Global Environmental issues

1. Acid Rain
Unit:3
Environmental Science

2.  Air is becoming increasingly polluted
Acid Rain -- sulfur dioxide (also nitrogen
oxides) from coal burning sources + rain =
ACID RAIN

3. Acid rain
Acid rain is rain consisting of water droplets that are
unusually acidic because of atmospheric pollution -
most notably the excessive amounts of sulfur and
nitrogen released by cars and industrial processes. Acid
rain is also called acid deposition because this term
includes other forms of acidic precipitation such as
snow.
Acidic deposition occurs in two ways: wet and dry. Wet
deposition is any form of precipitation that removes
acids from the atmosphere and deposits them on the
Earth’s surface. Dry deposition polluting particles and
gases stick to the ground via dust and smoke in the
absence of precipitation.

4. Causes of Acid Rain
Acid deposition can occur via natural sources like
volcanoes but it is mainly caused by the release of
sulfur dioxide and nitrogen oxide during fossil fuel
combustion.
When these gases are discharged into the atmosphere
they react with the water, oxygen, and other gases
already present there to form sulfuric acid, ammonium
nitrate, and nitric acid. These acids then disperse over
large areas because of wind patterns and fall back to
the ground as acid rain or other forms of precipitation.
The gases responsible for acid deposition are normally
a byproduct of electric power generation and the
burning of coal.

5. Effects of Acid Rain
There are several important impacts of acid deposition
on both natural and man-made environments. Aquatic
settings are the most clearly impacted by acid
deposition though because acidic precipitation falls
directly into them. Both dry and wet deposition also
runs off of forests, fields, and roads and flows into
lakes, rivers, and streams.
As this acidic liquid flows into larger bodies of water, it
is diluted but over time, acids can accrue and lower the
overall pH of the body. Acid deposition also causes clay
soils to release aluminum and magnesium further
lowering the pH in some areas. If the pH of a lake drops
below 4.8, its plants and animals risk death

6. Effects of Acid Rain
Acid deposition can significantly impact forests. As acid rain
falls on trees, it can make them lose their leaves, damage
their bark, and stunt their growth. By damaging these parts
of the tree, it makes them vulnerable to disease, extreme
weather, and insects. Acid falling on a forest’s soil is also
harmful because it disrupts soil nutrients, kills
microorganisms in the soil, and can sometimes cause a
calcium deficiency.
Finally, acid deposition also has an impact on architecture
and art because of its ability to corrode certain materials. As
acid lands on buildings (especially those constructed with
limestone) it reacts with minerals in the stones sometimes
causing it to disintegrate and wash away. Acid deposition
can also corrode modern buildings, cars, railroad tracks,
airplanes, steel bridges, and pipes above and below ground.

7. Problems from Acid Rain:
• Destruction of limestone and marble
monuments due to increased chemical
weathering
• Acidification of aquatic ecosystems
destroying the life in them and of
animals depending on them.
• Damage forests and other plants in a
variety of ways

8. 1

9. Ozone Depletion
• Losing Earth's Protective Layer
2

10. The ozone layer is a belt of naturally occurring ozone gas
that sits 9.3 to 18.6 miles (15 to 30 kilometers) above
Earth and serves as a shield from the harmful ultraviolet
B radiation emitted by the sun.
Ozone is a highly reactive molecule that contains three
oxygen atoms. It is constantly being formed and broken
down in the high atmosphere
Today, there is widespread concern that the ozone layer
is deteriorating due to the release of pollution containing
the chemicals chlorine and bromine. Such deterioration
allows large amounts of ultraviolet B rays to reach Earth,
which can cause skin cancer and cataracts in humans and
harm animals as well.

11. Causes:
Scientific evidence indicates that stratospheric
ozone is being destroyed by a group of
manufactured chemicals, containing chlorine
and/or bromine. These chemicals are called
"ozone-depleting substances" (ODS).
The primary cause of ozone depletion is the
presence of chlorine-containing source gases
(primarily CFCs and related halocarbons).
In the presence of UV light, these gases
dissociate, releasing chlorine atoms, which then
go on to catalyze ozone destruction.

12. • The main ODS are chlorofluorocarbons (CFCs),
hydrochlorofluorcarbons (HCFCs), carbon
tetrachloride and methyl chloroform.
• Halons (brominated fluorocarbons) also play a
large role. Their application is quite limited:
they're used in specialized fire extinguishers.
But the problem with halons is they can destroy
up to 10 times as much ozone as CFCs can.

13. Effects:
Increased UV: Ozone, while a minority constituent in Earth's
atmosphere, is responsible for most of the absorption of UVB
radiation. Its depletion causes increased UV radiation.
Biological effects
Ozone layer depletion is expected to increase surface UVB levels,
which could lead to damage, including increase in skin cancer
and cataract (eye damage) in human beings.
Increased tropospheric ozone: Increased surface UV leads to
increased tropospheric ozone. Ground-level ozone is generally
recognized to be a health risk, as ozone is toxic due to its
strong oxidant properties. The risks are particularly high for
young children, the elderly, and those with asthma or other
respiratory difficulties.

