Wetlands Ecology and Management

, Volume 4, Issue 4, pp 273–283 | Cite as

Denitrification in a South Louisiana wetland forest receiving treated sewage effluent

  • R. G. Boustany
  • C. R. Crozier
  • J. M. Rybczyk
  • R. R. Twilley


Although denitrification has the potential to reduce nitrate (NO3) pollution of surface waters, the quantification of denitrification rates is complex because it requires differentiation from other mechanisms and is highly variable in both space and time. This study first measured potential denitrification rates at a wetland forest site in south Louisiana before receipt of secondary wastewater effluent, and then, following 30 months of effluent application, landscape gradients of dissolved nitrate (NO3) and nitrous oxide (N2O) were measured. A computer model was developed to quantify N transformations. Floodwater NO3 and N2O concentrations were higher in the forest receiving effluent than in the adjacent control forest. Denitrification rates of NO3-amended soil cores ranged from 0.03–0.45 g N m−2 d−1 with an overall mean of 0.10 g N m−2 d−1. Effluent N is being applied at a rate of approximately 0.034 g N m−2 d−1, with approximately 95% disappearing along a 1 km transect. In the treatment forest, floodwater NO3 concentrations decreased from 1000 μM at the inflow point to 50 μM along the 1 km transect. Nitrous oxide concentrations increased from 0.25 μM to 1.2 μM within the first 100 m, but decreased to 0.1 μM over the next 900 m. The initial increase in N2O was presumably a result ofin situ denitrification. Model analyses indicated that denitrification was directly associated with nitrification and was limited by the availability of NO3 produced by nitrification. Due to different redox potential optima, coupling of nitrification and denitrification was a function of a balance of environmental conditions that was moderately favorable to both processes. N removal efficiency was largely dependent on the proportion of effluent NH4+ to NO3. When NH4+/NO3 was ≤1, average N removal efficiency ranged from 95–100%, but ratios that were >1 reduced average efficiencies to as low as 57%. Actual effluent NH4+/NO3 loading ratios at this site are approximately 0.2 and are consistently <1.


