25th International Meeting on Organic Geochemistry IMOG 2011

P-236
Distribution and Fate of Lignin in Dissolved Organic Matter in
World’s Large River Systems
Xiaojuan Feng 1,2 , Valier Galy 2 , Jorien E. Vonk 1 , Britta Voss 2 , Ying Wu 3 , Bernhard
Peucker-Ehrenbrink 2 , R. Max Holmes 4 , Daniel B. Montlucon 1,2 , Timothy I. Eglinton 1,2
1 Geological Institute, ETH, Zürich, Zurich, Switzerland, 2 Department of Marine Chemistry & Geochemistry,
Woods Hole Oceanographic Institution, Woods Hole, MA, United States of America, 3 State Key Laboratory
of Estuarine and Coastal Research, East China Normal University, Shanghai, China, 4 Woods Hole Research
Center, Woods Hole, MA, United States of America (corresponding author:xfeng@erdw.ethz.ch)
Dissolved organic matter (DOM) represents
one of the largest active organic carbon reservoirs in
the world and terrestrial organic carbon is a major
contributor to DOM in rivers, lakes and the coastal
ocean. As an important and ubiquitous component of
terrestrial organic matter, lignin is widely distributed in
riverine and oceanic DOM. However, we know very
little about the fate of lignin in riverine DOM — How
much does it contribute to the dissolved organic
carbon in rivers? What environmental parameters
control its supply to, and fate within the DOM? What
are the timescales involved in the transport of
dissolved lignin from land to rivers and the ocean?
Answers to these questions are crucial for
understanding the role of DOM within the global
carbon cycle. Here we investigate the distribution and
composition of lignin in the DOM from several major
river systems around the globe with contrasting
drainage basin properties, climate and hydrological
conditions (including Congo, Fraser, Ganges-
Brahmaputra, Kolyma, and Yangtze, etc.). Dissolved
lignin is collected from filtered river water onto C18
solid phase extraction cartridges and extracted using
CuO oxidation method. Lignin-derived phenols are
identified and quantified on gas
chromatography/mass spectrometry and normalized
to the dissolved organic carbon content of river water.
We compare the abundance, composition, and
degradation stage of dissolved lignin across these
different river systems to understand the
environmental variables that govern the transport and
transformation of lignin in aquatic systems. We also
compare lignin phenol composition in the riverine
DOM with that in the suspended particles collected
from the same river system to assess lignin
fractionation and degradation in the dissolved and
particulate phases during the land-river transport.
Furthermore, we collected large-volume samples of
riverine DOM and isolated lignin phenols by high
pressure liquid chromatography for compoundspecific
radiocarbon and stable carbon isotopic
analysis. The radiocarbon age of dissolved lignin
versus lignin in sedimentary particles provides
insights on the source and turnover time of terrestrial
organic matter within fluvial systems. Overall, this
project will provide new insights into the geochemical
cycling of terrestrial DOM in riverine environments.
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