Long Range Transport of Air Pollution

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Long Range Transport of Air Pollution

• By Cal Hilde

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Outline

• Definition of long range transport
• Scale
• What can be transported
• Mechanisms
• Required conditions
• Locations
• Effects
• Examples/Case Studies
• Arctic Haze
• African Dust
• Chinese Dust
• Volcanoes
• Forest Fires
• Mitigation (Covered by Ken Wilkening)

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Definition of Long Range Transport of Air
Pollution - Scale

• Distance
• Macroscale
• 1000km
• Day or longer
• Global circulation, jet streams
• Synoptic
• Subset of macroscale
• Of the order of 1000km
• Cyclones, antiyclones, fronts,
• Mesoscale
• 1000km gt x gt 5km
• Monsoon circulation, mountain/valley winds,
• Microscale
• 5km
• Hour or less

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Definition of Long Range Transport of Air
Pollution - Scale

• Distance
• Macroscale
• 1000km
• Day or longer
• Global circulation, jet streams
• Synoptic
• Subset of macroscale
• Of the order of 1000km
• Cyclones, antiyclones, fronts,
• Mesoscale
• 1000km gt x gt 5km
• Monsoon circulation, mountain/valley winds,
• Microscale
• 5km
• Hour or less

• Political
• Global
• Intercontinental
• Regional/Continental
• National
• Local

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Definition of Long Range Transport of Air
Pollution - Scale

• Distance
• Macroscale
• 1000km
• Day or longer
• Global circulation, jet streams
• Synoptic
• Subset of macroscale
• Of the order of 1000km
• Cyclones, antiyclones, fronts,
• Mesoscale
• 1000km gt x gt 5km
• Monsoon circulation, mountain/valley winds,
• Microscale
• 5km
• Hour or less

• Political
• Global
• Intercontinental
• Regional/Continental
• National
• Local

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What can be transported

• Particulate Matter (predominantly PM2.5)
• Dust erosion, volcanic eruptions, forest fires,
  industrial combustion, etc
• Sulphur containing compounds
• Volcanic eruptions, industrial sources, etc
• Carbon containing compounds
• Industrial combustion, vehicle combustion,
  volcanic eruption
• Halogen containing compounds
• CFCs
• Nitrogen containing compounds
• Combustion,
• Radioactive substances
• Nuclear explosions

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Mechanisms

• Required Conditions
• Good conditions for dispersion bad conditions
  for transport
• Turbulence, precipitation remove pollutant
• Requires initial stable conditions, high
  pressure, anticyclone
• Low winds, small amount of vertical and
  horizontal dispersion
• No weather fronts or precipitation
• Large amount of sunlight to heat ground
• Flat terrain (desert) to prevent frictional
  turbulence
• Creation of (low) inversion
• Conditions must remain for multiple days

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Mechanisms

• Required Conditions Continued
• High pressure system moves
• Pollution follows
• Restricted by inversion from vertically diluting
• Must be separated from surface to restrict
  frictional loss
• Higher winds exist at higher elevations
• (More Later!)

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Mechanisms

• Poleward movement
• Sun heats equator at larger rate
• Poles reflect radiation and receive less heat
• Results in temperature gradient and poleward
  movement of air
• Coriolis Effect
• Midlatitudes
• West to East
• Subtropics/Tropics
• East to West
• Poles
• East to West

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Mechanisms

• Locations
• Northern Hemisphere contains 88 of population
  majority of industry
• Poleward movement from temperature gradient
• West to East movement from Coriolis effect (mid
  latitudes)
• Results
• North America ? Europe
• Europe ? Asia Europe ? Arctic
• Asia ?North America
• Also
• North Africa ? North South America
• South America ? AustraliaSouth Asia ? Africa

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Mechanisms
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Effects

• Can increase pollutants in populated areas past
  acceptable levels
• Can introduce pollutants into remote areas where
  they would normally not be present
• Can create haze and act as nuisance
• Can affect energy balance
• Can react chemically with atmosphere

