G. Tyler Miller’s Living in the Environment 14th Edition Chapter 20 Air Pollution
Case Study: When is a Lichen Like a Canary
Key Concepts • Structure and composition of the atmosphere • Types and sources of outdoor air pollution • Types, formation, and effects of smog • Sources and effects of acid deposition • Effects of air pollution • Prevention and control of air pollution
Earth’s Atmosphere Compared to the size of the Earth (12000 km) The atmosphere is very thin (120 km) or (75 miles) http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm
If theEarthis compared to this Orange the Earth’s atmosphere would be thinner than the layer of pesticide on this Orange’s surface
Two Atmosphere Layers • Stratosphere is above the Troposphere • Ozone Layer blocks UV radiation • Troposphere is where we live • Weather occurs here • 78% Nitrogen, 21% Oxygen, 0.01%-4% water vapor, less than 1% Argon, 0.038% Carbon dioxide and trace amounts of several other gases • 72% of all air is below the cruising altitude of commercial airliners (33000 ft)
Atmospheric pressure (millibars) Temperature Pressure Mesopause Stratopause Tropopause 0 200 400 600 800 1,000 120 75 110 65 Thermosphere 100 90 55 80 Heating via ozone Mesosphere 50 mi. 45 70 Altitude (miles) 60 Altitude (kilometers) 35 50 Stratosphere 31 mi. 40 25 30 15 Ozone “layer” 20 Heating from the earth Troposphere 11 mi. 10 5 Pressure = 1,000 millibars at ground level 0 –80 –40 0 40 80 120 (Sea Level) Temperature (˚C)
O3 -The Good (15 - 40 km)blocks solar UV l<290 nm Beneficial Ozone that forms in the stratosphere protects life on earth by filtering out most of the incoming harmful UV radiation emitted by the sun
O3 -The Bad 6-10 km : greenhouse gas absorbs IR emitted by Earth O3 →O3 (v=1) Harmful or Photochemical ozone forms in the troposphere when various air pollutants undergo chemical reactions under the influence of sunlight. Ozone in this atmosphere near the earth’s surface damages plants, lung tissue, and some materials such as rubber.
O3 -The Ugly part of smog (bad, too)
Photochemical ozone 40 25 35 20 Stratosphere 30 25 Stratospheric ozone 15 Altitude (kilometers) Altitude (miles) 20 10 15 10 5 Troposphere 5 0 0 0 5 10 15 20 Ozone concentration (ppm)
20-2 Outdoor Air Pollution Air pollution is the presence of chemicals in the atmosphere in concentrations high enough to affect climate and harm organisms and material. Outdoor air pollutants come mostly from Natural sources (dust, VOC, decay of plants, forest fires, volcanic eruption, and sea spray) Burning fossil fuels Motor vehicles Power and industrial plants
Table 20-1 Major Classes of Air Pollutants Class Carbon oxides Sulfur oxides Nitrogen oxides Volatile organic compounds (VOCs) Suspended particulate matter (SPM) Photochemical oxidants Radioactive substances Hazardous air pollutants (HAPs), which cause health effects such as cancer, birth defects, and nervous system problems Examples Carbon monoxide (CO) and carbon dioxide (CO2) Sulfur dioxide (SO2) and sulfur trioxide (SO3) Nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O) (NO and NO2 often are lumped together and labeled NOx) Methane (CH4), propane (C3H8), chlorofluorocarbons (CFCs) Solid particles (dust, soot, asbestos, lead, nitrate, and sulfate salts), liquid droplets (sulfuric acid, PCBs, dioxins, and pesticides) Ozone (O3), peroxyacyl nitrates (PANs), hydrogen peroxide (H2O2), aldehydes Radon-222, iodine-131, strontium-90, plutonium-239 (Table 3-1, p. 49) Carbon tetrachloride (CCl4), methyl chloride (CH3Cl), chloroform (CHCl3), benzene (C6H6), ethylene dibromide (C2H2Br2), formaldehyde (CH2O2) Table 20-1Page 436
2 – SO4 NO3 – Primary Pollutants CO CO2 Secondary Pollutants SO2 NO NO2 SO3 Most hydrocarbons HNO3 H2SO4 Most suspended particles H2O2 O3 PANs Most and salts Sources Natural Stationary Mobile
Major Sources of Primary Pollutants Stationary Sources Combustion of fuels for power and heat – Power Plants Other burning such as Wood & crop burning or forest fires Industrial/ commercial processes Solvents and aerosols Mobile Sources Highway: cars, trucks, buses and motorcycles Off-highway: aircraft, boats, locomotives, farm equipment, RVs, construction machinery, and lawn mowers
