Download Greenhouse Effect and Global Warming

Chapter 15 Air Pollution
Acid Deposition
1
Background
Information
2
Atmosphere
3
Earth’s Atmosphere
Compared to the size of the
Earth (12000 km)
The atmosphere is very thin
(120 km)
4
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
5
Two Atmosphere Layers
• Stratosphere is above Troposphere
–Ozone Layer blocks UV radiation
• Troposphere is where we live
–Weather & Global Warming
• 72% of all air is below the cruising
altitude of commercial airliners
(33000 ft)
6
Acid Deposition – deposition of acidic or
acidic forming pollutants from atmosphere
onto the Earth’s surface.
•Precipitation – Acid Rain, snow, fog, sleet,
hail, or gases and dry particles
•Deposition can be Wet or Dry
7
Measuring Acid Rain
•Acid rain is measured using a "pH" scale.
–The lower the pH, the more acidic
•Pure water has a pH of 7.0
– Normal rain is slightly acidic and has a
pH of about 5.6
•Rainfall with a pH less than 5.6 is acid rain
•As of the year 2010, 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:
•
•
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.
sulphur dioxide, nitrogen dioxide
dissolve in rain water, various
acids are formed.
CO2 + H2O 
SO2 + H2O
H2CO3 (carbonic acid)
 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
“Wet” Acid Rain
Acidic water flows
over and through
the ground
Affects a variety of
plants and animals.
“Dry” Acid Rain
•
•
•
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/into
buildings, cars, homes, and trees.
http://svr1-pek.unep.net/soechina/images/acid.jpg
Nutrients
• Acidic water
–dissolves the nutrients and helpful
minerals in the soil
–washes nutrients away before plants can
use them to grow.
• Acid rain also causes the release of
substances, such as aluminum, that are
toxic to plants
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
• Both low pH and increased
•
aluminum levels are directly toxic
to fish.
Chronic stress that leads to lower
body weight
smaller size
•
•
Acid Rain and Forests
• Acid rain does not usually kill trees directly
• Weakens trees
–Damaging leaves
–Limiting nutrients available
–Toxic substances slowly released from the
soil.
Mongolia
Germany
Great Smoky
Mountains, NC