EESB05H3 Lecture Notes - Lecture 6: Cation-Exchange Capacity, Clay Minerals, Adsorption
10 Dec 2016
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Document Summary
Chapter 8: the colloidal fraction- seat of soil chemical and physical activity: Colloids: extra small fragments of organic matter and rock. They are highly reactive materials with electrically charged surfaces. Because of their size and shape they give an enormous amount of reactive surface area. The ions in soil colloids form electrostatic forces of attraction which thus reduces their loss in drainage waters. Plants can still access water and nutrients among them. Colloidal fraction: the clay and humus particles in the soil. Particles behave as colloids if they are less than about 1 micrometer in diameter. Surface area: because of their small size all soil colloids expose a large external surface area per unit mass. Some also possess extensive internal surface area between the layers of their plate-like crystal units. Surface charges: the internal and external surfaces of colloids carry positive and/or negative charges . For most colloids there is more negative than positive charges.
