Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: September 16, 2011
Publication Date: December 5, 2011
Citation: Gustafson, S., Buda, A.R., Boyer, E., Bryant, R.B., Gooseff, M., May, E. 2011. Influence of land management and hydrology on urea fate and transport within a Coastal Plain watershed dominated by intensive poultry agriculture [abstract]. American Geophysical Union. Paper No. B11C-0495. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Increasing nutrient loads delivered from the landscape to coastal ecosystems has widely been recognized as a major contributor to coastal eutrophication and as a driver of the escalation of harmful algal blooms (HABs). Urea, a form of organic nitrogen, is a common nutrient found in fertilizers, manures, and septic waste, and is gaining recognition as a preferred nutrient for the development of toxic HABs. While several studies have documented elevated urea concentrations in tributaries draining the Delmarva Peninsula and in the Chesapeake Bay, little is known about the key factors that influence urea delivery from the landscape to surface waters. Here, in attempt to address the need to better understand urea behavior, we investigated land management and hydrologic controls on urea loss, both spatially and temporally, in the Manokin River. The Manokin River is a Coastal Plain watershed (300 sq. km) on the Delmarva Peninsula that drains directly to the Chesapeake Bay and is characterized by extensive rural development coupled with intensive agriculture, particularly poultry production. Monthly synoptic sampling during baseflow conditions was conducted throughout the watershed in order to represent the variety of potential point and non-point sources of urea. Sampling was also conducted during stormflow conditions using time-weighted automated (SIGMA) samplers at selected sites within the watershed. Temporal baseflow trends illustrate higher average urea concentrations through the summer months (0.61 micromoles per L) and generally lower (0.35 micromoles per L) concentrations during the winter months. Spatial trends show higher average baseflow urea concentrations in the agricultural ditches and headwaters (0.93 micromoles per L) with decreasing concentrations moving downstream (0.37 micromoles per L). Stormflow was found to be the predominant urea delivery mechanism, as urea concentrations typically increased 3-9 times above baseflow concentrations (0.27 micromoles per L) during storms, with peaks in urea concentration generally following peaks in discharge. Results from this study will be used to determine whether there is a link between urea delivery from the Manokin River and harmful algal blooms in the Chesapeake Bay as well as to guide the development of best management practices to control urea loss from agricultural activities.