USGS logo

Photo from U.S. Geological Circular 1225--The Quality of Our Nation's Waters--Nuttients and Pesticides

graph showing percentage of ground-water samples that exceed the
drinking-water standard
The percentage of ground-water samples with concentrations of nitrate exceeding the drinking-water standard of 10 mg/L decreases as depth to water increases. Mixing of shallow ground water with deeper, uncontaminated water and increased thickness of protective, impermeable geologic materials with depth may help explain this relation.

 

up arrowBack