title: Role of Anaerobic Ammonium Oxidation (Anammox) in Nitrogen Removal from a Freshwater Aquifer.
abstract: Anaerobic ammonium oxidation (anammox) couples the oxidation of ammonium with the reduction of nitrite, producing N2. The presence and activity of anammox bacteria in groundwater were investigated at multiple locations in an aquifer variably affected by a large, wastewater-derived contaminant plume. Anammox bacteria were detected at all locations tested using 16S rRNA gene sequencing and quantification of hydrazine oxidoreductase (hzo) gene transcripts. Anammox and denitrification activities were quantified by in situ (15)NO2(-) tracer tests along anoxic flow paths in areas of varying ammonium, nitrate, and organic carbon abundances. Rates of denitrification and anammox were determined by quantifying changes in (28)N2, (29)N2, (30)N2, (15)NO3(-), (15)NO2(-), and (15)NH4(+) with groundwater travel time. Anammox was present and active in all areas tested, including where ammonium and dissolved organic carbon concentrations were low, but decreased in proportion to denitrification when acetate was added to increase available electron supply. Anammox contributed 39-90% of potential N2 production in this aquifer, with rates on the order of 10 nmol N2-N L(-1) day(-1). Although rates of both anammox and denitrification during the tracer tests were low, they were sufficient to reduce inorganic nitrogen concentrations substantially during the overall groundwater residence times in the aquifer. These results demonstrate that anammox activity in groundwater can rival that of denitrification and may need to be considered when assessing nitrogen mass transport and permanent loss of fixed nitrogen in aquifers.
authors.affiliation: National Research Program, U.S. Geological Survey , 3215 Marine Street, Boulder, Colorado 80303, United States.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Smith
authors.affiliation: National Research Program, U.S. Geological Survey , 431 National Center, Reston, Virginia 20192, United States.
authors.forename: J K
authors.initials: JK
authors.lastname: Böhlke
authors.affiliation: Virginia Institute of Marine Science, College of William and Mary , P.O. Box 1346, Gloucester Point, Virginia 23062, United States.
authors.forename: Bongkeun
authors.initials: B
authors.lastname: Song
authors.affiliation: Department of Marine Sciences, University of Connecticut , 1080 Shennecossett Road, Groton, Connecticut 06340, United States.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Tobias
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D000693:Anaerobiosis; D001419:Bacteria / Q000235:genetics; D001673:Biodegradation, Environmental; D058440:Denitrification; D005618:Fresh Water / Q000737:chemistry* / Q000382:microbiology; D005740:Gases / Q000032:analysis; D005843:Geography; D060587:Groundwater / Q000737:chemistry* / Q000382:microbiology; D008404:Massachusetts; D009584:Nitrogen / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D010802:Phylogeny; D013997:Time Factors
chemical_list: D064751:Ammonium Compounds; D005740:Gases; D009584:Nitrogen