Transcript Document

Air Pollution
Earth’s atmosphere:
1) provides essential
oxygen
2) moderates climate via
insulative properties
3) provides medium for
sound
4) shields solar radiation
& incoming particulate
matter
5) has been neglected
Two Sources of Atmospheric (Air)
Pollution
1) Natural Sources
- forest fires (CO2, ash)
- volcanic eruptions (sulfur, mercury)
2) Human Origin
- primarily since Industrial Revolution in
late 18th century
• Air pollution changing precipitation
patterns
• Air pollution (particulates) changing
temperature
• Air pollution impacting human &
ecosystem health
Major Pollutants
1) Carbon monoxide (CO) – by-product
of converting organic compounds
* > majority in atmosphere from natural
sources
* problem with small quantity (humancaused) condensed into small area
(cities have 50X > conc.)
* Clean Air Act of 1970 – helped reduce
these emissions via fuel-efficient
engines
2) Sulfur Oxides (SOx) – by-product of
burning sulfur-rich coal & oil
* vehicles, energy industry, factories
* “raw material” for acid deposition
* respiratory irritant/reduced function
Reducing Sox Emissions (Industry):
• Use low-sulfur coal
• Coal cleaning – separating out fool’s
gold
• Desulfurize flue gas in smoke stacks
with scrubbers
3) Particulates – suspended
particles/liquid
* industry & autos (combustion)
* wind erosion
* slash & burn farming in tropics
* respiratory dysfunction
* toxins & particulates
4) Hydrocarbons
* methane, benzene
* concentrations in urban areas; autos &
VOCs
5) Nitrogen Oxides (NOx) -- combustion
NO
NO2
O2
hydrocarbon + NOx = photochemical smog
photochemical smog:
hydrocarbon + NOx
O3 (ozone)
solar energy
• Hot, humid summer days & cars – ozone
warnings
• Respiratory irritant, damage to lung
tissue
Ozone damage to plants
e.g., necrosis of plant
tissue (O3 via gas
exchange)
Controlling Air Pollution (input vs. output
control)
Particulates:
1) filter bag house -traps/collect material
2) electrostatic precipitator – charged
small pollutant particles collected
3) cyclone filter – heavy dust filter
removed with cyclone air stream
Filter Bag House
Filter Bag House
Electrostatic Precipitator
Cyclone Filter
Controlling Air Pollution
SOx: review notes relative to input vs.
output control
Auto Emissions:
catalytic converters: attached along
exhaust system of car; “cleaning”
exhaust of CO, hydrocarbons, and NOx
What about input controls for auto
emissions?
> fuel efficiency; < volume; alternative
fuels; alternative engines; mass transit;
mgt of urban sprawl
Reduction Catalyst (A) & Oxidation Catalyst (B)
Honeycomb
Structure (C)
or ceramic beads;
Reduction Catalyst vs. Oxidation Catalyst
(located in honeycomb structure which is
coated with metal catalysts)
• Reduction – platinum & rhodium metals
NOx
N2 + 0 2
• Oxidation – platinum & palladium metals
02 + CO
CO2
Global Impacts of Air Pollution
Ozone Depletion
* in the stratosphere (25-50 km)
* absorbs ultraviolet (UV) radiation
* naturally, dynamic equilibrium
* chlorofluorocarbons (CFCs) – propellant
& coolant – escape to stratosphere &
react with ozone (persistant)
Ozone Depletion
CFCl3 + UV
O3 + Cl
Cl (free radical)
ClO + O2
Ozone Hole
• http://www.youtube.com/watch?v=qUfVMo
gIdr8&NR=1
Ozone Depletion
Harmful Effects (next 10-100+ yrs)
•
•
•
•
exasperate global warming
UV radiation = > skin cancer
< amphibian populations, > extinction
altered trophic structure of
communities
- 1987: 149 nations signed the Montreal Protocol.
Agreed to reduce the manufacturing of CFCs by
1/2 in 1998 and eventually phase out CFCs.
Global Impacts of Air Pollution
Global Climate Change
(“Greenhouse Effect”)
* CO2, H2O, O3, NO, methane (CH4), and
chlorofluorocarbons (CFCs)
•
•
greenhouse gases
trap infrared
radiation (IR) from
leaving atmosphere
CO2 concentrations
on the rise
correlated with rise
in temperatures
Global Climate Change
• 1990 – 2100 projected 2oC increase
Do the Pros Outweigh the Cons?
Some “Pros”
< heating costs , > growing season?
> crop production?
Some “Cons”
> ocean level (> 50 cm) , > variation in
weather patterns, salt water intrusion, >
species extinction, redistribution of ag.,
disease, species…..
Reducing the Threat of Global Warming
• Reactive vs. Proactive Management
• Optimism vs. Pessimism
1) Reduce auto emissions
2) Alternative fuels
3) Fuel taxes
4) Genetically engineered fuel crops
5) Stopping Deforestation & Increase
Restoration
6) Population Growth Management
* Tenets of Sustainable Development
Global Impacts of Air Pollution
Acid Deposition (“Acid Rain”)
* acidic rain, snow, or dust
* SO2 (sulfur dioxide) -- sulfuric acid
* NO2 (nitrogen dioxide) – nitric acid
* Differential acid precipitation patterns &
role of weather patterns in spreading
acid precursors
Acid Deposition
* But don’t volcanoes produce SO2
emissions?
• Remember it’s a question of (relative to
nutrient cycling, concentration, and
dispersion):
- Spatial & Temporal Scale
- Frequency & Intensity
Acid Deposition
* Differential vulnerabilities of ecosystems
dependent on buffering ability
(limestone vs. granite)
• Impacts of acid deposition on
northern lake systems
- relation to heavy metals
Acid Deposition
Harmful Effects
• > acidity of soil
• defoliation of vegetation
• fish reproduction impaired
(chemotaxis)
• altered trophic structure of aquatic
community
• > heavy metal availability
• abnormal development
Reducing Acid Deposition
• Reactive vs. Proactive Management
1) Low-Sulfur Coal (S)
2) Scrubbers (S)
3) Energy Conservation (S & N)
4) Renewable Energy Resources (S & N)
* Tenets of Sustainable Development