15. 1التربة من وزنية وحدة لكل الكاتيونات ادمصاص مواقع عدد هي -
the number of cation adsorption sites per unit weight
of soil
2التربة تدمصها أن يمكن التي المتبادلة للكاتيونات الكلي المجموع : هي أو -
the sum total of exchangeable cations that a soil can
adsorb.
* CEC is expressed in milliequivalents (meq) per 100 g
of oven dry soil.
40. Carbonic acid formation
• forms in soil water
CO2 + H2O H2CO3
H2CO3 H+
+ HCO3
-
----------------------------
CO2 + H2O H+
+ HCO3
-
• [CO2] is higher in soils than aboveground
The clay particle derives its net negative charge from the isomorphous substitution and broken bonds at the boundaries.
The negatively charged faces of clay particles attract cations in the water. The concentration of the cations decreases exponentially with the increasing distance from the clay particle. The negatively charged clay surface and the positively charged cations near the particle form two distinct layers, known as “electric double layer” or simply “double layer”.