Abstract
We evaluated the mineralization rates of humic substances in Infernao oxbow lake (State of Sao Paulo, Brazil). Experiments were conducted under aerobic and anaerobic conditions using fulvic acid and humic acid from four sources: Scirpus cubensis and Cabomba piauhyensis leachate submitted to a 120-day degradation process, sediment, and dissolved organic matter from the lake water. A fixed amount of substrate was added to 450 ml of water from Infernao lake, filtered over glass wool. After adding substrate, the flasks were incubated at 21.0°C under aerobic and anaerobic conditions. The dissolved organic carbon was monitored during 95 days. The results were fitted to first-order kinetics model, which pointed to one labile and one refractory fraction. The refractory fractions predominated, ranging from 71.4 to 84.3% for fulvic acid and from 73.4 to 85.0% for humic acid. Mineralization rates of the labile fractions of dissolved organic carbon were higher under aerobic than anaerobic conditions, while the converse was true for the refractory fractions.
Published Version
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