Urea Fluctuations in Stream Baseflow across Land Cover Gradients and Seasons in a Coastal Plain River System

Urea Fluctuations in Stream Baseflow across Land Cover Gradients and Seasons in a Coastal Plain River System

Urea‐N is a component of bioavailable dissolved organic nitrogen (DON) that contributes to coastal eutrophication. In this study, we assessed urea‐N in baseflow across land cover gradients and seasons in the Manokin River Basin on the Delmarva Peninsula. From March 2010 to June 2011, we conducted mo...

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Bibliographic Details
Published in:Journal of the American Water Resources Association Vol. 55; no. 1; pp. 228 - 246
Main Authors: Tzilkowski, Sarah S., Buda, Anthony R., Boyer, Elizabeth W., Bryant, Ray B., Kleinman, Peter J.A., Kennedy, Casey D., Allen, Arthur L., Folmar, Gordon J., May, Eric B.
Format: Journal Article
Language:English
Published: Middleburg Blackwell Publishing Ltd 01-02-2019
Subjects:
Agricultural land
Agricultural wastes
Bioavailability
Biological fertilization
Coastal plains
Coastal zone
Creeks & streams
Dissolved organic carbon
Dissolved organic nitrogen
Ditches
Drainage
Drainage ditches
Dynamics
Eutrophication
Fertilization
Gradients
Groundwater
Groundwater treatment
Land cover
Land use
Nitrogen
Organic nitrogen
Ratios
River basins
Rivers
seasonality
Streams
Tidal rivers
Tidal waterways
Urea
Ureas
Variation
Wastewater
Wastewater treatment
Wastewater treatment plants
water quality
Water temperature
watershed
Watersheds
Wetlands
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Summary:Urea‐N is a component of bioavailable dissolved organic nitrogen (DON) that contributes to coastal eutrophication. In this study, we assessed urea‐N in baseflow across land cover gradients and seasons in the Manokin River Basin on the Delmarva Peninsula. From March 2010 to June 2011, we conducted monthly sampling of 11 streams (4 tidal and 7 nontidal), 2 wastewater treatment plants, an agricultural drainage ditch, and groundwater underlying a cropped field. At each site, we measured urea‐N, DON, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), NO3−‐N, and NH4+‐N. In general, urea‐N comprised between 1% and 6% of TDN, with the highest urea‐N levels in drainage ditches (0.054 mg N/L) and wetland‐dominated streams (0.035–0.045 mg N/L). While urea‐N did not vary seasonally in tidal rivers, nontidal streams saw distinct urea‐N peaks in summer (0.038 mg N/L) that occurred several months after cropland fertilization in spring. Notably, the proportion of wetlands explained 78% of the variance in baseflow urea‐N levels across the Manokin watershed. In wetland‐dominated basins, we found urea‐N was positively related to water temperature and negatively related to DOC:DON ratios, indicating short‐term urea‐N dynamics at baseflow were more likely influenced by instream and wetland‐driven processes than by recent agricultural urea‐N inputs. Findings demonstrate important controls of wetlands on baseflow urea‐N concentrations in mixed land‐use basins. Research Impact Statement: The proportion of wetlands in a Coastal Plain river system was a key determinant of baseflow urea‐N concentrations in nontidal streams and tidal rivers.
ISSN:1093-474X
1752-1688
DOI:10.1111/1752-1688.12716