HR: 14:10h
AN: B43F-03    [Abstracts]
TI: Seasonal Aspects of the Biogeochemistry of the Chena River near Fairbanks, Alaska
AU: * Douglas, T A
EM: Thomas.A.Douglas@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory, PO Box 35170, Fort Wainwright, AK 99703-0170, United States
AU: Blum, J D
EM: jdblum@umich.edu
AF: University of Michigan Geological Sciences, 2534 CC Little Bldg 1100 North University Avenue, Ann Arbor, MI 48109-1005, United States
AU: Keller, K
EM: katy.keller@shell.com
AF: University of Michigan Geological Sciences, 2534 CC Little Bldg 1100 North University Avenue, Ann Arbor, MI 48109-1005, United States
AU: Guo, L
EM: laodong.guo@usm.edu
AF: University of Southern Mississippi, Department of Marine Science 1020 Balch Boulevard, Stennis Space Center, MS 39529-9904, United States
AU: Cai, Y
EM: yihua.cai@usm.edu
AF: University of Southern Mississippi, Department of Marine Science 1020 Balch Boulevard, Stennis Space Center, MS 39529-9904, United States
AB: The Alaskan Interior is currently undergoing climate warming and this has caused permafrost degradation that will likely affect river biogeochemistry. The Chena River watershed is underlain by discontinuous permafrost and is thus a suitable location for monitoring how permafrost degradation may affect riverine biogeochemistry. We collected surface water from the Chena River near Fairbanks, Alaska biweekly from March 2005 to February 2006. Our goal was to measure biogeochemical parameters during varied flow regimes to determine how seasonal and meteorological conditions affected the watershed. We measured major element concentrations, oxygen and hydrogen stable isotopes, strontium isotopes and carbon and nitrogen organic and inorganic species. Oxygen isotope values suggest a steady replacement of the spring snow melt signature with that of old water and summer precipitation over the course of the summer. Major element concentrations (Na, K, Ca, Mg, Sr, Cl, SO₄^2-, HCO₃^-) decrease in river waters as discharge increases suggesting a simple dilution of these ions in river waters. ⁸⁷Sr/⁸⁶Sr values become more radiogenic with increasing discharge during both spring melt and summer rain events further implying that during high flow the waters include a different mineral weathering signature than during base flow. Over 50% of the carbon we measured occurs as dissolved inorganic carbon while ~40% is dissolved organic carbon (DOC) and <10% is particulate organic carbon. A strong linear relationship between DOC and discharge indicates hydrological control of river DOC storage and export. Elevated DOC concentrations during spring runoff implies an accumulating soil leaching effect and/or a more efficient leaching of DOC from surface soils and overlying plant litter during spring melt. Our results suggest the biogeochemical signature of the watershed changes markedly during the year but flows can be categorized into six unique regimes. The complicated seasonal controls on river water biogeochemistry imply that monitoring campaigns in northern watersheds must apply long term sampling programs that bracket major precipitation and seasonal events before biogeochemical sources can be adequately measured or modeled.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1065 Major and trace element geochemistry
DE: 1806 Chemistry of fresh water
SC: Biogeosciences [B]
MN: 2007 Fall Meeting