Purpose. The interaction of biodegradable organic matter with metals was studied in sediments of a highly contaminated river of Mexico. Design/methodology/approach. A six fraction speciation procedure was performed on surface sediments, before and after two weeks of microbial activity, to determine metal-sediment association modifications. Findings. Associations of Cd, Cu and Pb evolved toward less available forms. Fe showed an opposite behaviour. The redox conditions showed more impact than the biodegradability of organic compounds on the results. Research limitations/implications. Longer experiments may generate additional metal movements. Originality/value. The results should serve to improve water quality of multi-contaminated rivers.
Keywords: speciation, heavy metals, freshwater sediments, organic matter biodegradation, metal behaviour, sediment contamination, water pollution, cadmium, copper, lead, iron, water quality