Soils

Soils

1. Surface charges

   • 1:1 clays = 1 tetrahedron, 1 octahedron which only external surface area
   • 2:1 clays = distance between layers where water can go in. External and internal surface area. expanding and has great surface area and electrical charge
   • clay and OM most active due large specific surface and surface electrical charge

2. specific surface area - internal and external surface area

   • important desorption (realasing) and absorption (catching) ions
   • clay particles specific surface is 2-3 order magnitude larger than sand or silt particles

3. permanent charge

   • occurs silicate clay surfaces (illite and smectite)
   • not affected by PH or Ion type and concentrations
   • isomorphous - subsitution one atom with another of similar size
     • permanent charge
     • occurs cystal formation

4. CEC - Cation exchange capacity

   • Low ph - Low CEC (hydrogen binds tightly and does not exchange readily
   • High Ph - high CEC (Na binds loosely and is readily exchanged
   • OM - CEC increases as OM increases
   • depends on amount of clay or OM and type of minerals cin clay