Factors affecting denitrification rates in experimental wetlands: Field and laboratory studies

Tanita Sirivedhin, Kimberly A. Gray*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

215 Scopus citations


To identify the conditions that promote high rates of denitrification we systematically investigated the interactions of wetland age, water temperature, organic carbon, macrophytic type and density, hydraulic conditions on denitrification rates in field and laboratory experiments. In the field, nitrate removal was consistently greater in a shallow, young, well-mixed constructed wetland, regardless of temperature and despite lower sediment denitrification potential (DNP), than in mature, more diverse, less well-mixed wetlands. We believe the presence of a benthic mesh, which supported a dense periphytic biofilm, to be partly responsible for the unexpectedly high observed rates. We measured the DNP of wetland sediments and periphyton in the laboratory with the acetylene block method under different temperatures, nitrate concentrations, and carbon sources. The overall DNP of periphyton was greater than the corresponding sediment samples on a per cell basis. We hypothesize that the organic carbon produced by the periphytic algae is readily degradable and promoted the higher denitrification rates. We found a positive relationship between DNP and biodegradable organic carbon concentration and identified chemical markers illustrating that biodegradability is promoted by a combination of polyhydroxyaromatic and polysaccharide parent structures. These findings highlight the importance of organic quality and the role of periphyton in accelerating the rates of denitrification in wetlands.

Original languageEnglish (US)
Pages (from-to)167-181
Number of pages15
JournalEcological Engineering
Issue number2
StatePublished - Feb 1 2006


  • Biodegradability
  • Biofilm
  • Denitrification
  • Nitrate
  • Organic carbon
  • Periphyton
  • Wetlands

ASJC Scopus subject areas

  • Environmental Engineering
  • Nature and Landscape Conservation
  • Management, Monitoring, Policy and Law


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