Hydrologic tehcnician collects a sample from a public-supply well

Groundwater in the Atlantic and Gulf Coastal Plain aquifers is old—more than 21,300 years old in more than half of the wells sampled. That ancient groundwater is more likely to contain naturally occurring concentrations of fluoride, arsenic, and polonium-210 that exceed a human-health benchmark for drinking water than younger groundwater, reports a study from the U.S. Geological Survey National Water Quality Program.

Here, a hydrologic technician collects a sample of untreated groundwater for analysis from a public-supply well in Clayton, New Jersey, that taps the North Atlantic Coastal Plain aquifer.