Chrysotile dissolution in the rhizosphere of the nickel hyperaccumulator Leptoplax emarginata

Ni phytoextraction processes need further understanding of the interactions between Ni availability in soils and its absorption by plant roots. The large metal uptake and root exudation by hyperaccumulator species could accelerate the weathering process of Ni-bearing phases in the rhizosphere. The aim of this work was to quantify the weathering of a Ni-bearing mineral phase in the rhizosphere of the Ni-hyperaccumulator Leptoplax emarginata. The studied mineral was chrysotile which was characterized by a low Ni solubility. Column experiments were performed to assess the effect of the Ni-hyperaccumulator L. emarginata and the contribution of rhizobacteria on the dissolution rate of chrysotile. Mineral weathering was monitored by measuring Ni and Mg transferred to leachates or plants throughout the experiment. Results showed that L. emarginata increased chrysotile dissolution by more than 2-fold . The hyperaccumulator L. emarginata accumulated 88% on average of total mobilized Ni. Inoculation with Ni-resistant bacteria in the rhizosphere of L. emarginata had no significant effect on chrysotile dissolution or plant accumulation of Ni in this context. Finally, after 15 weeks of culture, 1.65% of total Ni in the system was mobilized in the planted treatments compared with 0.03% in the unplanted treatments.