How chemical factors effect lake ecosystem? The presentation gives the quick knowledge on the properties of lake based on some chemical parameter.

1. CHEMICAL
PROPERTIES OF LAKE
DR. SURJYA KUMAR SAIKIA
DEPARTMENT OF ZOOLOGY
VISVA-BHARATI

2. What we will learn…….
 We will be able to know the major chemical factors of water
 We will be able to understand how these factors effect the aquatic body
 We will be able to know the COD and BOD of water

3. • The importance of chemical
factors is that they play major
role and effect the biotic
components of lake/water
body
• Thereby, they directly effect
on biological productivity of
the lake/water body
CHEMICAL FEATURES OF WATER BODY
Biotic
components
Chemical
players
Productivity

4. pH
Nutrients
Alkalinity Salinity
CO2
DO
Hardness

5. Dissolved Oxygen
Dissolved Oxygen is the amount of gaseous oxygen (O2) dissolved in
the water.
Oxygen enters the water by direct absorption from the atmosphere,
by rapid movement, or as a waste product of plant photosynthesis.
It is an important parameter in assessing water quality because of its
influence on the organisms living within a body of water.
A higher dissolved Oxygen level indicates better water quality.

6. www.fondriest.com www.globalspec.com

7. Low levels of oxygen (hypoxia) or no
oxygen levels (anoxia) can occur when
excess organic materials, such as large
algal blooms, are decomposed by
microorganisms.
Researchgate.net
Low levels of oxygen (hypoxia) or no
oxygen levels (anoxia) affect the biotic
communities in a Lake.

8. www.fondriest.com
Warm and Well
Oxygenated water
Rapid changes in
temperature and
oxygen
concentration
Cold. Oxygen may be
high or low
Oxygen level is low

11. Carbon dioxide
• Carbon dioxide content in air is only 0.03%,
but it is highly soluble in water unlike oxygen.
• CO2 stays in free (dissolved) or bound form
(bicarbonate and carbonate) in water
depending on the pH of the water.
• CO2 + H2O⇌H2CO3⇌H+ + HCO- ⇌H++ CO=
3 3

12. pressbooks.pub
pinimg.com

13. pH is defined as a negative
decimal logarithm of the
hydrogen ion activity in a
solution.pH
pH
pH

14. DESIRABLE FOR BIOTIC ORGANISMS

15. Carbon Dioxide linked to pH, alkalinity
• These aspects of water chemistry
are closely linked together.
• All these have great bearing on
the quality of water and these
help determine the productivity
of the water body.
CO2
pH
Alk

16. Diurnal fluctuations of pH will occur due to the amount of
aquatic life within a pond.
With higher algae concentrations, more CO2 is
removed from the system and hence pH levels will rise.
The reverse will occur at night when more CO2 is produced
therefore leading to a drop in pH levels.

17. Chemical oxygen demand (COD) is a measure of the capacity of
water to consume oxygen during the decomposition of organic
matter and the oxidation of inorganic chemicals such as Ammonia
and nitrite.
COD is expressed in mg/L
Higher COD levels mean a greater amount of oxidizable organic
material in the sample, which will reduce dissolved oxygen (DO) levels.
A reduction in DO can lead to anaerobic conditions, which is
deleterious to higher aquatic life forms.
Chemical oxygen demand (COD)
The COD test is often used as an alternate to BOD due to shorter
length of testing time.

18.  Chemical Oxygen Demand (COD) is a measure
of the oxygen equivalent of the organic matter in a
water sample that is susceptible to oxidation by
strong chemical oxidant such as dichromate.
 The concentration of COD in surface water ranges
from 20mg/L oxygen or less in unpolluted waters
to greater than 200 mg/L (in waters receiving
industrial effluents).

19.  Biochemical Oxygen Demand (BOD) is an
approximate measure of the biochemically
degradable organic matter present in the water
sample.
 It is defined as the amount of oxygen required for
aerobic microorganisms in a sample to oxidise
the organic matter to a stable inorganic form.
 Unpolluted water typically has BOD value of
2mg/L, but those receiving effluent may have
more than 10mg/L.

21. What we have learnt…..
The Dissolved Oxygen is a significant biotic chemical factor of
water. In lake, it changes with the season.
The Dissolved Oxygen also changes with the depth and
temperature.
The Free Carbon di oxide is another player contributing to aquatic
body.
The pH, Alkalinity, Carbon di oxide or dissolved oxygen combinly
effect the water quality.
Two of such measurable effects are COD and BOD.