ENVIRONMENTAL IMPACTS OF ENERGY USE

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PowerPoint 7 Air Pollution
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TEMPEARTURE IN THE ATMOSPHERE AND THERMAL
INVERSION
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TEMPEARTURE IN THE ATMOSPHERE AND THERMAL
INVERSION

• Consider a parcel of warm air released near
  surface of earth it will tend to rise because it
  has a lower density than surrounding, cooler air.
• If a parcel of warm, polluted air is released
  from a smokestack under normal meteorological
  conditions, it will rise to 10,000 meters, where
  is usually presents no immediate problems

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TEMPEARTURE IN THE ATMOSPHERE AND THERMAL
INVERSION

• A parcel of air will rise or fall in surrounding
  atmosphere depending on the temperature profile
  of the atmosphere and the adiabatic lapse rate
  (ALR)
• ALR - rate at which a parcel of air cools as it
  rises in the atmosphere under adiabatic
  conditions. As air parcel rises it expands, due
  to lower atmos. pressure above than below.
• Adiabatic - no heat energy is exchanged between
  air parcel and surrounding air.

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Atmospheric Temperature Profiles

• When temperature in atmosphere cools faster than
  ALR, unstable conditions exist and good mixing
  occurs. Less pollution at ground level.
• When temperature in atmosphere cools slower than
  ALR, stable conditions exist and little mixing
  occurs. More pollution at ground level.

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stable
Unstable
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THERMAL INVERSION
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Types of Thermal Inversions

• Radiative Earth cools during night by radiating
  thermal energy into space. In morning, air near
  surface will be cooler than air above creating
  thermal inversion. More frequent, but less
  problematic and persistent than -
• High pressure subsidence high pressure mass of
  air moves towards earth. Is compressed and
  heated, causing thermal inversion some distance
  above ground.

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Air Pollution System
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TYPES OF EMISSIONS

• Stationary Sources
• power plants, factories, industrial sites
• Mobile Sources
• cars, trucks, buses, trains, planes, aircraft,
  off-road vehicles
• Area Wide Sources
• agriculture, paved and unpaved roads,
  construction
• Natural Sources
• biogenic, wildfires, windblown dust

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EMISSIONS INVENTORIES

• E.I. used to estimate emissions from point, area
  and mobile sources.
• Uses a combination of actual measurements and
  computer models.
• EPA and CARB publish data on E.I.
• Can be found at
• http//www.arb.ca.gov
• http//www.arb.ca.gov/emisinv/eib.htm
• http//www.epa.gov/airsweb

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AIR POLLUTANTS

• Sulfur containing compounds
• Nitrogen containing compounds
• Carbon containing compounds
• Halogen containing compounds
• Toxic substances
• Radioactive compounds

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AVERAGE COMPOSITION OF THE ATMOSPHERE
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Primary and Secondary Pollutants

• Primary Pollutants Those emitted directly from
  sources (CO, SO2, VOC, CO, lead, PM)
• Secondary Pollutants Those formed in the
  atmosphere by chemical interactions among primary
  pollutants and normal atmospheric constituents.
  (Ozone, photochemical oxidants)

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Atmospheric Concentration Units

• Two concentrations commonly used
• 1. concentration (micrograms/cubic meter)
• 2. parts-per-million volume (ppm)

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Criteria Pollutants
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Sulfur Containing Compounds

• Carbonyl sulfide (COS), carbon disulfide (CS2),
  dimethl sulfide ((CH3)2)S), hydrogen sulfide
  (H2S), sulfur dioxide (SO2)
• Sources are biological decay, combustion of
  fossil fuels and organic matter.
• SO2 combines with water to produce sulfuric acid
  - major component of acid rain 2SO2 O2
  2SO3 SO3 H2O H2SO4

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U.S. SO2 Ambient Air Quality, 1988-97
http//www.epa.gov/oar/aqtrnd97/brochure/sixprin.h
tml
Bold line indicates national air standard
Source USEPA
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U.S. SO2 Emissions, 1988-97 1988-97 12
decrease 1996-97 3 increase
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California Statewide Oxides of Sulfur
Emissions1995 Average Daily Emissions
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Nitrogen-Containing Compounds

• Nitrous oxide (N2O) colorless, odorless,
  laughing gas, emitted by natural sources,
  chemically inert, not considered an air
  pollutant.
• Nitric oxide (NO) nitrogen dioxide (NO2) NOx
  emitted by combustion at high temperatures.
  Together with hydrocarbons are important in
  formation of ozone. Lifetime about 1 day.
  Combines with water to form nitric acid,
  component of acid rain.
• Released by stationary and mobile sources.

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California Statewide Oxides of Nitrogen Emissions
1995 Average Daily Emissions
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U.S. NO2 Air Quality, 1988-97
Bold line indicates national air standard.
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U.S. NOX Emissions, 1988-97
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Carbon Compounds

• CO - carbon monoxide criteria pollutant,
  colorless, odorless gas. Toxic - binds to
  hemoglobin preventing uptake of oxygen. Formed by
  incomplete combustion mainly in cars and trucks.
  Lifetime in atmosphere about one month

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Carbon Monoxide

• Carbon monoxide is a colorless, odorless,
  poisonous gas formed when carbon in fuels is not
  burned completely.
• It is a byproduct of highway vehicle exhaust,
  which contributes about 60 percent of all CO
  emissions nationwide. In cities, automobile
  exhaust can cause as much as 95 percent of all CO
  emissions. These emissions can result in high
  concentrations of CO, particularly in local areas
  with heavy traffic congestion.
• Other sources of CO emissions include industrial
  processes and fuel combustion in sources such as
  boilers and incinerators.

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California Statewide Carbon Monoxide
Emissions1995 Average Daily Emissions
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U.S. CO Air Quality, 1988-97
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U.S. CO Emissions, 1988-97
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Particulates

• Particles of average diameter 10 microns or less
  (PM10). Tend to be easily inhaled and lodge in
  lungs. Larger particles not readily inhaled.
• Sources are combustion process (particular diesel
  combustion), unpaved roads, fires.
• PM2.5 particles with average diameter less than
  2.5 microns. Considered even more problematic
  than PM10
• New EPA regs. For PM2.5 now under consideration

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Statewide Fine Particulate Matter Emissions1995
Average Daily Emissions
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PM-10 Air Quality, 1988-97
Bold line indicates national air standard.
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PM-10 Emissions, 1988-97
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Reactive Organic Compounds (ROG) and Ozone

• Sometimes called VOC (volatile organic compounds
  or hydrocarbons)
• Gasoline contains almost 100 hydrocarbons, such
  as octane, heptane, ethane. Evaporation of
  gasoline one source of HC into atmosphere
• Natural sources account for 85 of HC in air, but
  more reactive ones are anthropogenic

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U.S. VOC Emissions, 1988-97
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Statewide Reactive Organic Gases Emissions1995
Average Daily Emissions
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OZONE

• Secondary pollutant O3
• Formed in atmosphere by reaction of oxides of
  nitrogen, VOC and sunlight.
• Classified as a criteria pollutant
• Major component of photochemical smog

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Ozone Air Quality, 1988-97(annual 4th day 8 hour
maximum)
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