Labile dissolved organic carbon supply limits hyporheic denitrification Public Deposited

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  • We used an in situ steady state ¹⁵N-labeled nitrate (¹⁵NO₃⁻) and acetate (AcO⁻) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO⁻ influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl⁻ and Br) and reactive (¹⁵NO₃⁻) solute tracers had hyporheic median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (<1.5 mg O₂ L⁻¹). All receiving wells demonstrated ¹⁵N₂ production during ambient conditions, indicating that the hyporheic zone was an environment with active denitrification. The subsequent addition of AcO⁻ stimulated more denitrification as evidenced by significant δ¹⁵N₂ increases by factors of 2.7 to 26.1 in receiving wells and significant decreases of NO₃⁻ and DO in the two wells most hydrologically connected to the injection. The rate of nitrate removal in the hyporheic zone increased from 218 kg ha⁻¹ yr⁻¹ to 521 kg ha⁻¹ yr⁻¹ under elevated AcO⁻ conditions. In all receiving wells, increases of bromide and ¹⁵N₂ occurred without concurrent increases in AcO⁻, indicating that 100% of AcO⁻ was retained or lost in the hyporheic zone. These results support the hypothesis that denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.
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  • Zarnetske, J. P., R. Haggerty, S. M. Wondzell, and M. A. Baker (2011), Labile dissolved organic carbon supply limits hyporheic denitrification, Journal of Geophysical Research, 116, G04036, doi:10.1029/2011JG001730.
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  • This is the publisher’s final pdf.
  • Journal of Geophysical Research
  • description.provenance : Submitted by Deanne Bruner (deanne.bruner@oregonstate.edu) on 2012-02-10T01:05:48ZNo. of bitstreams: 1HaggertyRoyCEOASLabileDissolvedOrganic.pdf: 5038793 bytes, checksum: 3ad812c4bf5bd66cd4a6cde9d07dc17f (MD5)
  • description.provenance : Made available in DSpace on 2012-02-10T01:05:48Z (GMT). No. of bitstreams: 1HaggertyRoyCEOASLabileDissolvedOrganic.pdf: 5038793 bytes, checksum: 3ad812c4bf5bd66cd4a6cde9d07dc17f (MD5) Previous issue date: 2011
  • Vol. 116 no. G04036

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