Air Pollution
Ch.
Atmosphere
• Thin envelope of
gases surrounding the
earth
– Pressure, air
density,
temperature
change w/ altitude
Layers of the Atmosphere
• Troposphere
–
–
–
–
inner most layer
weather occurs
Chemical cycling
Ozone here is
considered smog
– 75% all atmospheric
gases
• 78% nitrogen
• 21% oxygen
• 1% Argon
• .036% CO2
• other trace
Layers of the Atmosphere
• Stratosphere
– 2nd layer
– less water vapor,
increased good
ozone-OZONE LAYER
HERE
– 95% UV rays filtered
• keeps earth warm
• protects from harmful radiation
• prevents oxygen from converting
to photochemical 03 (ozone)
Layers of the Atmosphere
• Mesosphere
– 3rd layer
– cold, low pressure
Stratosphere
Mesosphere
Troposphere
Layers of the Atmosphere
• Thermosphere
– 4th layer
– temperature varies; (close
proximity to sun but air to
thin to hold heat)
Layers of the Atmosphere
• Exosphere
– 5th layer
– Space-atmo. merger
Outdoor Air
Pollution
Air Pollution
• Presence of one or more chemicals in the atmosphere
that can:
– cause harm
– alter the climate
– solid, gaseous or liquid
• Majority of pollutants come from natural sources like
dust, forest fires & geological processes
• We add air pollution through burning of fossil fuels,
erosion of land, factory emissions
Major Outdoor Air Pollutants
–
–
–
–
Carbon oxides (CO, CO2)
Nitrogen oxides (NO, NO2, N2O)
Sulfur oxides (SO2, SO3)
Suspended Particulate Matter
• Solids (dust, soot, lead, nitrate and sulfate salts)
• Liquids (sulfuric acid, PCBs, pesticides, dioxins
– Photochemical Oxidants (ozone)
– VOCs (Hydrocarbons like methane, octane,
benzene; other compounds like formaldehyde)
– Hazardous Air Pollutants
• Cause cancer, birth defects, nervous system damage
• HAPs: benzene, formaldehyde, chloroform, lead,
radioactives)
• Most developed countries set maximum
allowable atmospheric concentrations for the
pollutants commonly found in outdoor air.
– Developing countries tend to have WORSE pollution.
Why?
Pollution Source
• Primary pollutants: are
put directly into troposphere
from natural events or human
activities in a potentially
harmful form
– CO2 & NOx gases from car
exhaust
– Ash produced from burning coal
– SO2 gas from volcanoes or
burning coal
Pollution Source
• Secondary pollutants:
when primary pollutants react
with one another or with basic
components of air to form
new pollutants
– SO2 from burning coal reacts
with water vapor in
atmosphere to form sulfuric
acid AKA acid rain
Photochemical smog
Formed when nitrogen oxides
and VOC’s react with heat
& sunlight
– assoc. w vehicle emissions
•
ORANGE SMOG
A recent study
has shown that
modern
fertilizers may
be responsible
for up to 51%
of NOx
emissions in
CA.
INDUSTRIAL smog
• Due to burning large amounts of coal and heavy oil
• Rarely a problem today in developed countries, but was
in the past: ex. London’s Pea Soup fog
• Prominent in urban areas of China, India, Urkraine, and
some eastern European countries
• Secondary Pollutant:
– Sulfur dioxide emissions react w/water 🡪 sulfuric acid (acid rain)
• GREY SMOG
Factors that influence
smog formation:
•
•
•
•
•
•
•
Local climate (temp, rainfall)
Population density
Amount of industry
Fuels used in the area
Urban buildings
Hills & mountains
Grasshopper effect
Natural factors that REDUCE air pollution
• 1. Rain and snow
– Help cleanse air of pollutants. So cities with dry climates
tend to have more photochemical smog
• 2. Salty spray from the ocean
– Can wash out particulates and other water soluble
pollutants
• 3. Winds
– Help sweep pollutants away, dilute them with cleaner air,
and bring in fresh air.
Rain reduces pollution
Thermal Inversions
• Normally
–
–
–
–
Sun warms air near the surface
Warm air rises
Mixes with cool air above
Creates a current and disperses pollutants
Thermal Inversions
• THERMAL INVERSION
– sometimes a warm air layer is over a cool air layer and no movement occurs
– pollutants are stuck below warm “blanket” layer
– LA, Denver & Mx. City prone to inversions
Noise Pollution
• Defined as sound at levels high enough
to cause physiological stress and
hearing loss
• Common sources- transportation,
construction, and domestic and
industrial activity
• Environmental effects include: masking
of sounds (for hunting, communication,
etc.), damaged hearing, changes to
migration routes