Nitrate in ground and surface waters in the vicinity of a concentrated animal feeding operation

Non-point source pollution by nitrates (NO3) from fertilizers and animal wastes has potential effects on human health and eutrophication of surface waters. Until now one problem in determining sources of NO3 has been the difficulty of identifying origin. Stable isotopes of nitrogen can be used as a signature of NO3 to identify origin from animal wastes. NO3 derived from animal waste has a delta(15) N signature of +10 +20 parts per thousand, which is uniquely high compared to delta(NO3)-N-15 from other sources. The purpose of this research was to describe the distribution of delta(NO3)-N-15, NO3 and Cl in wells, springs, seeps and lakes in the vicinity of a concentrated animal feeding operation (CAFO), which was the suspected source of contamination. Nitrate concentrations and delta(NO3)-N-15 were higher in wells just below the waste spray area of the CAFO than above it. Chloride ion concentrations in wells confirmed a contaminated area below the waste spray area. Surface water samples had a wide range of NO3 concentrations and were uncontaminated, except for samples from one seep and one spring. However, the mean delta(NO3)-N-15 in samples from springs were +3.9 to +5.0 parts per thousand, values that are in a range reported for soil NO3. Thus, although data are not available on groundwater movement, both stable isotope signatures and chloride concentrations indicate that animal wastes were the source of NO3 contamination.