Water Behavior in Soils

Chemical Properties of Water and Behavior in Soils
 The chemical properties of water govern its behavior in the environment and control many key processes occurring in soils as the aqueous phase interacts with organisms, mineral surfaces, and air spaces.As a result of its nonlinear structure and dipole moment, water has a high dielectric constant (80.1 at 20°C).This unique property of water also makes it a powerful solvent, allowing it to readily dissolve ionic solids.
 Another particularly important chemical property of water that impacts processes occurring within the soil solution is that it is amphoteric, meaning that it can act as either an acid or a base. Due to its polarity, water readily undergoes ionic dissociation into protons and hydroxide ions. Accordingly, when it reacts with a strong base, water acts as an acid, releasing protons; When it reacts with a strong acid, water acts as a base, accepting protons.
 The amphoteric behavior of water facilitates the acid-base chemistry and dictates the potential pH range of aqueous solutions, thereby imparting soil pH — a "master variable" of soils that influences soil formation, plant growth, and environmental quality.
 The ability of water to stabilize charged species in solution allows it to support the flow of electrons in soils. As such, water helps mediate oxidation and reduction (redox) reactions within the soil solution. Water itself may participate in these processes, and it is a product of cellular respiration in soils. In aerobic soils, water is produced from the oxidation of carbon in organic matter for energy production by microorganisms.

Physical Properties of Water and Behavior in Soils

 Liquid water is a key component of the three-phase (solid, liquid, gas) soil system, possibly occupying 50% or more of the total soil volume under saturated conditions. Even under relatively dry conditions, water held at large tensions within soil pores occupies approximately 5–10% of the soil volume.