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Environmental Science A Study of Interrelationships Tenth Edition Enger • Smith Chapter 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Air Quality Issues Chapter 17 2 Outline • • • • • • • • The Atmosphere Categories of Air Pollutants Control of Air Pollutants Acid Deposition Ozone Depletion Global Warming and Climate Change Addressing Climate Change Indoor Air Pollution 3 The Atmosphere • The atmosphere is composed of 78.1% N, 20.9% O and about 1% of other gases such as argon, carbon dioxide, methane, and water vapor. – Most of the atmosphere is held close to the earth by the pull of gravitational force, thus it gets thinner with increasing distance from the earth. 4 The Atmosphere • • • • Troposphere extends from the earth’s surface to about 10 km above the earth. Stratosphere extends from the top of the troposphere to about 50 km above the earth. – Most ozone located in a band between 15 and 30 km. Mesosphere extends from 50-80 km above the earth. Thermosphere extends to about 300 km above the earth. 5 The Atmosphere 6 The Atmosphere • • As the atmosphere absorbs heat from the earth, it expands and rises. – When heat is radiated into space, air cools, becomes more dense, and flows toward the earth. Air quality degraded by multiple sources. – Air pollution includes both aesthetic and human health problems. 7 Air Pollution and Population Centers 8 The Atmosphere • Many of the mega cities of the developing world have extremely poor air quality. – Increases death rate and lowers general health of the population. Chronic coughing and susceptibility to infections are common. 9 Categories of Air Pollutants • Primary Air Pollutants – Five major materials released directly into the atmosphere in unmodified forms. Secondary air pollutants form under reaction of primary pollutants and water or sunlight. – Criteria Air Pollutants are those pollutants for which specific air quality standards have been set. 10 Primary Air Pollutants • Carbon Monoxide - Produced when organic materials are incompletely burned. – Single largest source is the automobile. – Not a persistent pollutant. – Binds to hemoglobin in blood and makes the hemoglobin less able to carry oxygen. 11 Carbon Monoxide • Most dangerous in enclosed spaces. – Cigarette smoking an important source. U.S. levels have decreased by about 21% between 1993 and 2003. Increasing number of cars on the road and miles driven, can offset savings from catalytic converters. 12 Primary Air Pollutants • Particulate Matter - Minute pieces of solid materials (< 10 microns) dispersed into the atmosphere. – PM10 and PM 2.5 Larger than 2.5 microns are primary pollutants; Smaller than 2.5 are mostly secondary pollutants. Can accumulate in lungs and interfere with the ability of lungs to exchange gases. 13 Particulate Matter • Amount of PM10 has decreased 9% between 1996 and 2002. – U.S. EPA has been setting PM2.5 standards for a shorter period of time. Amount decreased 7% between 1996 and 2002. 14 Primary Air Pollutants • Sulfur Dioxide (SO2) - Sulfur and oxygen compound produced when sulfur-containing fossil fuels are burned. – Burning coal releases SO2. Today over 65% of SO2 released into the atmosphere is primarily from coal-burning power plants. U.S. levels of SO2 decreased 30% between 1993 and 2002. 15 Primary Air Pollutants • Nitrogen Dioxide – Oxides of Nitrogen (NOx) - Formed when combustion takes place in the air. N and O molecules from the air may react with one another. Nitrogen Monoxide NO Nitrogen Dioxide NO2 Automobile engine is primary source. U.S. levels decreased 10% between 1993 and 2002. 16 Primary Air Pollutants • Lead – Lead (Pb) can enter the body through breathing airborne particles or consuming lead deposited on surfaces. Leaded gasoline was primary source. North American lead levels fell 94% between 1982 and 2002. Currently, about 80% of gasoline sold in the world is unleaded. 17 Lead Emissions 18 Primary Air Pollutants • Volatile Organic Compounds – Hydrocarbons - Group of organic compounds consisting of carbon and hydrogen. Evaporated from automobile fuel or remnants of fuel incompletely burned. Catalytic converters used to burn exhaust gases more completely. U.S. levels decreased 25% between 1993 and 2002. 19 Ground-Level Ozone • Ozone (O3) is a molecule of three oxygen atoms bonded to one another. – Extremely reactive secondary pollutant. Permanent Lung Damage Damages Plants Destroys Chlorophyll 20 Photochemical Smog • A mixture of primary and secondary pollutants. Forms when primary pollutants interact under the influence of sunlight. – Two most destructive components: Ozone Peroxyacetyl Nitrates – Large cities ringed by mountains tend to have trouble with photochemical smog. 21 Daily Changes in Photochemical Smog 22 Photochemical Smog • Thermal Inversions - Warm air becomes sandwiched between two layers of cold air and acts like a lid on the valley. – Warm air cannot rise, causing smog accumulation. 23 Thermal Inversion 24 Hazardous Air Pollutants • Hazardous Air Pollutants (HAP) or Air Toxics are compounds that can harm human health or damage the environment. – Some released from consumer activities: Benzene escapes during automobile refueling. – Majority released from manufacturing: Perchloroethylene released from dry cleaning processes. 25 Control of Air Pollution • Motor Vehicle Emissions – U.S. regulations have pressured the automobile industry to reduce emissions. Positive Crankcase Ventilation Valve (PCV) Air Pollution Control Valves (APC) Catalytic Converters Lead-Free Fuel 26 Control of Air Pollution • Particulate Matter Emissions – Industrial Activities Mining – Improper Land Use Overgrazing – Fossil Fuel Burning Diesel Fuel – Personal Activities Fireplaces and Wood-Burning Stoves 27 Control of Air Pollution • Power Plant Emissions – Sulfur Removal Switch to low-sulfur fuel. Remove sulfur from fuel before use. Scrubbing gases emitted from smokestack. 28 The Clean Air Act • Clean Air Act – Series of detailed control requirements the federal government implements and states administer. Emissions of six worst air pollutants dropped 48% from 1973 to 2002, despite an increase in energy consumption of 42%. EPA estimates benefits have outweighed costs 40 to 1. 29 Acid Deposition • Acid Deposition is the accumulation of potential acid-forming particles on a surface. – Sulfur Dioxide and Nitrogen oxides are carried aloft by wind and form secondary pollutants (acids), and then are carried back to earth in wet (snow, rain, fog) and dry (particulate) form. 30 Sources of Acid Deposition 31 Acid Deposition - Harmful Effects • • • • Property / Structural Damage – Limestone Degradation Foliage Damage – Acidic Soil - Reduced Nutrient Absorption Weakened Plant Defenses – Stressors Lake Acidification Food Chain Disruption 32 Ozone Depletion • Ozone is formed in the stratosphere when high energy ultraviolet radiation splits diatomic oxygen into atomic oxygen. – The atomic oxygen may then combine with another diatomic oxygen molecule to form triatomic oxygen (Ozone - O3). 33 Ozone Depletion • In the 1970’s, it was discovered that CFCs were lowering the average concentration of ozone in the stratosphere. – CFCs take 10-20 years to make it into the stratosphere. Can react with ozone for up to 120 years. 34 Ozone Depletion • In the stratosphere, UV radiation breaks down CFC molecules, releasing atomic chlorine. A free chlorine atom reacts with an ozone molecule, converting it from O3 to O2. – Montreal Protocol (1987). Several industrialized countries agreed to reduce CFC production by 50% by 2000. As a result, emissions dropped 87% from their peak in 1988. 35 Global Warming and Climate Change • • Climatic records indicate over past 160,000 years, a correlation between greenhouse gas concentration and global temperatures. UN established Intergovernmental Panel on Climate Change (IPCC) – 1996 Assessment - Concluded climate change is occurring and it is highly probable human activity is importance cause of the change. 36 Global Warming and Climate Change • IPCC Conclusions – Average temperature of the earth increased .5 to 1.0 degrees Fahrenheit over the last 100 years. – Strong correlation between temperature increase and amount of greenhouse gases in the atmosphere. – Human activity greatly increases amounts of greenhouse gases in atmosphere. 37 Changes in Average Global Temperature 38 Causes of Global Warming and Climate Change • Greenhouse Effect – Greenhouse gases allow sunlight to penetrate the atmosphere. – Absorbed by earth’s surface. – Reradiated as infrared energy (heat). Absorbed by gases. 39 Greenhouse Effect 40 Greenhouse Effect • • • • Carbon Dioxide – Fossil fuel burning, deforestation. Chlorofluorocarbons – Refrigerants, cleaning solvents, propellants. Methane – Breakdown of organic material by anaerobic material. Nitrous Oxide – Biomass burning - Breakdown of nitrogenrich products. 41 Potential Consequences of Global Warming • • Rising Sea Level – Beach and coastal wetland erosion. Disruption of Water Cycle – Navigation – Hydropower – Water Supply and Demand – Flood Control – Environmental Quality and Recreation – Political Issues 42 Potential Consequences of Global Warming • Health Effects – Most direct effect of climate change would be impacts of hotter temperatures. Hot temperatures force cardiovascular system to work harder to cool the body. Heat exhaustion and some respiratory problems increase. Aggravate air quality problems. Ozone 43 Potential Consequences of Global Warming • • • Changing Forests – Geographic distributions of vegetation. Challenges to Agriculture – Increased CO2 concentration likely to increase crop yields in some areas and decrease yields in other areas. – Pest range expansion could increase vulnerability. Unanticipated Changes – Greatest risks may be those yet to be discovered. 44 Effects of Global Warming 45 Addressing Climate Change • • Energy Efficiency – Increase efficiency of energy utilization. Reduce carbon dioxide production. Carbon Tax Role of Biomass – Increase amount of carbon dioxide removed from the atmosphere. Increased vegetation growth. Short-term benefit. 46 Addressing Climate Change • Political and Economic Forces – Will be difficult to achieve global consensus to reduce CO2 emissions, as CO2 is released as a result of energy consumption which affects all sections of the economy. Resources and policies to increase investment in renewables and other long-term technologies will be needed. 47 Indoor Air Pollution • Growing evidence indicates air within homes and other buildings can be more seriously polluted than industrialized cities. – Adverse effects on human health. Asbestos Formaldehyde Airborne Pesticide Residues Perchloroethylene Paradichlorobenzene 48 Indoor Air Pollution • • • Smoking most important pollutant. Weatherizing to increase efficiency slows air exchange and tends to trap pollutants. Average person spends almost 90% of time indoors. – Movements to reduce indoor air pollution lag behind regulations governing outdoor air pollution. 49 Review • • • • • • • • The Atmosphere Categories of Air Pollutants Control of Air Pollutants Acid Deposition Ozone Depletion Global Warming and Climate Change Addressing Climate Change Indoor Air Pollution 50 51