There are several soil physical properties that affect the likelihood of chemicals leaching from the soil down into the
groundwater:
- Soil
Texture: This refers to the relative proportion of different sizes
of soil particles. Leaching is more rapid and deeper in coarse or light (sand
textured) soils than in fine or heavy (clay
textured) soils.
- Soil
Structure: This refers to the way soil grains are grouped together
into larger aggregates. Soil structure is affected by texture and organic
matter content. Pesticides and water can seep, relatively unimpeded, through
seams between the aggregates.
- Soil Porosity:
This is a measure of the amount of open space between soil and rock particles.
All other things being equal, chemicals are more likely to leach through more
porous soils.
- Soil Permeability: This is
a measure of the ease with which water can move through the soil. All other
things being equal, more permeable soils are more likely to transmit chemicals
faster.
- Soil
Moisture: This refers to the presence of water in the soil. Soil water
if the primary mechanism for transporting chemicals into the groundwater.