Journal
JOURNAL OF ENVIRONMENTAL MANAGEMENT
Volume 318, Issue -, Pages -Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2022.115538
Keywords
Mine tailings; Metals; Assisted phytostabilization; Laboratory pilot; Microbial diversity
Categories
Funding
- Region Centre-Val de Loire [2016-00108485]
- Labex Voltaire [ANR-10-LABX-100-01]
- PIVOTS project by the Region Centre-Val de Loire: ARD 2020 program, CPER 2015-2020
- European Union
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This study evaluated the effect of phytostabilization on a Pb-rich mine waste through a laboratory pilot-scale experiment. The results showed that the addition of biochar, manure, and iron-oxide-rich ochre promoted plant growth and decreased Pb concentration in the surface layer pore water. Observations suggested that Pb immobilization in the rhizosphere occurred through the mechanical entrapment of tailing particles by Agrostis capillaris plants. Additionally, phytostabilization led to changes in microbial communities.
Old mine waste repositories can present health and/or environmental issues linked to their erosion, inducing dissemination of metals and metalloids in air and water that can be attenuated through phytostabilization. Here, the effect of this widespread phytomanagement option on the biogeochemistry of a Pb-rich mine waste was evaluated with a laboratory pilot-scale experiment giving access to the non-saturated and saturated zones below the rhizosphere compartment. Amendment of the tailings surface with biochar, manure and iron-oxide-rich ochre promoted growth of the seeded Agrostis capillaris plants. These events were accompanied by an increase of pH and a decrease of Pb concentration in pore water of the surface layer, and by a transient increase of Pb, Zn, and Ba concentrations in the deeper saturated levels. Macroscopic and microscopic observations (SEM) suggest that Pb was immobilized in A. capillaris rhizosphere through mechanical entrapment of tailing particles. Microbial taxonomic and metabolic diversities increased in the amended phytostabilized surface levels, with a rise of the proportion of heterotrophic micro-organisms. Below the surface, a transient modification of microbial communities was observed in the non-saturated and saturated levels, however 11 months after seeding, the prokaryotic community of the deepest saturated zone was close to that of the initial tailings. pH and water saturation seemed to be the main parameters driving prokaryotic communities' structures. Results obtained at pilot-scale will help to precisely evaluate the impacts of phytostabilization on the temporal evolution of reactions driving the fate of pollutants inside the tailings dumps.
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