The School of Earth and Atmospheric Sciences Presents, Dr. Hilairy Hartnett, Arizona State University
Chasing Carbon Down the Colorado River: Characterization and Consequences
The transformation and fate of terrestrial organic carbon in rivers is a key factor in the export of organic carbon from the landscape to the coastal ocean. Terrestrial organic carbon may be degraded, sequestered, or altered by a range of processes in rivers, including; biological production and degradation as well as photochemical alteration.
The Colorado Watershed is among the largest in the continental US and the range of biogeochemical processes involved in and the breadth of sampling locations and times necessary to characterize this large, managed watershed are a bit daunting. By giving a portion of this investigation a central role in an upper-division Field Geochemistry course it has been possible to not only generate data from a wide range of locations, but also to conduct a large number of experiments evaluating the biogeochemical processes at work in this important river-reservoir system.
Here I present results of an integrated, longitudinal study of the amount and composition of dissolved organic matter in the Colorado River and from laboratory incubation experiments to assess carbon degradation rates. The downstream changes in carbon content and composition are the result of both photodegradation in large reservoirs and biological degradation along river reaches.
3D-fluorescence spectroscopy of the DOM reveals these two processes act on different pools of organic matter. Furthermore, in this system, photooxidation enhances the bioavailability of terrestrial DOM.