Chemical Effects of SOM

Cation Exchange Capacity

Definition: The amount of exchangeable cations in the soil; The number of moles of singly-charged cations that may be held by 1kg of clay/soil
The higher the CEC, the higher the quality of the soil
Since clay and humus particle have many negative charge (due to the presence of ions such as COO- and SiO4- (clay))
Various cations can be held by the clap and soil particles
Other cations dissolved in the soil can be bounded/ exchanged for other ions [H+ (clay) + K+ (aq) --> K+ (clay)+ H+(aq))

Improved Retention of Soil Nutrients

Reduced Leaching of Metal Ions into Bodies of Water

CEC of humus also allow soil particles to bind and hold onto potentially toxic metal ions
Prevents leaching of the metal ions into bodies of water
HOWEVER: may decrease soil quality

SOM particles act as an acid-base buffer system

Buffers keep the pH of solutions at a fairly constant level when small amounts of acid or base are added

	Created by IBMichelle over 10 years ago

IB Chemistry (E: Environmental Science (UNMODIFIED)) Note on E7 and E12: Soil (UNMODIFIED), created by IBMichelle on 08/04/2014.