Agriculture Reference
In-Depth Information
3
Interchange of Solutes between
Solid, Liquid and Gas Phases
This chapter is concerned with how ions and uncharged solutes in the water
and soil solution in submerged soils interchange between the solid, liquid and
gas phases present. This is a large topic. I give here the bare essentials needed
to understand the transport and transformation processes discussed elsewhere in
the topic, and I give references to more detailed treatments where appropriate.
The water and atmosphere overlying the soil are dealt with first and then the
additional complexities in the soil.
A. WATER
3.1 COMPOSITION OF THE WATER
The water contains:
•
dissolved matter
- free ions;
- inorganic and organic complexes;
- uncharged molecules.
•
particulate matter
- large organic and inorganic polymers;
- oxides;
- clay minerals;
- organic matter.
Because of their large surface areas, charged particles are very efficient scav-
engers of ions from solution, and where the sediment load is large the concentra-
tion of adsorbed ions may greatly exceed the concentration in solution. Similarly
for ions that form complexes with organic or inorganic ligands, their total con-
centration in solution may be far greater than the concentration of the free ion.
Complexation and sorption are especially important in regulating the concentra-
tions of trace metals in natural water systems. The interactions between ions and
charged particles are discussed in the sections on soil.
