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Title: Air: Climate and Pollution


1
Air Climate and Pollution
  • Chapter 9

2
Outline
  • Atmosphere and Climate
  • Climate Change
  • El Nino
  • Human Causes
  • Climate and Pollution
  • Kinds of Pollution
  • Sources
  • Transport
  • Effects of Air Pollution
  • Air Pollution Control

3
ATMOSPHERE AND CLIMATE
  • Weather - A description of short-term physical
    conditions of the atmosphere.
  • Climate - A description of the long-term weather
    pattern in a particular area.
  • Weather and climate are primary determinants of
    biomes and ecosystem distribution.
  • The atmosphere has 4 distinct zones of
    contrasting temperature due to difference
  • in absorption of solar energy

4
Troposphere
  • Tropospherelayer of air immediately immediately
    adjacent to the Earths surface.
  • Ranges in depth from 18 km over the equator to 5
    km over the poles.
  • Air circulates in convection currents.
  • Air temperature drops rapidly with increasing
    altitude.
  • Contains 75 of total air mass.
  • .

5
A Layered Envelope
  • Stratosphere
  • Extends from troposphere to about 50 km.
  • Similar composition to Troposphere, but much more
    dilute.
  • Temperature increases with altitude.
  • Almost no water vapor and 10 times more of ozone
    (O3) than in the troposphere.
  • Relatively calm

6
Stratosphere contd.
  • This ozone layer absorbs UV radiation which
    makes the stratosphere warmer towards the top.
  • Since UV normally damages living tissues,
    absorption of UV by stratosphere protects life on
    Earth.
  • The ozone layer over Antartica is depleting which
    will results in filtration of UV to the earth and
    causes skin cancer, mutations, crop failure etc.

7
A Layered Envelope
  • Above the Stratosphere , the temperature
    decreases creating the Mesosphere, the middle
    layer runs upto 85 km. Minimum temperature is
    about - 80o C
  • Thermosphere, the heated layer, begins at about
    85 km, runs for 600 km a layer of highly Ionized
    gases and high temperatures.
  • Ionosphere is the lower part of lower
    thermosphere which has high energy radiation
    which causes highly charged particles to glow
    called Aurora borealis (northern lights)
    A.australis (southern light)
  • .

8
Atmospheric Temperature Changes
9
Energy and the Greenhouse Effect
  • Solar Radiation
  • Solar energy not evenly distributed over the
    globe.
  • Of solar energy reaching outer atmosphere
  • 25 reflected
  • 25 absorbed
  • 50 reaches earths surface

10
Solar Radiation
  • Visible light passes through atmosphere
    undiminished.
  • Ultraviolet light is absorbed by ozone in the
    stratosphere.
  • Infrared radiation is absorbed by carbon dioxide
    and water in the troposphere.
  • Albedo surfaces that have high reflectivity
  • Fresh clean snow 90
  • Dark soil 3
  • Net average of earth 30

11
Solar Radiation
12
Solar Radiation
  • Most solar energy reaching the earth is visible
    light.
  • Energy re-emitted by the earth is mainly infrared
    radiation (heat energy).
  • Longer wavelengths are absorbed in the lower
    atmosphere, trapping heat close to the earths
    surface.
  • Greenhouse Effect (atmosphere is considered as a
    green house, transmit sunlight but traps heat
    inside).
  • Increasing atmospheric CO2 due to human
    activities appears to be causing global warming
    and the Greenhouse effect.

13
Convection and Atmospheric Pressure
  • Water vapor contains a large amount of energy
    stored as latent heat.
  • Evaporation converts solar energy into latent
    heat stored in evaporated water.
  • When water vapor condenses, this latent heat is
    released.
  • The redistribution of heat and water around the
    globe is essential to life on earth.

14
Why Does It Rain ?
  • Water vapor condenses,releasing latent heat
    causes air to rise, cool, and lose more water
    vapor.
  • Rising, expanding air creates an area of
    relatively high pressure at the top .
  • Air flows out of high-pressure zone towards areas
    of low-pressure.

15
Why Does It Rain ?
  • Subsiding air is compressed as it approaches the
    earths surface where it piles up and creates an
    area of high pressure at the surface.
  • Air flows out of this region back towards low
    pressure, closing the cycle.
  • If condensation nuclei (tiny particles of smoke,
    dust,spores, volcanic ash etc.)are present, or if
    temperatures are low enough, condensation will
    lead to precipitation.

16
Why it Rains? Contd.
  • Anytime when air is rising ,clouds, snow or rain
    might form.
  • Cooling occurs because of changes in pressure.
  • Air cools as it rises (as pressure increases) and
    if the air is moist it is likely to rain.
  • When air is sinking it warms up as it approaches
    the surface (increasing pressure).Available
    moisture evaporates.
  • Rainfall rarely occur in areas of high moisture (
    refer pg 199).

