Bardy M. auteur aut IRD Derenne S. auteur aut IRD Allard T. auteur aut IRD Benedetti M. F. auteur aut IRD Fritsch Emmanuel auteur aut IRD text journalArticle eng text/pdf born digital access In the Rio Negro basin, podzols develop at the expense of clay-depleted laterites through localized and spectacular weathering fronts. This natural process leads to the remobilization of previously accumulated organic matter (OM) which is redistributed within soil profiles and exported towards rivers, hence their typical black coloration. We investigate the fate of OM in the soil-water continuum in the Rio Negro basin through description of the composition of OM potentially mobile at different stages of podzol development and exploration of evidence for contributions from different soil horizons to the exportation of OM into waters. OM was water-extracted from seven key soil samples from a sequence representative of the transition between latosol and podzol on the low elevation plateaux of the Rio Negro basin, thus enabling following both vertical and lateral differentiations. The chemical structure of freeze-dried samples, investigated using C-13 nuclear magnetic resonance and thermally assisted hydrolysis and methylation (THM), shows contrasting features depending on the horizon considered. The bulk features of water extracts were first compared with samples collected in the water-tables and rivers draining the soil sequence. A molecular level comparison was then performed with groundwater draining the well-developed podzol. This approach evidenced a contribution from deep horizons of well-developed podzols. It highlights that OM is certainly remobilised after being accumulated in Bh horizons during the development of podzols through accumulation of OM redistributed from surface horizons. The identification of specific compounds opens new perspective to trace a "podzolic origin" of OM in drainage networks. specialized Amazon basin Black waters Podzols Water-extractable organic matter 062 068 106 1 71-88 2011 0168-2563 https://www.documentation.ird.fr/hor/fdi:010053858 10.1007/s10533-010-9564-9 0168-2563 [F B010053858] https://www.documentation.ird.fr/hor/fdi:010053858 https://www.documentation.ird.fr/intranet/publi/2011/10/010053858.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2011-11-07 2017-08-23 fdi:010053858 fre