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Toxicological response and bioaccumulation of strontium in Festuca rubra L. (red fescue) and Trifolium pratense L. (red clover) in contaminated soil microcosms

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This soil microcosm study exposed two common pasture plants to strontium chloride and measured germination, growth, soil sorption and strontium in shoots and roots. Strontium impaired germination and growth at higher doses. Red clover moved far more strontium into its shoots than red fescue, which the authors propose for phytoremediation.

Key numbers

  • Control shoots held 0.024 g/kg (red fescue) and 0.036 g/kg (red clover) strontium; roots 0.028 and 0.012 g/kg (Table 5, p. 9).
  • At 40 mM with combined exposure, shoot strontium reached 12.0 g/kg in red fescue and 17.4 g/kg in red clover (Table 5, p. 9).
  • Translocation factors (shoot to root) ranged from 0.64 to 3.68 in red fescue and 2.65 to 25.3 in red clover (Table 5, p. 9).
  • Soil adsorbed 41 to 96 percent of added strontium depending on dose and contact time, above 80 percent within 7 days at 20 and 40 mM (Table 2, p. 5).
  • Pre-germination exposure reduced red fescue shoot weight from 0.54 to 0.21 to 0.30 mg per plant at 5 to 40 mM (Table 4, p. 7).

Methods (brief)

Seeds were germinated in strontium chloride solutions (0 to 40 mM); soils were tested for strontium sorption; plants were grown for 10 weeks under pre-germination, post-germination and combined exposure. Dried tissue was microwave digested and analyzed by ICP-OES.

Evidence fitness

Supports evidence that stable strontium at high soil doses is phytotoxic and that forage legumes can concentrate it in shoots. Doses are far above normal agricultural levels, and the plants are pasture species, so the results do not support human exposure or food-crop statements.

Limitations

Spiked microcosms with very high doses and n = 3 per treatment. The abstract describes red fescue as an excluder, yet most of its translocation factors in Table 5 exceed 1; only two post-germination treatments fall below 1. Tissue values are on a dry weight basis per the translocation formula, but the table does not restate the basis.

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