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The Atmosphere and Atmospheric Pollution. Atmospheric Components. Chemical Components (elements) Nitrogen gas (N 2 ) makes up about 78% of the atmosphere Oxygen gas (O 2 ) makes up about 21% Other gases (Ar, He, etc.)
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The Atmosphere and Atmospheric Pollution
Atmospheric Components
• Chemical Components (elements)–Nitrogen gas (N2) makes up about 78% of
the atmosphere–Oxygen gas (O2) makes up about 21%–Other gases (Ar, He, etc.) <1%
Atmospheric Components
• Most abundant compounds:–Carbon dioxide (CO2)–Water vapor varies greatly• Evaporation ()• Transpiration by plants ()• Precipitation, condensation ()
Atmospheric Components
• Other components–Ozone (O3) - UV filter in upper
stratosphere; bad in troposphere–Dust - from volcanoes, sandstorms,
fires, etc. (pretty sunsets!)
Atmospheric Layers
Troposphere:• Closest to the Earth’s surface• All weather changes take place here• Most of CO2 and H2O vapor here• Height varies from about 20 km at equator
to about 8 km at poles - Why?• Temperature decreases with height
Atmospheric Layers
Stratosphere• Contains almost all the ozone (O3) in the
atmosphere 3O2 +UV 2O3
• Temperature rises with altitude• Gases released from volcanic eruptions
stay here for years• Tops of thunderclouds can penetrate
OUTDOOR AIR POLLUTION
Outdoor Air Pollution
The presence of atmospheric chemicals at concentrations high enough to harm organisms, ecosystem, or human-made materials
Come from natural sources: dust, wildfires, VOCs (plants)
Come from human sources: near industrialized/urban areas
Outdoor Air Pollution
Is air pollution a recent development?
Outdoor Air Pollution
Primary Pollutants: • emitted directly into the airSecondary Pollutants:• Products of chemical rxns of 1⁰ pollutants• Good news?• Bad news?• What is the biggest pollution threat to poor?
Outdoor Air Pollution
Point source: specific spots where large quantities of pollutants are discharged (power plants and factories)
Nonpoint source: more diffuse, consisting of many small sources (automobiles)
Outdoor Air Pollution
Carbon Oxides:CO and CO2
• CO a result of incomplete combustion• CO from vehicle exhaust, tobacco smoke, forest
fires, inefficient stoves, furnaces• Chronic exposure to CO: heart attacks, lung
diseases• Acute exposure to CO: headache, nausea,
drowsiness, death
Outdoor Air Pollution
Carbon Oxides:CO and CO2
• CO2 in the atm: 93% a result of carbon cycle, rest is from human activity
• Considerable evidence: human-introduced CO2 is changing the climate
Outdoor Air Pollution
Nitrogen oxides (NOx):Nitric oxide (NO)• Formed from high-temp engines, coal plants,
lightning, bacteria (N-cycle)2NO + O2 → 2NO2 (brownish gas; photochemical
smog)2NO2 + H2O → 2HNO3 (acid deposition)• Eye, nose, throat irritant, aggravate lung ailments
Outdoor Air Pollution
Sulfur oxides (SOx):Sulfur dioxide (SO2)• One-third comes from S cycle• Rest from coal-burning plants, oil refining,
smelting• Converted to aerosols of H2SO4 – more on this
later
Outdoor Air Pollution
ParticulatesSolid particles and liquid droplets small enough to
remain suspended• ~62% from natural sources• Human input: coal, cars, plowed fields, road
construction, tobacco smoke• Fine (< 10μ) and ultrafine (<2.5μ) particles most
damaging
Outdoor Air Pollution
Particulates• Aggravate asthma, bronchitis• Shorten lifeToxic particles (Pb, Cd, PCBs)• Cause mutations, reproductive problems, cancer• According to EPA: 60-70,000 deaths
Outdoor Air Pollution
Ozone• Part of smog• Causes coughing, breathing problems, aggravates
heart and lung disease• Reduce resistance to colds, etc.• Irritant; damages plants, fabrics, tires, paints• Good O3 v. bad O3
Outdoor Air Pollution
Volatile Organic Componds (VOCs)• Organic cpds that exist as gas• Most are hydrocarbons• Methane is one example• Others: benzene, trichloroethylene, vinyl chloride
are industrial solvents• Benzene →→ leukemia, blood disorders, immune
damage, et al.
Outdoor Air Pollution
Industrial Smog• Main components: SO2, H2SO4, other particulates
• Most of carbon in coal, oil → CO, CO2, soot• Ammonium sulfate also produced• Not as problematic in developed countries
Outdoor Air Pollution
Photochemical Smog• Activated by light• A mixture of 1⁰ and 2⁰ pollutants• Reactants: VOCs + NOx + sunlight
• Products: O3, aldehydes, oxidants, HNO3, peroxyacyl nitrates (PANs)
• Hotter days: more ozone• Natural smog: Smokey Mountains (terpenes)
Outdoor Air Pollution
Factors Affecting: natural reduction• Settling• Precipitation• Ocean spray wash-out• Winds• Chemical reactions
Outdoor Air Pollution
Factors Affecting: increase• Urban buildings slow winds• Hills/mountains• High temperatures (↑ rxn rates)• VOCs from oak, poplar trees, kudzu• Grasshopper effect – transport by global winds• Temperature inversion
Outdoor Air Pollution Control
Prevention, Technology, Innovation• Fluidized bed combustion: coal burned w/ CaCO3,
produces CaSO4, which is used to make sheetrock• Controlling T and O2 can reduce NOx
• Catalytic converters also reduce NOx (also led to removal of Pb from gasoline)
• Control of particulates: baghouse filters, electrostatic precipitators, scrubbers
Outdoor Air Pollution Control
Prevention, Technology, Innovation• Municipal restrictions developed, including
restrictions on dry-cleaners, gas stations, even bakeries (oh, no!), car use restrictions, carpool lanes
• Clean Air Act amendments → reduced sulfur emissions; buying and selling of allowances that allowed release of certain amount of S
ACID DEPOSITION
Acid Deposition
Industry Smokestacks• Reduce local air pollution• Increase regional pollution as SOx and
NOx are carried downwind• Sulfuric and nitric acids are formed
Acid Deposition
Acid Deposition• Remain in atmosphere 2 – 14 days• Fall as wet deposition (rain, snow) or dry
deposition (crystals)• Some regional soils can buffer• Worst acid deposition - Asia
Acid Deposition
Effects• Respiratory disease• Damages human-made structures• Leach toxic chemicals from soils/rock• Aquatic systems (ΔpH, release Al3+)• Forest, crop damage
Acid Deposition
Reduction• Reduce coal use/use low-sulfur coal• Increase natural gas, renewable energy• Remove SOx and NOx from smokestacks• Tax emissions• Cleanup: lime to lakes, phosphate
fertilizer
INDOOR AIR POLLUTION
Indoor Air Pollution
Common Pollutants• Pesticides, lead (brought in on shoes)• Organic solvents• Dust mites, droppings• Molds and mildews• Formaldehyde & other VOCs• Radon
Indoor Air Pollution
Alarming Facts (more harmful than outdoor)• Levels are generally higher in homes and
cars (5x, 18x, respectively)• In developed countries, people spend
more time inside• EPA: 18 indoor pollutants on carcinogen
list
Indoor Air Pollution
Sick Building Syndrome• Due in part to increased insulation• Indoor levels of VOCs and other
materials increase• Synthetic materials (glues, etc)• Ventilation, chemical contamination, air
intake, biological contamination
HEALTH EFFECTS
Health Effects
Natural Defense• Simple columnar epithelium contains
cilia and produce mucus• This line of defense gets broken down• Particulates embed in alveoli• Emphysema is irreversible; alveoli
damaged, lose surface area
DEALING WITH AIR POLLUTION
Legislation addresses pollution• Congress passed a series of laws starting in 1955• The Clean Air Act of 1970– Sets standards for air quality, limits on emissions– Provides funds for pollution-control research – Allows citizens to sue parties violating the standards
• The Clean Air Act of 1990– Strengthens standards for auto emissions, toxic air
pollutants, acidic deposition, stratospheric ozone depletion
– Introduced emissions trading
Laws
Ambient Air Quality Standards• Standards for 6 criteria pollutants – CO,
NOx, SO2, O3, Pb, & particulates• Standards for 188 hazardous chemicals• Public record: Toxic Release Inventory