Effect of pyoverdine-producing bacteria on lead speciation in non-point source contaminated soils

International audiencePhytoextraction has been studied for decades, and up to now has not been applied widely because of the extended period of time required for soil cleaning-up. To improve its efficiency, phytoextraction could be associated with soil bioaugmentation, in particular with siderophores producing bacteria (SPB). Siderophores are iron complexing agents able to complex others metals including lead (Pb). This study aims at evaluating the potential effect of pyoverdine (Pvd), a siderophore produced by Pseudomonas fluorescens, on Pb mobility and on phytoextraction efficiency in the example of a non-point source contaminated soils (geogenic vs. anthropic Pb).Brassica juncea is cultivated on three different soils: the first one contains geogenic Pb (soil E) and the two other soils were contaminated by anthropic activities (soils O and M). Soils E and O – same loamy-sandy texture and same total Pb concentration – were sampled from urban allotment gardens in Nantes (France). The soil M is a sandy-clay agricultural soil closed to Metaleurop, a former smelter located near Lille (France).Purified Pvd or bioaugmentation-assisted B. juncea were tested. Pvd-producing bacteria were previously selected based on biochemical tests. The content of Pb in shoots and roots of B. juncea is measured as well as the Pb speciation in soil by using chemical and physical methods: selective extractions with CaCl2 and DTPA, sequential extractions, XRD analysis on the most concentrated fractions, Raman analysis, etc.Work is in progress. Expected results are clay weathering and an impact of Pvd on others Pb bearing phases, as already shown by Hazotte et al. (2016) and the increase of phytoavailable Pb and eventually higher phytoextraction rate