17
CLIMATE CHANGE
  • Periodic weather cycles detected (periodic
    weather changes).Reasons
  • Solar magnetic cycles (changes in the sunlight
    intensity).
  • Milankovitch Cycles studied by a Serbian
    scientist and he observed a Periodic shifts in
    earths orbit and its axis of rotation.
  • The above changes results in change in
    distribution and intensity of sunlight reaching
    the earth.

18
El Nino
  • La Nina, El Nino or the Southern oscillation
  • A pool of warm surface water most of the years
    is held by the equatorial trade wind between
    Indonesia and the South America and moves this
    current westwards towards Indonesia.
  • Every 3-5 years the low-pressure system breaks in
    Indonesia.
  • This giant pool of warm water moves backward and
    forward between Indonesia and S America, this
    effect is called EL Nino.

19
El Nino Southern Oscillation
  • Large pool of warm surface water in Pacific Ocean
    moves back and forth between Indonesia and South
    America.
  • Most years, the pool is held in western Pacific
    by steady equatorial trade winds.
  • Every three-five years the Indonesian low
    pressure system collapses and the mass of warm
    surface water surges back east.

20
El Nino Southern Oscillation
  • During an El Nino year, the northern jet stream
    (normally over Canada) pulls moist air from the
    Pacific over the U.S.This is accompanied by
    intense storms and heavy rains (from California
    across the midwest States).
  • The counterpart to El Nino is La Nina when the
    eastern tropical Pacific cools down.
  • During intervening La Nina years, hot, dry
    weather is often present (California to midwest)
  • Together these cycles are called El Nino
    Southern Oscillation (ENSO)

21
El Nino Southern Oscillation
22
Human-Caused Global Climate Change
  • IPCC (Intergovernmental Panel on Climate Change
    (2001) released report stating recent changes in
    the worlds climate have had discernable impacts
    on physical and biological systems.
  • Concluded human activities must be at least
    partially responsible.
  • Noted that the earths surface temperature has
    risen by about 0.6 0C(1.1 0F) and IPCC concluded
    that human is partially to be blamed( Green house
    gases-CO2, methane,nitrous oxide).

23
Aerosol Effects
  • Burning fossil fuels, forests and grasslands and
    other human activities releases 30 billions of
    CO2 per year.
  • Aerosols counteract Greenhouse effect.
  • Aerosols( sulphate and soot) produced by same
    activities ) have a tendency to reflect sunlight
    and cool surface air temperatures.
  • Short-lived, thus effects are temporary.
  • Mt. Pinatubo erupted in 1991 and ejected enough
    ash and sulfate particles to cool global climate
    about 1o C for nearly a year.

24
Current Evidence of Climate Change
  • Precipitation increased 1 in last century.
  • Artic sea ice thinning.
  • Alpine glaciers retreating.
  • Coral reefs bleaching.

25
International Climate Negotiations
  • Kyoto Protocol (1997) signed in Japan as a follow
    up of the earths summit(1992) in Rio de Janeiro
  • 160 nations agreed to roll back carbon dioxide,
    methane, and nitrous oxide emissions about 5
    below 1990 levels by 2012.
  • Also included 3 other green house gases to be
    reduced hydrofluorocarbon (CFC), perfluorocarbon
    and sulphur hexafluoride.
  • The protocol sets different limits for different
    countries, depending on their output before
    1990,however poorer countries like China and
    India were exempeted from their emission limit to
    allow thse countries to develop.
  • They also argued that wealthier countries created
    this mess and they should sort out this problem.

26
Controlling Greenhouse Emissions
  • Switch to renewable energy sources such as solar,
    wind, biomass etc.
  • CO2 is lives longer in the atmosphere than
    Methane and other greenhouse gases.
  • Capture and Store CO2
  • Increase plantations of trees and farmland
  • Inject CO2 into underground strata or deep ocean
    (Read pg 208 for details).

27
Climate Air Pollution
  • According to EPA (Env. Protection Agency), US
    releases 147 million metric tons of air
    pollution(excluding CO2) per year and world wide
    emission of these pollutants is 2 billion metric
    tons per year.
  • Major Kinds of Pollutants Primary and secondary
    pollutants.
  • Primary pollutants are released in a hamrful way
    e.g Factory smoke and secondary pollutants become
    hazardous after reactions in the air.

28
CLIMATE AND AIR POLLUTION
  • Photochemical oxidants (compounds formed with
    solar energy) e.g atmospheric acids are probably
    the most important secondary pollutants.
  • Fugitive emissions - Do not go through smokestack
    e.g dust from soil erosions, rock crushing,
    building constructions.
  • Conventional Pollutants - Group of seven major
    pollutants that contribute the largest volume of
    air-quality degradation (sulphur dioxide, carbon
    monoxide, particulates,volatile organic
    compounds,nitrogen oxide,ozone,and lead).

