CU AND FE ASSOCIATED WITH HUMIC ACIDS IN SEDIMENTS OF A TROPICAL COASTAL LAGOON

The amount of Cu and Fe associated with humic acids was estimated in f ive sediment corks from a tropical coastal lagoon (Piratininga Lagoon, Rio de Janeiro, Brazil). Core samples were analysed for humic acid co ntents, total Fe and Cu content. Fe and Cu associated with humic acids were also measured. Results show amounts of humic acids ranging from 0.7 to 21.7% of the dry weight of sediment (average 4.6%, standard dev iation 4.4%). Concentrations of Fe and Cu ranged from 0.3 to 6.0% (ave rage 2.2%, S.D. 1.2%) and from < 1.0 to 65.0 mu g g(-1) (average 28.6 mu g g(-1), S.D. 16.4 mu g g(-1)), respectively. The results of strong ly bound metals show that while humic acids are the main carrier for C u, Fe does not seems to be significantly associated with this organic matter. (C) 1998 Elsevier Science Ltd. All rights reserved.