Rôle de métabolites bactériens dans la mobilisation du césium d’une illite dopée : étude mécaniste et application à la phytoextraction

摘要

Following nuclear accidents, various radionuclides such as cesium-137 (Cs) are dispersed in the atmosphere before being deposited on the soil. In order to eliminate Cs accumulated in the upper soil horizon, both in situ and at lower cost, phytoextraction is proving to be a promising method. The combination of bioaugmentation of soil and phytoextraction may reduce the treatment duration by increasing the fraction of Cs mobilized by the plant. Understanding the mechanisms that governs the Cs-soil-plant-bacteria interactions is the subject of this thesis. The first part of the thesis concerns the bioaccessibility of a purified and Cs-doped illite, considering the direct or indirect actions of bacterial metabolites (citric and oxalic acids, desferrioxamine mesylate, acetohydroxamic acid and pyoverdine (PVD) produced by P. fluorescens). PVD desorbs up to 45% of Cs from illite through direct (ion exchange) and indirect (illite weathering) mechanisms. In the second part, red clover (Trifolium pratense), chosen as accumulatorplant, is hydroponically grown, with or without PVD. Without PVD, 10.0 μmol of Cs per g of dry matter (DM) are accumulated in roots and 5.9 μmol.g-1 DM in its aboveground parts while in its presence, Cs accumulation by red clover is reduced by 25 to 70% but the translocation factor was higher (0.5 without PVD and 1.1 with PVD). In the third part, the red clover is grown in pots in the presence or absence of PVD. The results are similar to those measured in hydroponics (118 Cs μmol.g-1 MS in roots and 40 μmol.g-1 MS in the aboveground parts).