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Water Pollution in Lakes (causes, effects, sources)
6. Euphotic Zone
✘ The upper layer of water through
which sunlight can penetrate
✘ Plant growth
✘ Depth is determined by the
amount of turbidity blocking
sunlight penetration
✘ Plants produce more oxygen by
photosynthesis than they
remove by respiration
✘ Profundal zone – lies
below the euphotic
zone
✘ Light compensation
level – the transition
between the two zones
7. Littoral Zone
✘ The shallow water near the shore in which
rooted water plants can grow
✘ The extent of the littoral zone depends on the
slope of the lake bottom and depth of the
euphotic zone
✘ Cannot extend deeper than the euphotic zone
8. Benthic Zone
✘ Bottom sediments
✘ Bacteria are always present
✘ Presence of worms, insects and other higher life
forms
9. LAKE
PRODUCTIVITY
a measure of its ability to support a food
web and may be determined by
measuring the amount of the algal
growth that can be supported by the
available nutrients.
The base of the food web is algae
Increased productivity generally results
in reduced water quality because of
undesirable changes that occur as algal
growth increases.
11. Classification of Lakes
Oligotrophic Lakes
- have a low level of productivity due to
a severely limited supply of nutrients to
support algal growth.
- As a result, the water is clear enough
that the bottom can be seen at
considerable depths.
- Euphotic zone often extends into the
hypolimnion, which is aerobic.
13. Classification of Lakes
Eutrophic Lakes
- have a high productivity
because of an abundant supply of
algal nutrients.
- algae cause the water to be
highly turbid, so the euphotic
zone may extend only partially
into the epilimnion.
14.
15. Classification of Lakes
Mesotrophic Lakes
- lakes which are intermediate
between oligotrophic and
eutrophic
- substantial depletion of
oxygen may have occurred in
the hypolimnion, it remains
aerobic.
17. Classification of Lakes
Senescent Lakes
- very old, shallow lakes which have thick organic
sediments and rooted water plants in great
abundance
- these lakes wil eventually become marshes
19. EUTROPHICATION
Is a natural process in which lakes gradually
become shallower and more productive
through the introduction and cycling of
nutrients
Thus, oligotrophic lakes gradually pass through
the mesotrophic, eutrophic, and senescent
stages, eventually filling completely
20. Cultural Eutrophication
- caused when human activity speeds the
processes naturally occurring by increasing the
rate at which sediments and nutrients are added
to the lake.
- lake pollution can be seen as the intensification
of a natural process
22. C ARBON
✘ Obtained from carbon
dioxide in water
✘ When algae are either
consumed or die and
decompose, the organic
carbon is oxidized back to
carbon dioxide
23. N itrogen
✘ Usually in the form of nitrates [NO3
−
]
✘ Converting nitrogen gas to organic
nitrogen though nitrogen-fixing bacteria
such as cyanobacteria
✘ Comes from external sources by way of
inflowing streams or groundwater
✘ Aerobic
○ When taken for algal growth, forms
amino-nitrogen NO2
−
○ When algae dies, forms ammonia
[NH3 ]
✘ Anaerobic
○ Nitrate is reduced to [N2] through
denitrification
24. P hosphorus
✘ Originates from external
sources
✘ Taken up by algae in the
inorganic form [PO4
3−
] and
incorporated into organic
compounds
✘ When algae dies, returns to
its inorganic form
25. Trace elements
✘ a chemical element
required only in minute
amounts by living
organisms for normal
growth
✘ Most fresh waters have
sufficient amounts for a
substantial algal population
27. Acidification of lakes
Change towards more acidic conditions in
lakes
A lake can be considered acid or slightly
acid when pH is below neutral (<6.5). More
evident biological consequences will
develop at pH < 5.5.
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28. Causes
✘ Acid Rain
is caused by emissions of sulphur
dioxide and nitrogen oxide, which react
with the water molecules in the
atmosphere to produce acids.
✘ Buffer Solution
a solution that resists changes in pH
when acid or alkali is added to it.
29. Harmful Effects
✘ Fish and other aquatic animals will die in
water with low pH.
✘ Acidified water cannot be used for drinking.
First the water has to be neutralized (neutral
pH), as acidic water is damaging to your
health and could possibly cause kidney
problems.
✘ High aluminum concentrations are often the
trigger that kills fish
-lakes contain several distinct zones of biological activity
-largely determined by the availability of light and oxygen
-turbidity is due to algal growth in lakes
The soil usually has substances that ensure that the pH is neutral and that the acid will be removed: The Buffer solution.
If the buffer solution is finished then the soil will become acid.
This may cause toxic chemicals or nitrate to be released.
The rain will cause the nitrate or the toxic chemicals to rinse out the surface water or ground water, causing them to contaminate water.
1. Help restore natural ph of lakes
2. Reducing the use of SO2(Sulfur dioxide), [[NOx]] and NH3 (Ammonia).
Lowering the use of these substances is done by using low-Sulphur fuel, or flue gas desulphurization.