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Unit 10: Air Pollution, Climate Change, and Ozone Depletion
Chapters 18 and 19
Air Pollution
• The introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals and materials such as buildings, or to alter ecosystems.
• Generally refers to pollution in the troposphere aka “ground-level pollution”
Air Pollution sources and types
• Sources– Natural • Volcanoes, fires
– Anthropogenic• Automobiles, factories
• Types– Indoor air pollution– Outdoor air pollution– MDCs vs. LDCs
The Atmosphere
• Troposphere– Closest to the earth’s surface– Contains 75-80% of the earth’s air mass– 17 km or 11 miles above the earth’s surface at the
equator and 6 km or 4 miles at the poles– 78% nitrogen, 21% oxygen, remainder is H2O
vapor, CO2, CH4, Ar, O3, N2O, and particulates like soot and dust
– Is a global commons
US Clean Air Act of 1970
• Identified six major pollutants that significantly threaten human well-being, ecosystems, and/or structures
• Called “criteria” pollutants• EPA must specify allowable concentrations of
each pollutant• Has been amended multiple times
Major Pollutants
• Sulfur dioxide• Nitrogen oxides• Carbon oxides• Particulates• Photochemical oxidants – ozone• VOCs• *Lead and other metals
Primary and secondary pollutants• Primary pollutants– Are pollutants that come directly from
smokestacks, exhaust pipes, or a natural emission source.
– CO, CO2, SO2, NOx, VOCs, and particulates
• Secondary pollutants– Undergo transformation in the presence of
sunlight, water, oxygen, or other compounds– Solar radiation and water are often involved in the
transformation, so secondary pollution is lower at night
– Ozone– Acid Deposition
Atmospheric Brown Clouds
• Combination of particulates and ozone• Primary cause is the combustion of fossil fuels
and burning biomass• Primarily seen in cities, although some entire
regions have been affected (Asia)• Brownish tint is caused by black or brown
particles that absorb light and and NO2 gas
• Human health impacts• Economic impacts - ↓ tourism
Smog• Smoke and fog• Responsible for the hazy view and reduced
sunlight observed in many cities• Two types– Photochemical
• Primary component is ozone• aka: brown smog• Los Angeles
– Sulfurous• Primary pollutant SO2 and other sulfate compounds• gray smog• London
Production of photochemical smog
1. Is a chemical reaction activated by sunlight – occurs during the early hours of the day
2. Abundant nitrogen oxides (from car exhaust) and few VOCs – ozone is produced
3. Later morning, as sunlight intensity ↑, the nitrogen oxides combine with the ozone to form diatomic oxygen and nitrogen dioxide
4. When VOCs are present – they combine with nitrogen oxide, preventing the normal destruction of ozone, which allows ozone to build up to high levels
5. Products of photochemical smog – ozone, nitric acid, aldehydes, peroxyacyl nitrates (PANs),
Thermal Inversion• Normally, T↓ as altitude↑• Thermal inversion is when a relatively warm
layer of air at mid-altitude covers a layer of cold, dense air below
• The warm inversion layer traps emissions causing them to accumulate beneath the layer, creating a severe pollution event
• Common in cities with large amounts of vehicle and industrial emissions
• Los Angeles; London; Mexico City; Santiago, Chile
Geographic Requirements1. City with mountains on
3 sides and ocean on the 4th, with a sunny climate
2. Town or city located in a valley surrounded by mountains where the weather turns cloudy and cold during part of the year
Los Angeles, CaliforniaSantiago, ChileDenver, ColoradoMexico City, Mexico
Acid Deposition• NOx and SO2 are released into the atmosphere by both
natural and anthropogenic sources• In the presence of oxygen and water, these primary
pollutants are transformed into nitric and sulfuric acid• The acids break down into sulfate and nitrate ions• Wet deposition– Rain, snow, fog– Farther from the emission source, stays in the atmosphere
longer• Dry deposition– Particulate fallout– Close to emissison source, falls out within a few days
Impacts of Acid Deposition• Destruction of structures, statues• Respiratory effects in humans (not of the deposition
itself – but the particulate matter)• Leaches toxic metals into soils and water supplies –
fish have narrow ranges in which they can tolerate toxic metals
• Acidification of soils• Acidification of aquatic environments• Damages crops and threatens food security• Destroys forests – Leaches essential nutrients like calcium from forest soils– Releases ions of Al, Pb, Cd, and Hg to the soil where they
