SS3.04 Biogeochemistry of DOC/DON in a Watershed Context
Date: Wednesday, June 12, 2002
Time: 10:00:00 AM
Location: Carson B
 
MayorgaE, School of Oceanography, University of Washington, Seattle, USA, emiliom@u.washington.edu
Aufdenkampe, A, K, School of Oceanography, University of Washington, Seattle, USA, anthonya@ocean.washington.edu
Masiello, C, A, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, USA, 
Quay, P, D, School of Oceanography, University of Washington, Seattle, Canada, 
Hedges, J, I, School of Oceanography, University of Washington, Seattle, USA, 
Richey, J, E, School of Oceanography, University of Washington, Seattle, USA, 
Krusche, A, V, Centro de Energia Nuclear na Agricultura (CENA), Universidade de Sao Paulo, Piracicaba, Brazil, 
Llerena, C, A, Facultad de Ciencias Forestales, Universidad Nacional Agraria La Molina, Lima, Peru, 
Quintanilla, J, , Instituto de Investigaciones Quimicas, Universidad Mayor de San Andres, La Paz, Bolivia, 
 
DIC CYCLING FROM 14C AND 13C ISOTOPES IN MOUNTAIN AND LOWLAND RIVERS IN THE AMAZON BASIN
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As part of the CAMREX project studying the riverine biogeochemistry of the Amazon basin, we analyzed the 14C and 13C isotopic composition of DIC in Amazonian rivers ranging from mountain and lowland streams to the mainstem. Associated measurements include DIC, 14C and 13C of POC and DOC, organic geochemical tracers, and major ions. Our objectives are to: 1, characterize the sources, age, and residence time of DIC throughout the river system; 2, identify their environmental controls; and 3, examine DIC dynamics along longitudinal elevation and lowland transects. We use a hydrological model to estimate river discharge in ungaged rivers. Along the Ucayali river, old carbon from carbonate dissolution in the highlands persists for more than 2000 km, despite large influx of lowland tributaries. DIC in lowland streams and large lowland rivers with remote Andean headwaters generally has a bomb and terrestrial vegetation signature, indicating that in-situ respiration and terrestrial input predominate. However, there is evidence for isolated respiration contribution from very old C3 carbon. We will discuss general implications for carbon cycling in large river systems.