Source, Fate and Transport of Urea from Soils to Estuarine Systems: Current Research Synopsis.

Abstract – Phoenix Meeting Platform Presentation With the increased use of urea-N as a fertilizer and the heightened concern over urea as a contaminant in marine waters, UMES conducted a series of field and experimental studies to examine the potential for urea to enter estuarine waters of the Chesapeake Bay. Urea is favored by several species of diatoms as a nutrient source and in the process convert urea to domoic acid which in birds and mammals is a potent neurotoxin. A series of five separate studies were conducted between 2012 and 2015; field leachate study, water simulation field runoff experiment, chemical monitoring of the Manokin River, field monitoring at a private farm and a mesocosm experiment. Both the field leachate study and the water simulation experiment demonstrated that urea did not persist in the soil for any significant period of time (<48 hours); however in the Manokin River and private farm monitoring urea was found in excess of 500 ppb in some of the ditches. Further, the mesocosm experiment was able to recreate conditions which produced urea over 12 hours (>90ppb). Thus the completed research suggests that, while urea is not leaching into the soil or moving by runoff into ditches, another significant pathway exists that is producing urea. Since urea formation can only be through metabolic pathways of biological systems, it is clear that the urea is being formed through microbial activity. This paper will present results from the five previous studies showing how they integrate and how they helped form the logic for the sixth and final study examining changes in microbial community structure and function in response to nutrient input from agricultural and forest watersheds.