25th International Meeting on Organic Geochemistry IMOG 2011

P-509
Exploiting isotopic, organic, and inorganic geochemical tracers
of terrestrial matter in suspended particles of the Fraser River,
British Columbia
Britta M. Voss 1,2 , Bernhard Peucker-Ehrenbrink 1 , Timothy I. Eglinton 1,3 , Valier Galy 1 ,
Daniel B. Montluçon 1,3 , Ekaterina Bulygina 4 , R. Max Holmes 4 , Gregory Fiske 4 , Li Xu 1 ,
Sharon L. Gillies 5 , Steven Marsh 5 , Alida Janmaat 5 , Bryce Downey 5 , Jenna Fanslau 5 ,
Helena Fraser 5 , Garrett Macklam-Harron 5
1 Woods Hole Oceanographic Institution, Woods Hole, United States of America, 2 Massachusetts Institute of
Technology, Cambridge, United States of America, 3 Eidgenössische Technische Hochschule, Zürich,
Switzerland, 4 Woods Hole Research Center, Woods Hole, United States of America, 5 University of the
Fraser Valley, Abbotsford, Canada (corresponding author:bvoss@whoi.edu)
Rivers are a critical component of the global
transfer of terrestrial organic matter from land to the
ocean. Suspended particulate matter incorporates
weathered eroded lithologic material and organic
matter of geologic and biologic origin. The
association of organic carbon with mineral particles is
a complex process not adequately understood over
space and time throughout river transit and is highly
variable from one drainage basin to the next. The
Fraser River in southwestern Canada provides a
valuable testing ground for detailed geochemical
characterization of particle sources and
transformations across a large, climatically and
geologically diverse river basin with no dams on its
main stem. Bulk stable and radioisotopic analyses of
organic carbon on particles, as well as of dissolved
organic and inorganic pools, offer insight to the
sources of different components of the carbon load
carried—and possibly transformed within—the Fraser
River. We add to this suite of measurements detailed
analyses of the particles themselves, including
mineral surface area and scanning electron
microscopy visualization. We also measure various
elemental and organic compound concentrations on
particles, such as lipid biomarkers, lignin phenols,
trace metals, and 187 Os/ 188 Os. Radiogenic Os isotope
signatures provide lithological age information on
timescales far exceeding that of radiocarbon. This
coupling of organic and inorganic characterization of
particles along a river course, along with quantitative
and qualitative spatial metrics of individual particles,
offers a unique, in-depth perspective on organic
carbon-mineral association and exchange between
dissolved, particulate, and sedimentary phases from
weathering source to coastal sink. In addition to
detailed basin-wide snapshots, our collaboration with
scientists at University of the Fraser Valley in
Abbotsford has initiated time series sampling, which
will allow us to characterize seasonal variability in
particle flux and composition. In the future, these
methods will be extended to other rivers with very
different particle concentration and size spectrum
regimes (ranging from the particle-rich Ganges-
Brahmaputra River system to the much less turbid
Congo River). Ultimately, this work on the Fraser
River will serve as a foundation for similar studies on
other river systems in order to better constrain global
fluxes and transformations of carbon and other
biogeochemically important elements to the world
ocean, and the response of these processes to the
effects of climate change and other human-induced
alterations.
Segregation of carbon pools in the Fraser River by
stable and radiogenic isotope signatures: particulate
(POC) and dissolved (DOC) organic carbon and
dissolved inorganic carbon (DIC). Atmospheric,
biologic, and geologic endmembers are plotted for
reference. Samples collected at various points along
the Fraser River main stem and at significant
tributaries in late summer 2009.
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