Buffering By Soils From Cation Exchange

Question 0

The adsorption arises because of the

Answer 0

Net negative change of most soil particles.

This attracts and holds positively charged cations.

Question 1

Some cations, produced from weathering reactions, are absorbed onto the

Answer 1

Surface of clay minerals and organic particles where they can be retained for long periods.

Question 2

The net negative charge comes from

Answer 2

Isomorphous substitution in clays (permanent charge).

The dissociation of hydroxyl -OH groups in clays and organic matter (pH dependent charge).

Question 3

These cations are bonded by weak

Answer 3

Electrostatic forces; they can be removed or exchanged easily by other cations.

Question 4

The additional supply of hydrogen ions into soils from

Answer 4

Acid deposition, leads to the displacement of basic cations from soil particles.

Question 5

Cation exchange lowers the concentration of

Answer 5

Hydrogen ions in the soil water and neutralises acid deposition in the soil.

Question 6

Soil particles become acidified because they

Answer 6

Have given up basic cations and the base saturation of the soil is lowered.

Question 7

The neutralisation continues until all exchange sites have been filled with hydrogen ions. At this point the base saturation

Answer 7

Approaches zero and the hydrogen ions entering the soil form the atmosphere will pass through into the surface water as runoff.

Question 8

The flow of sulfate ions passing through the soil will be balanced by

Answer 8

More and more hydrogen ions, thus increasing the acidity of water leaving the soil and therefore will lead to freshwater acidification.