Air: Climate and Pollution

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Air Climate and Pollution

• Chapter 9

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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

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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

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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.
• .

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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

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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.

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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)
• .

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Atmospheric Temperature Changes
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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

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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

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Solar Radiation
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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.

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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.

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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.

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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.

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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).

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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.

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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.

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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.

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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)

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El Nino Southern Oscillation
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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).

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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.

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Current Evidence of Climate Change

• Precipitation increased 1 in last century.
• Artic sea ice thinning.
• Alpine glaciers retreating.
• Coral reefs bleaching.

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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.

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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).

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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.

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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).

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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

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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.)-

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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)

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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.

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