Soil type can greatly affect the likelihood of pesticides leaching
into the ground water. For example, sandy soils allow pesticides to
move towards the ground water more rapidly than soils with significant
clay content. If the soil
has clay minerals as part of its composition, the positively
charged pesticides can adsorb onto the negatively charged clay
particles. Soil with a high organic matter content
can also adsorb pesticides, thereby inhibiting their movement.
Soil Physical Properties
There are several soil physical properties that affect the
likelihood of pesticides leaching into the ground water:
Soil Texture:
the relative proportion of
different sizes of soil particles.
Leaching is more rapid in coarse or
light (sand textured) soils than in fine or
heavy (clay textured) soils.
Soil Structure:
the way soil grains are
grouped together into larger aggregates.
Soil structure is affected by texture and
organic matter content. Pesticides and
water can flow, relatively unimpeded,
through seams between larger the aggregates.
Soil Porosity:
all other things being equal, pesticides are
more likely to leach through more porous
soils.
Soil Permeability:
a measure of the ease with which
the soil can transmit the water. All other
things being equal, more permeable soils
are more likely to transmit water that may
contain pesticides.
Soil Moisture:
the presence of water in the
soil. The soil water ultimately transports
pesticides to the ground water.