HR: 17:45h
AN: B22D-07    [PDF]
TI: Dissolved Organic Carbon in the Yukon River Basin
AU: * Aiken, G
EM: graiken@usgs.gov
AF: U. S. Geological Survey, 3215 Marine Street, Boulder, CO 80005
AU: Striegl, R
EM: rstriegl@usgs.gov
AF: U. S. Geological Survey, P.O. Box 25046, MS 413 Denver Federal Center, Lakewood, CO 80225
AU: Schuster, P
EM: pschuste@usgs.gov
AF: U. S. Geological Survey, 3215 Marine Street, Boulder, CO 80005
AB: A critical question in carbon cycling is how climate change could alter the fate and chemical nature of dissolved organic carbon (DOC) released from watersheds and transported to rivers, lakes, estuaries and coastal waters. The spatial and temporal variability of DOC in surface waters associated with the Yukon River Basin is being studied to better define the processes controlling DOC in this system. The Yukon River Basin, a large and diverse ecosystem in northwestern Canada and central Alaska, is experiencing increasing temperatures, partial melting of permafrost, drying of upland soils and changing wetland environments. However, little is known about DOC transported in the system. Specific ultraviolet absorbance (SUVA) measurements, in combination with DOC and DOC fractionation analyses, were used to determine both the amount and nature of DOC in the Yukon River and major tributaries. DOC transported in the Yukon River and its tributaries was seasonally dependent. For example, DOC concentrations in the Yukon River at Steven's Village ranged from 2 to 17 mg C/L during 2003, and SUVA ranged from 2.0 to 3.5 L/mg C m, indicating a large variation in amount and nature of organic matter in the river. Lowest DOC concentrations and SUVA values were observed in winter under low flow conditions. Greatest DOC concentrations were measured on samples collected during the spring on the leading part of the hydrograph. These samples were also found to have the greatest SUVA values indicating that the organic matter transported during this period was more aromatic than DOC transported under low flow conditions. High SUVA values are indicative of greater amounts of organic material originating in soils and wetlands of the watershed. The amount and nature of organic matter transported by the tributaries appeared to be related to relief and wetland contribution to the watershed of the tributary. Based on DOC and SUVA data, the Yukon River tributaries can be classified as dark water (high DOC, high SUVA, large amount of humic material), clearwater (low DOC, low SUVA) and glacial (low DOC, low SUVA, high particulate load).
DE: 0400 Biogeosciences
DE: 1030 Geochemical cycles (0330)
DE: 1055 Organic geochemistry
DE: 1806 Chemistry of fresh water
DE: 4805 Biogeochemical cycles (1615)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting