Transcript air pollution 14

The World's Most Polluted Places
Our Atmosphere
The atmosphere’s composition
Atmospheric properties
• Atmospheric pressure =
the force per unit area
produced by a column of
air
• Relative humidity = the
ratio of water vapor air
contains to the amount
it could contain at a
given temperature
– High humidity makes it
feel hotter than it really is
Atmospheric pressure
decreases with altitude
Solar energy heats the atmosphere
• Energy from the sun:
– Heats and moves air
– Creates seasons
– Influences weather
and climate
• Solar radiation is highest
near the equator
• The spatial relationship between the Earth and sun
determines how much solar energy strikes the Earth
• Microclimate = a localized pattern of weather
conditions
Solar energy creates seasons
• Because the Earth is tilted, each hemisphere
tilts toward the sun for half the year
– Results in a change of seasons
Equatorial regions are
unaffected by this tilt, so
days average 12 hours
throughout the year
Solar energy causes air to circulate
• Air near Earth’s surface
is warm and moist
• Convective circulation =
less dense, warmer air
rises
– Creating vertical currents
– Rising air expands and
cools
– Cool air descends and
becomes denser
– Replacing rising warm air
Convection influences
weather and climate
The atmosphere drives weather and
climate
• Weather and climate involve the physical
properties of the troposphere
– Temperature, pressure, humidity, cloudiness, wind
• Weather = specifies atmospheric conditions
over short time periods and within small
geographic areas
• Climate = patterns of atmospheric conditions
across large geographic regions over long
periods of time
• Mark Twain said, “Climate is what we expect;
weather is what we get”
Circulation systems produce climate
patterns
• Convective currents contribute to climatic
patterns
• Hadley cells = convective cells near the equator
– Surface air warms, rises, and expands
– Causing heavy rainfall near the equator
– Giving rise to tropical rainforests
• Currents heading north and south are dry
– Giving rise to deserts at 30 degrees
• Ferrel cells and polar cells = lift air and create
precipitation at 60 degrees latitude north and
Global wind patterns
• Atmospheric cells interact with Earth’s rotation to
produce global wind patterns
– As Earth rotates, equatorial regions spin faster
• Coriolis effect = the apparent north-south
deflection of air currents of the convective cells
– Results in curving global wind patterns called the
doldrums, trade winds, and westerlies
Climate patterns and moisture
distribution
Global wind patterns
• Doldrums = a region near the equator with few
winds
• Trade winds = between the equator and 30
degrees
– Blow from east to west
– Weaken periodically, leading to El Niño conditions
• Westerlies = from 30 to 60 degrees latitude
– Blow from west to east
• People used these winds to sail across the ocean
• Wind and convective circulation in ocean water
Storms pose hazards
• Atmospheric conditions can produce dangerous storms
• Hurricanes = form when winds rush into areas of low
pressure
– Warm, moist air over the topical oceans rises
• Typhoons (cyclones) = winds turn counterclockwise in the
Northern Hemisphere
– Drawing up huge amounts of water vapor
– Which falls as heavy rains
• Tornadoes = form when warm air meets cold air
– Quickly rising warm air forms a powerful convective
current (spinning funnel)
Outdoor air pollution
• Air pollutants = gases and particulate material
added to the atmosphere
– Can affect climate or harm people or other organisms
• Air pollution = the release of pollutants
• Outdoor (ambient) air pollution = pollution
outside
– Has recently decreased due to government policy and
improved technologies in developed countries
– Developing countries and urban areas still have
significant problems
•
Natural
sources
pollute:
volcanoes
Release particulate
matter, sulfur dioxide,
and other gases
– Can remain for months or
years
• Aerosols = fine droplets
of sulfur dioxide, water,
oxygen
– Reflect sunlight back to
space
– Cool the atmosphere and
surface
Volcanoes are one source
of natural air pollution, as
shown by the Mount Saint
