Fluoride in Nebraska's ground water

Fluoride concentrations in ground water are generally low but play an impor tant role in dental health. This study evaluates the vertical and spatial d istribution of. fluoride in Nebraska's ground water and examines the geolog ical and geochemical processes that control its concentration; Data from 17 94 domestic wells sampled by the Nebraska Department of Health and Human Se rvices, Regulation, and Licensure (NDOH) had a range of fluoride concentrat ions from <0.1 to 2.6 mg/L and a median concentration of 0.3 mg/L. The medi an fluoride concentrations for Nebraska's 13 ground water regions varied fr om 0.2 to 0.7 mg/L. In each of these regions, individual wells may have eit her insufficient or overabundant F concentrations; we recommend that indivi dual private water systems be tested for fluoride. Based on these data, sys tem-specific recommendations can be made regarding the necessity for fluori dation. Geochemical data indicated that the majority of fluoride. occurs as F. Diss olution of F-bearing minerals controls fluoride occurrence. Apatite plus mi nor amounts of fluorite along with significant ground water residence times are the primary factors controlling F in the water from the Dakota Formati on in Knox County, as well as in other parts of northeastern Nebraska. In w estern and southwestern Nebraska, dissolution of volcanic glass is the most probable source of F. Long residence times plus fluorite also may contribu te to the F concentrations in the Chadron Formation.