Transcript Ozone - SECTION N


Earth is the largest and most massive of
the four terrestrial planets, but smaller
and less massive than the four giant, or
Jovian, planets.

Earth is third in distance from the Sun
among the four terrestrial planets.
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Earth
has
a
moderately
dense
atmosphere; 90 times less dense than
that of Venus but 100 times denser than
that of Mars.
Earth is unique in many respects:
Earth is the only planet with liquid water on its surface.
Earth’s atmosphere is the only one having a significant (21%) proportion of
molecular oxygen.
Earth is the only planet in the solar system having living organisms.
Earth is the only terrestrial planet having a moderately strong magnetic field.
Earth is the only terrestrial planet having a large satellite.
The Spheres of the Earth
• Atmosphere
• Hydrosphere
• Lithosphere
• Biosphere
• Cryosphere
• Anthrosphere
• A gaseous
sphere which
envelopes the
Earth.
• Consists of a
mixture of
gases
composed
primarily of
nitrogen,
oxygen, carbon
dioxide, and
water vapor.
Atmosphere
Earth's Atmosphere
Thin Gaseous envelope
99% of atmospheric gases, including water vapor, extend only 30
kilometer (km) above earth's surface.
Most of our weather, however, occurs within the first 10 to 15 km.
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Nitrogen - 78%
Oxygen - 21%
Water Vapor – 0 to 4%
Carbon Dioxide - .037%
Other gases make up the rest
Atmospheric Gases
Nitrogen, oxygen,
argon, water vapor,
carbon dioxide, and
most other gases
are invisible.
Clouds are not gas,
but condensed
vapor in the form of
liquid droplets.
Ozone – is the primary ingredient of smog!
Ground based
smog, which is
visible, contains
reactants of
nitrogen and ozone.
Aerosols & Pollutants
Human and
natural activities
displace tiny soil,
salt, and ash
particles as
suspended
aerosols,
as well as sulfur
and nitrogen
oxides, and
hydrocarbons as
pollutants.
Pressure & Density
Gravity pulls gases
toward earth's
surface, and the
whole column of
gases weighs 14.7
psi at sea level, a
pressure of 1013.25
mb or 29.92 in.Hg.
The amount of force
exerted Over an area of
surface is called
Air pressure!
Air Density is
The number of air
Molecules in a given
Space (volume)
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The rate at which air temperature
decreases with height.
The standard (average) lapse rate in
the lower atmosphere is about
6.5°C per 1 km or 3.6°F per 1000 ft.
Present distribution of major elements and U, Th, He
and Ar in the Earth’s atmosphere, crust and in seawater.
(Elements listed in order of abundance.
Evolution of Earth’s atmosphere from early Hadean (5 Bya) to present. Note
the changes from Stage I to Stage II, particularly the evolution of nitrogen,
(N) the virtual disappearance of hydrogen (H) and methane (CH4).
The important change from Stage II to Stage III was the rise in oxygen (due
to evolution of photosynthetic algae). Note the presence of the noble gases,
Ar, Ne, He and Kr. Most likely from the degassing upper mantle which
continues to today.
Hydrosphere
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All of the
water on
Earth
71% of the
earth is
covered by
water and
only 29% is
terra firma
•
Ocean water
• 96.5 % H2O by mass
• Remainder: various salts
• Temperature:
– Warmer near the surface
– Deep water (below ~1000 m) is equally cold
• Density:
– Colder, saltier water is denser = deep water
Freshwater
• Where is the freshwater on Earth, and in
approximately what percentages?
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Ice caps, glaciers:
Aquifers:
Surface water:
Atmosphere:
69 %
30 %
0.9%
0.1%
Aquifers
• Rock layers below the surface of the earth
that are porous and hold water.
• Water moves through an aquifer just as
water moves in a river.
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Lithosphere
The Earth's solid surface,
often called the crust of the
earth. It includes continental
and oceanic crust as well as
the various layers of the
Earth's interior.
The Lithosphere
The crust and the upper layer of the
mantle together make up a zone of rigid,
brittle rock called the Lithosphere.
Biosphere
• All life on earth,
including man, and
all organisms.
• The life zone on
our planet
distinguishes our
planet from the
others in the solar
system.
• Biosphere is the biologically inhabited portion of the Earth in
which ecosystems operate
Studies of the biosphere are linked with geology, ecology, soils,
atmospheric processes and climate, oceans.
Humans influence the biosphere through a range of deliberate and
inadvertent practices.
Biomes are major global scale zones with characteristic life forms
of plants and animals.
Cryosphere
• The portion of the
Earth's surface where
water is in a solid
form
• Snow or ice: includes
glaciers, ice shelves,
snow, icebergs, and
arctic climatology
Anthrosphere
• Man and his direct
ancestors, hominids.
• The human
population, it’s
buildings, dams and
other constructions.
Internal Structure of Earth
The Earth is composed of four
different layers. The crust is
the layer that you live on, and
it is the most widely studied
and understood. The mantle
is much hotter and has the
ability to flow. The outer
core and inner core are
even hotter with pressures so
great you would be squeezed
into a ball smaller than a
marble if you were able to go
to the center of the Earth!
Inner Core –
1200 km made
of solid Fe, Ni.
 Outer Core –
2250 km made
of liquid Fe, Ni.
 Mantle – 2900
km made of
dense rocks.
 Crust – 5 – 40
km made of
solid lighter
rocks.

Lithosphere (Crust and MOHO)
– 100km thick.
MOHO = Mohorovicic
Discontinuity
The Crust
The Earth's Crust is like
the skin of an apple. It is
very thin in comparison to
the other three layers. The
crust is only about 3-5
miles (8 kilometers) thick
under the oceans (oceanic
crust) and about 25 miles
(32 kilometers) thick
under the continents
(continental crust).
The Crust
The crust is composed of two rocks. The continental
crust is mostly granite. The oceanic crust is basalt.
Basalt is much denser than the granite. Because of this
the less dense continents ride on the denser oceanic
plates.
The Lithospheric Plates
The crust of the Earth is broken into many pieces called
plates. The plates "float" on the soft, semi-rigid
asthenosphere.
The Asthenosphere
The asthenosphere
is the semi-rigid
part of the middle
mantle that flows
like hot asphalt
under a heavy
weight.
The Mantle
The Mantle is the
largest layer of the Earth.
The middle mantle is
composed of very hot
dense rock that flows like
asphalt under a heavy
weight. The movement of
the middle mantle
(asthenosphere) is the
reason that the crustal
plates of the Earth move.
Convection Currents
The middle mantle "flows"
because of convection
currents. Convection
currents are caused by the
very hot material at the
deepest part of the mantle
rising, then cooling and
sinking again --repeating
this cycle over and over.
The Outer Core
The core of the Earth
is like a ball of very
hot metals. The
outer core
is so
hot that the metals in
it are all in the liquid
state. The outer core
is composed of the
melted metals of
nickel and iron.
The Inner Core
The inner core of
the Earth has
temperatures and
pressures so great that
the metals are
squeezed together and
are not able to move
about like a liquid, but
are forced to vibrate in
place like a solid.
• Lecture 2
Atmospheric Layers
8 layers are defined by
constant trends in average
air temperature (which
changes with pressure and
radiation), where the outer
exosphere is not shown.
1.
2.
3.
4.
5.
6.
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Troposphere
Tropopause
Stratosphere
Stratopause
Mesosphere
Mesopause
Thermosphere
Exosphere
Lower Layers of Atmosphere
• Troposphere: lowest layer –
extends up to 10km; contains
99% of the water vapor and
atmospheric gases
• The troposphere is the first layer
above the surface and contains
most clouds and half of the
Earth's atmosphere.
 Weather occurs in this layer.
 Most of the layer’s heat is
from Earth
 Temperature cools about 6.5
degrees Celsius per kilometer
of altitude.
Lower Layers of Atmosphere
• Stratosphere – directly above
troposphere, extending from 10
km to about 50 km above Earth’s
surface
 Portion of the upper layer
contains high levels of a gas
called ozone
 Many jet aircrafts fly in the
stratosphere because it is very
stable. Also, the ozone layer
absorbs harmful rays from the
Sun.
Stratosphere
Temperature inversion in stratosphere
ozone plays a major part in heating the air
at this altitude
• Mesosphere – extends from the
top of the stratosphere to about
85 km above Earth
 Coldest layer with little ozone
 Ionosphere here – layer of
charged particles
Mesosphere
Middle atmosphere – Air thin, pressure low,
Need oxygen to live in this region. Air
quite Cold -90°C (-130°F) near the top
of mesosphere
Upper Layers of Atmosphere
Thermosphere
“Hot layer” – oxygen molecules absorb
energy from solar Rays warming the air.
Very few atoms and molecules in this
Region.
• Thermosphere – thickest
atmospheric layer found
between 85 km and 500 km
above Earth’s surface
• The thermosphere is a layer
with auroras, known for its
high temperatures.
 Warms as it filters out Xrays and gamma rays from
the Sun
 Ionosphere here, too – help
carry radio waves.
Upper Layers of Atmosphere
• Exosphere - The atmosphere
merges into space in the extremely
thin exosphere. This is the upper
limit of our atmosphere.
• Outer layer where space shuttle
orbits.
Temperature in atmospheric layers
• The troposphere is warmed
primarily by the Earth’s
surface; temperature decreases
as altitude increases in this
layer.
