Lecture Marine environmental studies Topic Chemical aspects of the ocean

Lecture Marine environmental studies Topic: Chemical aspects of the ocean. In this topic, the following content will be discussed: Effects of water on land, physical weathering, is there any difference between weathering and erosion? Biological characteristics of the ocean,...

CHEMICAL ASPECTS OF THE OCEAN

Gohoho Emmanuel Sena

Effects of water on land

• Number of processing occurs when it rains

• WEATHERING

• 2 types

• Physical and Chemical weathering

Physical weathering

It involves the breakdown of large rocks, boulders, pebbles and finally to dust

It occurs through a number of ways

• Water enters into cracks and opens them out resulting into the breakdown of rocks

• As a result of heating and cooling resulting in expansion and contrasting

• The scouring action of air borne gas

• The grinding action of glaciers

• Roots of plants growing into cracks may put

pressure on the surrounding rock, eventually breaking rocks apart as the roots grow

• Forest and range fires can cause rocks that are located along the surface of the ground to

weather

Chemical weathering

Rain water leaches soluble salt and other chemicals out of the rocks and carry these chemicals away into the rivers and

eventually into the ocean.

The average salinity of the sea water is

about 35%

Is there any difference between weathering and

erosion?

Principles of existence of constant salt in the ocean

Two principles

• Principles of constant composition

• Principles of steady state ocean

Principles of constant composition

• It states that the concentration of the major ions of sea water are in constant ratio

• The major constitutes are those which

have measurable contribution to salinity

and they have concentration of not less

than 1mg/kg

• Major ions are those which behave

consecutively These includes sodium ion Na+, K+, Ca2+, Sr2+ , Cl-, So42-, F-, Br-(cations: Na+, K+, Ca2+, Sr2+,) ( anions: Cl-, So42-, F-, Br-)

The minor constituents have concentration less than 1mg/kg they include Fe, CO, n, cu,

ZN, Cd, Hg, Pb, Mn

This does not include dissolve gases,

nutrients, radioactive, etc

Selected dissolved materials in 35% seawater

Principles of Steady State Ocean

• It states that the rate at which natural chemical are added to the sea water is equal to the rate at which they are

removed from the seawater

Nutrients

• These are ions needed for the growth of plants They are phosphates and sulphates The quantity and concentration are valued according to the

depth, seasons and areas

Dissolved Gases

any gases that can be found in the atmosphere can also be found

in the oceans

Examples are, Oxygen, phosphate, etc.

Biological characteristics of the

ocean

• This is simply production or productivity in the ocean

• Productivity in the ocean is the synthesis

of organic compound from the inorganic constituents of the sea water by activity of organisms

the single cell plankton (phytoplankton) make use of sunlight, nutrient and carbon dioxide to produce food and that is known as primary

production.

primary production is therefore basically

photosynthesis and the phytoplankton is

known as primary producer.

The biological conditions are influenced by

both physical and chemical characteristics of the ocean

• The chemical conditions ensure the

distribution of the nutrients in the ocean.

• The physical characteristics has to do with the oceanic motion.

The physical characteristics is

important for a number of reasons

It provides a near uniform medium for organisms

It enhances the mixing and diffusion processes so as to minimize variations

in temperature and salinity

It carries swimming and floating organisms as well as their reproductive products

It disperses pollutants and spit out their dilutions

• Oceanic motion is made up of waves, currents, tides and

vertical motions

• Wind- is created as a result of differential heating of the ocean water

• Waves- are created as a result of wind blowing over the ocean The water column does not move and the size of the wave

depends on the velocity of the wind

• Currents- they are generated by wind blowing over the surface

of the ocean

• Tides- are generated as a result of gravitational attraction

between the sun and the earth and between the moon and the earth The moon effect on tide is greater because it is closer to the earth

• Vertical motion- this is made up of sinking

(downwelling) and upwelling.

• The sinking (downwelling) is due to the increase

in density of the water and the density is affected

by surface temperature and salinity

• Upwelling-normally occurs along the western

margin of the continent Surface currents move

the water towards the equator and the subsurface move up to replace the water blown away This

process brings the water rich in nutrients which

gives greater number of fish in that particular area

to feed on the nutrient.

Assignment

• Submission date : a week from today

• Why is sea water salty?

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