Transcript 23_Air
Announcements – Oct 25 Test results are in. CNN Booming China's acid rain 'out of control' November 30, 2004 China's explosive economic growth is outpacing environmental protection efforts, leaving the country awash in "out of control" acid rain. Acid rain fell on more than 250 cities nationwide and caused direct annual economic losses of $13.3 billion, equal to nearly three percent of the country's gross domestic product. Two major causes were the rapidly growing number of cars and increasing consumption of cheap, abundant coal as the country struggles to cope with energy shortages and meet power demand. China is the world's largest source of soot and sulphur dioxide (SO2) emissions from coal, which fires three-quarters of the country's power plants. Third of China 'hit by acid rain' Sunday, 27 August 2006 One third of China is suffering from acid rain caused by rapid industrial growth, an official report quoted by the state media says. Pollution levels have risen and air quality has deteriorated, the report found. This comes despite a pledge by the authorities to clean up the air. CNN, November 16, 2004 Study links smog increase, urban deaths CHICAGO, Illinois (Reuters) -- Increases in air pollution caused by cars, power plants and industry can be directly linked to higher death rates in U.S. cities. Reducing such ozone pollution by about 35 percent on any given day could save about 4,000 lives a year across the country. The conclusion came from a look at 95 urban areas where about 40 percent of the U.S. population lives, comparing spikes in ozone pollution there with death rates from 1987 to 2000. Ground-level ozone typically increases when temperatures rise. While short-term increases have been recognized as causing jumps in hospital admissions, this study provides strong evidence of short-term effects of ozone on mortality," said Francesca Dominici, an author of the study. Air Quality I Lecture Objectives: 1) What are the major types and sources of airborne pollutants? 2) What are the issues with ozone? 3) Has the Clean Air Act been effective? Atmosphere Atmosphere - air above the earth 78% nitrogen, 21% oxygen, 1% carbon dioxide, water, other gases Atmosphere Divided into four zones: Troposphere, Stratosphere, Mesosphere, Thermosphere Decrease in density further from Earth Troposphere is where weather takes place Stratosphere contains most of the ozone Atmosphere Airborne particles mix, dilute, but remain in atmosphere Accumulate in direction of winds Can lead to health problems Asthma Adults with asthma: 14 million (6.9%) (2001) Children with asthma: 6.3 million (8.7%) (2001) Number of deaths: 4,269 (2001) http://www.cdc.gov/nceh/airpollution/about.htm Air pollutants Primary air pollutants Materials that when released pose health risks in their unmodified forms Secondary air pollutants Primary pollutants interact with one another, sunlight, or natural gases to produce new, harmful compounds Primary Air Pollutants Five major materials released directly into the atmosphere in unmodified forms. Carbon monoxide Hydrocarbons Particulate matter (2.5 mm and 10 mm) Sulfur dioxide Nitrogen oxides 189 substances are regulated under the Clean Air Act Carbon Monoxide (CO) Produced by burning of organic material (coal, gas, wood, trash, etc.) Automobiles biggest source (80%) Decreases because of fuel efficiency, catalytic converters Offset by increase in number of cars, time spent driving Cigarette smoke another major source Carbon Monoxide (CO) Toxic because binds to hemoglobin, reduces oxygen in blood Not a persistent pollutant, combines with oxygen to form CO2 Most communities now meet EPA standards, but rush hour traffic can produce high CO levels Hydrocarbons (HC) Hydrocarbons - organic compounds with hydrogen, carbon From incomplete burning or evaporated from fuel supplies Major source is automobiles, but some from industry Contribute to smog Improvements in engine design have helped reduce Particulates Particulates - small pieces of solid materials and liquid droplets (2.5 mm and 10 mm) Examples: ash from fires, asbestos from brakes and insulation, dust Easily noticed: e.g. smokestacks More attention, more regulation Particulates Can accumulate in lungs and interfere with the ability of lungs to exchange gases. Some particulates are known carcinogens Those working in dusty conditions at highest risk (e.g., miners) pollution decreased 88% from 1970 - 2000 Sulfur Dioxide (SO2) Produced by burning sulfur containing fossil fuels (coal, oil) Coal-burning power plants major source Reacts in atmosphere to produce acids One of the major components of acid rain Sulfur Dioxide (SO2) When inhaled, can be very corrosive to lung tissue London 1306 banned burning of sea coal 1952 “killer fog”: 4,000 people died in 4 weeks tied to sulfur compounds in smog Nitrogen Oxides (NO, NO2) Produced from burning of fossil fuels Contributes to acid rain, smog Automobile engine main source New engine technology has helped reduce, but many more cars Acid Rain Sulfur dioxides and Nitrogen oxides combine with water in the atmosphere to form sulfuric acid and nitric acid The pollutants remain airborne for ~1-3 days and travel 250-750 miles Combine with water in the atmosphere, fall back as rain, snow, etc. – water with pH more acidic than normal rainfall. US and Canadian governments officially recognized effects in 1986 Effects of Acid Rain Can degrade buildings and monuments made of limestone Effects of Acid Rain Can acidify freshwater lakes (pH<4.7) Disrupt physiological processes Release of toxic compounds normally bound to soil (e.g. aluminum) Inhibition of nitrification, build up of ammonia Causes loss of game fish & other desirable species 25,000 lakes in N. America altered by acidification Midwest lakes often on limestone, which neutralizes acids Photochemical Smog Photochemical smog – secondary pollutants formed by reaction of nitrogen oxides and HC with sunlight Includes ozone (O3) destroys chlorophyll, injures lung tissue ground-level ozone is “bad ozone” Photochemical Smog Biggest problems in cities, mountains can make it even worse Mountain ranges, wind directions lead to thermal inversions when cool air is trapped below layer of warm air pollutants accumulate, aren’t released to upper atmosphere http://www.epa.gov/airnow/ozone.html Hazardous Air Pollutants Hazardous Air Pollutants (HAP) are compounds that can harm human health or damage the environment. Some released from consumer activities. Benzene escapes during automobile refilling. Most released from manufacturing Toxic chemicals released from smelters Chemical and petroleum industry are primary sources Indoor Air Pollution In U.S., 90% of time spent indoors; inside air often more polluted than outside air Problems with weatherized building: little air exchange Asbestos, carbon monoxide, formaldehyde, lead, pollen, dust, smoking Causes diseases: emphysema, heart attacks, strokes, lung cancers Other Air Quality Issues Ozone Depletion Ozone in the stratosphere is “good ozone” Shields us from harmful ultraviolet light Skin cancer and cataracts Chlorofluorocarbons Used as refrigerants, cleaning solvents, propellants 1970s – discovery that average concentrations of Ozone in the stratosphere were declining UV radiation breaks down CFC molecules, releasing atomic chlorine. A free Chlorine atom reacts with an ozone molecule, converting it from O3 to O2. One chlorine atom can break apart more than 100,000 ozone molecules. Chlorofluorocarbons CFCs take 10-20 years to make it into the stratosphere. Can react with ozone for up to 120 years. 1970s – CFCs as propellants in spay cans banned in US 1987 – Montreal Protocol No increase in CFC production 50% reduction of production by 2000 1991 – DuPont announced new refrigerant 1996 – US stopped producing CFCs Control of Air Pollution Different Approaches Regulations on auto industry Fines to enforce bans Switch from high sulfur coal to low sulfur coal Switch to oil, gas, wind, solar, nuclear power “Scrubbers” on smoke stacks to remove sulfur after use expensive -- $200 million per power plant Much of regulation done under Clean Air Act Clean Air Act (1970, 1977, 1990) Control requirements the federal government implements and states administer All sources subject to ambient air quality regulation (NAAQS) New sources subject to more stringent controls Hazardous pollutants and visibility reducing emissions regulated August 2003 changes reduce control no pollution control devices if “routine maintenance” repairs are < 20% of the replacement value of the entire process unit Clean Air Act Since Clean Air Act passage, EPA reports air pollution cut by 1/3 and acid rain cut by 25%. EPA estimates human health, welfare, and environmental benefits have outweighed costs by 40 to 1. Old coal-fired power plants and SUVs, diesel trucks and buses are still major problems Improvement in Air Quality 4/5 primary air pollutants decreased since 1970 Nitrogen oxides per vehicle down, but overall emissions increased due to larger number of cars Lead emissions way down after switch to unleaded gasoline Points to know – Nov 29 1) Know the types and proportions of the gases that make up the atmosphere. In which zone of the atmosphere does weather take place? Which contains ozone? 2) Distinguish between primary and secondary air pollutants. What are the 5 major primary air pollutants, where do they come from, and what problems do each cause? 3) What is photochemical smog, and how do thermal inversions contribute to the problem? 4) Why should we be concerned with indoor air pollution? 5) Distinguish between “bad” ozone and “good” ozone. What is causing depletion of the “good” ozone? 6) What does the Clean Air Act regulate, and how successful has it been?