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Examples/Case Studies

• Ozone Depletion
• Release of CFCs into atmosphere causing breakdown
  of ozone layer
• Greenhouse Effect
• Release of large amounts of greenhouse gasses
  (CO2, Methane, etc) into atmosphere causing
  imbalance of world energy budget
• Nuclear explosion/fallout
• Release of large amounts of particulate matter
  into atmosphere
• Release of radioactive material into atmosphere
• Persistent organic pollutants
• Pesticides, DDT,
• Attach to particulate matter, transported to
  remote areas, accumulate in cold regions, resides
  in fat tissue
• Accumulates in animals and advances through food
  chain and damages environment

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Examples/Case Studies

• Arctic Haze
• Discovered in 1957 by J. Murray Mitchel in Alaska
• Band of Haze in sky
• Discovered to be not natural in 1970s
• Possibly from many different locations
• North America, China/Japan ruled out due to high
  dispersion
• Deemed to be from Europe and (then) USSR
• Most frequent in Winter
• Subzero temperature, low precipitation and high
  stability causes build up of pollution in Europe.
  
• Process can take as little as 3 days
• Northern Europe is north of Polar front in Winter
• Air mass moves northward
• Due to low dispersion in arctic air and winter
  conditions the pollution remains concentrated
• Introduces particulate matter, SO2, greenhouse
  gasses, CFCs, POPs, to the arctic.

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Examples/Case Studies

• Dust Clouds
• Majority of particulate matter from sea salt and
  mineral dust
• Mineral dust originates from deserts and
  topographical lows (ex. North Africa, China,
  Central/South Asia)
• Desertification
• Caused by overgrazing, over cultivating,
  deforestation
• Plants/trees prevent erosion of soil
• When removed can greatly increase erosion
• Cause haze and increases PM levels past limits

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Examples/Case Studies

• North African Dust
• Naturally occurring and crucial to nature due to
  introduction of minerals into mid-ocean
• Desertification increasing levels
• Intense heating, dry air, high mixing
• Strong winds created
• Dust erodes and disturbs more dust
• Large amount of particulate in high temperature
  air over flat terrain
• Hits cool ocean and moves above much cooler ocean
  air
• Cloud formation is suppressed and washout is
  prevented
• Larger particles removed due to gravity leaving
  particles of 1 ? 3µm
• Can travel for 10 to 20 days
• In summer dust from Sahara reaches Barbados
• In Winter dust from South of Sahara reaches South
  America

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Examples/Case Studies

• Chinese Dust
• Naturally occurring
• Enhanced by desertification
• Strong winds erode particulates
• Hits cold front and is prevented from depositing
• Originates in Gobi and Takla Makan deserts
• Travels to North Pacific over Japan and to Hawaii
  and West Coast of North America
• Takes upwards of 2 weeks

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Examples/Case Studies

• Volcanoes
• Expel water vapour, CO2, SO2, particulate matter
  (ash)
• Ash can take days to several weeks to fall
• Can introduce pollutants into stratosphere (16-32
  km high)
• Mount St. Helens sent ash 20-27km high
• SO2 ? formation of sulphuric acid (H2SO4)
• Acid rain formation
• Introduction of PM raises albedo and affects
  energy balance
• Unable to control

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Examples/Case Studies

• Forest Fires
• Introduces CO2, H2O, C2H6, Nox, SO2 and
  particulates into atmosphere
• Dry weather, extreme heat
• Pollutants injected high into atmosphere
• Can travel over 1000km until removed by wet
  deposition
• Most significant effects in immediate area
• Can affect energy balance CO2 levels
• Canada ? Europe, Russia ? Northern Hemisphere,
  Europe ? Arctic, South America ? Australia

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Mitigation

• International problem
• Easy (relatively) to control local pollution
  sources
• Extremely difficult to control pollution sources
  originating from a different continent
• No easy solution
• Law Of The Atmosphere?
• Ken Wilkening