Photochemical Degradation of Dissolved Organic Matter and Dissolved Lignin Phenols from the Congo River

Authors

Robert G. M. Spencer
Aron Stubbins, Old Dominion University
Peter J. Hernes
Kenneth Mopper, Old Dominion UniversityFollow
Anthony K. Aufdenkampe
Rachael Y. Dyda
Vincent L. Mwamba
Arthur M. Mangangu
Jose N. Wabakanghanzi
Johan Six

Document Type

Article

Publication Date

2009

DOI

/2009jg000968

Publication Title

Journal of Geophysical Research: Biogeosciences

Volume

114

Pages

G03010 (12 pages)

Abstract

Photochemical degradation of Congo River dissolved organic matter (DOM) was investigated to examine the fate of terrigenous DOM derived from tropical ecosystems. Tropical riverine DOM receives greater exposure to solar radiation, particularly in large river plumes discharging directly into the open ocean. Initial Congo River DOM exhibited dissolved organic carbon (DOC) concentration and compositional characteristics typical of organic rich blackwater systems. During a 57 day irradiation experiment, Congo River DOM was shown to be highly photoreactive with a decrease in DOC, chromophoric DOM (CDOM), lignin phenol concentrations (Σ8) and carbon-normalized yields (Λ8), equivalent to losses of ~45, 85–95, >95 and >95% of initial values, respectively, and a +3.1 % enrichment of the δ¹³C-DOC signature. The loss of Λ8 and enrichment of δ¹³C-DOC during irradiation was strongly correlated (r = 0.99, p < 0.01) indicating tight coupling between these biomarkers. Furthermore, the loss of CDOM absorbance was correlated to the loss of Λ8 (e.g., a₃₅₅ versus Λ8; r = 0.98, p < 0.01) and δ¹³C-DOC (e.g., a₃₅₅ versus δ¹³C; r = 0.97, p < 0.01), highlighting the potential of CDOM absorbance measurements for delineating the photochemical degradation of lignin and thus terrigenous DOM. It is apparent that these commonly used measurements for examination of terrigenous DOM in the oceans have a higher rate of photochemical decay than the bulk DOC pool. Further process-based studies are required to determine the selective removal rates of these biomarkers for advancement of our understanding of the fate of this material in the ocean.

Comments

Web of Science: "Free full-text from publisher -- gold open access."

Original Publication Citation

Spencer, R. G. M., Stubbins, A., Hernes, P. J., Baker, A., Mopper, K., Aufdenkampe, A. K., . . . Six, J. (2009). Photochemical degradation of dissolved organic matter and dissolved lignin phenols from the Congo River. Journal of Geophysical Research: Biogeosciences, 114, G03010. doi:10.1029/2009jg000968

ORCID

0000-0002-3994-1946 (Stubbins), 0000-0001-8089-6019 (Mopper)

Repository Citation

Spencer, Robert G. M.; Stubbins, Aron; Hernes, Peter J.; Mopper, Kenneth; Aufdenkampe, Anthony K.; Dyda, Rachael Y.; Mwamba, Vincent L.; Mangangu, Arthur M.; Wabakanghanzi, Jose N.; and Six, Johan, "Photochemical Degradation of Dissolved Organic Matter and Dissolved Lignin Phenols from the Congo River" (2009). Chemistry & Biochemistry Faculty Publications. 123.
https://digitalcommons.odu.edu/chemistry_fac_pubs/123