EVOLUTION OF CONTAMINATED GROUNDWATER IN HOLT COUNTY, NEBRASKA

The theoretical absence of the in situ formation of most common mineral phases and the high vertical permeability of the relatively inert soils and unsaturated layer permit detection of man‐induced environmental changes in the dilute groundwater of Holt County. Correlation coefficients show many significant associations for the major ions in groundwater affected by point and nonpoint‐source contamination. Large areas of nonpoint contamination are attributed to fertilization and irrigation of the sandy soils. In these areas increases in the average annual groundwater concentrations of Cl−, SO42−, and NO3− average 0.44, 0.57, and 4.9 mg/l/yr, respectively. A proposed model suggests that 50% of the applied nitrogen fertilizer infiltrates to the groundwater reservoir. Copyright 1979 by the American Geophysical Union.