The following four graphics illustrate how pollution can impact groundwater quality
Step 1: Pollutant is Released
A hazardous substance is released at or near ground surface
A spill occurs at ground surface and a hazardous substance enters the unsaturated area just below the surface. This unsaturated area is known as the vadose zone. Once released, the contaminant mixes with soils and sediments. Precipitation percolating down through the soils and sediments will carry the contaminant towards the water table, which marks the beginning of saturated sediments. Many organic compounds can linger in the soil for years before either evaporating into the atmosphere, or breaking down through microbial action.