Helens eruption in 1980
sources
pollute:
fires
• FiresNatural
pollute the
atmosphere
with soot
and gases
• Over 60 million ha (150 million acres) of forests
and grasslands burn per year
• Human influence makes fires worse
– Fuel buildup from fire suppression, development in
fire-prone areas, “slash-and-burn” agriculture
– Climate change will increase drought and fires
In 1997,
unprecedented forest
fires sickened 20
million and caused a
plane to crash
Natural sources pollute: dust storms
• Wind over arid land
sends huge amounts of
dust aloft
– Even across oceans
• Businesses, schools,
and governments close
• Unsustainable farming
and grazing promote:
– Erosion
– Desertification
We create outdoor air pollution
• Air pollution comes from mobile or stationary
sources
• Point sources = specific spots where large
quantities of pollutants are discharged (power
plants and factories)
• Non-point sources = more diffuse, consisting of
many small sources (automobiles)
• Primary pollutants = directly harmful and can
react to form harmful substances (soot and
carbon monoxide)
• Secondary pollutants = form when primary
Outdoor Air Pollution
Primary Pollutants
CO
SO2
CO2
NO
NO2
Most hydrocarbons
Most suspended
particles
Natural
Stationary
Mobile
Secondary Pollutants
SO3
HNO3
H2O2
SO4
–
H2SO4
O3
Most NO3 and
PANs
2–
salts
Pollutants exert local and global
effects
• Residence time = the time a pollutant stays in the
atmosphere
• Pollutants with brief residence times exert
localized impacts over short time periods
– Particulate matter, automobile exhaust
• Pollutants with long
residence times exert
regional or global impacts
– Pollutants causing
climate change or
– ozone depletion
U.S.
air
pollution
In 2008, the U.S. emitted 123 million tons of the six
monitored pollutants
The average U.S.
driver emits 6 metric
tons of CO2/yr as well
as other pollutants!
Criteria Pollutants monitored
closely by the EPA
Complete the Criteria Air Pollutants table
listing the:
Cause and/or Source
Effects on Plants, Animals,
Humans, and Materials
Smog: our most common air quality
problem
• Smog = an unhealthy
mixture of air pollutants
over urban areas
• Sulfur in burned coal
combines with oxygen to
form sulfuric acid
• Industrial (gray air) smog =
industries burn coal or oil
– Regulations in developed
countries reduced smog
• Coal-burning industrializing
Smog in Donora
killed 21 people
and sickened 6,000
Photochemical
• Produced
by a series of(brown
reactions air)
smog
– Formed in hot, sunny cities surrounded by
mountains
• Light-driven reactions of primary pollutants and
atmospheric compounds
– Morning traffic releases NO and VOCs
– Irritates eyes, noses, and throats
• Los Angeles smog kills 3,900/year and costs $28
High levels of NO2 cause
billion/year smog to
photochemical
form a brown haze over
cities
Creation of industrial and photochemical
smog
Industrial smog
Photochemical smog
Photochemical Smog
• Photochemical smog is a
mixture of air pollutants
formed by the reaction of
nitrogen oxides and volatile
organic hydrocarbons when
they are exposed to sunlight.
• More than 100 primary and
secondary pollutants can be
formed.
Photochemical Smog (brown air smog)
F
Photochemical Smog
VOC + NOx + heat + sunlight
ground level ozone (O3)
+ other photochemical
oxidants
+ aldehydes
+ other secondary air
pollutants
Smog Disasters
 Meuse Valley, Belgium, 1930
 Donora, Pennsylvania, 1948
 Poza Rica, Mexico, 1950
 London, England, 1952
 London 1956, 56, 62
 New York, New York, 1953,
1962-1963, 1966
6000 people ill, 63 deaths
in a few days
6000 people ill, 20 deaths
in three days
22 dead & 320 hospitalized
in 25 minutes
4,000 dead in three days
2500 deaths attributed to coal
smoke (smog)
In 1962, increased to 269
due to photochemical smog
Industrial Smog – Gray Air Smog
Particulates
Sulfur Dioxide
Sulfuric
Acid
Distribution of Global Aerosols
Animation
• https://www.youtube.com/watch?feature=pla
yer_embedded&v=YtJzn8A725w
Examples of Industrial Air Pollution
China’s Air Pollution Problem
http://www.nbcnews.com/video/
nightly-news/53760431
http://www.scmp.com/news/chinainsider/article/1406793/beijing-hit-firstbout-charts-air-pollution-new-year
• http://www.youtube.com/watch?