14. Effects on crops:
An increase of UV radiation
would be expected to affect
crops. A number of
economically important
species of plants, such as rice,
depend
on cyanobacteria residing on
their roots for the retention
of nitrogen. Cyanobacteria are
sensitive to UV radiation and
would be affected by its
increase. Thus crop growth will
be affected. NASA projections of
stratospheric ozone
concentrations if
chlorofluorocarbons had not
been banned.
3

15. Global warming
Global warming is the
unequivocal and continuing rise
in the average temperature of
Earth's climate system.
 Since 1971, 90% of the
warming has occurred in the
oceans. Despite the oceans'
dominant role in energy
storage, the term "global
warming" is also used to refer
to increases in average
temperature of the air and sea
at Earth's surface.

16. • Scientists were more than 90% certain that most of
global warming was being caused by increasing
concentrations of greenhouse gases produced by
human activities.

17. Greenhouse gases
• The greenhouse effect is the process by
which absorption and emission of infrared radiation by
gases in a planet's atmosphere warm its lower atmosphere
and surface.
• On earth, naturally occurring amounts of greenhouse gases
have a mean warming effect of about 33 °C
• The major greenhouse gases are water vapor, which causes
about 36–70% of the greenhouse effect; carbon
dioxide (CO2), which causes 9–26%;methane (CH4), which
causes 4–9%; and ozone (O3), which causes 3–7%.
• Changes in the concentration of greenhouse gases, which
occur both naturally and as a result of human activities, also
influence Earth’s climate.

18. Increasing greenhouse gases
trap more heat
4

19. • Earth’s surface absorbs heat from the sun and then re-
radiates it back into the atmosphere and to space.
• Much of this heat is absorbed by greenhouse gases, which
then send the heat back to the surface, to other
greenhouse gas molecules, or out to space. Though only
1% of atmospheric gases are greenhouse gases, they are
extremely powerful heat trappers.
• By burning fossil fuels faster and faster, humans are
effectively piling on more blankets, heating the planet so
much and so quickly that it’s hard for Mother Nature and
human societies to adapt.

20. CO2 comes from a variety of sources. For example,
plants take up carbon dioxide in the air to make wood,
stems, and leaves, and then release it back into the
air when the leaves fall or the plants die. The concern
today is that fossil fuel use is putting huge amounts of
CO2 in the atmosphere at a rate faster than the
climate system can adapt to.

21. • Certainly, past temperatures past have been
lower than today, and CO2 concentrations have
also varied.
• Large global swings were probably caused by
such things as changes in Earth’s orbit, which
changed the distribution of sunlight over the
planet. When this caused warming, more CO2
and other greenhouse gases were released,
producing additional warming.

22. • Earth is getting warmer by virtually every
measure we know, and the temperature has
been well above normal for more than 25
years. Although increases of 1.0-1.6°F (0.6-
0.9°C) over the last century or so may not
sound very threatening, remember that’s a
global average.
• The warming is stronger over land than over
oceans and in the higher latitudes than in the
tropics.

23. Sea-level rise
projections : a few
inches to a few feet
•2 ft: U.S. would lose
10,000 square miles
•3 ft: Would inundate
Miami
•Affects erosion, loss
of wetlands,
freshwater supplies
•Half of the world’s
population lives along
coasts
•Big question: Ice
sheets

24. Why should we care?
5

25. • Global average temperatures are expected to
increase by about 2-13°F (1-7°C) by the end of
the century. That may not sound like a lot, so
what’s the big deal? The problem is that small
changes in global average temperature can
lead to really large changes in the
environment. Let’s look at some of the
expected changes.

26. 6

27. • There will always be natural variability, and some
places and some years will be warmer or cooler than
average. In general, however, summers will get
hotter, not only because of higher temperatures but
also because humidities will increase. That means
that heat waves, like the one that killed 35,000
people in Europe in 2003, will become more
common.
• On the plus side, winters will be warmer in many
places, reducing heating bills. And the number of
days with frosts is likely to decrease.

28. References/Sources
1. https://lh3.ggpht.com/VpghZaXZE2No81LCRdJwvYvZ8y9h7ld51Q4vTZXKPT2bH
2. https://lh3.ggpht.com/xNtvJ_BaQS5k6uYGiLK5FpE8i08-
NKGIVDGyrla0xZ3CPhwvXJRAiW8ZXAzIWzcMXMr4NxM=s113
3. https://lh3.ggpht.com/OuxQWgnPi4ND_Ix7PfjEU9o6ahjFnXwz1skcMc9f
CLw47lAzCh49h8a6V78Aid7pQO-3CQ=s119
4. https://lh6.ggpht.com/McSsK4-mfj0DMKcmNPVOHz4Ucc24kWsF-
B0wL89M982Bp_r61vlmGRvL0IIr73yiuiqhZg=s113
5. https://lh5.ggpht.com/jymlJFxrbl9SwM0NMsr_1Qh4Vmd6yC4ty9zd7B2-
Njdv338-Cjh4n_druUdZYK24FOtIQQ=s170
6. https://lh6.ggpht.com/pm95_mJWfD-
XDQl8x4JP88dtd767HkF7DOaPtkllk3v5zlzG2aBgsMeHYBlzuQIvccIc=s115

29. Book/Web Resources
• Environmental Pollution: Causes, Effects & Control by K.C Agarawal