Transcript Air Pollution

Air Pollution
• What causes air pollution?
– Human activities and natural events
Air Pollution
• Natural
Events
–Volcanoes
• Ash and toxic
gases
–Forest or
Grass fires
• Smoke
Air Pollution
• Primary pollution:
Pollutants released
directly into the air in
a harmful form.
– Examples: Ash and
toxic gas from
volcanoes, smoke
from industry, gases
and soot from
vehicles.
Air Pollution
• Secondary
pollution:
Pollutants that are
not released
directly into the air
but form in the
atmosphere.
– Examples: Brown
haze, smog.
Photochemical Smog
• Photochemical smog: Forms when
vehicles, industry and power plants
release nitrogen compounds and organic
compounds into the air. These
substances react to form nitrogen
dioxide which reacts in the
presence of sunlight to form
ozone.
Smog
• Nitrogen dioxide is a reddish-brown gas which
contributes to the color.
Nature and Smog
• Winds can disperse smog in many locations.
• In some areas mountains can trap the smog
from being dispersed.
Temperature Inversion
• Normally temperatures near Earth’s
surface are warmer than higher in the
lower atmosphere.
• During a temperature inversion,
warm air overlies cool air,
trapping the cool air near Earth’s
surface.
Temperature Inversion
Temperature Inversion
• Reduces the amount of mixing in the
atmosphere and can cause pollutants to
accumulate near Earth’s surface.
Acid Rain
• What is neutral pH?
Acid Rain
• Substances with a pH above 7 are basic and
substances with a pH below 7 are acid.
• Rainwater is slightly acidic.
– Pollution can cause rainwater to be even more acidic.
Acid Rain
• Natural lakes and
streams have a ph
between 6 and 8.
• Acid rain has a pH
below 5.6.
– Acid rain can cause
the pH of lakes and
streams to drop.
Acid Rain
• Power plants
burn fuels to
produce
electricity.
• Transportation
burns fuel.
Acid Rain
• When fuels burn they release primary
pollutants, such as:
– Sulfur dioxide
– Nitrogen oxides
• These compounds rise into the
atmosphere and combine with moisture in
the air to form secondary pollutants
sulfuric and nitric acids.
Acid Rain
• Winds carry these
acids long distances.
• The acids return to
the Earth in
precipitation.
Acid Rain
Acid Rain
• Soils and rocks in the Midwest are more
basic than in the northeast.
• Therefore acid rain falling the New York
can decrease the pH of soils, lakes and
streams more than in for example Indiana.
• Many lakes in the northeastern United
States have few fish due to acid rain.
Particulate Pollution
• Particulate matter:
Solid particles and
liquid droplets
suspended in air.
• Some particles enter
the air directly such
as smoke (from a fire)
or soot (from a bus)
– These would be
primary pollutants.
Particulate Pollution
• Liquid droplets
can form from
gases such as
nitrogen or
sulfur oxides
as they
combine with
water in the air.
Particulate Pollution
• Coarse particulate matter:
– Carried by the wind from dusty sites.
– Can be seen when there is a lot in the air.
• Fine particulate matter:
– Much smaller than the coarse.
– Release from smoke, vehicle exhaust,
factories and power plants.
– Can damage plants, buildings and your lungs
Particulate Pollution
Toxic Pollutants
• Toxic air pollutants: More
than 180 different substances.
–Might cause cancer or other
health problems.
–Most toxic pollutants are
released by humans.
Toxic Air Pollutants
Toxic Air Pollutants in NC
Toxic Air Pollutants
• Carbon Monoxide is formed when fossil
fuels are not completely burned.
– In a typical city 95% of Carbon Monoxide
(CO) is caused by transportation.
– CO is odorless and colorless.
– High concentrations are poisonous.
• Can be fatal.
Chlorofluorocarbons
• Chlorofluorocarbon
s (CFC)
– Were used in aerosol
sprays, air
conditioners and
refrigerators.
– CFC’s rise up into the
atmosphere and
damage the ozone
layer.
Ozone Depletion
• Ozone layer:
About 20 km
above the earth.
– Ozone is a
molecule made up
of 3 oxygen atoms.
– Ozone absorbs
some of Sun’s
harmful rays.
Ozone Depletion
• A chlorine (Cl)
atom from a CFC
breaks up an
ozone molecule in
an oxygen
molecule.
• The Cl atom can
destroy nearly
100,000 molecules
of ozone.
Ozone Depletion
• CFC production
was halted in 1996
by all industrialized
countries.
• CFC levels are
beginning to
decrease in the
atmosphere.