Yasmina Lahlah1, Pierre Renault2, Aurélie Buzet1, Patrick Cazevieille3, Jean-Louis Hazemann4, Philippe Cambier1, Manfred Womes4, and Jean-Claude Jumas4. (1) INRA, UMR 1114 INRA-UAPV Climat, Sol et Environnement, Domaine Saint-Paul, Site Agroparc, Avignon Cedex 9, 84914, France, (2) INRA Avignon, INRA, UMR Climat, Sol et Environnement, Domaine St Paul, Site Agroparc, Avignon Cedex 9, (Non U.S.) 84914, FRANCE, (3) CIRAD, UR Risque environnemental lié au recyclage, TA 70/01 Avenue Agropolis, Montpellier Cedex 5, 34398, France, (4) CNRS, Laboratoire de Cristallographie, Avenue des Martyrs, Grenoble, 38043, France
Spreading vinasse on soil enhances the risks of anaerobiosis, metal mobilization, and solid alterations. Our aims were to check whether the return to aerobic conditions after an anaerobic event erases anaerobic effects on metal mobility and solid properties. Batch incubations of ferralsol slurry were performed according to the sequence aerobiosis (7 d) – anaerobiosis (0, 2, 7, 14, 21 or 28 d) – aerobiosis (28 d), rum vinasse being supplied at the beginning of anaerobiosis. Along the incubations, we characterized gases, organic and mineral solutes, and solids (Fe and Mn oxidation states, cation exchange capacity of the soil). Before anaerobiosis, metal concentrations in solution were low. During anaerobiosis, Fe and Mn were mobilized mainly from soil minerals, their concentrations reaching 4.05 and 6.20 mM, respectively. Thereafter, Fe was immobilized during the first 24 h of aerobiosis through oxidation. Although Mn immobilization was also important, it led to quickly stabilized concentrations of about 1 mM that probably resulted from equilibrium with solids without oxidation. In solids, up to about 35% of Fe was reduced during the 28 d of anaerobiosis, the return to aerobiosis enabling its partial or total re-oxidation in about 4 d. During anaerobiosis, K+, Pb2+, Ni2+, Ca2+ and Mg2+ were also mobilized, the vinasse amendment supplying 143, 120, 31, 56 and 50 % of their maximum concentration in solution, respectively. The variations in exchangeable K+, Ca2+ and Mg2+ suggest their partial exchange in anaerobiosis with mobilized Mn2+ and Fe2+, and it would have been probably the same for Pb2+ and Ni2+. This assumption is consolidated by positive correlations between Mn2+ and other metal concentrations, which could be simulated by a model of cation exchange. The soil cation exchange capacity also increased in anaerobiosis and does not return to its initial state after return to aerobic condition.