Spatial-temporal variations of dissolved organic nitrogen molecular composition in agricultural runoff water

Liguang Li, Zhenli L. He, Malak M. Tfaily, Patrick Inglett, Peter J. Stoffella

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Leaching of dissolved organic nitrogen (DON) has been reported as a pathway of N loss from agriculture, but the molecular composition of DON in agricultural water is poorly understood. Runoff water samples were collected from citrus grove furrows (CGF), ditches (CGD) and pasture ditches (PD) in four seasons. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to investigate molecular composition of DON. Chemodiversity index of DON had spatiotemporal variations, while the molecular composition of total DON showed minimal variations, except for PD in November. Lignin derivatives constituted 61% of the total DON compounds. Relative abundance of aliphatic compounds, char and condensed aromatics of unique DON compounds varied spatiotemporally and had a significant correlation with DON concentration. Aromaticity index decreased from CGF to connected CGD, implying that photodegradation is possibly the dominant process that alters molecular composition of aquatic DON during the transport. Significant differences in unique DON composition between CGD and PD indicates that fertilization and land use affect DON composition. The information on molecular characterization of DON should be useful for tracking DON source and developing technologies to remove DON in the agricultural runoff water.

Original languageEnglish (US)
Pages (from-to)375-383
Number of pages9
JournalWater research
StatePublished - Jun 15 2018
Externally publishedYes


  • Mass spectrometry
  • Organic nitrogen molecules
  • Photodegradation
  • South Florida
  • Water quality

ASJC Scopus subject areas

  • Water Science and Technology
  • Ecological Modeling
  • Pollution
  • Waste Management and Disposal
  • Environmental Engineering
  • Civil and Structural Engineering


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