• Temperatures increase as
altitude increases in the
stratosphere, particularly in the
upper portion – ozone
• Temperatures decrease with
altitude in the mesosphere
• Thermosphere and exosphere
are the first to receive Sun’s
rays, so they are very hot
The Ozone Layer
What is Ozone? Ozone Layer?
• Ozone (O3) is a highly-reactive from of oxygen.
• Unlike oxygen (O2), ozone has a strong scent and
is blue in color.
• Ozone exists within both the tropospheric and
stratospheric zones of the Earth’s atmosphere
• In the troposphere, ground level ozone is a major
air pollutant and primary constituent of
photochemical smog
• In the stratosphere, the ozone layer is an
essential protector of life on earth as it absorbs
harmful UV radiation before it reaches the earth.
Ozone formation
Ozone (O3)
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Chemically forms when UV hits on stratosphere
Oxygen molecules dissociate into atomic oxygen
O2 + sunlight  O + O
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Atomic oxygen quickly combines with other oxygen molecules
to form ozone
O + O2
O3
What is CFCs?
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Chlorofluorocarbons (CFCs)
Developed in 1930 by DuPont
CFCs were welcomed by industries:
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CFCs are used in aerosol sprays l
Low toxicity
Chemical stability
Cheap
Usage:
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As refrigerants
As blowing agents
For making flexible foam
As cleaning agents
As propellants
CFCs were used as refrigerants
CFC’s and ozone depletion
• Chlorofluorocarbons are
created and used in
refrigerators and air
conditioners. These
chlorofluorocarbons are not
harmful to humans and have
been a benefit to us. Once
released into the atmosphere,
chlorofluorocarbons are
bombarded and destroyed by
ultraviolet rays. In the process
chlorine is released to destroy
the ozone molecules
Present situation
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Stratospheric ozone over Antarctica:
– Has been depleted over the last 15 years
– The ozone hole:
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enlarging
large enough to cover most of the North America
would take at least 50 years to restore
Destruction of ozone by chlorine
Molecular oxygen is broken down in the stratosphere by solar
radiation to yield atomic oxygen, which then combines with
molecular oxygen to produce ozone. The ozone is then
destroyed by chlorine atoms.
Ozone destruction by UV rays
• UV radiation from the sun
releases the radicals Cl and
ClO.
• Ozone is a highly unstable
molecule so it readily donates
its extra oxygen molecule to
free radical species such as
hydrogen, bromine, and
chlorine.
• These compound species act
as catalysts in the breakdown
of ozone molecules.
Destruction of ozone layer
Chlorine atoms from CFCs attack the
ozone, taking away ozone and
forming chlorine monoxide (ClO).
O3 + Cl  O2 + ClO
Chlorine monoxide then combines with
another oxygen atom to form a new
oxygen molecule and a chlorine atom.
ClO + O  Cl + O2
The chlorine atom is free to destroy up to 100,000 ozone
molecules
Consequences of less ozone
• Because CFCs has long life span
and very stable, it continuous to
attack the ozone layer and more
UV-B reach our earth.
Responsibility for ozone damage
each year
Effects of UV rays on Aquatic
Ecosystems
Ozone depletion causes increases in UV
rays’s effects on aquatic ecosystems by:
1. decreasing the abundance of phytoplankton –
affects the food stock for fishes and the
absorption of CO2
2. decreasing the diversity of aquatic organisms –
reduces food stock and also destroys several
fish and amphibians.
Effects of UV rays on Terrestrial
Ecosystems
• Damage to plant cell DNA molecules - makes
plants more susceptible to pathogens and pests
• Reductions in photosynthetic capacity in the
plant - results in slower growth and smaller leaves
• Causes mutations in mammalian cells and destroys
membranes
Harmful effects of UV rays on people
• Skin cancer
• Premature aging (photoaging) of the skin
(different from normal chronological aging)
• Cataracts and eye disorders (corneal
sunburn and blindness)
• Immune system damage
Factors affecting UV exposure
• Clouds cover - partly cloudy days do little to
reduce UV exposure but rainy or substantially
overcast days reduce UV exposures
• The time of day – peak exposure time is 12:00
noon - 1:00 p.m. UV intensity is reduced by about
half at three hours before and three hours after the
peak exposure time.
Factors affecting UV exposure..2
• The time of year - more UV is received in
the late spring and early summer and much
less is received in the late fall and early
winter.
• Life style – determines a person’s risk to
UV exposure. Skiing, sunbathing, or
swimming can lead to extremely high
exposures. Use of tanning parlors also
increase risk.
Radio Wave Propagation
(Ionosphere Radio Prop)
AM radio waves are long enough to interfere with ions in the suncharged D layer, but at night the D layer is weak and the AM
signal propagates further, requiring stations to use less power.