AIR POLLUTION AND CLIMATE CHANGE

							AIR POLLUTION AND
CLIMATE CHANGE
    Air Pollution Notes

      June 8, 2012
ATMOSPHERE
   We live at the bottom of a sea
    of air
    –   Atmosphere
    –   The whole mass of air
        surrounding the Earth
   Divided into several layers
    divided by abrupt changes in
    temperature due to
    differences in absorption of
    incoming solar energy
ATMOSPHERE
       Troposphere
    –        About 75%-80% of
             atmosphere is in this layer
             (picture to the right says
             90%)
    –        About 12 km (7.5 miles) thick
    –        Weather breeder
    –        Gas content
              78% = Nitrogen
              21% = Oxygen
              0.01% - 4% = Water Vapor
              Some argon, carbon dioxide,
               and other gases
ATMOSPHERE
       Stratosphere
    –        Extends from 12 km up to 50 km
             (21.1 miles)
    –        Important layer of atmosphere
             containing OZONE
              Ozone (O3) is special form of oxygen
              Blocks large amounts of solar
               ultraviolet (UV) radiation (about
               95% of harmful UV radiation)
              Produced when some oxygen
               molecules interact with UV radiation
    –        In the study of air pollution, the
             troposphere and the
             stratosphere are the most
             important
ATMOSPHERE
   Mesosphere
    –   Extends from 50 km up to about 80
        km (49.7 miles)
    –   Warm at the lower levels, but cold at
        its highest level
    –   Shooting stars burn in this layer
   Thermosphere
    –   Begins 80 km above Earth and
        extends to 320 km (195.6 miles)
    –   Temperatures go up when moving
        farther away from ground level due to
        sun’s energy
    –   Some satellites found here
AIR POLLUTION
       Presence of one or more chemicals in the atmosphere in
        sufficient quantities and duration to cause harm to us,
        other forms of life or alter climate
       Environmental Protection Agency (EPA) classifies
        pollutants as…
    –       Criteria Pollutants: Pollutants identified as being both common
            and detrimental to human welfare and are found over all the
            United States
              Carbon Monoxide (CO)
              Sulfur Oxides (SOx)
              Nitrogen Oxides (NOx)
              Ozone (O3)
              Lead (Pb)
              Particulate Matter (PM)
AIR POLLUTION
       Environmental Protection Agency (EPA)
        classifies pollutants as…
    –    Hazardous Air Pollutants (HAPs): Pollutants that
         are known or suspected to cause cancer or
         other serious health effects
            Examples
             –   Benzene: found in gasoline
             –   Mercury: from coal combustion
             –   Perchloroethylene: emitted from some dry cleaning facilities
             –   Methylene chloride: used as a solvent by a number of
                 industries
AIR POLLUTION
   Pollutants can be
    from…
    – Natural Sources
       Volcanoes
       Trees
       Geysers
    – Human Sources
       Power plants
       Motor vehicles
       Etc
AIR POLLUTION
   Pollutants can also be…
    – Primary Pollutants
         Emitted directly into the
          troposphere in a potentially
          harmful form
    – Secondary Pollutants
         Primary pollutants react with
          one another or with basic
          components of air to form new
          pollutants
AIR POLLUTION
       Lastly, pollutants can come from…
    –        Stationary Sources: Non-moving sources
              Point Source
               –   Large, stationary sources of emissions that have specific locations
                   and release pollutants in quantities above an emission threshold
                   (source at a fixed point that emits air pollutants)
               –   Smokestack, storage tank
              Area Source
               –   Facilities or activities whose individual emissions are small, but
                   collectively can release significant amounts of a pollutant (Series of
                   small sources that together can affect air quality in a region)
               –   Community using woodstoves, dry cleaners, vehicle refinishing
                   facilities, gas stations
    –        Mobile Sources: Sources that move
SMOG
       The term “smog” was probably
        introduced by a physician in 1905
        to describe poor air quality
        resulting from mix of “smoke”
        and “fog”
       PHOTOCHEMICAL SMOG
    –     Sometimes called L.A.-Type Smog or
          Brown-Air Smog
    –     Solar radiation important
    –     Results from automobile emissions
          reacting with solar radiation
    –     Involves complex reactions between
          sunlight, nitrogen oxides and
          hydrocarbons
    –     Produces brownish smog
SMOG
       INDUSTRIAL SMOG
    –     Sometimes called London-Type Smog or Gray-Air Smog
    –     Produced primarily by burning coal or oil at large power plants
    –     Sulfur oxides and particulates combine under certain meterological
          conditions (see diagram)
    –     Produces concentrated sulfurous smog
    –     In 1952, London experienced
          some stagnant air which increased
          local cloud cover
            Dropped noon air temp to 30oF
            Resulted in increased use of heating =
             coal
            Resulted in sulfur dioxide, soot and ash
             emissions
            This resulted in more clouded/polluted air
            Eventually caused 4000 deaths between
             December 4 and 10
INVERSIONS
   Usually, the sun warms the surface of the
    Earth during the day, warm air rises, and
    any pollutants this air contains get dispersed
   Under certain atmospheric conditions, a
    layer of warm air can lie atop a layer of
    cooler air nearer the ground =
    TEMPERATURE INVERSION
    – Cooler air denser and does not rise
    – Pollutants can concentrate in this
      stagnant layer of cool air near the
      ground
INVERSIONS
   Two Types
    – SUBSIDENCE TEMPERATURE INVERSION
      Large mass of warm air moves into a region at
       high altitude
      Floats over mass of colder air near the ground
      Air becomes stagnant and prevents mixing and
       dispersion of air pollutants
      Pollutants can accumulate and build up to
       harmful levels
INVERSIONS
   Two Types
    – RADIATION TEMPERATURE
      INVERSION
      Typically occurs at night
      Air near ground cools faster than the air
       above it
      Sun rises and warms the Earth’s surface
       and condition usually disappears around
       noon
INVERSIONS
   Areas susceptible to prolonged inversions have
    certain topography and weather conditions
    –   Radiation Temperature Inversion
           City or town located in a valley surrounded by
            mountains with cloudy and cold weather during part
            of the year
           Surrounding mountains and clouds block winter sun
            needed to reverse nightly radiation temperature
            inversion
           Mountains block air from moving away laterally
           As these conditions persist, concentrations of
            pollutants in the valley will build to harmful and even
            lethal concentrations
INVERSIONS
   Areas susceptible to prolonged inversions have
    certain topography and weather conditions
    –   Subsidence Temperature Inversion
           City with several million people and motor vehicles in area
            with sunny climate, light winds and mountains on three
            sides and ocean on the other
           Makes photochemical smog worse
           Los Angeles basin has prolonged STI over half the year
            (mostly during summer and fall)
           High-pressure air off coast of California creates
            descending warm air mass
           Air below is cooled by nearby ocean
           Surrounding mountains prevent the light sea breezes from
            blowing away the polluted air
ACID DEPOSITION
   What happens
    –   Coal-burning power plants, ore smelters, other industrial
        plants and motor vehicles emit sulfur dioxide, suspended
        particles and nitrogen oxides
    –   These pollutants form secondary pollutants in the
        atmosphere
           Nitric acid vapor
           Droplets of sulfuric acid
           Particles of acid-forming sulfate and nitrate salts
    –   Drift many miles away and descend to Earth’s surface in
        two forms
           Wet deposition: acidic rain, snow, fog and cloud vapor
           Dry deposition: acidic particles
           Resulting mixture gives us ACID DEPOSITION, commonly called
            acid rain
ACID DEPOSITION
   Result
    –   Typical precipitation in eastern U.S. has a pH of 4.2-4.7
           Normal rain has a pH of 5.6
           pH of 4.6 is 10x as acidic
    –   Some eastern U.S. forests and east of L.A. get rain that
        is as acidic as lemon juice (pH of 2.3)
    –   Most of the pollution that causes this comes from coal-
        burning power plants
    –   Many acid-producing pollutants are generated in one
        country and drift to another
           Pollution from Ohio valley ends up in Canada
           Pollution from China ends up in Japan and Korea
ACID DEPOSITION

   Effects of Acid Deposition
    – Health, Materials and Economy
         Contributes to human respiratory disease
         Pulls toxic metals from water pipes into drinking
          water
         Damages statues, buildings, metals and car finishes
         Lower productivity in fisheries, forests and farms
         Loss of tourism in scenic areas
ACID DEPOSITION
   Effects of Acid Deposition
    – Aquatic Ecosystems
       Loss of essentially all fish populations below a
        pH of 4.5
       Causes release of aluminum ions into water
        which asphyxiates fish
       In U.S. about 9,000
        lakes are threatened
        with excess acidity
ACID DEPOSITION
   Effects of Acid Deposition
    – Plants and Soils
         Direct damage to needles and leaves
         Pulls essential nutrients from the soil
         Releases ions in soil that are toxic to plants
         Weakens trees and makes them more susceptible to
          disease, insects, drought and harmful mosses
ACID DEPOSITION
   What can be done?
    – Reduce air pollution by improving energy
      efficiency
    – Reduce coal use
    – Increase natural gas use
    – Increase use of renewable energy sources
    – Burn low-sulfur coal
    – Remove SO2 and NOx from smokestack gases
    – Remove NOx from motor vehicle exhaust
    – Tax emissions of SO2