HR: 1340h
AN: H23D-1452    [Abstracts]
TI: Regional and temporal variation in riverine nitrogen species across the United States: Importance of organic nitrogen
AU: * Scott, D
EM: dtscott@unl.edu
AF: University of Nebraska - Lincoln, 214 Bessey Hall P.O. Box 880340, Lincoln, NE 68588-0340 United States
AU: Harvey, J
EM: jwharvey@usgs.gov
AF: U.S. Geological Survey, 430 National Center, Reston, VA 20192 United States
AU: Alexander, R
EM: ralex@usgs.gov
AF: U.S. Geological Survey, 413 National Center, Reston, VA 20192 United States
AB: Nitrogen delivery from the landscape to aquatic environments has increased drastically over the last 50 years. Much of the current emphasis on nitrogen export relates to nitrate inputs at annual time scales. However, the riverine nitrogen pool consists of seasonally variable ammonia, nitrate and organic nitrogen. Here we illustrate (1) regional differences in nitrogen speciation across the U.S., (2) temporal changes within the in-stream nitrogen pools, and (3) down-stream changes in nitrogen speciation using 30-year flow and water quality records from over 800 U.S.G.S. monitoring sites. The regional spatial patterns in N-speciation are largely controlled by nitrogen sources (e.g. high inorganic N inputs in the Midwest), but we hypothesize that down-stream N-alterations result in temporal and downstream changes in the riverine N-pool, which in turn alters N-reactivity. Furthermore, organic nitrogen is more than 50% of riverine nitrogen in many regions across the U.S. (southeast; intermountain west). Therefore, we suggest that future research related to riverine N export needs to address interactions between and temporal variation of the organic and inorganic N-species. Such an approach has the potential to improve our understanding of the delivery and impacts of anthropogenic nitrogen in our aquatic environments.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: Fall Meeting 2005