HR: 1330h
AN: B33A-03    [Abstracts]
TI: The Contribution of Labile Organic Matter in Groundwater to Carbon Sources Fueling CO2 Evasion From River Surfaces
AU: * Remington, S
EM: sunny9@u.washington.edu
AF: University of Washington, School of Oceanography Box 355351, Seattle, WA 98195 United States
AU: Neto, S
EM: sneto@cena.usp.br
AF: CENA/USP, Av. Centenario 303 , Piracicaba, SP 13400-970 Brazil
AU: Richey, J
EM: jrichey@u.washington.edu
AF: University of Washington, School of Oceanography Box 355351, Seattle, WA 98195 United States
AB: Labile dissolved organic matter (DOM) transported from land to river channels via groundwater may be an important source of carbon fueling CO2 evasion from river surfaces in the Amazon basin. The importance of DOM transported to rivers via groundwater will vary with hydrologic regime. We measured metabolism, DOM size fractions, pCO2 and dissolved O2 in various flow paths at two locations with contrasting hydrologic regimes in the Amazon basin. In Oxisol soils located north of Manaus, hydraulic conductivity is constant with depth and vertical infiltration of rainfall dominates during storm events. At our Ultisol-dominated site, stream flow is more event-dependent due to decreasing hydraulic conductivity with depth and subsequently more lateral surface flow during rainfall events. At this site, we found high in-stream respiration rates with a sharp decrease to one-fourth of the initial rate during the first thirty minutes of stream flow-generating precipitation events. A second peak in respiration rate occurred after about one hour. The two peaks suggest that two different pools of labile DOM are flushed into the river and respired to CO2 during storms by time-dependent, surface flow paths. In contrast, stream flow in Oxisol-dominated regions is less event-dependent due to more infiltration of rain water. In these regions, labile DOM in groundwater may be a larger part of the carbon pool contributing to CO2 evasion from river surfaces.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2005 Joint Assembly