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a thin blanket of air surrounding the earth - 99% lies within 30 km of earth's surface
divided into 5 main layers with temperature of each layer varying with altitude:
1. TROPOSPHERE - harbors nearly all living things and nearly all human activity, temperature temperature decreases as altitude increases
2. STRATOSPHERE - temperature increases as altitude increases
3. THERMOSPHERE - temperature increases as altitude increases
4. EXOSPHERE - boundary of outer space, and so thin that satellites orbit there for months or even years |
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| comprised by volume 78% nitrogen (N2), 21% oxygen (O2), 1% argon (Ar) (then CO2 .04%, trace substances .002%) |
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| contains up to 4% water vapor |
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nitrogen and oxygen generally exist in the atmosphere as a mere mixture of gases that don't react - but when they do, life forms
nitrogen is essential to living things, but most animals and plants cannot assimilate N2 (atmospheric nitrogen) directly - it must be FIXED (combined with another element - which isn't easy because of nitrogen's triple bond) |
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lightning fixes nitrogen by causing it to combine with oxygen, forming nitrogen monoxide (nitric oxide) (NO)
then nitrogen dioxide (NO2)
then reacts with water to form nitric acid (HNO3)
nitric acid falls in rainwater adding to supply of available nitrates in ocean and soil, acidifying streams & lakes
most fixation is performed by bacteria in the roots of legumes - then other plants take up nitrates from soil - animals get nitrogen from plants
finally other microbes use nitrate ion as oxygen source in decomposition of organic matter and release N2 back into atmosphere |
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| industrial nitrogen fixation |
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by the Haber-Bosch process - combining nitrogen with hydrogen to form ammonia
increases the availability of fixed nitrogen for food production (often the limiting factor)
excessive runoff from fertilizer has led to serious water pollution problems in some areas and algal blooms and dead zones in others |
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decay and combustion of plant and animal materials consume oxygen and produce carbon dioxide, and burning of fossil fuels, and rusting of metals and weathering of rocks
simplified oxygen cycle - phytoplankton and plants use CO2 for photosynthesis, release oxygen, atmospheric mixing, people breathe oxygen and oxidation of metals takes oxygen, breathing and pollution release CO2 back |
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occurring in the stratosphere
oxygen is formed by the action of ultraviolet rays on water molecules
then oxygen with UV energy is transformed into ozone
which blocks other harmful UV rays that would kill organisms on earth |
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| temperature/thermal inversion |
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when the air is still, and the lower layer of cold air becomes trapped by the layer of warm air above it, trapping pollutants near the ground in the cold air
can also happen when a warm front collides with a cold front |
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| pollution through the ages |
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natural sources: wildfires, windblown dust, volcanic eruptions
winds and precipitation do purify the air, but we are pouring more pollutants into the atmosphere than it can readily handle |
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| too much of any substance in the wrong place or at the wrong time - something may be helpful in one place and harmful in another |
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contraction of the words smoke and fog
polluted air associated with industrial activities
characterized by the presence of smoke, fog, sulfur dioxide, and particulate manner such as ash and soot
high-grade coal is a complex combination of organic (carbon - burns when combusted) and inorganic materials (minerals that wind up in ash, also unburned carbon goes into air) |
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readily absorbed into respiratory system, a powerful irritant
sulfur trioxide (results from reacting with oxygen in air)
sulfur trioxide then reacts with water to form sulfuric acid
sulfuric acid becomes fine droplets as aerosol, and a strong acid and even more irritating to respiratory tract that sulfur dioxide |
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solid and liquid particles of greater than molecular size (usually in air, water, gas, etc.)
ex. soot - unburned carbon
small particles less than 10 nanometers in diameter are especially harmful (PM10) |
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| PM can be removed from a smokestack in several ways |
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electrostatic precipitator - induces electric charges on the particles, which are then attracted to oppositely charged plates and deposited
bag filtration - like a vacuum bag, passing through filters to be shaken out
cyclone separator - arranged so stack gases spiral out, hitting particulates against the walls and settled out, to be collected at the bottom
wet scrubber - removes PM by passing stack gases through water |
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| effects of relatively harmless PM combining to create a deadly combination (asbestos and cigarette smoke) |
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formed when insufficient oxygen is present during combustion
makes up more than 60% by mass of all air pollutants entering the atmosphere (TRANSPORTATION)
nonirritating, invisible, odorless, tasteless gas that kills by tying up hemoglobin in blood (oxygen transporters) leading to oxygen deprivation - only symptom is drowsiness |
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formed when N2 and O2 react at high temperatures
nitrogen oxides can be formed during the combustion of any fuel regardless of whether nitrogen is present in fuel (because nitrogen & oxygen are in air already)
nitrogen dioxide is an amber-colored gas that causes eye irritation and brownish haze
nitric oxide at high concentrations reacts with hemoglobin (like CO) and leads to oxygen deprivation
nitrogen dioxide is an eye and respiratory irritant
most serious environmental effect of nitrogen oxides is their leading to smog formation |
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| volatile organic compounds (VOCs) |
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major contributors to smog formation - many are hydrocarbons released from a variety of natural sources - only 15% in atmosphere are from people
processing of gasoline is a source of hydrocarbons (evaporating somewhere along the line) - act as pollutants even when not burned - alkenes combine with oxygen atoms or ozone molecules to form ALDEHYDES (foul, irritating odors)
another series of rxns lead to formation of peroxyacetyl nitrate (PAN) - destructive aspect of smog |
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smog produced through sunlight acting upon atmospheric pollutants (unburned hydrocarbons, nitrogen oxides) as a visible, amber haze - usually occurs in dry, sunny weather
NO2 absorbs a photon of sunlight and breaks into NO and O, which are very reactive, and combine with other elements in the atmosphere to create harmful pollutants including ozone
could be improved by improving on storage and dispensing devices, also CATALYTIC CONVERTERS which reduce hydrocarbon and carbon monoxide emissions from automotive exhausts (has saved 12 billion tons of harmful exhaust gases in last 30 years) |
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| defined as having a pH less than 5.6, coming mainly from sulfur oxides emitted from power plants and smelters and from nitrogen oxides discharged from power plants and automobiles |
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CO is dangerous inside - sources include:
woodstoves, gas stoves, cigarette smoke, unvented gas and kerosene space heaters, radon and daughter isotopes and radioactive decay, mold |
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| two different forms of the same element (ex. O3 and O2) |
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high in the atmosphere, it absorbs short and long-wavelength (but still lethal UV rays, shielding us from harmful radiation, and converts back into oxygen molecules and atoms
ozone layer thickness varies with latitude and season - cycling of ozone concentration is most prevalent over Antartica in part because chemical reactions responsible for ozone destruction occur much more rapidly on the surfaces of ice crystals
CFCs (used as dispersing agents for aerosol, foaming agents for plastics, and refrigerants) are essentially insoluble in water and inert to most things, travel high up in the atmosphere where they are finally broken apart by strong UV rays, and the Cl reacts with ozone, breaking it apart and forming free radicals that break up more ozone with a chain reaction
CF2Cl2 + energy (UV) --> CF2Cl + Cl (free radical)
Cl (fr) + O3 --> ClO (fr) + O2
ClO (fr) + O --> Cl (fr) + O2
CFCs have been banned in the US and many other countries |
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gases that in the atmosphere let in sun's visible light to warm the surface, but when the Earth radiates infrared energy back toward space, these gases absorb and trap the energy, gradually raising the temperature of the earth
(like a car in the sun with the windows closed - sun gets in, heats up, but doesn't let heat out)
ENHANCED greenhouse effect is caused by increased concentrations of CO2 and other greenhouse gases in atmosphere - leading to global warming
water vapor also acts as a greenhouse gas as it traps heat in the air
methane also |
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the removal of CO2 from the atmosphere by collection and transportation of concentrated CO2 from large emission sources, such as power plants and factories, and subsequent storage in underground reservoirs
also the removal of CO2 from the atmosphere by forestry and agricultural practices, such as planting trees and stopping deforestation |
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| are the source of almost 1/2 by mass of all air pollutants |
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| WHO's rated worst pollutant |
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