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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
Illuminated darkness: Molecular signatures of Congo River dissolved organic matter and its photochemical alteration as revealed by ultrahigh precision mass spectrometry
Limnology and Oceanography, Volume 55, No. 4, Year 2010
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Description
Congo River water was filtered and then irradiated for 57 d in a solar simulator, resulting in extensive photodegradation of dissolved organic matter (DOM). Whole-water (i.e., unfractionated) DOM was analyzed pre- and post-irradiation using ultrahigh resolution Fourier transform ion cyclotron mass spectrometry (FT-ICR MS), revealing the following three pools of DOM classified based upon their photoreactivity: (1) photo-resistant, (2) photo-labile, and (3) photo-produced. Photo-resistant DOM was heterogeneous, with most molecular classes represented, although only a small number of aromatics and no condensed aromatics were identified. The photo-produced pool was dominated by aliphatic compounds, although it included a small number of aromatics, including condensed aromatics. Aromatic compounds were the most photoreactive, with > 90% being lost upon irradiation. Photochemistry also resulted in a significant drop in the number of molecules identified and a decrease in their structural diversity. The FT-ICR MS signatures of two classes of refractory organic matter, black carbon and carboxylic-rich alicyclic molecules (CRAM), were present in the sample prior to irradiation, indicating that the Congo River could be a significant exporter of recalcitrant DOM to the ocean. All black carbon-like molecules identified in the initial sample were lost during irradiation. Molecular signatures consistent with CRAM were also highly photo-labile, demonstrating that environmental solar irradiation levels are capable of removing these refractory compounds from aquatic systems. Irradiation also shifted the molecular signature of terrestrial DOM toward that of marine DOM, thereby complicating the task of tracking terrestrial DOM in the ocean. © 2010, by the American Society of Limnology and Oceanography, Inc.
Authors & Co-Authors
Stubbins, Aron
United States, Norfolk
Old Dominion University
Spencer, Robert G.M.
United States, Davis
University of California, Davis
Chen, Hongmei
United States, Norfolk
Old Dominion University
Hatcher, Patrick G.
United States, Norfolk
Old Dominion University
Mopper, Kenneth
United States, Norfolk
Old Dominion University
Hernes, Peter J.
United States, Davis
University of California, Davis
Mwamba, Vincent L.
Democratic Republic Congo, Kinshasa
Congo Atomic Energy Commission
Mangangu, Arthur M.
Democratic Republic Congo, Kinshasa
Congo Atomic Energy Commission
Wabakanghanzi, Jose N.
Democratic Republic Congo, Kinshasa
Congo Atomic Energy Commission
Six, Johan W.
United States, Davis
University of California, Davis
Statistics
Citations: 548
Authors: 10
Affiliations: 3
Identifiers
Doi:
10.4319/lo.2010.55.4.1467
Research Areas
Environmental
Study Locations
Congo