Acid Rain
AP Environmental Science
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This is the Island known as Earth
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Background
Information
3
Atmosphere
4
Earth’s Atmosphere
Compared to the size of the
Earth (12000 km)
The atmosphere is very thin
(120 km)
5
http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm
If the Earth is
compared to this
Orange
the Earth’s
atmosphere
would be
thinner than the
layer of
pesticide on this
Orange’s
surface
6
Two Atmosphere Layers
• Stratosphere is above Troposphere
–Ozone Layer blocks UV radiation
• Troposphere is where we live
–Weather occurs here
• 72% of all air is below the cruising
altitude of commercial airliners
(33000 ft)
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Measuring Acid Rain
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•
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Acid rain is measured using a "pH" scale.
–The lower a substance's pH, it is more
acidic
Pure water has a pH of 7.0
– Normal rain is slightly acidic and has a pH
of about 5.6
Any rainfall has a pH value less than 5.6 is defined
as acid rain
As of the year 2000, the most acidic rain falling in
the US has a pH of about 4.3.
Two Forms…
Wet
Refers to acid
rain, fog, sleet,
cloud vapor
and snow.
• Dry
Refers to acidic
gases and
particles.
Compounds
Two main contributers to acid deposition:
•
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Sulfur Dioxide (SO2)
Nitrogen Oxides (NOx)
* 66% of all sulfur dioxides and 25% of all nitrogen
oxides comes from electric power generation
that produces energy by burning fossil fuels.
When gas pollutants e.g. sulfur
dioxide, nitrogen dioxide
dissolve in rain water, various
acids are formed.
CO2 + H2O  H2CO3 (carbonic acid)
SO2 + H2O  H2SO3 (sulphorous acid)
NO2 + H2O  HNO2 (nitrous acid) + HNO3 (nitric
acid)
Primary Pollutants
SO2
NO2
Secondary Pollutants
H2SO4
HNO2
sulfuric acid nitric acid
acidic precipitation
vegetation
direct toxicity
indirect health effects
water
Fossil fuels
Power plants
Industrial emissions
soils
sediments
Auto emissions leaching of mineralsleaching aluminum
Acidic
Precipitation
Wind
Transformation to
sulfuric acid (H2SO4)
and nitric acid (HNO3)
Windborne ammonia gas
and particles of cultivated soil
partially neutralize acids and
form dry sulfate and nitrate salts
Sulfur dioxide (SO2)
Nitric oxide (NO)
and NO
Acid fog
Ocean
Dry acid
deposition
(sulfur dioxide
gas and particles
of sulfate and
nitrate salts)
Wet acid deposition
(droplets of H2SO4 and
HNO3 dissolved in rain
and snow)
Farm
Lakes in
deep soil
high in limestone
are buffered
Lakes in shallow
soil low in
limestone
become
acidic
“Wet” Acid Rain
Acidic water flows
over and through
the ground, it
affects a variety of
plants and animals.
“Dry” Acid Rain
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Dry deposition refers to acidic gases
and particles.
About half of the acidity in the
atmosphere falls back to earth
through dry deposition.
The wind blows these acidic
particles and gases onto buildings,
cars, homes, and trees.
http://svr1-pek.unep.net/soechina/images/acid.jpg
Effects of Acid Rain
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Has a variety of effects, including damage to
forests and soils, fish and other living things,
materials, and human health.
Also reduces how far and how clearly we can
see through the air, an effect called visibility
reduction.
Effects of acid rain are most clearly seen in the
aquatic environments
Most lakes and streams have a pH between 6
and 8
http://cica.indiana.edu/projects/Biology/movies.html
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In areas where buffering capacity is low,
acid rain also releases aluminum from soils
into lakes and streams
Aluminum is highly toxic to many species of
aquatic organisms.
http://home.earthlink.net/~photofish/fish_photos/sw10_thumb.jpg
Nutrients
• Acidic water
–dissolves the nutrients and helpful
minerals in the soil
–washes them away before trees and
other plants can use them to grow.
• Acid rain also causes the release of
substances that are toxic to trees and
plants, such as aluminum, into the soil.
Effects on Wildlife
• Generally, the young of most species
are more sensitive to environmental
conditions than adults.
• At pH 5, most fish eggs cannot hatch.
• At lower pH levels, some adult fish die.
• Some acid lakes have no fish.
Effects on Wildlife
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Both low pH and increased aluminum levels
are directly toxic to fish.
In addition, low pH and increased aluminum
levels cause chronic stress that may not kill
individual fish, but leads to lower body
weight and smaller size and makes fish less
able to compete for food and habitat.
Acid Rain and
Forests
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Acid rain does not usually kill trees directly.
Instead, it is more likely to weaken trees
–Damaging their leaves
–Limiting the nutrients available to them
–Exposing them to toxic substances slowly
released from the soil.
Mongolia
Germany
Great Smoky
Mountains, NC
http://nadp.sws.uiuc.edu/amaps2/
1984
Sulfate Ion Concentrations
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