Human Impact on Atmosphere Burning Fossil Fuels Using Nitrogen fertilizers and burning fossil fuels Refining petroleum and burning fossil fuels Manufacturing Adds CO2 and O3 to troposphere Global Warming Altering Climates Produces Acid Rain Releases NO, NO2, N2O, and NH3 into troposphere Produces acid rain Releases SO2 into troposphere Releases toxic heavy metals (Pb, Cd, and As) into troposphere www.dr4.cnrs.fr/gif-2000/ air/products.html
Criteria Air Pollutants EPA uses six "criteria pollutants" as indicators of air quality Nitrogen Dioxide: NO2 Ozone: ground level O3 Carbon monoxide: CO Lead: Pb Particulate Matter: PM10 (PM 2.5) Sulfur Dioxide: SO2 Volatile Organic Compounds: (VOCs) EPA established for each concentrations above which adverse effects on health may occur
Table 20-2 Major Outdoor Air Pollutants CARBON MONOXIDE (CO) Description: Colorless, odorless gas that is poisonous to air-breathing animals; forms during the incomplete combustion of carbon-containing fuels (2 C + O2 2 CO). Major human sources: Cigarette smoking (p. 409), incomplete burning of fossil fuels. About 77% (95% in cities)comes from motor vehicle exhaust. Health effects: Reacts with hemoglobin in red blood cells and reduces the ability of blood to bring oxygen to body cells and tissues. This impairs perception and thinking; slows reflexes; causes headaches, drowsiness, dizziness, and nausea; can trigger heart attacks and angina; damages the development of fetuses and young children; and aggravates chronic bronchitis, emphysema, and anemia. At high levels it causes collapse, coma, irreversible brain cell damage, and death. • EPAStandard:9 ppm
Table 20-2Page 438 Table 20-2 Major Outdoor Air Pollutants NITROGEN DIOXIDE (NO2) Description: Reddish-brown irritating gas that gives photochemical smog its brownish color; in the atmosphere can be converted to nitric acid (HNO3), a major component of acid deposition. Major human sources: Fossil fuel burning in motor vehicles (49%) and power and industrial plants (49%). Health effects: Lung irritation and damage; aggravates asthma and chronic bronchitis; increases susceptibility to respiratory infections such as the flu and common colds (especially in young children and older adults). Environmental effects: Reduces visibility; acid deposition of HNO3 can damage trees, soils, and aquatic life in lakes. Property damage: HNO3 can corrode metals and eat away stone on buildings, statues, and monuments; NO2 can damage fabrics. • EPAStandard: 0.053 ppm
Table 20-2Page 438 Table 20-2 Major Outdoor Air Pollutants SULFUR DIOXIDE (SO2) Description: Colorless, irritating; forms mostly from the combustion of sulfur containing fossil fuels such as coal and oil (S + O2 SO2); in the atmosphere can be converted to sulfuric acid (H2SO4), a major component of acid deposition. Major human sources: Coal burning in power plants (88%) and industrial processes (10%). Health effects: Breathing problems for healthy people; restriction of airways in people with asthma; chronic exposure can cause a permanent condition similar to bronchitis. According to the WHO, at least 625 million people are exposed to unsafe levels of sulfur dioxide from fossil fuel burning. Environmental effects: Reduces visibility; acid deposition of H2SO4 can damage trees, soils, and aquatic life in lakes. Property damage: SO2 and H2SO4 can corrode metals and eat away stone on buildings, statues, and monuments; SO2 can damage paint, paper, and leather. • EPA Standard: 0.3 ppm (annual mean)
