Outdoor Air Pollution

AP Environmental Science Mr. Grant Lesson 46 Outdoor Air Pollution

Objectives: • Define the term Montreal Protocol. • Identify major pollutants, outline the scope of outdoor air pollution, and assess potential solutions. • Explain stratospheric ozone depletion and identify steps taken to address it. • Define acidic deposition and illustrate its consequences.

Define the term Montreal Protocol. Montreal Protocol: International treaty ratified in 1987 in which 180 signatory nations agreed to restrict production of chlorofluorocarbons (CFC’s) in order to forestall stratospheric ozone depletion. Because of its effectiveness in decreasing global CFC emissions, the Montreal Protocol is considered the most successful effort to date in addressing a global environmental problem.

Identify major pollutants, outline the scope of outdoor air pollution and assess potential solutions. • Natural sources such as windblown dust, volcanoes, and fires pollute the atmosphere, but human activity can worsen some of these phenomena. • Human-emitted pollutants include primary and secondary pollutants from point and non-point sources. • To safeguard public health under the Clean Air Act, the U.S. EPA and state governments monitor ambient concentrations of six criteria pollutants (carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter and lead). • Agencies monitor emissions of these pollutants and of volatile organic compounds. • Emissions in the United States have decreased substantially since the Clean Air Act of 1970, and ambient air quality is much improved in most respects.

Identify major pollutants, outline the scope of outdoor air pollution and assess potential solutions. • Emissions of 188 toxic air pollutants are also declining, but they still pose health risks. • Industrializing nations such as China and India are experiencing some of the world’s worst air pollution today. • Rural areas suffer air pollution from feedlots and other sources. • Industrial smog produced by fossil fuel combustion is still a problem in urban and industrial areas of many developing nations. • Photochemical smog like that which affects Los Angeles, Tehran, and other cities today is created by chemical reactions of pollutants in the presence of sunlight. It impairs visibility and human health in urban areas.

Outdoor air pollution • Air pollutants = gases and particulate material added to the atmosphere • Can affect climate or harm people or other organisms • Air pollution = the release of pollutants • Outdoor (ambient) air pollution = pollution outside • Has recently decreased due to government policy and improved technologies in developed countries • Developing countries and urban areas still have significant problems

Natural sources pollute: volcanoes • Release particulate matter, sulfur dioxide, and other gases • Can remain for months or years • Aerosols = fine droplets of sulfur dioxide, water, oxygen • Reflect sunlight back to space • Cool the atmosphere and surface Volcanoes are one source of natural air pollution, as shown by the Mount Saint Helens eruption in 1980

Natural sources pollute: fires • Fires pollute the atmosphere with soot and gases • Over 60 million ha (150 million acres) of forests and grasslands burn per year • Human influence makes fires worse • Fuel buildup from fire suppression, development in fire-prone areas, “slash-and-burn” agriculture • Climate change will increase drought and fires In 1997, unprecedented forest fires sickened 20 million and caused a plane to crash

Natural sources pollute: dust storms • Wind over arid land sends huge amounts of dust aloft • Even across oceans • Businesses, schools, and governments close • Unsustainable farming and grazing promote: • Erosion • Desertification

We create outdoor air pollution • Air pollution comes from mobile or stationary sources • Point sources = specific spots where large quantities of pollutants are discharged (power plants and factories) • Non-point sources = more diffuse, consisting of many small sources (automobiles) • Primary pollutants = directly harmful and can react to form harmful substances (soot and carbon monoxide) • Secondary pollutants = form when primary pollutants interact or react with components of the atmosphere • Tropospheric ozone and sulfuric acid

Pollutants exert local and global effects • Residence time = the time a pollutant stays in the atmosphere • Pollutants with brief residence times exert localized impacts over short time periods • Particulate matter, automobile exhaust • Pollutants with long residence times exert regional or global impacts • Pollutants causing climate change or • ozone depletion

Legislation addresses pollution • Air Pollution Control Act (1963) funded research and encouraged emissions standards • The Clean Air Act of 1970 • Set standards for air quality, limits on emissions • Provided funds for pollution-control research • Allowed citizens to sue parties violating the standards • The Clean Air Act of 1990 strengthened regulations for auto emissions, toxic air pollutants, acidic deposition, stratospheric ozone depletion • Introduced emissions trading for sulfur dioxide

The EPA sets standards • The EPA sets nationwide standards for emissions and concentrations of toxic pollutants • States monitor air quality • They develop, implement, and enforce regulations • They submit plans to the EPA for approval • The EPA takes over enforcement if plans are inadequate • Criteria pollutants = pollutants that pose especially great threats to human health • Carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, lead

Criteria pollutants: CO and SO2 • Carbon monoxide(CO) = colorless, odorless gas • Produced primarily by incomplete combustion of fuel • From vehicles and engines, industry, waste combustion, residential wood burning • Poses risk to humans and animals, even in small concentrations • Sulfur dioxide (SO2) = colorless gas with a strong odor • Coal emissions from electricity generation, industry • Can form acid precipitation

