Elevated Levels of Urea Nitrogen Exist in Coastal Waters: A Study of Sources and Causes.

Recent studies conducted by University of Maryland Eastern Shore and USDA-ARS scientists suggest that the transfer of recently applied urea fertilizers to water bodies is unlikely under normal climate conditions and management. Evidence suggests that N-rich groundwater delivered to field ditches may be converted to urea as flows recede. Further, urea that is generated in situ maybe available for hydrologic transport in subsequent storm events. We hypothesize that legacy nitrogen in groundwater may play a key role in urea cycling and movement, and that urea generated in situ is available for hydrologic transport in subsequent storm events to adjacent water bodies. This poster will present the results of a mesocosm study that was designed to mimic a range of field conditions. Seventy two conditions involving three ditch sediment types and a wetland sediment, 2 nitrogen (N) sources (ammonium chloride, sodium nitrate) added to the mesocosms at 2 liters per mesocosm, 3 concentrations based on the average total N (0, 5, and 10 mg L-1), were incubated at three temperatures (15, 22.5, and 30 °C) for 72 hours. Water samples were taken at 1, 2, 4, 8, 16, 24, 48, and 72 hours and analyzed for urea, ammonium, and nitrate N. Results suggest that regeneration of urea does occur within 8 hours of introduction of N solution and that sediments from un-cleaned agriculture ditches exhibited the greatest degree of urea production (>0.2mg L-1).