Table 20-2Page 438 Table 20-2 Major Outdoor Air Pollutants SUSPENDED PARTICULATE MATTER (SPM) Description: Variety of particles and droplets (aerosols) small and light enough to remain suspended in atmosphere for short periods (large particles) to long periods (small particles; Figure 20-6, p. 441); cause smoke, dust, and haze. Major human sources: Burning coal in power and industrial plants (40%), burning diesel and other fuels in vehicles (17%), agriculture (plowing, burning off fields), unpaved roads, construction. Health effects: Nose and throat irritation, lung damage, and bronchitis; aggravates bronchitis and asthma; shortens life; toxic particulates (such as lead, cadmium, PCBs, and dioxins) can cause mutations, reproductive problems, cancer. Environmental effects: Reduces visibility; acid deposition of H2SO4 droplets can damage trees, soils, and aquatic life in lakes. Property damage: Corrodes metal; soils and discolors buildings, clothes, fabrics, and paints. EPA Standard: 50 ug/m3 (annual mean)
Table 20-2Page 438 Table 20-2 Major Outdoor Air Pollutants OZONE (O3) Description: Highly reactive, irritating gas with an unpleasant odor that forms in the troposphere as a major component of photochemical smog (Figures 20-3 and 20-5). Major human sources: Chemical reaction with volatile organic compounds (VOCs, emitted mostly by cars and industries) and nitrogen oxides to form photochemical smog (Figure 20-5). Health effects: Breathing problems; coughing; eye, nose, and throat irritation; aggravates chronic diseases such as asthma, bronchitis, emphysema, and heart disease; reduces resistance to colds and pneumonia; may speed up lung tissue aging. Environmental effects: Ozone can damage plants and trees; smog can reduce visibility. Property damage: Damages rubber, fabrics, and paints.
Table 20-2Page 438 Table 20-2 Major Outdoor Air Pollutants LEAD Description: Solid toxic metal and its compounds, emitted into the atmosphere as particulate matter. Major human sources: Paint old houses), smelters (metal refineries), lead manufacture, storage batteries, leaded gasoline (being phased out in developed countries). Health effects: Accumulates in the body; brain and other nervous system damage and mental retardation (especially in children); digestive and other health problems; some lead-containing chemicals cause cancer in test animals. Environmental effects: Can harm wildlife. • EPAStandard: 1.5 ug/m3
VOCs (Volatile Organic Compounds) Properties: organic compounds (hydrocarbons) that evaporate easily, usually aromatic Effects: eye and respiratory irritants; carcinogenic; liver, CNS, or kidney damage; damages plants; lowered visibility due to brown haze; global warming Sources:vehicles(largest source),evaporation of solvents or fossil fuels, aerosols, paint thinners, dry cleaning Class: HAPs (Hazardous Air Pollutants) Methane Benzene Chlorofluorocarbons (CFCs), etc. Concentrations indoors up to 1000x outdoors 600 million tons of CFCs
Other Air Pollutants Carbon dioxide ChloroFluoroCarbons Formaldehyde Benzene Asbestos Manganese Dioxins Cadmium Others not yet fully characterized
Carbon dioxide Should it be classified as an Air Pollutant Most scientist would add it to the gang of six criteria air pollutants EPA, under pressure from most U.S. oil and coal companies, says its not April 2007 Supreme Court ruled that the EPA has the authority under the Clean Air Act to regulate global warming emissions
CO2 should be considered a pollutant 1.In high enough concentrations any chemical in the air can be a pollutant. 2. We have been increasing the concentrations of CO2 in the troposphere by burning fossil fuels and clearing carbon dioxide –absorbing trees faster than they are growing back in many areas. 3. The troposphere is warming and there is considerable evidence that the additional CO2 added to the troposphere by human activities plays a role in this change. 4. Global warming can change how much precipitation falls, affects where we can grow food, and flood some areas of the world. Thus higher levels of CO2 can cause harm to some people, economies, and ecosystem.
Mercury Naturally released by volcanoes, weathering of rocks, and evaporation of sea water. Arises anthropogenically from coal combustion, incineration, and smelting. The acute effects of mercury toxicity are difficultly walking, loss of coordination, difficulty swallowing, and tremors. Chronic effects include hallucinations, psychosis, and irreversible brain damage. Fetal exposure results in mental retardation, attention disorders, seizures, and blindness.
Smog Forms ...when polluted air is stagnant (weather conditions, geographic location) • Photochemical Smog is a mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbon compounds under the influence of light Los Angeles, CA
Photochemical Smog UV radiation H2O + O2 Primary Pollutants NO2 + Hydrocarbons Secondary Pollutants HNO3 O3 nitric acid ozone Photochemical Smog Auto Emissions
How can trees Contribute to Photochemical Smog? Trees certainly have environmental benefits Emit oxygen, absorb CO2, provide shade, and help absorb and remove various pollutants from the air. Some trees (some oak species, sweet gums, Poplars, and Kudzu) in and around urban areas play a large role in smog formation They emit VOCs (like isoprene) that are ingredients in the development of photochemical smog. Plants in urban areas should be trees that emit low levels of VOCs.
Formation & Intensity Factors Local climate (inversions, air pressure, temperature, humidity) Topography (hills and mountains) Population density Amount of industry Fuels used by population and industry for heating, manufacturing, transportation, power Weather: rain, snow,wind Buildings (slow wind speed) Mass transit used Economics
Thermal Inversion cool air Pollutants cool air warm air (inversion layer) warm air • surface heated by sun • warm air rises (incl. pollutants) • cools off, mixes with air of equal density & disperses • surface cools rapidly (night) • a layer of warm air overlays surface • polluted surface air rises but cannot disperse remains trapped
Solar radiation Photochemical Smog Ultraviolet radiation NO Nitric oxide O Atomic oxygen O2 Molecular oxygen NO2 Nitrogen dioxide H2O Water Hydrocarbons PANs Peroxyacyl nitrates Aldehydes (e.g., formaldehyde) O3 Ozone HNO3 Nitric acid P h o t o c h e m i c a l S m o g
Industrial Smog • Industrial smog- mixture of SO2, droplets of sulfuric acid, and a variety of suspended solid particles emitted by burning coal • Gray-air smog- the tiny suspended particles such as salts and carbon (soot) give the resulting industrial smog a gray color.
Measuring Acid Rain Acid rain is measured using a "pH" scale. The lower a substance's pH, the more acidic it is. Pure water has a pH of 7.0. Normal rain is slightly acidic and has a pH of about 5.6 Any rainfall has a pH value less than 5.6 is defined as acid rain As of the year 2000, the most acidic rain falling in the US has a pH of about 4.3.
Two Forms… Wet Refers to acid rain, fog, sleet, cloud vapor and snow. Dry Refers to acidic gases and particles.
Compounds Two main contributors to acid deposition: Sulfur Dioxide (SO2) Nitrogen Oxides (NOx) * 66% of all sulfur dioxides and 25% of all nitrogen oxides comes from electric power generation that produces energy by burning fossil fuels.
When gas pollutants e.g. carbon dioxide, sulfurdioxide, nitrogen dioxidedissolve in rain water, various acids are formed. • CO2 + H2O H2CO3 (carbonic acid) • SO2 + H2O H2SO3 (sulfurous acid) • NO2 + H2O HNO2 (nitrous acid) + HNO3 (nitric acid)
Causes of Acid Rain Sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal.
Acidic Precipitation Primary Pollutants SO2 NO2 Secondary Pollutants H2SO4 HNO2 sulfuric acid nitric acid acidic precipitation vegetation direct toxicity indirect health effects water Fossil fuels Power plants Industrial emissions Auto emissions soils leaching of minerals sediments leaching aluminum
Emission Acid deposition SO2 H2O2 PANs NOX O3 Others Increased Susceptibility to drought, extreme cold, insects, mosses, and disease organisms Reduced photosynthesis and growth Direct damage to leaves and bark Soil acidification Tree death Reduced nutrient and water uptake Leaching of Soil nutrients Root damage Release of toxic metal icons Acid Groundwater
Acidic Precipitation Wind Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Wet acid deposition (droplets of H2SO4 and HNO3 dissolved in rain and snow) Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Sulfur dioxide (SO2) and NO Nitric oxide (NO) Acid fog Farm Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic Ocean
BIOL 349 Atmosphere Fig. 17.10, p. 428