Criteria pollutants: NO2 • Nitrogen dioxide (NO2) =a highly reactive, foul-smelling reddish brown gas • Nitrogen oxides (NOx) = formed when nitrogen and oxygen react at high temperatures in engines • Vehicles, industrial combustion, electrical utilities • Contribute to smog and acid precipitation

Criteria pollutants: tropospheric ozone • Tropospheric ozone (O3) = a colorless gas with a strong odor • Results from interactions of sunlight, heat, nitrogen oxides, and volatile carbon-containing chemicals • A secondary pollutant • A major component of smog • Participates in reactions that harm tissues and cause respiratory problems • The pollutant that most frequently exceeds EPA standards

Criteria pollutants: particulate matter andlead • Particulate matter = suspended solid or liquid particles • Primary pollutants: dust and soot • Secondary pollutants: sulfates and nitrates • Damages respiratory tissue when inhaled • From dust and combustion processes • Lead = in gasoline and industrial metal smelting • Bioaccumulates and damages the nervous system • Banned in gasoline in developed, but not in developing, countries

Areas in the U.S. fail air quality standards Many Americans live in areas with unhealthy levels of criteria pollutants

Agencies monitor emissions • State and local agencies monitor, calculate, and report to the EPA the emissions of these pollutants: • Carbon monoxide, sulfur dioxide, particulate matter, lead, and all nitrogen oxides • Tropospheric ozone has no emissions to monitor • It is a secondary pollutant • Agencies monitor volatile organic compounds (VOCs) = carbon-containing chemicals • Used and emitted by engines and industrial processes • VOCs can react to produce ozone

U.S. air pollution In 2008, the U.S. emitted 123 million tons of the six monitored pollutants The average U.S. driver emits 6 metric tons of CO2/yr as well as other pollutants!

We have reduced air pollution • Total emissions of the six monitored pollutants have declined 60% since the Clean Air Act of 1970 • Despite increased population, energy consumption, miles traveled, and gross domestic product

We reduced emissions and improved theeconomy • Technology and federal policies • Cleaner-burning engines and catalytic converters • Permit-trading programs and clean coal technologies reduce SO2 emissions • Scrubbers = chemically convert or physically remove pollutants before they leave smokestacks • Phaseout of leaded gasoline

Toxic substances pose health risks • Toxic air pollutants = substances that cause: • Cancer, reproductive defects • Neurological, developmental, immune system, or respiratory problems • The EPA regulates 188 toxic air pollutants from metal smelting, sewage treatment, industry, etc. • Include heavy metals, VOCs, diesel, urban hazards • Clean Air Act regulations helped reduce emissions by more than 35% since 1990

U.S. health risks vary geographically Non-cancerous respiratory ailments Nationwide cancer risks

Industrializing nations suffer increasing pollution • Outdoor pollution is getting worse in developing nations • Factories and power plants pollute • Governments emphasize economic growth, not pollution control • People burn traditional fuels (wood and charcoal) • And more own cars • China has the world’s worst air pollution • Coal burning, more cars, power plants, factories • Causing over 300,000 premature deaths/year

Pollution in developing nations is high Smog in Beijing surrounds an Olympic stadium More people own cars

Air pollution in China • The government is trying to decrease pollution • Shutting down heavily polluting factories and mines • Phasing out some subsidies for polluting industries • Installing pollution controls in factories • Encouraging renewable and nuclear energy • Mandating cleaner burning fuels • Air is improving in Beijing but not in other places • Asian (Atmospheric) Brown Cloud = a 2-mile-thick layer of pollution over southern Asia • Decreased plant productivity, increased flooding, etc.

Air quality is a rural issue, too • Airborne pesticides from farms • Industrial pollutants from cities, factories, and power plants • Feedlots, where cattle, hogs, or chickens are raised in dense concentrations • Voluminous amounts of dust, methane, hydrogen sulfide, and ammonia • Also create objectionable odors • People living or working nearby have high rates of respiratory illness

Smog: our most common air quality problem • Smog = an unhealthy mixture of air pollutants over urban areas • Sulfur in burned coal combines with oxygen to form sulfuric acid • Industrial (gray air) smog = industries burn coal or oil • Regulations in developed countries reduced smog • Coal-burning industrializing countries face health risks • Coal and lax pollution control Smog in Donora killed 21 people and sickened 6,000

Photochemical (brown air) smog • Produced by a series of reactions • Formed in hot, sunny cities surrounded by mountains • Light-driven reactions of primary pollutants and atmospheric compounds • Morning traffic releases NO and VOCs • Irritates eyes, noses, and throats • Los Angeles smog kills 3,900/year and costs $28 billion/year High levels of NO2cause photochemical smog to form a brown haze over cities

