ); lead, asbestos Hydrocarbons, CO, CO 2, SO 2,NO,NO 2 Volatile Organic Compounds (VOCs); paints, aerosols, dry cleaners Secondary Pollutants: caused by reaction of primary pollutants with the atmosphere SO 3, HNO 3, H 2 SO 4, H 2 O 2

5 Fig p. 421

6 Measurement Units Most common is parts per million (ppm) Example: concentration of 400 ppm of carbon monoxide would be equal to 0.04% Other common measurements: parts per billion (ppb or nano) and parts per trillion (ppt or pico)

7 Smog Photochemical smog (brown air smog): air pollution that is a mixture of primary and secondary pollutants catalyzed by sunlight Nitrogen-based NO 2 is responsible for the brown haze that hangs over cities during sunny afternoons Hydrocarbons, oxygen and NO 2 react to produce peroxyacyl nitrates (PANs) NO 2, O 3, and PANs are called photochemical oxidants Net Result: NO + VOCs + O 2 + UV = O 3 + PANS

8 Photochemical Smog

9 Smog cont Industrial Smog( gray air smog): consists of sulfur dioxide, sulfuric acid and aerosols Suspended particles of ammonium sulfate salts and carbon soot give the air a gray color. Urban industrial smog big problem in China, India, Ukraine where there are inadequate pollution control

10 Fig p. 424

11 Temperature Inversions Air temp. increases with height above the ground (normally decreases temp. with height) A layer of warm air lies atop a layer of cool air near the ground Because cooler air is denser than the warm air above it, the air near the ground cannot rise Pollutants can concentrate in this layer of cold air near the ground. 2 types: Subsidence temperature inversion (Los Angeles) Radiation temperature inversion

12 Acid Deposition Sometimes called acid rain Consists of rain, snow, dust, or gas with a ph lower than 5.6 In U.S. acid deposition regional problem in eastern states because coal burning power plants in Ohio Valley emit largest quantities of sulfur dioxide. Eastern precipitation has average ph and can get as low as 2.3 in some areas. Basic compounds CaCO 3 (limestone) can buffer some inputs of acids.

13 Indoor Air Pollution Come from 1) infiltration of polluted outside air and 2) chemicals used or produced inside buildings Health risks are magnified because people spend 70-98% if their time inside EPA linked pollutants inside buildings to sickbuilding syndrome 3 most dangerous pollutants Cigarette smoke, formaldehyde, radon-222 gas Radon very common in homes, seeps into through the soil into foundations and drain openings

14 Solutions: Preventing and Reducing Air Clean Air Acts Pollution 1963** (set emission standards for stationary sources power plants, etc) 1970** (included mobile sources; established Primary standard: protects human health Secondary standard: prevents environmental and property damage Directed EPA to establish national ambient air quality standards (NAAQS)

15 Improving the Clean Air Act To help reduce SO 2 emissions, CAA 1990 allows emissions trading policy Enables 110 most polluting power and industrial plants to buy and sell SO 2 pollution rights. Each year given certain # of credits that allow it to emit SO 2 Environmentalists point to deficiencies: Continuing to rely on pollution clean-up than prevention Failing to increase fuel efficiency for cars Not adequately regulating emissions