It is one of my best presentation

1. Oceanography Lecture
By
Dr. Pramod Kumar Anthwal

2. Sources of salinity in seawater
• River caring variety of dissolved substance in PPM and discharging it into sea
water.
• Question is how much and how?

3. • River dissolved chemicals due to chemical weathering of rocks on land.
• Chemically reactivity of the water is determined by presence of hydrogen ions
which may be introduced through the chemical reactions.
• H+ ions determines the chemically reactivity of the water. (Imp)

4. • The hydrogen ion derived from the reaction will replace by the cations such as
potassium, sodium that are bound to minerals in various type of rocks.

6. How river water introduce salts to Oceans and
how much?
• The chemical weathering of orthoclase leads to formation of Kaolinite and silica.
• The river transport these materials to the ocean into distinct forms one is as a
dissolved Load and second one is as a suspended load that is fine particles
suspended in river water.
• Dissolved substance that is potassium and silica where as suspended load is
Kaolinite.
• Dissolved potassium and silica contribute to the sea water salinity whereas
suspended particles deposited as a mud on the sea bottom.

7. • Since we cannot see the dissolved solids in river water and fresh water does not
taste salty then how we can determine that how much salts are dissolved in river
water?
• The annual river input of dissolved material to the ocean is about 2.5×1015 and
4×1015 grams.
• It means 2.5×1015 to 4×1015 grams of dissolved salts are introduced to the ocean
by the rivers.

8. What is the point then
• The point is rivers are supplying the dissolved salts which are contributing in
calculating the sea water salinity, but the fact is over all sea water salinity is about
35 parts per thousands or we can say the average salinity of sea water is about
35parts per thousands, so if the salts are regularly introduced to the sea water then
why there is not appreciable increment in sea water salinity.
• And the second point is the fact of river water reveals that most abundant
constituent of river water as a solute is bicarbonate and in sea water the most
abundant solute is chloride.
• Why is this so?

9. • Fossils records and the sedimentary rocks themselves indicates that oceans has
exist on the for at least along as 3.4 billion of years .
• Over this large period of time the sea water salinity has changed little over the
past 1.5 billion years despite of regular supply of dissolved solids through river
water and de gassing at the mid oceanic ridges and at the volcanic arcs of the
subduction zone.

10. Steady state equilibrium
• The Balance between the input and output of the salts to the oceans is called
steady state equilibrium.
• Input of the material is called source and output of the material is called sink.
• The source of the material is river water, volcanic activities at mid oceanic
ridges and the subduction zone.
• The sink is due to evaporation, geochemical and biochemical activities,
absorption of the cations why certain clay minerals uptake of silicon and
calcium by Diatems and foraminifera respectively supersaturation causes
precipitation of dissolved salts such as sodium chloride that is halite and
gypum, calcite

11. Fundamental question is why there is the difference in relative
composition of solutes in sea water and river water???
• Here we got the concept of Residence Time
• Residence time can be defined as the average length of time that an ion remain in
solution.

13. What is the benefits of residence time
• Residence time helps to explain the principal of constant proportion.
• The rapid cooling and long residence time assure the fact that they are uniformely
disturbed through out the oceanic water.

14. Water Reservoirs
• Water cover greater than 60% in northern hemisphere and water cover is greater
than 80% in southern hemisphere.
• The water in oceans is about 97.25% of water in terms of volume.
• Fresh water reservoirs-
• Ice mass> groundwater > lakes> atmosphere> rivers> biospheres.
• The volume of ground water is greater than the water of river+ lake+
atmosphere.

15. • 97.2% in world ocean
• 2.15% in glaciers
• 0.62% in groundwater and soil moisture
• 0.02% streams and lakes
• 0.001% as water vapors in the atmosphere.

16. Quizz Questions
• Which ions determines the chemical reactivity of the oceans?
• The principle behind the different composition of solutes in sea water
and river water……………
• Which one is the largest fresh………
• The water covers in southern hemisphere is approximately…..
• Which one is a most abundant dissolved salts in river water……
• The residence time of chloride is…..
• Steady state equilibrium represents balance betweem…..