Creation of industrial and photochemical smog Industrial smog Photochemical smog

We can reduce smog • Regulations require new cars to have catalytic converters • Require cleaner industrial facilities • Close those that can’t improve • Financial incentives to replace aging vehicles • Restricting driving • Vehicle inspection programs (“smog checks”) • Reduce sulfur in diesel; remove lead in gasoline • Electronic pollution indicator boards raise awareness • But increased population and cars can wipe out advances

Explain stratospheric ozone depletion and identify steps taken to address it. • CFCs and other persistent human-made compounds destroy stratospheric ozone, and thinning ozone concentrations pose dangers to life because they allow more ultraviolet radiation to each Earth’s surface. • Ozone depletion is most severe over Antarctica, where an “ozone hole” appears each spring. • The Montreal Protocol and its follow-up agreements have proven remarkably successful in reducing emissions of ozone-depleting substances. • The long residence time of CFCs in the atmosphere accounts for a time lag between the protocol and the full restoration of stratospheric ozone.

Synthetic chemicals deplete stratospheric ozone • Ozone layer = ozone in the lower stratosphere • Blocks incoming ultraviolet (UV) radiation • Protecting life from radiation’s damaging effects • Ozone-depleting substances = human-made chemicals that destroy ozone by splitting its molecules apart • Halocarbons = human-made compounds made from hydrocarbons with added chlorine, bromine, or fluorine • Chlorofluorocarbons (CFCs) = a halocarbon used as refrigerants, in fire extinguishers, in aerosol cans, etc. • Releases chlorine atoms that split ozone

CFCs destroy ozone • CFCs are inert (don’t react) • CFCs remain in the stratosphere for a century • UV radiation breaks CFCs into chlorine and carbon atoms • The chlorine atom splits ozone • Ozone hole = decreased ozone levels over Antarctica One chlorine atom can destroy 100,000 ozone molecules

The Antarctic ozone hole • High-altitude polar stratospheric clouds form during the dark, frigid winter • Nitric acid in clouds splits chlorine off of CFCs • A polar vortex (swirling winds) traps chlorine • UV radiation in September (spring) sunshine dissipates the clouds and releases the chlorine • The chlorine destroys the ozone • December’s warmer air shuts down the polar vortex • Ozone-poor air diffuses, while ozone-rich air enters

The Montreal Protocol • Montreal Protocol = 196 nations agreed to cut CFC production in half by 1998 • Follow-up agreements deepened cuts, advanced timetables, and addressed other ozone-depleting chemicals • Industry shifted to safer, inexpensive, and efficient alternatives • Challenges still face us • CFCs will remain in the stratosphere for a long time • Nations can ask for exemptions to the ban

The Montreal Protocol is a success • It is considered our biggest environmental success story • Research developed rapidly, along with technology • Policymakers included industry in helping solve the problem • Implementation of the plan allowed an adaptive management strategy • Strategies responded to new scientific data, technological advances, and economic figures • The Montreal Protocol can serve as a model for international environmental cooperation

Protecting the ozone layer International agreements reduced ozone-depleting substances The hole in the ozone has stopped growing

Define acidic deposition and illustrate its consequences. • Acidic deposition results when pollutants such as SO2 and NO react in the atmosphere to produce strong acids that are deposited on Earth’s surface. • Acidic deposition may be wet (e.g., “acid rain”) or dry, and it may occur a long distance from the source of pollution. • Water bodies, soils, trees, animals, and ecosystems all experience negative impacts from acidic deposition. • Regulation, cap-and-trade programs, and technology are all helping to reduce acid deposition in North America, yet more needs to be done, and industrializing nations will need to tackle the problem as well.

Acid deposition • Acid deposition is another transboundary issue • Acidic deposition = the deposition of acid, or acid-forming pollutants from the atmosphere onto Earth’s surface • Acid rain = precipitation containing acid • Rain, snow, sleet, hail • Atmospheric deposition = the wet or dry deposition on land of pollutants (mercury, nitrates, organochlorines) • From automobiles, electric utilities, industrial facilities

Burning fossil fuels produces acid rain • Burning fossil fuels releases sulfur dioxide and nitrogen oxides • These compounds react with water, oxygen, and oxidants to form sulfuric and nitric acids

Impacts of acid deposition • Nutrients are leached from topsoil • Soil chemistry is changed • Metal ions (aluminum, zinc, etc.) are converted into soluble forms that pollute water • Affects surface water and kills fish • Damages agricultural crops • Erodes stone buildings, corrodes cars, erases writing on tombstones

pH of precipitation in the U.S. • The acid-neutralizing capacity of soil, rock, or water impacts the severity of acid rain’s effects Many regions of acidification are downwind of major sources of pollution

We have begun to address acid deposition • Reducing acid deposition involves reducing the pollution that contributes to it • The Clear Air Act of 1990 established an emissions trading program for sulfur dioxide • Benefits outweighed costs 40:1 • New technologies such as scrubbers have helped • Acid deposition is worse in the developing world • Especially in China, which burns coal in factories lacking pollution control equipment

Outdoor Air Pollution