Phytoremédiation des organochlorés. Etude mécanistique et fonctionnelle des capacités épuratrices du système plante-rhizosphère

摘要

Organochlorines (OCs) -molecules used in industrial processes and in agricultural applications which are prohibited from use nowadays- are classified as very persistent pollutants and show an environmental risk for surface water and groundwater, soil and atmosphere. To restore polluted sites, alternative methods are developed using ecoremediation technologies in situ. The aim of this thesis is to study the OCs phytoremediation capacities using two model plants, Zea mays and Phragmites australis. OCs slected for this work are, lindane (γHCH), monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB) and 1,2,4-trichlorobenzene (TCB). The work strategy was to compare the effects on plant physiological functions when plants were exposed to each OC (mono-exposure) and to a mixture of all OCs (multi-exposure). This study highlighted a synergistic effect of the OCs mixture. However, Z. mays and P. australis were able to tolerate OCs mixture concentrations much higher than the environmental concentrations measured in situ. The OCs phytoextraction was demonstrated by our experiments under controlled conditions and using 14C-OCs molecules. OCs were mostly bioconcentrated in the underground parts of the plants. This study also demonstrated an adaptation of the rhizospheric bacterial microflora under a gradient of OCs exposures (multi-exposure). The techniques used (16S rRNA, SSCP, 454 pyrosequencing) held to the detection of strains potentially able to provide OC-rhizodegradation.