acid deposition - willis' science · 2017. 2. 28. · acid dep. from so 2 ... controlling acid...
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Acid Deposition
Measuring Acidity
• pH scale (log scale)
• 0-6: acid,
7: neutral,
8-14: base
Each step is a power of 10
Ex: pH 4 is 100x’s stronger than
pH 6
Normal Rain Water•pH of 5-6
•Due to CO2
+ H2O
H2CO3
(carbonic
acid)
Acid Rain pH
•pH is a 3-4
Acid Dep. from SO2
• SO2: Coal combustion from power utilities.
• SO2 + H2O --->H2SO4
(Sulfuric acid)
• NO2: Gasoline combustion and
fertilizer application
• NO2 + H2O --->HNO3- (Nitric acid)
Acid Dep. from NO2
Effects of Acid
Deposition
Destroys Limestone!Before
After
An
extra
hole…
Fish Deaths• Acid in lakes declining fish
pops
• Can only tolerate certain pH
ranges.
Hmm…
Dinner!
Plant Deaths• Acid in soils declining agricultural
productivity
• Plants can only tolerate certain pH
ranges too!
External damage to bark & leaves
Little resistance to pests
Lower rate of photosynthesis
Tree Damage
• Metals become ionic at lower pH
taken up via ion channels of fish gills
(Hg+2 /K+)
Metal accumulation in food web
metal toxicity in fish
In Rivers and Oceans
Plant Metal Toxicity
• If metals sit in ground taken up by plants (plant
metal toxicity)
Soil Leaching• If it rains after acid breaks up metals
into ions, then metals leave soil (soil leaching). Loss of nutrients
Changes
in Rain
pH
Why
East
Coast?
Controlling Acid Deposition
Reduce SO2 and NO2
emissions Switch to alternative energies (solar,
hydroelectric)
• Legislation: Clean Air Act
Set standards on how much NO2
and SO2 are allowed to be emitted
(NAAQS).
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