Photochemical changes in chemical markers of sedimentary organic matter source and age |
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| Authors: | Lawrence M. Mayer Linda L. Schick Thomas S. Bianchi Laura A. Wysocki |
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| Affiliation: | 1. Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands;2. Department of Marine Organic Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands;3. Palaeoecology, Department of Physical Geography, Faculty of Geosciences, Utrecht University, 3584 CD, Utrecht, The Netherlands;4. Department of Marine Geology, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands;5. Marine Biogeosciences, Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, Germany;1. Department of Earth Sciences, University of Gothenburg, P.O. Box 460, SE 405 30, Sweden;2. 50 Long Acre, Bingham, Nottingham NG13 8AH, UK;1. Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany;2. Federal Maritime and Hydrographic Agency (BSH), Hamburg, Germany;3. Hans Ertel Center for Weather Research, Data Assimilation Branch, German Weather Service, Germany;1. Department of Marine Sciences, University of Georgia, Athens, GA 30602, USA;1. Institute of Environment & Biogeochemistry (eBig), School of Earth Science, Zhejiang University, Hangzhou 310027, China;2. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;3. Yantai Institute of Coastal Zone Research, CAS, Yantai, Shandong 264003, China |
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| Abstract: | Several chemical markers of organic matter source and age are shown to be susceptible to light-induced alteration. To test for the photochemical lability of markers previously employed for sediments from the Louisiana coastal zone, we subjected sediments under resuspension conditions to simulated sunlight, and monitored changes in C:N and Br:OC ratios, δ13C, Δ14C, and lignin composition. Markers of terrigenous origin (high C:N, lignin) decreased and δ13C became enriched in sediments containing primarily terrigenous organic matter, while a marker of marine organic matter (Br:OC) decreased in samples containing significant contributions from this source. Preferential loss of 14C from all sediments indicated enhanced photochemical lability of organic matter of relatively recent origin, consistent with the changes in chemical markers. Most, but not all, experimental alterations are consistent with field distributions of these markers. Relatively small experimental changes in the markers in combination with confounding processes in the environment, however, prevent these parallel trends from providing any more than a consistency test for the importance of photochemical reactions in this region. |
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