Urea release by intermittently saturated sediments from a coastal agricultural landscape

Mason D. King, Ray B. Bryant, Louis S. Saporito, Anthony R. Buda, Arthur L. Allen, Lindsey A. Hughes, Fawzy M. Hashem, Peter J.A. Kleinman, Eric B. May

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Abstract

Urea-N is linked to harmful algal blooms in lakes and estuaries, and urea-N-based fertilizers have been implicated as a source. However, the export of urea-N-based fertilizers appears unlikely, as high concentrations of urea-N are most commonly found in surface waters outside periods of fertilization. To evaluate possible autochthonous production of urea-N, we monitored urea-N released from drainage ditch sediments using mesocosms. Sediments from a cleaned (recently dredged) drainage ditch, uncleaned ditch, forested ditch, riparian wetland, and an autoclaved sand control were isolated in mesocosms and flooded for 72 h to quantify urea-N, NH4 +-N, and NO3 --N in the floodwater. Sediments were flooded with different N-amended solutions (distilled H2O, 1.5 mg L-1 NH4 +-N, 3.0 mg L-1 NH4 +-N, 2.6 mg L-1 NO3 --N, or 5.1 mg L-1 NO3 --N) and incubated at three water temperatures (16, 21, and 27°C). Urea-N concentrations in mesocosms representing uncleaned and cleaned drainage ditches were significantly greater than nonagricultural sediments and controls. While flooding sediments with N-enriched solution had no clear effect on urea-N, warmer (27°C) temperatures resulted in significantly higher urea-N. Data collected from field ditches that were flooded by a summer rainstorm showed increases in urea-N that mirrored the mesocosm experiment. We postulate that concentrations of urea-N in ditches that greatly exceed environmental thresholds are mediated by biological production in sediments and release to stagnant surface water. Storm-driven urea-N export from ditches could elevate the risk of harmful algal blooms downstream in receiving waters despite the dilution effect.

Original languageEnglish (US)
Pages (from-to)302-310
Number of pages9
JournalJournal of Environmental Quality
Volume46
Issue number2
DOIs
StatePublished - Jan 1 2017

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All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution
  • Management, Monitoring, Policy and Law

Cite this

King, M. D., Bryant, R. B., Saporito, L. S., Buda, A. R., Allen, A. L., Hughes, L. A., Hashem, F. M., Kleinman, P. J. A., & May, E. B. (2017). Urea release by intermittently saturated sediments from a coastal agricultural landscape. Journal of Environmental Quality, 46(2), 302-310. https://doi.org/10.2134/jeq2016.08.0304