PESTICIDE - Overview - Geologic and Hydrologic Characteristics

Geologic and Hydrologic Characteristics

Some of the geologic and hydrologic characteristics that help determine the risk of pesticide contamination of the ground water include:

  • Soil type and composition
  • Soil physical properties
  • Slope of ground surface
  • Depth to ground water
  • Abundance and location of surface water

Soil Type and Composition

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.

Back Arrow Return to Pesticide Overview
© Copyright