Degradation of softwood [14C lignin] lignocelluloses and its relation to the formation of humic substances in river and pond environments |
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Authors: | Eliane Fustec Eric Chauvet Gilbert Gas Daniel Lacaze Michèle Escautier |
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Affiliation: | (1) Centre d'Ecologie des Ressources Renouvelables, (LP CNRS no 8211), 29, rue Jeanne Marvig, 31055 Toulouse Cedex, France;(2) Centre de Physiologie Végétale (U.A. CNRS no 241), Université Paul Sabatier, 118, route de Narbonne, 31062 Toulouse Cedex, France |
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Abstract: | The fate of lignin in water and sediment of the Garonne river (France) and of a pond in its floodplain was examined using specifically labeled [14C-lignin] lignocelluloses. No significant differences appeared in the mineralization rate of alder, poplar or willow [14C-lignin] in running water samples. Conversion of total radioactivity to 14CO2 ranged between 18.7% and 24.4% after 120 days of incubation. Degree of 14C-labeled lignin mineralization in standing water and sediments was clearly lower, especially in submerged sediments, and was correlated with oxygen supply. After 60 days of incubation 3.3% to 7.9% of the 14C-labeled lignin was recovered in water samples as dissolved organic carbon originating from microbial metabolism. In water extracts from sediment the percentage of dissolved organic 14C was only 0.4% to 1.3% of the applied activity. In the humic fraction extracted from sediments it did not exceed 4.4% which was much lower than in soils. No significant difference appeared between river and pond conditions for humic substances formation. |
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Keywords: | [14C lignin] lignocelluloses degradation humic substances river pond |
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