denitrification Louisiana nitrate nitrous oxide wastewater wetland 


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  1. Ambus, P. and Christensen, S. 1995. Spatial and seasonal nitrous oxide and methane fluxes in Danish forest-, grassland-, and agroecosystems. J. Environ. Qual. 24: 993–1001.Google Scholar
  2. Anthony, W.H., Hutchinson, G.L. and Livingston, G.P. 1995. Chamber measurement of soil-atmosphere gas exchange: linear vs. diffusion-based flux models. Soil Sci. Soc. Am. J. 59: 1308–1310.Google Scholar
  3. Conner, W.H. and Day, J. W. 1989. A use attainability analysis of forested wetlands for receiving treated municipal wastewater. Report to the city of Thibodaux, Louisiana.Google Scholar
  4. Davidson, E.A. and Firestone, M.K. 1988. Measurement of nitrous oxide dissolved in soil solution. Soil Sci. Soc. Am. J. 52: 1201–1203.Google Scholar
  5. Davidson, E.A. and Swank, W.T. 1990. Nitrous oxide dissolved in soil solution: an insignificant pathway of nitrogen loss from a southeastern hardwood forest. Water Resour. Res. 26: 1687–1690.CrossRefGoogle Scholar
  6. Dieberg, F.E. and Brezonik, P.L. 1984. Nitrogen and phosphorus mass balances in a cypress dome receiving wastewater.In: Ewel, K.C. and Odum, H.T. (eds). Cypress Swamps. pp. 112–118. University Presses of Florida, Gainsville, FL.Google Scholar
  7. Engler, R.M. and Patrick, Jr. W.H. 1974. Nitrate removal from floodwater overlying flooded soils and sediments. J Environ. Qual. 3: 409–413.Google Scholar
  8. Flessa, H. and Fischer, W.R. 1992. Plant-induced changes in the redox potentials of rice rhizospheres. Plant and Soil 143: 55–60.Google Scholar
  9. Focht, D.D. and Verstraete, W. 1977. Biochemical ecology of nitrification and denitrification.In: Alexander, M. (ed.), Advances in Microbial Ecology. Volume 1. pp. 135–214. Plenum Press, New York.Google Scholar
  10. Groffman, P.M. 1994. Denitrification in freshwater wetlands. Current Topics in Wetland Biogeochemistry 1: 15–35.Google Scholar
  11. Groffman, P.M., Axelrod, E.A., Lemunyon, J.L. and Sullivan, W.M. 1991. Denitrification in grass and forest vegetated filter strips. J. Environ. Qual. 20: 671–674.Google Scholar
  12. Healy, R.W., Striegl, R.G., Russell, T.F., Hutchinson, G.L. and Livingston, G.P. 1996. Numerical evaluation of staticchamber measurements of soil-atmosphere gas exchange: identification of physical processes. Soil Sci. Soc. Am. J. 60: 740–747.Google Scholar
  13. Kemp, G.P. and Day, Jr. J.W. 1984. Nutrient dynamics in a Louisiana swamp receiving agricultural runoff.In: Ewel, K.C. and Odum, H.T. (eds). Cypress Swamps. pp. 286–293. University Presses of Florida, Gainesville, FL.Google Scholar
  14. Lamontagne, M.G. and Valiela I. 1995. Denitrification measured by a direct N2 flux method in sediments of Waquoit Bay, MA. Biogeochemistry 31: 63–83.CrossRefGoogle Scholar
  15. McKenney, D.J., Drury, C.F. and Wang, S.W. 1996. Effect of acetylene on nitric oxide production in soil under denitrifying conditions. Soil Sci. Soc. Am. J. 60: 811–820.Google Scholar
  16. Minami, K. and Ohsawa, A. 1990. Emission of nitrous oxide dissolved in drainage water from agricultural land.In: Bouwman, A.F. (ed.). Soils and the Greenhouse Effect. pp. 503–509, John Wiley and Sons Ltd., Chichester, England.Google Scholar
  17. Mosier, A.R. and Mack, L. 1980. Gas chromatographic system for precise, rapid analysis of nitrous oxide. Soil Sci. Soc. Am. J. 44: 1121–1123.Google Scholar
  18. Nichols, D.S. 1983. Capacity of natural wetlands to remove nutrients from wastewater. J. Water Pollut. Control Fed. 55: 495–505.Google Scholar
  19. Nishio, T., Koike, I., and Hattori, A. 1981. N2/Ar and denitrification in Tama estuary sediments. Geomicrobiol. J. 2: 193–209.Google Scholar
  20. Nowicki, B.L. 1994. The effect of temperature, oxygen, salinity, and rutrient enrichment on estuarine denitrification rates measured with a modified nitrogen gas flux technique. Estuar., Coastal Shelf Sci. 38: 137–156.Google Scholar
  21. Parkin, T.B. 1987. Soil microsites as a source of denitrification variability. Soil Sci. Soc. Am. J. 51: 1194–1199.Google Scholar
  22. Payne, W.J. 1973. Reduction of nitrogenous oxides by microorganisms. Bacteriol. Rev. 37: 409.PubMedGoogle Scholar
  23. Reddy, K.R., Patrick, Jr. W.H. and Lindau, C.W. 1989. Nitrification-denitrification at the plant root-sediment interface in wetlands. Limnol. Oceanogr. 34: 1004–1013.Google Scholar
  24. Rybczyk, J.M., Zhang, X.W., Day, Jr. J.W., Hesse, I. and Feagley, S. 1995. The impact of Hurricane Andrew on tree mortality, litterfall, nutrient flux, and water quality in a Louisiana coastal swamp forest. J. Coastal Res. 21: 340–353.Google Scholar
  25. Strickland, J.D.H. and Parsons, T.R. 1972. A practical handbook of seawater analysis. Bulletin 167 (2nd edn). Fisheries Research Board of Canada. Ottawa, Canada.Google Scholar
  26. Tiedje, J.M. 1982. Denitrification.In: Page, A.L. (ed.), Methods of Soil Analysis, Part 2. Chemical and Microbiological Properties—Agronomy Monograph no. 9 (2nd edn). pp. 1011–1026. American Society of Agronomy, Madison, WI.Google Scholar
  27. Twilley, R.R. and Kemp, W.M. 1986. The relation of denitrification potentials to selected physical and chemical factors in sediments of Chesapeake Bay.In: Wolfe, D.A. (ed.), Estuarine Variability. pp. 277–293. Academic Press. Inc., Orlando, FL.Google Scholar
  28. U.S. Environmental Protection Agency. 1979. Methods for chemical analysis of water and wastes. USEPA-600/4-79-020, Cincinnati, OH.Google Scholar
  29. van Kessel, C., Pennock, D.J. and Farrell, R.E. 1993. Seasonal variations in denitrification and nitrous oxide evolution at the landscape scale. Soil Sci. Soc. Am. J. 57: 988–995.Google Scholar
  30. Weier, K.L., Doran, J.W., Power, J.F. and Walters, D.T. 1993. Denitrification and the dinitrogen/nitrous oxide ratio as affected by soil water, available carbon, and nitrate. Soil Sci. Soc. Am. J. 57: 66–72.Google Scholar
  31. Zhang, X. 1995. Use of a natural swamp for wastewater treatment. Ph.D. Dissertation. Louisiana State University, Baton Rouge, LA.Google Scholar

Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • R. G. Boustany
    • 1
  • C. R. Crozier
    • 2
  • J. M. Rybczyk
    • 3
  • R. R. Twilley
    • 4
  1. 1.Department of BiologyUniversity of Southwestern LouisianaLafayetteUSA
  2. 2.Wetland Biogeochemistry InstituteLouisiana State UniversityPlymouthUSA
  3. 3.Coastal Ecology InstituteLouisiana State UniversityBaton RougeUSA
  4. 4.Department of BiologyUniversity of Southwestern LouisianaLafayetteUSA

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