Transcript Environmental Chemistry web

Environmental Chemistry
The Environment
Air (Atmosphere) ** Water (Hydrosphere)
Land (Lithosphere)
Parts of the Atmosphere
Troposphere:
• From earth’s surface to 15 km
• The air we breathe
Stratosphere
• 15 – 50 km
• Ozone layer
Parts of the Atmosphere
Troposphere:
• From earth’s surface to 15 km
• The air we breathe
Stratosphere
• 15 – 50 km
• Ozone layer
Composition of the Troposphere
• Contains 75% of all gases
• Mostly N2 and O2
• Also dust, ice, salt, liquid water
Composition of the Stratosphere
• Lighter gases (H2, He)
• Ozone Layer – high
concentration of
ozone (O3)
Earth’s Water - Hydrosphere
• Surface water: oceans, streams, rivers
• Groundwater: beneath the surface
Earth’s Water - Hydrosphere
• Most of the water on earth is undrinkable (salt
water)
Water Cycle
3
3
2
5
6
Earth’s Crust - Lithosphere
• Oxygen is most abundant element
Earth’s Crust - Lithosphere
Resources: - Minerals (gold, silver, diamonds)
- Fuels (crude oil, natural gas, coal)
- Groundwater
Earth’s Crust - Lithosphere
• Groundwater: water located beneath the earth’s
surface in the spaces between soil particles.
Pollution
• Introduction of contaminants (chemicals) into the
natural environment.
• Types of pollution:
• Air pollution
• Water pollution
• Soil contamination
• Groundwater contamination
Pollution
• Air Pollution Sources
Pollution
• Water Pollution Sources
Pollution
In Southern California, all storm water drains to the
ocean.
Pollution
• Soil and Groundwater Pollution Sources
Pollution
Where does it go?
1. Spill 20 gallons of gasoline on the dirt
2. Burning coal in a power plant
3. Burying hazardous chemicals in a landfill
4. Dumping toxic chemical in the gutter on your
street
5.
Spraying pesticides on crops
Where does it go?
6. Driving your car
7. Dumping mercury down the drain in the
chemistry lab sink
8. A leaking diesel tank on a boat in a lake
9. Using nail polish remover (acetone)
10.Waste discharge from a factory into a river
Making Air Pollution in a Cup
- Nitrogen oxides (NO and NO2) – Cocoa
- Hydrocarbons – Blue food coloring
- Carbon monoxide (CO) – Red Food Coloring
- Sulfur dioxide (SO2) – Drink mix
- Dust – Charcoal
- Ozone – Yellow color
Making Air Pollution in a Cup
• If the air pollution around you were this apparent,
would you want to breathe the air?
• What other sources of air pollution, beyond those
mentioned in this demonstration, could you think
of as being produced in a single day?
• What could you do to reduce the number of
pollutants released each day?
Chemistry in the Troposphere
• SMOG: Smoke + fog
- In London, known for centuries.
- In 1879 – 4 continuous months of
smog
- In December 1952, smog killed 200
people in London.
- This led to the beginning of our Air
Laws in the U.S.
Chemistry in the Troposphere
• PHOTOCHEMICAL SMOG
- In Los Angeles (and Denver, Mexico City),
smog is created when sunlight reacts
with air pollutants.
- Most pollutants are from vehicles:
- Nitrogen oxides (NO and NO2)
- Hydrocarbons
- Carbon monoxide (CO)
- Sulfur dioxide (SO2)
- Dust particles
Chemistry in the Troposphere
• PHOTOCHEMICAL SMOG (Ozone)
• In the troposphere, ozone is produced in
the atmosphere.
• It irritates eyes & lungs and causes asthma
and pneumonia
- NO2 + UV light  NO + O
- O + O2  O3
Pollution
Acid Rain
Acidic particles are produced when pollutants SO2 and
NO2 mix with water vapor in the atmosphere.
Acid Rain
• SO2 forms sulfuric acid (H2SO4).
• NO2 forms nitric acid (HNO3).
Acid Rain
Acidic particles fall to Earth in two different
ways: wet deposition and dry deposition.
Acid Rain
Wet Deposition: Rain is naturally acidic because
of dissolved CO2, but acid rain has a pH of less
than 5.6. Can also be acidic hail, snow or fog.
Acid Rain
Dry deposition takes place when acidic
particles attach to dust particles in the
atmosphere and fall to the ground.
These particles stick
to cars, buildings,
and trees. The acidic
particles make any
rain water run off or
wash water acidic.
http://www.youtube.com/watch?v=HrBzrkZxIBo
Effects of Acid Rain
Effects of Acid Rain
•
Lowers the pH of lakes and streams.
• Most fish cannot survive if pH is less than 5
Effects of Acid Rain
•
Harms trees and forests
• Damages tree leaves and changes the
chemistry of forest soil
Effects of Acid Rain
•
Damages buildings and statues, especially those
containing calcium carbonate (limestone &
marble).
1908
http://www.youtube.com/watch?v=MqHw1hMEkAQ
1968
Effects of Acid Rain
•
Damages metal structures (the copper Statue of
Liberty) and automotive paint.
REVIEW
1. What two ways do acidic particles fall to Earth?
- Wet deposition (rain) and dry deposition
2. What two pollutants cause acid rain?
- SO2 forms sulfuric acid (H2SO4) and NO2 forms
nitric acid (HNO3).
3. Why is acid rain harmful to fish?
- Most fish cannot survive if the pH < 5
4. What else does acid rain damage?
- trees & forests, buildings & statues,
automotive paint
Chemistry in the Stratosphere
• Ultraviolet (UV) radiation
from the sun is absorbed by
the ozone layer.
• UV radiation causes cancer.
• The purpose of the Ozone
Layer: to absorb most of the
UV radiation from the sun
and reduce the amount that
reaches Earth.
Chemistry in the Stratosphere
How ozone forms in the
stratosphere:
a) O2 + UV  O + O
b) O + O2  O3*
c) O3 * + N2  O3 + N2*
d) O3 + UV  O + O2
* Energized molecule
Chemistry in the Stratosphere
Refrigerants – chlorofluorocarbons (CFCs)
Freon: CCl2F2
• Were used in refrigerators and air conditioners
- released to the atmosphere when they leaked
• Were also used in aerosol sprays
Chemistry in the Stratosphere
CFC Refrigerants are:
• Very stable in the troposphere, but
• Break down in the stratosphere to form chlorine
atoms.
CF2Cl2 + UV  CF2Cl + Cl
• Chlorine atoms react with ozone to form O2
Cl + O3  ClO + O2
ClO + O  Cl + O2
• Chlorine acts as a
catalyst.
Chemistry in the Stratosphere
• Chlorine atoms catalyze the destruction of ozone
Cl + O3  ClO + O2
ClO + O  Cl + O2
Chemistry in the Stratosphere
One Chlorine
atom can last 2
years and
destroy
100,000 ozone
molecules
CFC Ban
•
CFCs were banned from aerosol products in 1978
•
CFCs were completely banned in the U.S. in 2000
•
CFCs were completely banned in developing
countries in 2010!
REVIEW
1. What is the function of the ozone layer in the
stratosphere?
- To absorb UV radiation from the sun
2. What household products cause damage to
the ozone layer?
- Refrigerators, air conditioners and
aerosols using chlorofluorocarbons (CFCs)
3. What is “SMOG”?
- Smoke + fog
4. What is photochemical smog?
- Air pollution caused by air pollutants
reacting with sunlight
Greenhouse Effect
• “Goldilocks Effect”:
• Venus is too hot, Mars is too cold, Earth is just right.
• Earth has an average surface temperature comfortably
between the boiling point and freezing point of water, and
thus is suitable for our sort of life.
• This is due to the Greenhouse Effect.
Greenhouse Effect
• Earth’s atmosphere traps about 50% of the solar radiation
• This warming is necessary to maintain life on Earth.
• Without it Earth would be -18°C (~0°F) compared to
18°C (60°F)
1. High energy
radiation
hits the
Earth’s
surface
2. This
incoming
energy is
converted to
heat
3. Infrared
radiation hits
greenhouse gas
molecules in
the atmosphere
4. Greenhouse
gas molecules
in the
atmosphere reemit infrared
radiation back
towards Earth
5. This keeps the
temperature
changes each day
relatively small.
For example, on
the moon, the
temperature
changes from
123°C (253°F)
during the day to
-153°C (-243°F)
at night.
•
•
Greenhouse Gases
GREENHOUSE GAS: A gas in the atmosphere
that absorbs and emits infrared radiation.
The major components of the atmosphere
(N2, O2, Ar)
do not
absorb
Infrared.
•
•
Greenhouse Gases
Most diatomic gas with two different atoms
(carbon monoxide, CO, but not N2 or O2)
All gases with three or more atoms.
Percentage contribution to the greenhouse effect:
Most abundant:
 H2O 36-70%
 CO2 9-26%
 CH4 4-9%
 N2O 4-7%
Greenhouse Gases
Carbon dioxide () is one of the greenhouse gases. It consists of one carbon atom
with an oxygen atom bonded to each side. When its atoms are bonded tightly
together, the carbon dioxide molecule can absorb infrared radiation and the
molecule starts to vibrate. Eventually, the vibrating molecule will emit the
radiation again, and it will likely be absorbed by yet another greenhouse gas
molecule. This absorption-emission-absorption cycle serves to keep the heat near
the surface, effectively insulating the surface from the cold of space.
Selected Greenhouse Gases
• Water (H2O)
– Natural Sources: Clouds, water vapor (water cycle)
– Sinks (water removed from atmosphere): Precipitation
Selected Greenhouse Gases
• Carbon Dioxide (CO2)
– Natural Sources: CO2 dissolved in oceans, decay of plants
– Human Sources: Fossil fuel burning, deforestation
– Sinks: Ocean and photosynthesis by plants
 Increase in human sources since 1750: 40%
Selected Greenhouse Gases

Methane (CH4)
– Natural Sources: Decay from marshes, cattle and sheep
digestion
– Human Sources: Rice cultivation, cattle & sheep ranching,
decay from landfills, production of natural gas, coal and crude
– Sinks: Destruction in the atmosphere by hydroxyl radicals
Selected Greenhouse Gases

Nitrous oxide (N2O)
– Natural Sources: Reaction of ammonia (NH3) and NO3 in
the atmosphere (from agriculture)
– Human Sources: Industry and agriculture (fertilizers),
combustion of fossil fuels
The annual fluctuation is caused by variations in uptake of carbon dioxide by plants.
Historical Concentration of CO2, CH4, N2O
http://www.epa.gov/climatechange/science/overview.html#natural-causes
Historical Concentration of CO2, CH4, N2O
http://www.esrl.noaa.gov/gmd/aggi/aggi_2012.fig2.png
Greenhouse Effect & Global Warming
• The “greenhouse
effect” & global
warming are not the
same thing.
–Global warming
refers to a rise in
the average
temperature of the
surface of the earth
–Also called “Climate
Change”
Average Global Temperature Over Time
14.5
58.0
14.4
57.8
14.3
Variability
57.6
14.2
57.4
Average
14.1
14.0
57.2
13.9
57.0
13.8
56.8
13.7
56.6
13.6
56.4
13.5
56.2
13.4
1840
1860
1880
1900
1920
1920
www.gcrio.org/ipcc/qa/cover.html (modified)
1940
1960
1980
2000
Greenhouse Effect FACTS:
• The concentration of greenhouse gases (CO2, CH4
and N2O) have increased significantly since the
Industrial Revolution (~1900s).
• The average temperature on Earth has increased by
1.5°C since 1860.
Greenhouse Effect & Global Warming
One theory:
• An increase in the concentration of
greenhouse gases leads to an increase in the
magnitude of the greenhouse effect.
• This results in global warming
REVIEW:
1. What is the greenhouse effect?
- Earth’s atmosphere traps about 50% of
the solar radiation and keeps the
temperature warm enough for human life
2.
What is global warming?
- a rise in the average temperature of the
surface of the earth
GLOBAL WARMING?
Are emissions of greenhouse gases
by humans causing Global
Warming?
https://www.youtube.com/watch?v=3v-w8Cyfoq8