Chemical distribution of trivalent iron in riverine material from a tropical ecosystem: a quantitative EPR study

International audienceDistribution of trivalent iron has been measured in riverine materials from a tropical hydrosystem (Nyong basin, South Cameroon, central Africa). The speciation and the respective amounts of the iron species have been determined using electron paramagnetic resonance spectroscopy on freeze-dried samples separated by ultrafiltration. Trivalent iron occurred mainly in two forms, linked to organic matter (Fe-OM) and as iron oxides. Ln the Nyong, Fe occurred mainly as oxides (82%), while in the Mengong, a minor river, it was mainly linked to organic matter (64%). This indicates that iron in suspended matter results from mechanical erosion in the main Fiver and from chemical erosion in the minor river. Moreover, the similar size distribution of Fe-OM in both rivers suggests a conservative inheritance of organics-mediated transport of iron in the hydrographical network