TRACING NITRATE TRANSPORT AND ENVIRONMENTAL IMPACT FROM INTENSIVE SWINE FARMING USING DELTA NITROGEN-15

Animal waste-generated nitrate generally takes on a nitrogen isotopic signature greatly enriched in nitrogen-15 relative to other nitrate sources. Sampling and field measurements were performed in North Carolina beneath intensive swine farms. The study shows that the median values of the relative difference in nitrogen-15/nitrogen-14 ratios between sample and atmospheric nitrogen, for shallow groundwater beneath and adjacent to site sprayfields, for a stream draining sprayfields and for waters up to 1.5 km downstream were +15.3±0.2 to +15.4±0.2‰. The nitrogen-15-enriched nitrate in groundwater beneath swine waste sprayfields can be successfully traced during transport and discharge into nearby surface water.