29
Conventional Pollutants
  • US Clean Air Act designated seven major
    (conventional or criteria) pollutants for which
    maximum ambient (Air around us) air levels are
    mandated. EPA sets allowable limits for
    concentrations of these pollutants
  • Sulfur Dioxide
  • Carbon Monoxide
  • Particulates
  • Hydrocarbons
  • Nitrogen Oxides
  • Photochemical Oxidants
  • Lead

30
Major Pollutants
  • Unconventional Pollutants
  • Compounds produced in less volume than
    conventional pollutants, but are especially toxic
    or hazardous (e.gAsbestos,benzene, mercury etc.)
  • Aesthetic Degradation
  • Reduce quality of life (e.g noise,odors,dust
    particles etc.)-

31
Lead and Other Toxic Elements
  • Toxic metals and halogens are chemical elements
    that are toxic when concentrated and released in
    the environment.
  • Metals
  • Lead, mercury, arsenic, nickel, beryllium,
    cadmium, thallium, uranium, cesium, and
    plutonium.
  • Halogens
  • Fluorine, chlorine, bromine, and iodine.

32
Stratospheric Ozone
  • Discovered stratospheric ozone levels were
    dropping rapidly during September and October.
  • Occurring since at least 1960.
  • At ground-level, ozone is a pollutant, but in the
    stratosphere it screens UV radiation.
  • A 1 decrease in ozone results in a 2 increase
    in UV rays reaching the earth.

33
Stratospheric Ozone
  • Pollution and chemical reactions has led to a
    phenomenon known as ozone hole.
  • The ozone hole is thinning of the ozone layer of
    the stratosphere.
  • Chlorofluorocarbon (CFCs) and other gases are the
    principal agent for ozone depletion.
  • Ozone(O3) aborbs UV rays which harms plants and
    animal tissues.
  • A 1 loss of ozone could result in a million
    extra human skins cancers per year.

34
EFFECTS OF AIR POLLUTION
  • Human Health
  • EPA estimates each year 50,000 people die
    prematurely from illnesses related to air
    pollution.
  • Likelihood of suffering ill health is related to
    intensity and duration of exposure.
  • Inhalation is the most common route, but
    absorption through the skin and consumption via
    food can also occur.

35
Effects of Air Polution
  • Consequences of breathing dirty air leads to
    increased probability of heart attack,lung
    diseases and cancers.
  • 250 000 people in US suffer from pollution
    related bronchitis per year
  • Conditions are much worse in developing
    countries.
  • City dwellers are more prone to pollutant related
    diseases than countryside dwellers.

36
Acid Deposition
  • Acid Precipitation/Acid rain - Deposition of
    wet, acidic solutions or dry, acidic particles
    from the air.
  • pH scale ranges from 0-14
  • 7 Neutral lt7 Acidic gt7 Basic
  • Unpolluted rain generally has pH of 5.6.
  • Rain water react with CO2 in the air and carbonic
    acid is formed.
  • Rainfall acidity thus falls to pH 4.3.

37
AIR POLLUTION CONTROL
  • Reducing Pollution
  • Most effective strategy for controlling pollution
    is to minimize polluting activities.
  • Best effective strategy is to conserve energy
    reducing electricity consumption,insulating homes
    and offices,better public transport to reduce air
    pollution.
  • Alternative energy source wind solar.
  • Technological advances

38
Air Pollution Control contd.
  • Particulate Removal Filtering Air Emission
    Remove particles physically by trapping them in a
    porous mesh which allows air to pass through but
    holds back solids.
  • Removal of sulfur, Nitrogen oxides ,hydrocarbon
    and others by advance technology.

39
Reducing Pollution
  • Sulfur Removal
  • Fuel Switching
  • Switch from soft coal with a high sulfur content
    to low sulfur coal.
  • Limestone Injection
  • Can reduce sulfur emissions by 90 by mixing
    crushed limestone with coal before it is fed into
    a boiler.

40
CLEAN AIR LEGISLATION
  • Clean Air Act (1963) - First national air
    legislation pollution control.
  • Clean Air Act (1970) rewrote original Act.
  • Identified critical pollutants.
  • Established ambient air quality standards mainly
  • Primary Standards to protect human health
  • Secondary Standards to protect materials,
    environment, and comfort.

41
Clean Air Act
  • Since 1970 the Clean Air Act has been modified
    amended Revision in1990 and have addressed
    principal problems
  • Acid Rain
  • Urban Smog
  • Toxic Air Pollutants
  • Ozone Protection
  • Marketing Pollution Rights
  • Fugitive emissions of volatile organics
  • Ambient ozone, soot, and dust.
  • NOx emissions (Nitrogen oxides)

42
CURRENT AND FUTURE CONDITIONS
  • Read while you relax
  • In the United States, air quality has improved
    dramatically in the last decade in terms of major
    large-volume pollutants.
  • Cities where pollution is largely from traffic
    still have serious air quality problems.
  • Major metropolitan areas of many developing
    countries are growing at explosive rates, and
    environmental quality is very poor.

43
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