can damage tree roots
Pollution Control, Prevention, and Cleanup• Use fuel sources with low levels of sulfur, or
remove sulfur during the refining process• Increase efficiency• Conserve energy, thereby using less fuel• Particulate Controls• Remove particles after combustion
• Gravitational settling• Scrubber• Baghouse filter• Electrostatic Precipitator• Catalytic converters
Scrubber
Electrostatic Precipitator
Catalytic Converter 4:50 - 5:47
Indoor Air Pollution • Causes more deaths per year than outdoor air
pollution• Pollution indoors poses significant health risks
due to the length of time people are exposed and the level of pollutants
• LDCs: cooking, burning biomass• MDCs: insulation, time spent indoors, materials
made of plastics or other petroleum based products
• Acute respiratory infections, pneumonia, bronchitis, cancer
Indoor Air Pollutants• Tobacco Smoke• Asbestos• Carbon monoxide• Radon-222• VOCs– Formaldehyde– Detergents– Dry-cleaning fluids– Solvents– Plastics
Sick Building Syndrome
• Causes headaches, nausea, throat or eye irritation, fatigue
• Four Causes– Inadequate or faulty ventilation– Chemical contamination from indoor sources such
as glues, carpeting, furniture, cleaning agents, and copy machines
– Chemical contamination in the building from outdoor sources such as vehicle exhaust transferred through the air intakes for the building
– Biological contamination from inside or outside, such as molds or pollen
Regulation of Air Pollution • Clean Air Act 1970 (1977, 1990)• Two standards– Primary: limits set to protect human health– Secondary: limits set to prevent environmental
and property damage• Hazardous air pollutants– EPA has published emission standards for 188
compounds that may cause serious health and ecological effects
– VOCs, toxic metals, chlorinated hydrocarbons
Toxic Release Inventory• Requires refineries, power plants, mines,
chemical manufacturers, and factories to report their releases and waste management methods for 667 toxic chemicals
• First TRI was released in 1988 • Reported emissions of toxic chemicals have
dropped since• Carroll County TRI– Xylene • Flammable, toxic, Teratogenic
Emissions trading• Cap and Trade• Enables the 110 most polluting coal-fired power
plants in 21 states to buy and sell pollution credits• Each plant is given a number of pollution credits
which allow them to emit a specific amount of SO2
• Utilities can sell off unused pollution credits to other plants, or save them for later use or expansion
• Has been relatively successful
Plants Ranked in Top 50 for Emission Rate and Total Tons SO2 (2006)State Power PlantsAlabama Gaston, GorgasGeorgia Harllee Branch, Bowen, Wansley, YatesIndiana Cayuga, Gallagher, Warrick9, Wabash RiverMaryland MorgantownOhio Beckjord, Cardinal, Conesville, Eastlake, Kyger Creek, Miami Fort,Pennsylvania Brunner Island, Hatfield’s Ferry, Homer City, Keystone, MontourTennessee JohnsonvilleTexas Big BrownVirginia ChesterfieldWest Virginia Fort Martin
SO2 Polluting Coal Fired Power Plants
Earth Day
• Symphony of Science - We can change the world
• Commercial – Nissan• Meet your Earth• Earth• Elton John - Circle of Life
Global Change• Change that occurs in the chemical, biological,
and physical properties of the planet– Global climate change• Refers to changes in the climate of the earth (the
average weather that occurs in an area over a period of years or decades)• Can be natural or anthropogenic
– El Nino, volcanic erruption, fossil fuel combustion, deforestation
– Global warming• The warming of the oceans, landmasses, and the
atmosphere of the earth
Greenhouse Effect
• The physical and biogeochemical systems that regulate temperature at the surface of the earth– Concentration of gases– Distribution of clouds– Atmospheric currents– Ocean currents
• Greenhouse gases
Sources of greenhouse gases
• Natural– Volcanic eruptions (particles)– Animal digestion (methane)– Plant and animal decomposition (methane)– Denitrification (nitrous oxide; N2O)
– Evaporation and evapotranspiration in plants (H2O)
Sources of greenhouse gases
• Anthropogenic– Burning of fossil fuels (CO2, particulates)
– Agricultural practices (N2O, CH4)• Fertilizers, cows, manure
– Deforestation (CO2)
– Landfills (CH4)– Industrial production (VOCs, CFCs)– Motor vehicle exhaust (N2O)• Production of ozone in the presence of sunlight
Major Findings of IPCC(Intergovernmental Panel on Climate Change)
1. Lower atmosphere is warming, primarily due to CO2
emissions and other greenhouse gases2. Human activities are contributing to the increase in
greenhouse gases3. These human-induced changes are beginning to change the
earth’s climate4. If gas emissions continue to increase, the earth is likely to
experience rapid atmospheric warming and climate disruption this century
5. Rapid and significant climate disruption will likely cause ecological, economic, and social disruption: degrading food and water supplies, flooding low-lying coastal communities, destruction of habitats and extinction of species
Possible Effects of Global Warming
• Severe drought• Melting ice and snow in the Arctic and Antarctic• Thawing permafrost• Rising sea levels• Extreme weather events• Loss of biodiversity• Crop productivity could decrease• Health effects: Dengue fevel and yellow fever
The problem of climate change
• It is a global concern• It is a long term political issue• The impacts will not be spread evenly around
the globe (Canada, Russia vs. equatorial nations)
• Many proposed solutions are controversial because they require changes in our lifestyle and can have economic effects
How to slow climate change• Prevent and reduce greenhouse gas emissions– Improve energy efficiency– Use low-carbon emitting renewable energy sources– Stop deforestation and plant more trees– Changes in agriculture to sustainability
• Collect and store greenhouse gas emissions– Tree-planting, restoring wetlands, and planting
degraded land w/switchgrass– Seeding the oceans w/iron to promote growth of
marine algae and plankton which absorb CO2
– Carbon capture and storage
How to slow climate change cont.• Geoengineering• Government regulations– Strictly regulate carbon dioxide and methane
emissions– Carbon taxes or fees– Cap and trade for pollution credits– Government subsidies for green energy– Give away our advanced technology (for free) to LDCs – Slow population growth
How to slow climate change cont.
• International climate agreements– Kyoto Protocol (1997) – 187 countries ratified the agreement (not U.S.)– Requires the 36 MDCs to decrease their emissions
of carbon dioxide, methane, and nitrous oxide to an average of 5.2 % below their 1990 levels by 2012
Atmosphere • Stratosphere– Second layer– Extends from 11-30 miles or 17-48 km above the earth’s surface– Contains less gas particles(↓ density), similar composition of
nitrogen and oxygen, but much less water vapor and much more ozone.
• Stratospheric Ozone Layer– The ozone is concentrated in a single band in the stratosphere
called the ozone layer– Acts as a global sunscreen and keeps about 95% of the suns
harmful UV rays from reaching the earth’s surface and protects us from sunburn, skin and eye cancers, cataracts, immune system damage
– Oxygen molecules interact with UV light to form ozone3 O2 + UV → 2 O3
Chlorofluorocarbons
• Chlorofluorocarbons –CFCs– A family of organic compounds – Stable, inert, nontoxic, nonflammable• refrigeration and air conditioning• Aerosol propellants • Injecting air into styrofoam products
Chlorofluorocarbons
• After release into the atmosphere– UV radiation breaks the bond holding the chlorine,
which creates a free chlorine– Chlorine reacts with ozone to form ClO and O2
– A free oxygen then pulls the oxygen from the ClO making a diatomic oxygen and leaving behind a free chlorine that can once again break apart ozone
– One chlorine can catalyze the breakdown of as many as 100,000 ozone molecules before it leaves the stratosphere
Additional anthropogenic sources of ozone destruction
• Nitrogen Oxides– Fertilizer and manure
• Halocarbons– Fire extinguishers
• Bromines – used as fumigants for soil pests like termites
• Carbon tetrachloride – cleaning solvents
Depletion of the ozone layer
• Ozone Depletion Explanation• Ozzy Ozone• First noticed in the mid-1980s over Antarctica• Greatest at the poles, but occurs worldwide• Some depletion is seasonal
Efforts to reduce ozone depletion• Montreal Protocol on Substances that Deplete the
Ozone Layer (1987)• 24 nations signed and committed to reducing CFC
production by 50% by the year 2000• A series of increasing stringent amendments were
added, requiring the elimination of CFC production and use in the developed world by 1996
• In total, the protocol addressed 96 ozone depleting compounds
• Eventually signed by 180 countries• Atmospheric concentration of CFCs has stabilized at
about 5 ppb and should fall to 1 ppb by 2100• Ozone levels should start to rebound over the long
term
