Incidences d'interactions racines-microorganismes-état hydrique sur la mobilisation et redistribution de métaux dans des sols nickélifères

Abstract : In New Caledonia Ferralsols, nickel, chromium and cobalt are contained in iron and manganese (oxy-hydr)oxides and are released during weathering, particularly by iron reducing bacteria. So it is of major interest to know the biogeochemical cycle of Fe, Mn, and associated trace elements in soils and rhizosphere of crop plants. The aim of this work is to define the effect of rhizosphere, microorganismes and hydric conditions on iron and manganese oxyhydroxides weathering, and mobilization of trace elements (Ni, Cr, Co). Experiments have been done using pot cultures of maize or axenic column, and batch devices in controlled conditions. Iron and manganese reducing bacterial communities have been isolated from maize rhizosphere. Weathering of mineral phases has been monitored by transfer elements to the plant, dissolution and redistribution of metals between the different geochemical compartments, from the most available (watersoluble elements) to the most stable (iron oxides). Results show an improvement of bioavailability of Fe, Mn, Ni, Cr and Co, which were trasfer to maize. Mineral phases weathering involve a mobilization of the metals from oxides and their redistribution to most stable or most available compartments. The presence of the plant, iron and manganese reducing communities, and waterlogged conditions during plant culture, increases the element bioavailability. Biodegradation of soil organic matter has an important influence on the occurrence of conditions favourable to the weathering.
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Isabelle Paskiewicz. Incidences d'interactions racines-microorganismes-état hydrique sur la mobilisation et redistribution de métaux dans des sols nickélifères. Sciences de la Terre. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10042⟩. ⟨tel-01754320⟩

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