HR: 1340h
AN: H43D-0399    [Abstracts]
TI: The Role Of Hydrologic Pathways And Biogenic Methane In The Sarita Wetland, St. Paul, Minnesota
AU: * Riveros, D A
EM: driveros@montana.edu
AF: Department of Land Resources and Environmental Sciences Montana State University, 334 Leon Johnson Hall P.O.Box 173120, Bozeman, MT 59717-3120 United States
AU: King, J Y
EM: jyking@umn.edu
AF: Department of Soil, Water & Climate University of Minnesota-Twin Cities, 439 Borlaug Hall 1991 Upper Buford Circle, St. Paul, MN 55108 United States
AU: Alexander, E C
EM: alexa001@umn.edu
AF: Department of Geology & Geophysics University of Minnesota-Twin Cities, 310 Pillsbury Dr. SE , Minneapolis, MN 55455 United States
AB: Biogenic methane in wetlands and wetland sediments has been studied for its role in the carbon cycle, atmospheric chemistry and global warming, but the interaction of wetland pore-waters with groundwater and the dynamics of dissolved methane in groundwater are unclear. We investigated the role of groundwater recharge and advection in the distribution of dissolved methane, and the mechanism by which methane produced in the surface could be carried into the groundwater system. We present isotopic measurements of biogenic methane and dissolved inorganic carbon (DIC) in the Sarita Wetland, on the St. Paul Campus of the University of Minnesota, and also in six monitoring wells located in its watershed. Carbon isotopic values range between -58.4 and -10.6 permil in methane and between -14.1 and 0.8 permil in DIC. Results show that there is a major component of acetate fermentation in the production of the biogenic methane found in the wetland and in the groundwater. Hydrologic pathways are controlling the distribution of methane in the groundwater. As methane concentration decreases, the residual methane becomes more 13C-enriched. These results indicate that groundwater flow paths constitute a key element in the allocation and oxidation of dissolved methane. The degree of methane oxidation increases as methane moves in the flow path. This is an important observation since carbon allocation to groundwater as methane has not generally been taken into account for carbon budgets.
DE: 1831 Groundwater quality
DE: 1030 Geochemical cycles (0330)
DE: 1040 Isotopic composition/chemistry
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting