Decomposition of sedimentary organic matter and methane formation in the recent sediment of Lake Bled (Slovenia)

Citation
S. Lojen et al., Decomposition of sedimentary organic matter and methane formation in the recent sediment of Lake Bled (Slovenia), CHEM GEOL, 159(1-4), 1999, pp. 223-240
Citations number
36
Categorie Soggetti
Earth Sciences
Journal title
CHEMICAL GEOLOGY
ISSN journal
00092541 → ACNP
Volume
159
Issue
1-4
Year of publication
1999
Pages
223 - 240
Database
ISI
SICI code
0009-2541(19990708)159:1-4<223:DOSOMA>2.0.ZU;2-T
Abstract
Decomposition of sedimentary organic matter and methane formation in a eutr ophic dimictic subalpine lake (Lake Bled, NW Slovenia) were investigated by measurement of in situ concentrations of dissolved inorganic carbon (DIC) in the pore water and its stable carbon isotopic composition, as well as by incubation experiments. The isotopic composition of carbon in the methane produced during incubation experiments was also studied. The ratio between methane produced by acetate fermentation and CO2/H-2 reduction was estimate d from delta(13)C-DIC vs. DIC concentration profiles in sediment pore water using a mathematical model developed by LaZerte [LaZerte, 1981. The relati onship between dissolved carbon dioxide and its stable isotope ratio in aqu atic sediments. Geochim. Cosmochim. Acta 45, 647-656]. It was found that in the spring acetate fermentation is dominant when about 65% of methane is p roduced by this reaction pathway, whereas in the autumn, over 90% of the me thane results from CO2 reduction. delta(13)C of methane released during a 6 -week incubation experiment with sediment taken in the autumn varied betwee n - 70 to - 85% V-PDB, i.e., values typical of methane produced by CO2/H-2 reduction, in spite of methane oxidation evident from the low delta(13)C-CO 2 values, thus confirming the results obtained by mathematical modelling. ( C) 1999 Elsevier Science B.V. All rights reserved.