3. Acidity • Rain is naturally slightly
acidic pH 5.6
• Caused by carbon
dioxide in the air
dissolving into the water
forming carbonic acid
4. https://www.youtube.com/watch?v
=Nf8cuvl62Vc • However, when sulfur
and nitrogen oxides
dissolve in the rain they
form sulfuric and nitric
acid and can have a
very low pH (1-3)
• pH scale is logarithmic,
pH1 is x10 more acidic
that pH 2, and x100
stronger than pH 3
6. Chemistry of acidified precipitations
Acid deposition can be either wet or dry:
Wet deposition - acidic rain, snow, or other
precipitation
Dry deposition - acidic gas or dry particles,
not mixed with water
Pollutants can be classified as either primary or
secondary:
Primary pollutants - those directly emitted by
a factory or automobile
SO2 - sulfur dioxide
NO and NO2, usually identified as NOx
8. Chemistry Cont.
Secondary pollutants - primary pollutants react
with other substances in the atmosphere and
create different pollutants
H2SO3 - sulfurous acid
H2SO4 - sulfuric acid
HNO3 - nitric acid
9. Effects of acid deposition on
environment
Direct effects (Know 1):
Inhibits embryonic development of fish
Chlorophyll loss & yellowing of tree leaves and
buds → diminished growth
Thinning of cuticle (the waxy coating on
needles)
Symbiotic root microbes killed (i.e. Rhizobium
spp. and other beneficial fungi)
10. Effects of acid deposition on
environment
Toxic effects (Know 1):
Aluminum (Al) leaches out of soil into streams
Al disrupts salt, water, and oxygen regulating
mechanisms in fish
Al can also adhere to fish gills, causing
suffocation
Lichens sensitive to SO2 gases and used as
indicator species
11. Effects of acid deposition on
environment
Nutrient effects (Know 1):
Soil particles can’t retain Ca, Mg, K, and
other nutrients in acidic environment, so
those nutrients are leached out of soil and
not available to trees
Dissolved Al ions damage root hairs (the
smallest roots, which are the most
effective at absorbing nutrients), so the
trees are unable to absorb as many
nutrients
N-fixing bacteria don’t function as well, so
less N is added to soil matrix
12. Effects of acid deposition on
environment
Damage to human infrastructure:
acid rain dissolves limestone structures,
especially buildings and statues
13. Acid deposition is regional
Acid precipitation falls
back to Earth rather than
entering stratospheric jet
stream
Most areas are
downwind of pollution
sources
Canadian forests
damaged by coal-fired
power plants in USA
Scandinavian and
German forests
14. Potential problem areas
because of sensitive soils
Potential problem areas because
of air pollution: emissions leading
to acid deposition
Current problem areas
(including lakes and rivers)
15. Reducing the effects of acid
deposition
find out about the following techniques:
Liming lakes to neutralise acidity.
Precombustion (before burning) techniques.
End of pipe measures (after burning).
Of course we could always reduce our use of
fossil fuels to help solve this problem.
Nuclear power? Electric cars?
16. Pollution management strategies
for acid deposition
See Table 15.7 on p.298 of the IB ESS 2010 Course
Companion
Replace
Switch to renewable energy sources (reduce fossil fuel
use)
Increase energy efficiency (better light bulbs and
appliances)
More public transportation (fewer automobiles on the
road)
Use low-sulfur fuels
Regulate
Install ‘scrubbers’ on smokestacks of coal-fired power
plants to remove SO2
Catalytic converters installed on automobiles (required
17. Management cont.
Restore
Add limestone to acidified lakes and streams
Using limestone or calcium carbonate (CaCO3) can
neutralize (buffer) the impact of acids.
Freshwater ecosystems much more vulnerable
Expensive and hard to determine how much to add
18.
19. Remember, this is not a Global problem but a
regional one most serious in
Mountain top forests
Areas with high auto traffic
Areas downwind from industrial centers
20. CASE STUDY
Research the effect of acid deposition and
intergovernmental agreements or legislation and their
effectiveness
In groups you are going to create a poster to
show the impact and pollution management
strategies in one of the cases below.
Canada affected by acid deposition from the
USA.
Sweden and Norway affected by acid deposition
from Poland, Germany and UK.
China
