HR: 10:45h
AN: NB22E-02    [Abstracts]
TI: Nitrogen Dynamics in Hyporheic Zone Sediments
AU: * Crenshaw, C
EM: chelsea1@unm.edu
AF: University of New Mexico, Department of Biology , Albuquerque, nm 87131 United States
AU: Sheibley, R
EM: rich.sheibley@edcc.edu
AF: Arizona State University, Department of Biology, Phoenix, AZ United States
AU: Dahm, C N
EM: cdahm@sevilleta.unm.edu
AF: University of New Mexico, Department of Biology , Albuquerque, nm 87131 United States
AU: Grimm, N B
EM: nbgrimm@asu.edu
AF: Arizona State University, Department of Biology, Phoenix, AZ United States
AU: Pershall, A D
EM: alaina@unm.edu
AF: University of New Mexico, Department of Biology , Albuquerque, nm 87131 United States
AB: Understanding uptake and transformation of NO3 in hyporheic sediments in streams with varying levels of anthropogenic N inputs addresses a basic question of how human disturbance (urbanization and agriculture) affects these processes. Co-injections of bromide and 15N-NO3 were conducted over 24 hours in multiple streams (native, urban, and agricultural areas) in the southwestern USA. Groundwater wells were sampled along a longitudinal gradient within the15N injection sites. Water and gas samples were taken prior to, during, and after injections and were analyzed for O2, major cations and anions, DOC and 15N (gaseous and aqueous). Transient storage parameters were calculated using OTIS-P and As/A values ranged from 4.04E-01 to 3.92E-03 and alpha (storage zone exchange coefficients) ranged from 3.35E-04 to 6.35E-05 sec-1 in native and impacted sites, respectively. Wells contained >80% surface water at three sites with varying N-loads. These wells also had higher enrichment levels of 15N for various transformation products of NO3 than stream water. These data suggest that hyporheic zones may be a significant site of uptake and processing of NO3 in human disturbed streams.
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
DE: 1878 Water/energy interactions
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly