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Air Pollution and Stratospheric Ozone Depletion
Chapter 15 Air Pollution and Stratospheric Ozone Depletion
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Air Pollution Is the contamination of the atmosphere with chemicals, particulates, or pathogens that harm living things or alter ecosystems Can be natural or anthropogenic Can be indoors or outdoors Can come from point or nonpoint sources
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Major Pollutants Are also called criteria pollutants for their EPA allowable levels Include oxides Sulfur dioxide Nitrogen oxides Carbon oxides Include particulates Include ozone Include lead
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Sulfur Dioxide (SO2) Is a gas caused by burning fossil fuels
Mostly coal and oil Release sulfur into the atmosphere Sulfur reacts with atmospheric oxygen to form SO2 Is a respiratory irritant Can form other pollutants Sulfuric acid H2SO4 Smog Can come from forest fires and volcanic eruptions
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Nitrogen Oxides (NOx) Can be nitrogen oxide (NO) or nitrogen dioxide (NO2) Can transform from one to the other Are gases caused by the burning of fossil fuels Can come from forest fires and volcanic eruptions
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Carbon Oxides (COx) Can be carbon monoxide (CO) or carbon dioxide (CO2) Are gases caused by combustion of carbon Fossil fuels, wood, manure Are asphyxiants in high doses Can come from forest fires and volcanic eruptions
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Particulates Also called particulate matter (PM)
Range from 0.01 μm to 100 μm Can come from combustion of pretty much anything Can also come from pollen, dust, forest fires, and volcanic eruptions Scatter light and create haze Large amounts can reduce sunlight and photosynthesis
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Lead (Pb) Comes from burning leaded gasoline No longer used in the US
Lead is an additive that prevents engine knock No longer used in the US Still used in other countries Can also be found in old paint Do not eat paint chips!
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Ozone (O3) Can be produced naturally
Can be produced from photochemical reactions Sunlight reacts with nitrogen oxides and sulfur dioxide
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Smog Comes from combining the words smoke and fog
Can be created from direct emissions from industries and homes Industrial smog Can be created by reactions between sunlight and chemicals Photochemical smog
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Industrial Smog Also called sulfurous smog Forms from combustion
Coal power plants are most common cause Has particulates, carbon, and sulfur released from burning fossil fuels and/or wood
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Photochemical Smog Also called brown smog
Atmospheric Brown Cloud Forms from sunlight breaking down nitrogen compounds Mostly from vehicle emissions Has nitrogen compounds, ozone, and particulates
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Non-Criteria Major Pollutants
Include volatile organic compounds (VOCs) VOCs are targeted particularly because they contribute to photochemical smog Include metals other than lead Are also regulated by EPA standards
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Volatile Organic Compounds (VOCs)
Are chemicals that become vapors at typical atmospheric temperatures and pressures Often have a strong smell Are often involved in photochemical reactions Are found in gasoline, paint and perfume Can come from plants
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Metals Include some of the same metals found in water pollution
Mercury and cadmium Come from the burning of fossil fuels and metal smelting
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Primary Air Pollutants
Come directly from the emission source Include the following: SO2 COx NOx VOCs Can become secondary pollutants
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Secondary Air Pollutants
Are primary pollutants that have undergone chemical transformation Can be caused by photochemical reactions and interactions with oxygen Include ozone, smog, and acids Are best controlled by reducing the primary pollutants that create them
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Natural Sources of Air Pollution
Are not regulated or controlled Can range from 30-80% of total air pollution Forest Fires Particulates, NOx, CO Volcanoes Particulates, SO2, CO, NOx Lightning Creates NOx Plants VOCs, particulates (pollen) Dust Particulates
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Thermal Inversions Are the opposite of normal atmospheric conditions
Occur when a warm layer of air traps a layer of cold, dense air Traps pollutants in the cold layer underneath Occur more frequently in valleys or areas bounded by mountains
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Acid Deposition Forms from NOx and SO2
Create nitric and sulfuric acid Occurs when atmospheric acids dissolve in rain or are deposited in dry form onto surfaces Is pH 4.5 and below Can occur far from the source of the primary pollutants
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Pollution Prevention Regulates anthropogenic pollution
Is mandated through the Clean Air Act National Ambient Air Quality Standards (NAAQS) Includes reducing emissions
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Pollution Prevention Requires newer and better technology
Chemicals Scrubbers Requires legislation and enforcement Treats persistent and non-persistent pollution differently Can involve economic incentives Cap and trade, tolls
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Reducing SO2 Emissions Involves changing how coal is burned
Uses fluidized bed combustion Calcium carbonate is added to coal as it is burned Heated calcium carbonate absorbs sulfur and forms calcium sulfate
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Reducing NOx Emissions
Involves reducing the heat and/or oxygen used in combustion of any fuel that contains nitrogen Reducing heat can lower the efficiency of the combustion process Creates less electricity and more waste
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NOx Emissions and Cars Have been reduced through the use of catalytic converters Convert NOx emissions to N2 gas, H2O, and CO2
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Reducing Particulate Emissions
Can use gravity Larger particles fall to the bottom of a smokestack Can use baghouse filters Emissions are passed through a series of bags that filter out particles
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Reducing Particulate Emissions
Can use scrubbers Water is sprayed on emissions to trap particles Can use electrostatic precipitators Use electrically charged electrodes to attract charged particles
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Unique Pollution Control Legislation
Regulating businesses that generate VOCs Allow car driving every other day Tiered toll systems Costs more to drive at peak traffic times Location-based toll or permit systems Costs more to drive in high-traffic areas
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Cap and Trade Is how the US has reduced sulfur emissions
Sulfur emitters get a number of allowances for sulfur emissions Each allowance is for 1 ton of sulfur Sulfur emissions must be equal to or less than the allowances or a fine is levied Unused allowances can be sold or traded
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Do The Math p. 424 Calculate total percentage reduction of sulfur emissions 23.5 million metric tons – 10.3 million metric tons = 13.2 million metric tons total reduction (13.2 million metric tons /23.5 million metric tons) x 100 = 56%
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Do The Math p. 424 Calculate annual percentage reduction of sulfur emissions 2008 – 1982 = 26 years (reductions began in 1982, latest year for which data is available is 2008) 56% / 26 years = 2.2% per year
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Stratospheric Ozone Is beneficial as it absorbs UV radiation
Constantly breaks down and re-forms Can be destroyed by chlorofluorocarbons (CFCs) Chlorine permanently bonds to oxygen, disrupting the ozone formation cycle CFCs are persistent in the upper atmosphere
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The Ozone Hole Forms at the South Pole, where ozone concentrations are thinnest Forms from springtime release of Cl2 that is bound to ice crystals in air during winter Results from the overall thinning of the ozone layer Allows more UV radiation through to the troposphere
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The Montreal Protocol Was signed in 1987
Targeted chemicals that deplete ozone Aimed to reduce CFC emissions by 50% by 2000 Addendum required production of CFCs to stop by 1996
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The Montreal Protocol Succeeded because:
There was a clear cause to the problem that could be eliminated Developers of substitutes for CFCs stood to gain financially Has reduced CFC emissions to 5 ppb/year, and these levels will continue to drop We should see the ozone layer begin to rebuild around
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Indoor Air Pollution Can come from combustion
Particulates Carbon monoxide This is more often found in developing countries Can come from chemicals used in construction and consumer goods Asbestos Radon VOCs Is a problem in developed countries because of better-insulated buildings
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Indoor Particulates Can come from cooking and heating fires
Can be biological Hair, dander, dust mites, bacteria, viruses 95% of dust is dead skin A human generates 1.5 lbs of skin cells a week Bioaerosols Sweat, skin oil, urine, feces Cause respiratory diseases Cancer, emphysema, asthma, bronchitis
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Asbestos Is a thin fiber made of silicates Is an excellent insulator
Was common in many building materials Now banned in the US Individual fibers are usually less than 10 μm in diameter Cause asbestosis (scarring of lungs) and cancer if they are inhaled Is only dangerous when exposed or disturbed Cleanup must be carefully monitored and contained
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Radon (Rn) Is a colorless, odorless, radioactive gas
Decays into polonium Forms from breakdown of granitic rock Often found in rock layers and soil Can seep into a home through cracks in the foundation Basements can accumulate it Causes lung cancer Second leading cause behind smoking
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Indoor VOCs Are found in plastics, building materials, furniture, paint, glue, dry cleaning solvent, deodorizers A good example is formaldehyde Biological fixative Suspected carcinogen
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Sick Building Syndrome
Results from sealing drafts and increasing insulation to maintain energy efficiency Can cause diseases in its occupants Can be caused by: Poor ventilation Indoor chemicals Outdoor contaminants transferred inside Buildup of mold or bacteria
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