Acid Rain
What goes up, must come down
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Key Points

Enhanced acidity (average pH < 5.0)
– rain naturally weakly acidic from dissolved CO2
A product of industrial air pollution
 Problems in regions downwind
 Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

Acidity of Rainfall (pH) 1996

National Acid Deposition Program
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution

–
–
SO2 from coal, oil
NOx from automobiles, electric generation
Problems in regions downwind
 Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

Principal
Sources
 Electric
Generators
 Refineries
How Acid Rain Is Formed

U.S. Environmental Protection Agency
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution
 Problems in regions downwind

–
–
–
Kills fish in lakes
Destroys paint, stonework
Contributes to forest dieback / decline
• Buffered temporarily by basic soils
Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

Tolerance of Fish to Acidity
Effects of Acid Rain on
Lakes
 Range from no effect to completely barren
Variable from lake to lake
 Basic rocks (e.g. limestone) neutralize acidity in
groundwater

http://www.geocities.com/RainForest/Vines/7948
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution
 Problems in regions downwind

–
–
–
Kills fish in lakes
Destroys paint, stonework
Contributes to forest dieback / decline
• Buffered temporarily by basic soils
Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

Acid Rain on Structures
Accelerates decay of stonework
 Ruins finishes on cars and other paint work

King’s College, Cambridge, England : The Chapel
Decay of Stonework

German sandstone statue from 1702 photographed
in 1908 (left) and 1969 (right).


Photo: Westfäliches Amt für Denkmalpflege.
Courtesy Norwegian Department of Environment
Effects on Marble

Column capital volute, Jefferson
Memorial, Washington, D.C.

Marble surfaces exposed to rain develop a rough
"sugary" texture because the calcite grains are
loosened as the edges dissolve in the rain water.
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution
 Problems in regions downwind

–
–
–
Kills fish in lakes
Destroys paint, stonework
Contributes to forest dieback / decline
• Buffered temporarily by basic soils
Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

Forest dieback
Many causes of
dieback
– shade
– insects
– climate
 Acid rain
contributes

–
–
leaf damage
nutrients
leached from
soil
Alan
Rebertus- University of Missouri
Effects of
Acid Rain?
 German
forest
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution
 Problems in regions downwind
 Sulfate aerosol conceals greenhouse warming

– cools Northern Hemisphere continents by day
– global effect much less than CO2 induced warming
– controlling acid rain increases global warming

Reduction facilitated by SO2 emissions trading
Sulfate Aerosol
& Global Warming
 SO2
->Sulfate aerosol -> Acid Rain
 Sulfate aerosol reflects sunlight
-> cools the Earth -> part offsets CO2
 Cooling over N.H. continents by day
Estimated contributions to
global warming

Intergovernmental Panel on Climate Change
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution
 Problems in regions downwind
 Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

– Established in U.S. by Clean Air Act 1990
– Enables stricter standards than command and control
approach
– Presumes effective monitoring of actual emissions
– Prototype for international allowance trading of CO2
Causes of Acid Rain

U.S. Environmental Protection Agency
Regulation of Emissions
large point sources
 Command
–
–
–
the traditional approach
mandate cleanup technology
accept best efforts
 Market
–
–
–
–
and control
incentives
novel approach Clean Air Act 1990
allowance required for actual emissions
open market for trading allowances
mandate total allowances issued
Trading Emissions
Allowances
Requires credible monitoring of actual
emissions
 Market value of allowances

–
–
provides incentive to invest in more
efficient technology
allows individual scheduling of plant
replacement
Price rises till weak demand controls
total emissions
 Less political intrusion in management

Application to SO2
Assumes unit emissions in different places
are equivalent ( a rough approximation)
 Electric utilities only

–
–
–
most of the problem (for SO2)
well organized institutions
forward planning usual
Allowances may be banked for future use, but
not used ahead of time
 Congress set total emissions through 2025

–
the screws tighten in 2000
$ Price of 1 ton SO2
Emissions

U.S. Environmental Protection Agency
Emission Allowances
Trading: a Good Idea?
 A right to pollute?
– We all pollute the environment

Can emissions be credibly monitored?
–

Essential to link responsibilities to rights
Is there an efficient market?
– Low transaction costs, no monopolies
Do similar emissions have equivalent effect?
 So far, so good ...
– A prototype for international CO2 controls

•
Joint Implementation
Key Points
Enhanced acidity (average pH < 5.0)
 A product of industrial air pollution

–
–

SO2 from coal, oil
NOx from automobiles, electric generation
Problems in regions downwind
–
–
–
Kills fish in lakes
Destroys paint, stonework
Contributes to forest dieback / decline
• Buffered temporarily by basic soils
Sulfate aerosol conceals greenhouse warming
 Reduction facilitated by SO2 emissions trading

Sources of Information
 U.S.
Environmental Protection Agency