Sources and Concentrations of Nitrate‐Nitrogen in Ground Water of the Central Platte Region, Nebraska ^a

Abstract

ABSTRACT During 1976‐1977 nitrate‐nitrogen (NO3‐N) concentrations exceeded 10 mg/1 in 183 of the 256 ground‐water samples collected from parts of Buffalo, Hall, and Merrick counties in Nebraska. Comparison of the isotopic values with those of potential nitrate sources suggested that the primary source of contamination in most wells was fertilizer and that a small percentage of the wells contained significant concentrations of NO 3 ‐N derived from animal wastes. A combination of two or more sources of contamination was assumed for those samples for which the source could not be identified. Significant negative correlations between δ 15 N and NO 3 ‐N (‐0.35 in Buffalo and Hall Counties) and between δ 5 N and depth to water (–0.55 in Merrick County) indicate that denitrification is the major factor in isotopic fractionation of nitrogen from the nitrate sour