Bacteria and fungi isolated from rare earth mine tailings were combined into two inoculants and tested in pots of soil spiked with yttrium. A bacterial mix lowered yttrium in lettuce roots and in rhizosphere soil solution while increasing lettuce growth, and a fungal mix raised soluble yttrium around the hyperaccumulator plant Solanum nigrum. The authors frame this as a way to protect crops while recovering rare earth elements.
Key numbers
- Soil spiked to a final 250 mg/kg yttrium (Methods, Section 2.2).
- Bacterial consortium I lowered lettuce root yttrium by 47% (p < 0.01) and rhizosphere soil-solution yttrium by 56% (Results, Section 3.2).
- Consortium I raised lettuce shoot dry weight by 33% and total dry weight by 26% (Results, Section 3.2).
- Fungal consortium II raised yttrium in Solanum nigrum rhizosphere soil solution by 89% (p < 0.05) without a matching rise in plant tissue (Results, Section 3.2).
Methods (brief)
A forest soil and sand mix was spiked with yttrium solution, amended with organic fertilizer and autoclaved. Pots (five per treatment) received weekly inoculant or sterile water over 45 days. Yttrium in plant tissues and pore water (Rhizon samplers) was measured by ICP-MS; stress markers, soil enzymes, microbial community sequencing and soil metabolomics were also run.
Evidence fitness
Supports statements that rhizosphere microbes can shift yttrium availability and lettuce uptake in spiked soil, as a remediation concept. Absolute yttrium concentrations are shown only in figures, and the study does not support field occurrence, food levels or human exposure statements.
Limitations
Autoclaved, spiked soil rather than field-contaminated soil; one spike level and 45-day pots. Results are reported as percentage changes; absolute values are only in Figure 1. The chemical form of the yttrium spike is not specified in the main text.
Related evidence
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