v=GsjANjFlK0M
• http://www.cbsnews.com/news/
pollution-from-china-altersweather-in-us-west/
Temperature Inversions
During daylight hours, the sun warms the ground
which warms the air near the Earth’s surface.
The warm air rises as more dense cool air
displaces it. Any pollution in the air normally
disperses in the turbulence caused by the mixing
of the air. When a layer of warm air traps the
layer of cool air near the Earth’s surface, then the
situation is known as a temperature inversion. In
this case, pollutants are not dispersed but
continue to build up in the still, stagnant air.
Temperature Inversions
http://www.youtube.com/watch?v=EKW0bW1WVEY
We have reduced air pollution
• Total emissions of the six monitored pollutants
have declined 60% since the Clean Air Act of 1970
– Despite increased population, energy consumption,
miles traveled, and gross domestic product
We reduced emissions and improved
the
economy
• Technology and federal
policies
• Cleaner-burning engines
and catalytic converters
• Permit-trading programs
and clean coal
technologies reduce SO2
emissions
• Scrubbers = chemically
convert or physically
remove pollutants before
Los Angeles
Descending warm air mass
Increasing altitude
Inversion layer
Sea breeze
Mountain
range
Decreasing temperature
Sea breezes keep the air and pollution onshore,
and the mountains prevent the air from escaping.
The cold air aloft acts as a lid.
Emission Reduction
Electrostatic Precipitator
Cleaned gas
Electrodes
Dust discharge
Dirty gas
Bags
Baghouse Filter
Cleaned gas
Dirty gas
Dust discharge
Cleaned gas
Dirty gas
Cyclone Separator
Dust discharge
Cleaned gas
Dirty gas
Clean
water
Wet
gas
Dirty water
Wet Scrubber - Remove 98% of SO2 and particulate matter
Solutions
Motor Vehicle Pollutions
Prevention
Mass transit
Bicycles and walking
Less polluting fuels
Get older, polluting
cars off the road
Give buyers tax writeoffs for buying lowpolluting, energyefficient vehicles
Cleanup
Emission control
devices
Improve fuel efficiency
Less polluting engines
Car exhaust
Inspections
twice a year
Restrict driving in
polluted areas
Stricter
emission
standards
Carpooling????
Solutions
Air Pollution
Prevention
Cleanup
Reduce
poverty
Improve energy
efficiency
to reduce fossil fuel
use
Rely more on lowerpolluting natural gas
Rely more on
renewable energy
(especially solar cells,
wind, and solarproduced hydrogen)
Transfer technologies for
latest energy efficiency,
renewable energy, and
pollution prevention to
developing countries.
Reduce or ban
indoor smoking
Develop simple and
cheap test for indoor
pollutants such as
particulates, radon,
and formaldehyde
How Can Laws Be Improved?
 Rely on pollution prevention rather than cleanup.
 Force Congress to increase fuel efficiency standards for
cars, SUVs and light trucks.
 Regulate the emissions from inefficient 2 cycle engines
(lawnmowers, leaf blowers, jet skis, outboard motors, etc)
 Regulate pollution from oceangoing ships in American
ports.
 Amend the Clean Air Laws to deal with emissions of
carbon dioxide and other greenhouse gases.
 Better enforcement of the Clean Air Acts